Category Dreams, Technology, and Scientific Discovery

I left Pasadena with Henry Richter for Washington on Thursday, 20 February, to deal with the ground station readiness problem.8 Finally, on Saturday, over a week before the scheduled launch, I was on my way from Washington to Florida. After hitching a ride from the Orlando airport to Cocoa Beach with Roger Easton, Marty Votaw, and other NRL personnel, I checked in at the Sea Missile Motel. Early on Monday morning, I joined the JPL and Army Ballistic Missile Agency (ABMA) crews at Cape Canaveral and we all worked, steadily and methodically, to prepare for the second Jupiter C launch.

Being at the Cape for a full 10 days during the preparations for the initial Deal II launch attempt, I received an extraordinarily complete and exciting exposure to the myriad activities involved in launching a large multistage rocket. With the countless components that had to work together flawlessly, the handling of highly corrosive fuels and cryogenic oxidizers, and the pushing of the state-of-the-art in materials and electronics, I still marvel that it was possible to launch the first satellites at all.

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Cape Canaveral was an isolated piece of real estate before it was tapped for its rocket-testing mission. A nineteenth-century lighthouse is still located near its tip. The few early inhabitants had to contend with swamps and myriad pests, including coral snakes and rattlesnakes, wildcats, deer, armadillos, alligators, and, of course, the always troublesome swarms of mosquitoes.

The first rocket launches from Cape Canaveral had taken place on 24 and 29 July 1950. They were of the two-stage combination of the German V-2 boosters topped by JPL WAC Corporals, the so-called Bumper rockets. They took place from a site, later identified as Launch Complex 3 but long since dismantled, near the lighthouse.

The evolution of the complete Cape Canaveral and Merritt Island area into the massive complex of today is a fascinating story in itself. The layout of the portion of the Cape that was active in 1958 is shown in Figure 10.3.

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The satellite preparations at Cape Canaveral were centered at the Spin Test Facility, located not far from Launch Complex LC-26, from which the Deal satellites were launched. The Spin Test Facility was a simple blocklike structure containing a single large bay with a high ceiling. It was built for the express purpose of stacking and checking the Jupiter C second-, third-, and fourth-stage solid rockets. The satellite received its final assembly and electrical checkout in a trailer just outside the Spin Test Facility. It was then carried into the Spin Test Facility, subjected to a payload spin test, and mated with the final rocket stage. That top assembly was spin tested, and then mated to the rest of the rocket cluster. Finally, the composite second-, third-, and fourth-stage assembly was balanced and spin tested.

The roof of the Spin Test Facility served as a wonderful observation post. It placed us in the open above the scrub growth so that we had a clear view of all launches then being conducted at the Cape. The Redstone and Jupiter pads with their blockhouses were just over a mile away. The Thor site was only one and a half miles away, and the Vanguard site was one and three-quarters miles distant. The Atlas pads were taking shape in Intercontinental Ballistic Missile (ICBM) row about four miles away. (The Titan pads shown on the map had not yet been built in early 1958.)

From the vantage point of the Spin Test Facility roof, during 1958, we observed a steady parade of launches, of both spacecraft and military rockets. This was a truly overpowering experience, even if not very wise, as we were so close that a stray missile would have been impossible to dodge. Sometime later that year, Cape officials moved the security line farther back when launches were scheduled, and we had to do our recreational watching at a roadblock somewhat farther away.

Even there, the launches were spectacular beyond words. The sense of unleashed raw power as the vehicles lifted from their pads and arched into the blue or nighttime sky was awesome, indeed. During my many visits to the Cape from 1958 through 1965, I watched launches of Bomarc, Matador, Navaho, Snark, Polaris, Juno, Thor, and Atlas rockets. Many were failures. On one occasion, I observed a particularly memorable show—an evening launch attempt of a Thor by the Air Force. It exploded only a few thousand feet into the air. The resultant burning of aluminum and magnesium parts lit the nighttime sky like a monstrous flare, so bright that objects on the ground were as clearly visible as though it were daytime.

To my great disappointment, I was never able to witness a Saturn or Shuttle launch, but by extrapolation, I can imagine the intense sensations of hearing and feeling that must be conveyed by the launch of those much larger vehicles.

Back to Deal II: the JPL satellite payload crew and I concentrated on the detailed checkout of the three identical flight instruments. Those tests included electrical performance, spin, and radiated power tests. For some of those tests, we used a

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special interrogation station set up in the nearby Atlas Radio Inertial Guidance (RIG) area. For all three payloads, I read and analyzed a seemingly endless stream of data recordings, concentrating on the performance of the onboard recorders. Although some of the tests used radioactive sources to stimulate the GM counters, others required extended periods to register the less frequent natural cosmic rays.

We also performed a major radio frequency interference test by mounting the Spare Payload atop the fully assembled multistage rocket in its launch gantry. During that test, we displayed the instrument’s signal, both in real time from the test-site receiver and post facto from data recordings made at the fully functioning ground station located some distance away. Part of that test included interrogating the onboard data recorder via the transmitter at the RIG site. Those tests worked well. Unfortunately, we were not able to spin the tub containing the three upper rocket stages and instrument atop the Redstone booster. That omission resulted in considerable anguish later, during the actual launch countdown.

On Monday and Tuesday (the two days before launch), I briefly summarized the results of the complete array of tests on all three payloads in my notebook.9 Flight Payload 1 was “no good,” with much skipping of the data tape recorder’s toothed ratchet. Flight Payload 2 and the Spare Payload were both generally satisfactorily, although there were some conditions under which the Flight Payload 2 data recorder also skipped.

It was at that time that I learned with tremendous relief that NRL had completed and tested all of their interrogating ground stations.

On the day before launch, it was time to make a final decision on the selection of the flight payload. Since Flight Payload 1 was not acceptable, it was a question of whether to fly Flight Payload 2 or the Spare Payload. Milt Brockman, the JPL payload manager, strongly preferred Flight Payload 2. It had been fully assembled and tested back at JPL, whereas the Spare Payload had been finally assembled at the Cape and had received less testing. Furthermore, a thermistor substitution had been made in the Spare Payload, and that component had not been as thoroughly calibrated. I had a slight preference for the Spare Payload, as the tape recorder operation was more dependable. I noted, “The tape recorder [in the Spare Payload] does not skip when jarred so easily. P. L. [Payload] II is quite bad in this respect. However it seems to be OK when kept still.” After lengthy discussions, I reluctantly acquiesced to Brockman’s recommendation, and Flight Payload 2 was selected for launch. That payload is shown in the photographs of Figure 10.4.

The cosmic ray experiment that led to the radiation belt discovery was the one that Van Allen first proposed in November 1954.6 Its objectives were “(a) To measure total cosmic ray intensity above the atmosphere as a function of geomagnetic latitude and (b) To measure fluctuations in such intensity and their correlation with solar activity.”

Less than a year later, on 25 September 1955, and less than two months after Eisenhower’s announced decision to include a satellite program as a part of the U. S. contribution to the International Geophysical Year (IGY), Van Allen submitted a revised and extended version of that proposal to Joseph Kaplan, chairman of the U. S. National Committee for the IGY. The first paragraph of that letter read, “There is enclosed a ‘Proposal for Cosmic Ray Observations in Earth Satellites.’ Recent discussion with Dr. G. F. Schilling has indicated that it is appropriate to submit definite proposals at this time.”7 He followed that letter with a further-expanded version that he presented at the forty-third meeting of the Upper Atmosphere Rocket Research Panel at Ann Arbor, Michigan, on 26-27 January 1956.8 The latter proposal was eventually accepted as the basis for our development of the Vanguard cosmic ray instrument.

The January 1956 proposal stated its general objective as a “study of the cosmic-ray intensity above the atmosphere on comprehensive geographical and temporal bases for the first time.” It included extended discussions of the interpretation of expected data with respect to (1) the effective geomagnetic field, (2) the magnetic rigidity spectrum of the primary radiation, (3) time variations of intensity, and (4) cosmic ray albedo of the atmosphere.

Cosmic ray albedo refers to particles that leave (splash out from) the Earth’s atmo­sphere as a result of nuclear interactions caused by primary cosmic rays crashing into the atmosphere from above. Van Allen’s paper included a figure that plotted

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lune-shaped regions in the Earth’s vicinity within which particles of particular mag­netic rigidities and traveling in certain directions might be trapped.

That drawing and its discussion reflected the fact that there had already been a substantial body of earlier study into the behavior of charged particles in the Earth’s magnetic field.9 Sightings of the aurora Polaris (aurora borealis, popularly the northern lights, in the north polar region and aurora Australis in the southern hemisphere) had been recorded for centuries. A substantial amount of theoretical and experimental work was done during the first half of the twentieth century in attempting to explain those aurorae. Many of those early studies were conducted in Scandinavia, quite naturally, since populated portions of those countries lie well within the northern auroral zone. Kristian Olaf Bernhard Birkeland (1867-1917) was one of the leading early auroral researchers and, even today, is considered one of Norway’s greatest scientists. He published the first realistic theory of the north­ern lights, including his belief that they resulted from charged particles ejected from the Sun that were somehow captured or focused by the Earth’s magnetic field.

To help prove his theory, Birkeland performed his famous torella experiment. He directed an electron beam toward a conducting sphere that had a dipole magnetic field. The sphere’s surface was sensitized, and the experiment was conducted in near­vacuum. Electrons were seen to hit the sphere primarily in two rings that suggested auroral ovals similar to those seen on Earth.

With that finding, Birkeland asked his former teacher, Jules Henri Poincare (1854­1912), to examine the motion of electrons in magnetic fields. Poincare was able to solve mathematically the problem of the motion of charged particles near a magnetic monopole. Although magnetic monopoles have not been seen in nature, his work showed convincingly that the electrons were guided toward the poles of a real dipole magnet, thus preparing the way for later work. Birkeland suggested this problem to a mathematician friend, Carl Fredrik Mulertz Stormer (1874-1957), who devoted much of his career to its further study.10

One of Stormer’s most important contributions was to show that, for electrically charged particles of various combinations of mass, charge, and vector velocity, two dynamical regions exist within a dipolar magnetic field such as that of the Earth. One is of unbounded motion, and helps to account, for example, for the arrival of particles from outside the Earth’s immediate neighborhood (from the Sun, for example) into the Polar Regions.

The second region is one containing bounded trajectories. Stormer showed that certain classes of charged particles can spiral around the magnetic lines of force and that, as their centers of motion move north or south, they are reflected by the converging magnetic field lines. Moving then toward the opposite pole, the same action takes place, and the particles continue to mirror back and forth between the poles until

CHAPTER 12 • DISCOVERY OF THE TRAPPED RADIATION 323

they are scattered by irregularities in the magnetic field or interactions with other particles.

It is clear that the early researchers tended to view the region from the outside in. That is, they envisioned the particles as approaching the Earth from the Sun and beyond, and they referred to the region of the magnetic field that we now refer to as the trapping region as the forbidden zone, i. e., a region within which particles from the outside could not enter. Although they certainly realized that a particle injected by some mechanism into that zone with the proper rigidity and direction could be reflected back and forth by the action of the magnetic field, they did not appear to harbor any expectation that there might be a substantial reservoir of particles durably trapped there.

We at the Iowa campus enjoyed a special treat during the first semester of the 1954— 1955 school year, when Sydney Chapman joined us as a visiting distinguished pro­fessor. During that semester, Chapman taught a course titled Physics and Chemistry of the Upper Atmosphere. Among other things, he included extended discussions of the aurorae, and of theories that attempted to describe them, including the works of Birkeland and Stormer. Detailed notes from his lectures were assembled by Ernie Ray as a mimeographed, unpublished compendium.11 The formal course was accom­panied by many stimulating informal discussions by Chapman, the faculty members, and us students.

Interest in the trajectories of charged particles in the Earth’s geomagnetic field, especially after the interaction with Chapman, resulted in a flurry of activity within the State University of Iowa (SUI) Physics Department. Ernie Ray and Joe Kasper undertook concentrated studies of that phenomenon. With Van Allen and others, they began to apply that knowledge to help explain the auroral soft radiation that had been detected, first on the 1953, 1954, and 1955 rockoon expeditions, and then by Carl McIlwain with his rocket shots at Fort Churchill, Canada, in 1957-1958.

In their studies, which involved tracing the charged particle motions near the Earth, Ernie made some of his earliest attempts to program the newly evolving digital computers to solve the differential equations involved. Joe configured the analog differential analyzer that he had developed for his master’s thesis for a similar purpose.

During that period, there were many spirited discussions of Stormer trajectories, cosmic ray motion, auroral mechanisms, and other related topics, both on our campus and within the larger research community. The field was abuzz with activity, both experimental and theoretical.

S. Fred Singer, as early as April 1956, suggested that the motions of charged particles in the Earth’s magnetic field, by the process hypothesized by Stormer many years

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earlier, might account for the Earth’s ring current. The ring current is an electric cur­rent, predominantly consisting of protons and heavier negative ions drifting westward around the Earth, which slightly perturbs the magnetic field at its location. Studies of the ring current had occupied Singer’s attention for some time, and that was the object of Laurence Cahill’s rockoon flights during the fall of 1957, as recounted in an earlier chapter.

Singer further elaborated on his ideas related to particle trapping in April 1957:

The [magnetic] storm decrease is produced by the high-velocity particles following the shock wave (up to nine hours later) which enter because of field perturbations into the normally inaccessible St0rmer regions around the dipole. Here they are trapped and will drift, producing the ring current which gives rise to the storm decrease. Particles with a small pitch angle, however, can reach the Earth’s atmosphere and contribute to aurora, the airglow, and ionospheric ionization.12

However, before the discovery of the high-intensity radiation by Explorers I and III, no one within the worldwide community of researchers, including Singer, had made the intellectual leap to suggest that a huge population of particles might be trapped there to form a durable region of intense radiation surrounding the Earth.

As in the case of the earlier Explorers, paper strip-charts were produced as a first data reduction step for Explorer IV, using the equipment setup shown earlier in Figure 11.4. But for Explorer IV, the process was a bit more complicated because of the highly classified nature of the Argus Project. For the initial month (before the first Argus detonation), during which all of the data were unclassified, data reduction was much as it had been for Explorers I and III.

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 377

However, during the month following the first nuclear burst, i. e. during the times that portions of the data showed the effects of the tests, Carl McIlwain served as a data screener. He diverted the charts containing indications of the Argus tests for special handling, where he served as the primary data reader.

Explorer IV results were disclosed in three steps: (1) an initial public release of the unclassified results, (2) an exchange of classified Argus data and results within a small circle of appropriately cleared personnel, and (3) a public release of the Argus results sometime later.

Work on the unclassified portion of the Explorer IV data was straightforward, even though rushed. The first tentative written expression of results was on 2 August 1958 in the form of a telegram from Van Allen.19 On the same date, the same information, with the addition of a block diagram of the instrument package, was recorded as a report in the Physics Department’s serial report series.20

Those two documents provided a very sketchy report based on the examination of only 15 station recordings from 26 through 29 July in the northern hemisphere and covering the altitude range from about 165 to 1000 miles. They reported that the instruments were operating properly and gave some very tentative information on the rapid increase in radiation intensity, as the satellite climbed above 250 miles height. Some first-ever information from Carl’s detector about the total energy density was also included.

Due to Van Allen’s, Mcllwain’s, and my heavy involvement in the Explorer IV effort, Ernie Ray was the only one from our laboratory to attend the Fifth General Assembly of the IGY Committee in Moscow on 30 July through 9 August 1958. While there, he received a telegram from us that conveyed a summary of the information from the two documents mentioned above. He presented that information at the conference.21

Additional releases quickly followed. On 20 August, a slightly expanded report based on a larger collection of data from the first two weeks of Explorer IV opera­tion was released.22 Among other things, it reported fluxes of both penetrating and nonpenetrating components, with the penetrating particles predominating at lower latitudes (in what came to be known as the inner radiation belt) and the nonpenetrat­ing particles predominating at the higher latitudes (at the horns of the outer radiation belt).

By late November 1958, our analysis had progressed far enough for us to issue a substantially expanded Department of Physics report.23 That paper included a number of interesting figures, one of which is reproduced here as Figure 13.3. The shape of the contours around 30 degrees north latitude provided a first hint of what was later recognized as the gap between the inner and outer radiation belts, with the cusp north of 30 degrees being the lower tail of the outer belt.

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FIGURE 13.3 A sketch from the 20 August Physics Department report showing initial results from Explorer IV. This is a meridional section through the Earth showing counting rates from the relatively unshielded GM counter. The data were taken between 26 July and 26 August 1958 within the longitude range west 60 to 100 degrees. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Libraries.)

The contours in that set of figures led to a speculative extrapolation of the radiation levels farther into space, reproduced as Figure 13.4. Actually, that particular model of the high-intensity radiation was one of two being considered when the paper was prepared. A second model, suggested and particularly advocated by Carl McIlwain, regarded the high-latitude cusps appearing consistently in the set of data plots to be the lower ends of a second distinct region of high-intensity radiation. Later observations from Pioneer 3 (described in the next chapter) showed Carl’s model to be the correct one.24 Since those Pioneer data were not available when the November 1958 report was prepared, the “simpler” of the two models, i. e., the one showing a single region of trapping, was chosen for publication.

The November report was presented at a meeting of the American Physical Society in Chicago in early 1959 and was published in March in the Journal of Geophysical Research}5 Since it had been actually mailed for publication late in 1958, well before the Pioneer 3 results were available, it still included this Figure 13.4, showing the single donut-shaped region of high-intensity radiation.

In addition to the variation in intensity with altitude and latitude provided in the first reports, the new paper provided information on the intensity variation with longitude, the angle of arrival of particles, and the nature of the radiation. In summary, the in­tensity varied with longitude in the way that one might expect from knowledge of the actual shape of the Earth’s magnetic field. Second, there was a strong dependence of radiation intensity on detector pointing angle. That was interpreted as indicating that the particles were moving predominantly in discs lying nearly perpendicular to the

lines of the magnetic field, thus helping to substantiate the model of particle trapping by spiral movement along the field lines. Third, although information on the compo­sition of the trapped radiation was very sketchy, electrons seemed to predominate at the higher latitudes, and there was a major proton component at the lower latitudes.

The last section in that paper, in both its November 1958 and March 1959 forms, was devoted to extended remarks on the interpretation of the data. It considered as well established that the “great radiation belt” around the Earth (by then the singular term belt was still being widely used) consisted of charged particles, temporarily trapped in the Earth’s magnetic field in Stormer-Treiman lunes. The paper went on to state that the overall decrease in intensity at the lower altitudes was almost certainly due to atmospheric scattering and collisional energy loss. Scattering would predominate for electrons and collisional loss for protons.

As to the injection rate, which would have to equal the loss rate in order to maintain a stable belt intensity, the paper stated that the decay of neutrons moving out from the atmosphere as a result of cosmic ray collisions with atmospheric molecules might

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help feed the belt, but that that source was inadequate by a large factor to produce the observed intensity. The paper asserted that solar plasma must replenish the reservoir of stored particles from time to time, working its way into the outer reaches of the Earth’s magnetic field under some conditions, and then being trapped in the magnetic field.

Finally, the paper suggested that the leakage of electrons from the trapping region at high latitudes might be the direct cause of the aurorae.

Earth is the cradle of humanity, but one cannot live in a cradle forever.

Konstantin Tsiolkovsky From a letter written in 1911

rom the perspective of 50 years since the event, there is little doubt that the quasi-political Soviet launch of Sputnik 1 injected the world into the Space Age as no purely scientific research program could have done. Without the U. S. national humiliation and the space race that followed, there would probably be no NASA today, no man would have set foot on the Moon, and we would not be using spacecraft as widely for research, Earth observations, and the wide array of other scientific and practical applications.

This point of view was expressed by Wernher von Braun in an April 1958 article he wrote for the Des Moines Sunday Register: “The Russian Communists may well have done themselves an ill turn by humbling us in the space race. Unwittingly, they made the sleeping American giant awaken.”1

A comment by Hugh Dryden, one of the early NASA deputy administrators, to Anatoly Blagonravov, his Soviet counterpart, at an International Astronautical Federation congress in Washington in 1961 succinctly expressed the same thought: “If we had [had] cooperation, neither of us would have a space program.”2

The new discoveries being made today with large and marvelously discriminating instruments such as those on the Hubble Space Telescope are truly remarkable. The exceedingly useful environment-observing instruments, the reconnaissance satellites, and the huge array of communications and position-locating satellites have taken us into a new world of observation, information gathering, and global connectedness.

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The instruments of the 1950s were almost laughably simple by present standards. In the first Explorer, we put a single Geiger-Muller counter and a handful of transistors and other components together to produce a data stream of only a few digital bits per second from only a few hundred miles in near-Earth space. Today, that simple circuitry could be replaced by a few square millimeters of circuitry on a silicon chip. Its information could be carried in a small fraction of the bandwidth used by today’s space probes from billions of miles away.

But keep in mind that back then, we were on the very forefront of technological progress.

The first half of the twentieth century was marked by many key Industrial Age developments that presaged the entry into space. The century was opened by the first powered flight by the Wright brothers. Only a quarter century later, the first tests of liquid fueled rockets were being conducted. Rocketry made tremendous advances during World War II, culminating in Germany’s development of the V-2 rocket. Electronics moved from the invention of the first vacuum tube by DeForest to Marconi’s first transmissions across the Atlantic to the invention of the transistor. All those advances paved the way for entry into space in 1957.

The situation today in space parallels that with respect to aviation at mid-century. We were a nearly equal distance beyond the Wright brothers’ pioneering flight then as we are today beyond the first space launch. Fifty years after the first powered aircraft flight, there were thousands of aircraft in the air on any given day. Today, the world’s space-faring nations have successfully launched more than 4000 major objects into Earth orbit and beyond.

The initial foray into space in the middle of the twentieth century profoundly and enduringly influenced our daily lives, in much the same way that aeronautics influenced the first half of the century. Space has become an integral part of our culture. We all employ space technology every day, often without thinking about it— it has become an inextricably interwoven element of telephone, Internet, television, and military communications; weather observation, forecasting, and dissemination; other environmental monitoring and appraisal; land-use surveying; global position determination; and so on.

Space terminology has even entered our everyday terse speech. In the same way that people say “bring your transistor” when referring to a transistor radio, they now say “turn on the satellite” when referring to their satellite receivers.

The opening of the Space Age had a profound effect on our physics and engineer­ing educational curricula. Sputnik aroused an immediate general sense that science and engineering training in the United States needed a shot in the arm. Higher ed­ucational standards were quickly established, and introductory texts soon appeared

Carl Edwin McIlwain was born on 26 March 1931 in Houston, Texas. He lived there during his primary and secondary school years except for the years 1942 to 1945, when his father was engaged in war work and the family lived in the states of Georgia and Kentucky.20

Showing an early aptitude for music, Carl obtained his first flute at age 10. By the time he reached high school—his family was back in Houston by that time—he was already an accomplished flutist, playing in both the school band and orchestra. During that period, he took lessons from the first flutist of the Houston Symphony Orchestra. Receiving a music scholarship at North Texas State College (now North Texas University), he spent the next four years there, obtaining his bachelor of music education degree in the spring of 1953.

During his undergraduate years at North Texas, he had an unusual experience in connection with his music training. His flute teacher, Professor George Morey, recognized a unique talent in him and served as a mentor in much the way that Van Allen did later in physics at Iowa. Carl found himself helping in teaching Morey’s students. By the time he was in his junior year, he had his own teaching studio similar to those of the teaching faculty members. He carried an active teaching load for his last two undergraduate years.

From an early age, Carl also developed a great interest and possessed a considerable natural aptitude in science. He remembers that by the time he was eight, he was often engaged with his chemistry and Erector sets. After the war, he went regularly to the army surplus stores to buy all kinds of electronic equipment for his tinkering. He took a number of high school courses in science. A physics teacher took a special interest in him and gave him the run of the laboratory, where he performed his own “play-experiments.” On one occasion, that teacher gave him an aptitude test and reported to Carl he had the highest score he had ever seen. When Carl later reported to him that he was going to North Texas to study music, the teacher expressed his surprise that he was not going into science. Carl responded, “Well,

I have a scholarship in music and none in science.” Reflecting his continuing interest in science, however, Carl also took the courses in geology, calculus, and noncalculus physics that North Texas offered.

Upon college graduation, Carl rejected several enticing high school band director’s offers and moved to Iowa City in early 1954 with his new bride, Mary, also a flutist. His initial goal was to study the physics of music. An academic position, to begin in the fall, had been arranged by his teacher and mentor in Texas, who was a former graduate of the Iowa Music Department. Carl discovered upon arrival, however, that he had been edged out of the paying teaching position by a graduating student who had decided to stay and join the Iowa faculty.21 Nevertheless, he promptly secured a chair as second flutist in the SUI orchestra, and he played with them during his first semester. However, he had to scramble to find paying work. Initially, Carl worked as a gas station attendant.

That summer, he was delighted by his employment as an hourly employee in the Physics Department’s Cosmic Ray Laboratory. One of his first tasks was to design and make a bracket to hold a large capacitor on one of the Deacon rocket circuit boards. This was his introduction to laboratory work on research instruments. It appeared to have been promising, as Van Allen gave him a research assistantship that fall.

In the academic arena, Carl signed up as a physics graduate student and enrolled in a set of undergraduate mathematics, chemistry, and physics courses to, as he put it, “get his feet on the ground.” Although his undergraduate work at Texas had not been in physics, at that time, Iowa’s only academic requirement to become a graduate student in any of its departments was to have a bachelor’s degree in any subject.

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Carl won his master’s and Ph. D. degrees in physics in June 1956 and June 1960, staying on at Iowa as an assistant professor for about a year and a half. He accepted an invitation in March 1961 to visit the campus of the University of California at San Diego, located at La Jolla, California. He and Mary were immediately taken by the research opportunities, location, and climate. They moved there, with Carl as a tenured associate professor, in February 1962. Appointed as a full professor in 1966, he continued his work there for the rest of his professional career. In addition to conducting a highly productive space research program, he served over the years in a number of important national advisory capacities.

Carl agreed to take on the development of the Loki rockoon for his master’s thesis. He later admitted that he had no appreciation whatever of the challenge that was presented by breaking into the space instrumentation business with no more electron­ics experience than he possessed.22 I still marvel that Carl was able to become so outstandingly effective in this work in such a short time.

The instrument that Carl developed used a single GM counter to continue the high-latitude survey that had been the original goal of the Iowa rockoon program, that is, to learn more about the energy spectrum of the primary cosmic radiation by measuring its geomagnetic latitude dependence. The very high acceleration of the Loki rocket (270 times the Earth’s gravity [g], compared with 60 g for the Deacon rocket) presented a special design problem. Carl tested individual components to 1000 g in a centrifuge and conducted static load tests on an assembled payload to make sure that they would withstand the launching forces. The final instrument, of which several are seen in Figure 2.9, was a marvel of miniaturization, weighing only 6.8 pounds. He completed the design work and built a complement of 10 instrument payloads in time for the 1955 expedition. That was accomplished at very low cost— the funding provided by the National Science Foundation for designing and building the instruments and procuring the flight hardware was only $2000!23

The third goal of the 1955 expedition was to see if the basic rockoon technique could be extended to reach higher altitudes. Van Allen had envisioned a balloon – launched, two-stage Deacon-Loki rocket combination that might carry the instruments to great altitudes, perhaps as high as 180 miles. To test this concept, Carl Mcllwain mated a Loki I rocket (with his GM counter package) to the top of a Deacon rocket by means of a specially designed adapter. The whole assembly was to be carried to firing altitude by a much larger Skyhook balloon. Two such assemblies were prepared to test the concept, and to attempt to obtain the first ultra-high-altitude data.

The summer of 1955 was a hectic period, as we all worked in a near-frenzy to complete the flight hardware and supporting ground equipment. In addition to McDonald, Carl, and me, the overall construction and testing effort included a heavy workload in the

instrument shop and the capable and energetic help of very talented and dedicated student assistants and aides. Although Carl had his instruments in essentially complete form by the time they had to be shipped, Frank and I were further behind. We had to complete some of our final detector mounting, checkout, and calibrations later aboard the ship.

The field team consisted of Frank, Carl, Joe Kasper, and me. Frank served as the team leader, and Joe went as a general assistant, providing his invaluable help to the rest of us throughout the expedition.

That field expedition was a tremendously exciting and broadening experience and a highlight of my undergraduate years, but it did represent my first extended separation from my family since leaving the Air Force. Daughter Barbara was three, Sharon had just passed her second birthday, and Ros and I had just passed our fifth wedding anniversary.

I felt the strong desire to share this new experience with her. As no letters could be sent from the ship, I kept a fairly detailed diary, which I presented to her upon my return. That diary provided substantial information for this account. In addition to it and my other records, I drew upon published accounts by Carl McIlwain and Frank

CHAPTER 2 • THE EARLY YEARS 43

McDonald.24,25 Carl also kindly made his personal slides available, and Meredith’s unpublished notes provided further details.26

Joe and I, serving as an advance party, left from the Iowa City airport on a United Airlines DC-4 early on Tuesday, 13 September. Although I had accumulated many hours as a pilot in the Air Force, this was my first flight on a commercial airliner. That was in the more relaxed days before aircraft hijackings and terrorist attacks, and I was able to go into the cockpit to watch the pilots at their work. We had a few hours layover at Washington, D. C., and Joe and I hired a cab for a drive-by tour of many of the standard tourist attractions. We arrived at Norfolk, Virginia, late that afternoon and stayed overnight in a downtown hotel. The next morning, Joe called the port director for our ship’s location, and we went aboard.

It was the USS Ashland, a Landing Ship, Dock (LSD), with a 500 foot long open hold.27 The rear of its hold was closed by an immense watertight door that could be lowered to form a ramp. The whole ship could be lowered in the water by flooding the hold and ballast tanks. Smaller boats could then move into the hold, the gate could be closed, and the water in the hold and the ballast could be pumped out so that the ship with its load of boats could rise from its lowered position. The ship could then steam at normal speed while the captive craft could be serviced, outfitted, and loaded as needed. The mother ship was fitted with extensive machine shops, cranes, and other facilities for that purpose. Another wartime role for the LSDs was for amphibious landings, where flotillas of Landing Crafts, Assault (LCAs), Landing Ships, Tank (LSTs), and other craft could be carried in their flooded holds and disgorged at a beach. Thirty-one of these LSDs were built during World War II (WWII).

Ours, LSD-1, was the first one built, and the last one to remain in active service. It was powered by reciprocating steam engines rather than by the turbines that drove later models. A flat superstructure about 70 feet wide by 150 feet long, erected over the rear of the open hold to serve as a helicopter landing deck, served as our work platform for inflating and launching the rockoons. Although fully operational, old LSD-1 looked shopworn—I irreverently (and privately) rechristened it the USS Ashcan. Its primary mission on this trip was to carry supplies to Thule AFB in northern Greenland—our scientific expedition was accommodated as a secondary task.

As was customary for scientific expeditions aboard Navy ships, civilian scientists were accorded officer privileges and lived in officer’s quarters. Since Joe and I were the first of the scientists aboard, we had our pick of the available staterooms. We chose one on the bridge deck next to the officer’s wardroom. Our passageway led to the bridge, which served as a great vantage point for watching shipboard activities. I enjoyed those pleasures for only a short time, until the rest of the equipment and team arrived. As soon as that happened, I was completely absorbed during every waking

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hour with helping to set up our laboratory, completing our instruments, and launching the rockoons.

During that initial slack period, Joe and I struck up a close friendship with Navy Commander Augustus (Gus) A. Ebel and Commander Bracken. Gus, a Ph. D. physicist assigned to the ONR, took care of all liaison matters between the scientific teams and the Navy, both on ship and on shore. Mr. Bracken was the ship’s executive officer. During the next several evenings, the two of them led us on evening shore excursions where we discovered the mysteries of nearby streets that boasted countless bars, arcades, and brothels, whose primary purpose was to relieve sailors of as much of their money as possible during their shore leaves.

Our equipment arrived and was hoisted aboard on Thursday. The batteries for our instruments were appropriately stowed in the battery-charging room, and the rockets were placed in the ammunition magazine. Joe and I took over a large room belowdecks to serve as a shipboard laboratory, and we began setting up our equipment. We also began searching for a suitable additional room to serve as a darkroom for developing the film from our ground data recorder.

Ed Lewis and Herbert Ballman from Winzen Research, along with a General Mills observer, arrived that day. Winzen Research, with Lewis in charge, conducted that expedition’s balloon operations.

Frank and Carl also arrived late that Thursday night. The next morning Carl discovered, to his great dismay, that some of the Loki rockets had been shipped with one inch stub fins suitable only for low-altitude launches. He had asked when ordering them that they be fitted with larger fins to assure stability during the high-altitude launches, but that request had been ignored. Frank and Carl made an emergency trip to a Norfolk hardware store for sheet aluminum, returned, cut appropriately sized fins, and screwed them onto the rocket’s stub fins. They worked!

Two NRL rockoon-launching groups also accompanied this expedition. Les Mered­ith by that time had joined NRL and set up his own research program there. His instru­ments were also designed to further study the auroral soft radiation. Accompanying Les were Leonard (Leo) R. Davis and Howard M. Caulk. The NRL also fielded an optics group led by James (Jim) E. Kupperian Jr. and accompanied by Robert (Bob) W. Kreplin. The trailer that supported both NRL groups arrived on Friday and was hoisted aboard and firmly anchored on a corner of the flight deck. I marveled at the ease with which their trailer-based laboratory was put in operation—as soon as it was connected to electrical power, they were in business. Because of the simplicity of that process, the NRL groups were able to relax and enjoy pleasant hours with the ship’s crew for several days, while Frank and I labored to set up our laboratory belowdecks.

The helium also arrived on Friday—I was impressed by the large number of helium bottles required. At that time, virtually all the helium in the United States was being

produced at a single plant in Texas. I was told that our balloon expeditions used a substantial portion of the then-current worldwide production capacity. The bottles were stowed in the ship’s massive hull, as depicted in Figure 2.10.

That evening, we were invited to the Captain’s presailing cocktail party. This was our first opportunity to talk at length with Captain Bryce, who was wonderfully accommodating and helpful throughout the entire expedition.

Frank and I ran into our first serious problem on Saturday as we were trying to get our ground station in operation. The ship’s primary electrical power was direct current—there was very limited alternating current (AC) power. Of course, all of our laboratory equipment required AC. Although an AC power receptacle had been found on deck for the NRL trailer, there was none in or near our laboratory. Our extension cords were not heavy enough to carry the load from any available source. Joe and I made an emergency trip to a Norfolk hardware store to buy enough AWG #8 residential service cable to make a super extension cable. The crew installed it for us—for an easily negotiated price of six rolls of Scotch-brand electrical tape. We were able to complete the installation of the laboratory equipment and receiving station on that day and immediately started on the final assembly and calibration of our instruments.

At that point, we had another major interruption—Hurricane Ione was heading straight for us. On Saturday evening, our ship, along with more than 80 other Navy ships, put out for hurricane anchorage in the middle of the Chesapeake Bay. As the ship

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steered with its head into the wind throughout the blow, there was surprisingly little rolling or pitching. This interlude gave Frank, Carl, and me more time to continue the work on our instruments. We rode out the storm’s near-approach for the next several days, returning to the Norfolk area on Tuesday. The hurricane turned out to be a relatively mild one, and no significant damage was done to ships or other Navy facilities.

By Wednesday, 21 September, the water was calm, the sky was clear and blue, and the crew was able to complete the ship’s loading and fueling. We made way for the ocean that afternoon. By then, Frank and I had completed work on 4 of our 10 instrument packages. Once we reached the open ocean and began experiencing a 10 degree roll with some pitching, we began to appreciate the difficulties in working in the ship’s cramped and wildly gyrating quarters. The demanding precision work became remarkably inefficient. Nevertheless, we made reasonable progress.

Thursday night, we paused to rendezvous with a coast guard cutter near Woods Hole, Cape Cod. One of the ship’s radar men had had an acute attack of appendicitis. He was very fortunate that it happened there rather than later, as there was no doctor aboard.

On Friday, 23 September, at about 4:00 PM, off the lower tip of Nova Scotia, we sent off the first rockoon, one of Carl Mcllwain’s Lokis. It was a success in every way—the first time that the initial shot on one of these expeditions had worked properly. I manned our receiving antenna located on the roof of the NRL trailer during the ascent and reported my sighting of the visible trail when the rocket fired. We determined later that it had fired at 72,000 feet and climbed to about 230,000 feet altitude. Although the signal was lost for a moment at the time of ignition, Carl soon retuned the receiver to a slightly shifted frequency. Once acquired, the signal remained strong throughout the rest of the flight. Carl was elated by his early success. Of course, this far south, the auroral soft radiation was not seen, nor expected.

By that time, Frank and I had six of our Deacon instruments completely checked and ready to go. The next day, Saturday, we launched the first of them. Figure 2.11 shows the balloon preparation for a typical launch. My diary entry for that event provides a summary of the process, and clearly reflects the elation of a proud young university student experiencing his first successful field launch:

Success! The exuberance of first success! Today we fired a Deacon. We got a very good cosmic ray record. The auroral effect was not found, but we didn’t expect it this far south. The main thing is that the equipment has been proven OK. It’s a wonderful feeling when something you’ve lived with closely for so many months works as planned. I’ve done more working, planning, sweating, and worrying about this project than any I’ve tried before. But when the sound of the subcarrier oscillators, modulated as they should be, comes over the receiver, and the Brush recorder keeps on writing down the data, it is all worth it.

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When I went to bed last night, the plans were laid. We were scheduled to fire at 10:00 this morning. So, for a change, this morning I was up bright and early at 6:45 for breakfast. Breakfast consisted of scrambled eggs, sausage, toast, and three cups of coffee. The com­panionship of the other scientists (that is what they call us aboard ship) is very pleasant and gratifying. It is great to sit around the table and sip coffee while talking over problems and plans.

After breakfast, Frank and I went down to our recording station. We started putting the rocket head that we intended to use through its final paces. There is the checking of counting rates, the calibration of the system for recording pulse heights, the checking of battery voltages as the instrument operates on its own power, the readying of the recording equipment, and finally, the cone is slipped over the equipment and tightened by its 18 screws. The cone is now sealed and operating, not to be opened again.

Meanwhile, the people on the launching deck have been working. Joe [Kasper] and Mr. [.sic: Commander] Ebel have been putting the fins on the rocket, arming it, attaching the firing box, and placing the bag over the rocket. The Winzen Research people have been inflating the 75 foot diameter balloon in preparation for the launch.

After the head [instrumented payload] was sealed, Frank carried it up and they attached it to the rocket. I remained at the recording station to keep a check on it. I noticed noise on the channels at times, and variations of signal strength. I tried to have someone up on the deck check on it (we have telephone communication between recording station, van, and antenna) but there I learned one lesson. When a launching goes that far, it is almost impossible to interrupt it. The balloon is already partly inflated and the only way to abort or delay a launching is simply to cut the balloon loose and start over from scratch. Since the equipment was working a little we decided to go ahead.

Finally came the word—cut loose—the rocket was on its own. Then began the scramble to find out what was causing the trouble. (Our setup used the antenna, preamplifier, and receiver on the NRL trailer on deck, with a line passing the signal from the trailer to the remaining equipment in our laboratory belowdecks.) First of all, they discovered that something was

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wrong with the preamplifier. That still did not cure the trouble, but soon we decided that the trouble was not in the rocket, but rather with the NRL equipment in the trailer. We had our own receiver standing by down in our recording station, so we bypassed all NRL equipment, going directly from antenna down to our receiver. Success! There was still a loose connection somewhere, causing occasional interference, but not serious. It didn’t foul up more than a few seconds of data.

The balloon ascent took about an hour and a half. Finally, at about 70,000 feet, the Racon quit, our frequency shifted slightly, and the rocket was off. The rocket flight lasted four and one-half minutes, during which time there was a constant scurry, to check everything (the recording of the signal), check time on the chronograph, etc., etc.

Finally, the signal faded out quickly, there was nothing but noise on the Brush recorders, and the flight was over. The rocket, its nose assembly containing months of labor, and all that beautiful electronic equipment, was deep in the sea. But we have 200 feet of paper and 100 feet of film that testify to the fact that it was well spent.

The signal strength remained above 100 microvolts during the balloon ascent and above 5 microvolts during the rocket flight, except when they were aiming the antenna. Since we had made such a quick changeover on the receivers, the meter for directing the person aiming the antenna could not be connected, and orders had to be given orally. This doesn’t work too well, so we have that fixed now. We installed a line to operate the meter.

We had been somewhat concerned about the subcarrier frequencies. Before leaving home, I discovered a strong dependence of frequency on filament voltage. But all during the flight, until rocket firing, they held steady. After firing, I was too busy worrying about other things to look, but I’m sure they are OK. At least the information came over them and that is the final criterion.28

That same day we got off another of Carl’s Lokis—also a success. Sunday we passed over the Grand Banks east of Newfoundland. In the relatively shallow water, the seas were still showing the effects of Hurricane Ione that had preceded us up the coast. The USS Ashland was, to say the least, not well suited for rough weather. With its broad bottom, it took up a wild rolling and pitching motion. At times, the ship would seem to remain poised on one of its sides for a few moments, and then over we would go with a sickening whop to the other side. Throughout the night, we heard lockers and other gear crashing and banging in the passageways. Most of the scientists and many of the crew were seasick, but fortunately, I escaped that indignity. By wedging myself between the front rail and rear of my bunk, I was even able to get a reasonable night’s rest. Figure 2.12 shows a sample of the tricky inflation exercise near the Grand Banks.

Soon after passing to the north of Newfoundland, the swells abated, the weather began to turn colder, and I broke out my parka. Rockoon launching soon settled into a busy but purposeful routine as we proceeded farther north. Since Carl’s scientific objective was a comprehensive latitude survey of the primary cosmic rays, he spread his flights out en route through the Davis Strait between 43 degrees and 73 degrees north geographic latitude (about 54 degrees to 84 degrees north geomagnetic latitude). In contrast, the primary objective of the Deacon flights (except for the early shakedown launch) was to study the auroral soft radiation. We launched the rest of our instruments

between 57 degrees and 68 degrees north geographic latitude (68 degrees to 79 degrees north geomagnetic latitude).

The second Deacon rockoon was launched on Tuesday afternoon, 27 September, at a geomagnetic latitude of about 69 degrees. Everything worked well, and we saw a large flux of auroral soft radiation—the counting rate was about seven times the rate that it would have been without the auroral radiation. Three other attempts were made by other groups that day, but unfortunately, they all failed. On one by Les Meredith’s NRL group, the rocket fired, but the flight data turned out to be unusable. In the attempt by Kupperian’s NRL group, the rocket failed to fire. During Carl’s next Loki attempt, his GM counter went into continuous discharge, so that he received no useful data.

The elaborate traditional initiation into Ye Royal Order of the Blue Nose for our first crossing of the Arctic Circle was also held on that day. Since it took place when Frank, Gus Ebel, and I were busily preparing for our launch, we were excused from that boisterous and disgustingly messy rite of passage. I was delighted that we received our certificates anyway!

The pace of our operations peaked during the next two days, with three more flights by Frank and me (all three successful), one each by the two NRL groups (both failures), and the flights of both of our two-stage rockoons (also failures). The auroral effect was seen again in Frank’s and my second and third flights, a 2.5 times normal effect at about 72 degrees geomagnetic latitude and a 2 times effect at 76 degrees. On the fourth flight at about 78 degrees north geomagnetic latitude, we saw no excess radiation and surmised that we were too far north to observe it. We decided to hold

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the remaining five Deacons for the return trip and concentrated on completing the final preparation of the remaining instruments during the rest of the northbound trip.

The prospect for reaching an unprecedented high altitude with small two-stage rockets was an exciting one.29 The field operation, however, was risky. Frank, Carl, and I still shudder when we think about it, especially in the light of the later accidental misfiring of a Loki rocket on the ship’s deck. We had limited means for assembling the tall two-stage configuration on the ship, as its combined height was more than 17 feet. As seen in Figure 2.13, we used the NRL trailer and a stepladder as our “gantry,” first setting the Deacon rocket (with its igniter in place but not connected) vertically on the deck, then carefully mating the Loki rocket (also with its igniter installed) atop the Deacon-Loki adapter.

CHAPTER 2 • THE EARLY YEARS 51

Then came the perilous task of moving the nearly 200 pound assembly across about 75 feet of deck to position it directly under the, by then, inflated and tethered balloon. Since we had no suitable wheeled conveyance, several of us encircled the Deacon rocket with our arms and, with the Loki teetering above, manhandled the assembly across the deck.

Once under the balloon, the Loki’s firing lanyard was attached to the top of the Deacon. Its function was to ignite the Loki once the Deacon had completed its burn and differential atmospheric drag had separated the two rockets. For safety’s sake, barometric pressure and acceleration-activated switches were included to prevent the Loki from firing until it reached altitude, and until after the Deacon had fired. The Deacon firing box was tied by its cord to the bottom of the Deacon’s tail fins and connected to the igniter.

At that point, the balloon’s tether was reeled out so that it could take up the slack on the load line, and then the whole assembly was released. The balloon carried the multistage rocket to its launch altitude.

In the first attempt, the Deacon rocket fired, but there was no second-stage ignition. Carl surmised that he had made the fit of the adapter between the top of the Deacon and the Loki rocket nozzle too tight, so that the two stages did not drift apart. With a file, he reduced the diameter of the coupling for the second attempt. On that attempt, the balloon ascended and both the Deacon firing and Loki ignition were normal. The GM counter operated properly initially, but two and a half seconds after Loki ignition, the transmitted signal was strongly modulated by noise for about a second, and then ceased altogether.

After Carl returned home, he mentioned this attempt to one of the engineers at the Jet Propulsion Laboratory, who responded, “Why didn’t you tell us what you were going to do? We would have told you that the thin aluminum nose cone would melt.” After some confirmatory calculations, Carl and Van realized that they had grossly underestimated the aerodynamic heating of the Loki’s aluminum nose cone at its initial flight velocity of greater than 5000 miles per hour, and the nose cone and instruments probably did melt.

Van Allen stated later, “It is probable that an inexpensive two-stage rockoon can be made to carry small payloads (~7 lb.) to summit altitudes of over 1,000,000 ft. [about 190 miles] if temperature-resistant materials (e. g. stainless steel) are used for the nose cone and the tail fins of the second stage.”30 Van Allen also stated, “Retrospectively, it appears likely that this inexpensive technique, given a heat – resistant nose cone, would have resulted in discovery of the geomagnetically trapped radiation.”31

No further attempts were ever made with that configuration. The Van Allen Ra­diation Belt discovery had to wait for two and a half more years for the flight of the Explorer I and III satellites.

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The voyage continued. After passing a steady parade of icebergs for several days, we reached Thule on the northwest coast of Greenland on Saturday morning, the first day of October. We were presented with a frigid and barren-looking scene, with not a tree in sight. This sizable military outpost was spread out on gently sloping land between the indentation of the bay and background hills to the south. The dominant color was brown, with a few snow banks still showing on the northern slopes of the hills. Being just past fall equinox, the Sun crept low across the southern horizon during the day and just beyond the northern horizon during the lengthening night.

Even today, whenever I look at a globe, I am impressed anew by how far north Thule lies. It is above 76 degrees north geographic latitude—about 400 miles more northerly than Point Barrow and Barter Island on the northern coast of Alaska, and only a little more than 1600 miles below the North Pole.

Since Frank and I had completed the preparation of our remaining Deacon in­struments by that time, and there was a large enough crew without me to handle the rest of the launches, I left the expedition at Thule for Iowa City to return to the classes that would complete my undergraduate studies. Les Meredith also needed to return for a White Sands rocket launch. We hitched a ride on an Air Force C-54 and made an uneventful trip stateside. Arriving back in Iowa City on Tuesday, 4 October, I was over two weeks late in starting my fall classes (advanced calculus, differen­tial equations, modern physics, and electricity and magnetism). I struggled mightily throughout the rest of the semester to try to catch up but was never able to do so to my satisfaction.

On the ship, Carl still had three of his Loki rockets to launch, and Frank had five more of our Deacons. The ship’s first order of business, however, was to make a side trip to Pond Inlet on the north end of Baffin Island to pick up a Catholic priest. Frank, Carl, and Joe were told that he had “lost his mind over the local custom of slipping unwanted girl babies under the ice.”

Shortly out of Pond Inlet, on 4 October, Carl made another successful Loki launch. Two days later, Frank successfully launched another Deacon rockoon. After several days’ stop at Frobisher Bay to drop off supplies, Frank continued with the launching of the remaining four of our Deacon rockoons as the ship progressed again through the auroral zone. Two of those were successful and provided good data on the auroral soft radiation, but two rockets failed to ignite.

Carl’s next attempt resulted in a highly disturbing and potentially tragic incident, the unexpected ignition of a Loki rocket on the ship’s deck. By Frank McDonald’s account:

A Loki rocket ignited in its horizontal cradle as the ONR representative, G. Ebel, was adjusting the backup timers in the control box that was suspended below the rocket. The rocket struck a stack of helium tanks and exploded, covering the deck with smoke and debris.

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Ebel’s face was badly burned. The ship had a medical corpsman but no doctor so we headed for the nearest port. Ebel had a rapid and complete recovery. I returned via Washington to receive the full wrath of ONR for what had already been a traumatic and unsettling event. In a test at Iowa, C. McIlwain found that the length of the wires connecting the rocket [igniter] to the control box was such as to probably produce standing waves, and trigger the igniter.32

Carl added further details. His tests upon returning to Iowa showed that the trans­mitter in his instrument package probably induced a current in excess of 0.2 amperes in the igniter wires, and that was enough to set off the rocket. Parenthetically, he mentioned that this had been his “best” transmitter, having been tuned to produce the greatest output power of all of his instruments.33

The less than one second normal burning of the rocket was essentially a controlled explosion. The blast centered on Gus Ebel’s shoulder, where it burned through his thick clothing and embedded bits of igniter wire in his flesh. Joe Kasper was standing nearby, and his eardrums were ruptured, his coat was blown off, and bits of propellant were embedded in his lips and face. Carl was about six feet to one side and suffered only mild noise trauma. As the rocket accelerated, its sharp fins sliced through the three-quarter inch thick plywood brackets that formed its supporting cradle, then snipped the phone wire draped from the headset of the sailor who was serving as the talker in contact with the bridge. He took an instinctive giant leap backward and landed, luckily, in a gun turret adjacent to the flight deck rather than in the icy sea. By the time the rocket had traveled about 50 feet and struck the stack of empty helium cylinders, it had already reached supersonic speed. Upon impact, the rocket exploded, spreading parts of the rocket, flight instrument, and burning propellant over the entire ship.

Captain Bryce immediately ordered that the remaining Loki rocket be dumped overboard, but Carl saved his remaining highly prized instrumented payload. The scientific work was terminated, and the ship proceeded as quickly as possible to St. Johns, Newfoundland, to get medical attention for Gus Ebel. The ship returned to port at Norfolk in mid-October without further incident.

Carl’s tenth rocket instrument was put to good use later. On the morning of 23 February 1956, a breathless call from John Simpson at the University of Chicago stated that a gigantic solar storm was bombarding the Earth with cosmic rays. Carl hurriedly attached his unused payload to a cluster of rubber balloons and launched it from the university’s athletic field, and it reached peak altitude about 17 hours after the onset of the storm. Too late for the main event, the rig found that solar cosmic rays were still adding about 40 percent to the expected galactic cosmic ray counting rate. That event served as the subject for Carl’s first published paper.34

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I was elated by the expedition’s success. Frank’s and my instruments operated perfectly on all 10 flights. Eight of the 10 flights reached their expected altitude and provided useful data. Carl’s success rate was excellent for the first field trial of a new rocket, with four successes out of the six single-stage attempts. Those flights provided the basis for Carl’s master’s thesis.35 The NRL flights were more disappointing. Both of Jim Kupperian’s attempts failed, and Les Meredith was successful with only two of his six attempts.

This record solidly established the Loki rocket as a viable carrier for rockoon launches. After honorable service during four shipboard expeditions, the Deacon rocket was retired as a rockoon component at the end of the 1955 campaign. An improved version of the Loki rocket (Loki Phase II) was used exclusively on the later Iowa rockoon expeditions.

The end of 1956 and beginning of 1957 saw a major change in emphasis. The focus changed to the merging of subassemblies to form a complete prototype package.

138

Robert Baumann had given me the first full set of dimensioned drawings of the satellite shell. It included details of the envelope for our instrument package and of the structure for supporting and thermally insulating it. With that information, I drew a diagram of the physical arrangement of our instrument package, as reproduced in Figure 5.3.18 That notebook sketch was followed by a detailed weight breakdown that totaled 13.3 pounds (including the telemetering system and its batteries).

Thus, by the end of 1956, all of the key satellite and instrument features and parameters had been established.

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT 139

The Vanguard instrument testing program The satellite had to operate in a pre­viously unencountered physical environment. The effects of a completely isolated thermal environment for an extended period were unknown. It was expected that the satellites would be subject to small dust particles traveling at great speed, but their numbers and sizes were unknown, so that their effect on the satellite could not be predicted. The satellite and its internal instruments would have to survive the extreme vibration and acceleration of the rocket launches.

The attempt was made to design the satellite to operate over as wide a range of the environmental parameters as possible to span the range of uncertainties. An elaborate testing program was devised to verify the design, as well as to weed out any incipient component failures. Homer Newell had informed us as early as November 1955 that the expected conditions for the satellite instruments included operation over a temperature range of at least 41 degrees to 122 degrees Fahrenheit (5 degrees to 50 degrees centigrade). He also indicated that the instruments would have to survive spin rates of250 to 400 revolutions per minute and very high initial linear acceleration values.19

The testing program continued to evolve. On 7 May 1956, a more complete set of conditions was promulgated:20

• Operation in a complete vacuum

• Operation after a temperature cycle lasting 90 minutes from values of -28 degrees to +104 degrees Fahrenheit (-30 degrees to +40 degrees centi­grade)

• Survival of sinusoidal vibration at levels of 8g (eight times the Earth’s gravity), varying in frequency from 20 to 2000 cycles per second, with tests lasting for 10 minutes in each of three mutually perpendicular directions

• Survival of random vibration (similar to acoustic “white noise”) at levels of 20 g RMS, with a uniform spectral density in the range 20 to 2000 cycles per second, with tests lasting for five minutes in each of the three mutually perpendicular directions

• Survival after a steady acceleration of 50g for 15 minutes along the primary axis

Final test specifications were issued at the December 1956 meeting.21 There were to be two series of tests. The first series, of design level tests, was to help assure that the instruments could survive the launch phase and then operate over an extended period in space. Those levels were set somewhat higher than the levels actually expected to occur, to provide some extra margin in the design. As those tests might overstress the hardware and components, the design test hardware would not be flown.

The second set of tests, referred to as flight acceptance tests, were to be applied to all flight payloads. They were carefully set at levels that would not unduly stress

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the instruments but that would help detect deficiencies in assembly and incipient weaknesses of electronics components and mechanical assemblies.

Responsibilities for conducting the tests were also established at that meeting. In Iowa City, we were to run design-level vacuum and temperature tests on our subassem­blies and the complete prototype instrument package, and design-level vibration tests to the limits of our capabilities at Iowa. As it turned out, all vibration tests were performed at NRL, since we were unable to obtain the necessary test equipment at Iowa in time for the tests.

The NRL was responsible for design-level vibration tests of a prototype data recorder in late January 1957 and of a complete Iowa prototype package in mid­May. They would also perform the vibration and acceleration tests for the complete satellite. And they would be responsible for the entire gamut of acceptance tests (vacuum, temperature, temperature cycling, vibration, and acceleration) for the flight hardware. Those were scheduled to begin on 15 June.

February 1957 As we entered 1957, I completed the assembly and initial temper­ature testing of the first flight-realistic electronics deck, a binary scale of 128. That test item is pictured in Figure 5.4. Other major work included GM counter measure­ments, tape recorder tests, preliminary design of a 700 volt power supply for the GM counter, design and testing of the tuning fork time standard, and assembly of the second electronics deck.

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT 141

We were especially concerned about the ability of the GM counter and tape recorder to withstand the expected vibration and acceleration levels. Special tests of those components were conducted in the NRL vibration test facilities on 18 February.

I referred to the package that I assembled for that test as prototype unit 1, or simply PT1. Although some of its circuit boards and battery modules were dummies, the GM counter and tape recorder, along with minimal circuits and batteries to operate them, were mounted in a realistic manner. The packages assembled later for the June, August, and October tests were referred to in my working documents, respectively, as PT2, PT3, and PT4.

Robert Baumann, several of his technicians, and I installed PT1 in one of the early NRL-designed satellite shells. In addition to testing our package, the vibration test was intended to test a number of mechanical features of the shell, as well as an array of solar cells that the NRL engineers were considering for use on later satellites.

With fingers crossed, we began the tests. They consisted of three sets of runs, one along the instrument’s vertical axis, that is, along the launch rocket’s primary thrust axis, and others along two mutually perpendicular horizontal axes. A series of four tests covering different frequency ranges and with increasing vibration amplitudes was to be completed for each of those orientations.

The first set of runs along the vertical axis was completed without incident. Runs along the first horizontal axis were also satisfactorily completed. But the test series along the second horizontal axis, with sinusoidal vibration sweeping over the fre­quency range 2000 to 16 cycles per second, resulted in a number of failures. Specif­ically, (1) two antenna rods broke off, (2) the satellite shell cracked at its bottom because several screws had loosened, (3) the bottom broke out of the NRL-supplied instrument container, (4) two Kel-F thermal insulators broke, and (5) the satellite internal support tubing broke in two places. There is little doubt that one or some of those failures caused others, but there was no way to determine which one occurred first and precipitated the chain of events.

Happily for me, my instruments survived the tests with no failures—there was no damage to either the GM counter or tape recorder. [1]

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great confidence in their work and led, eventually, to the collaborative arrangement whereby they designed the high-voltage power supplies for the GM counters and supplied component parts kits that we assembled in the early Explorers.

Returning from Fort Monmouth, I stopped for a visit with Gerhardt Groetzinger at the Glenn L. Martin Company’s Research Institute for Advanced Studies (RIAS) in Baltimore, Maryland. He was developing a cosmic ray ion chamber that he hoped to fly in the Vanguard program but that eventually flew on Explorer 7. Needing long-term data storage, he was interested in my tape recorder, and I showed him my plans, a sample recorder, and a sample scaler deck. Eventually, I supplied him with complete tape recorder fabrication plans and a sample unit, and he incorporated it into his instrument design, as described in Chapter 14.

In early March, Ed Manring from the Air Force Cambridge Research Center visited us in Iowa City, and we began detailed planning for integrating their micrometeorite instrument into our package. That marked the beginning of a very enjoyable working relationship that resulted in the inclusion of their instrument in the Vanguard payload and on the later Explorers I, II, and III.

April 1957 All Vanguard satellite designers met again at NRL on 24 through 27 April 1957 (Figure 5.5).23 That gathering began with brief status reports by Bob Baumann (satellite structure), Roger Easton (Minitrack), Whitney Mathews (teleme­try), Jim Heppner (magnetometer experiment), Herman LaGow (environmental ex­periments), Herbert Friedman (Lyman-alpha experiment), the author (cosmic ray experiment), Ed Manring (micrometeorite experiment), Vern Suomi (radiation bal­ance experiment), Bill Stroud (cloud cover experiment), and Warren W. Berning (resonant reflecting dipole experiment). Working sessions with the experimenters and individual NRL engineers occupied the next several days.

The working sessions were followed by a meeting of Van Allen’s Working Group on Internal Instrumentation. At that meeting, held in the old “temporary” Navy building T-3 on the west end of the Washington Mall, each experiment group gave a status report reflecting their progress.

My SUI report contained a final block diagram of the instrument, a description of its operation, and a summary of our status. It also included a drawing of the arrangement of our instrument in the satellite shell, reproduced here as Figure 5.6. I showed models of our instrument mockup and the tape recorder, and reported in detail on our power and weight requirements. My report concluded with the statement, “SUI expects to be able to deliver the first instrument package, complete in every respect and operating, to NRL for vibration testing on 15 June 1957. We further expect to deliver three flight units to NRL on 1 August 1957 which are to be given acceptance tests by NRL during the six months period following that date.”24

My notebook entry on 3 May 1957 indicates that I was, by then, providing detailed information about our cosmic ray instrument to Ernst Stuhlinger at the Army Ballistic Missile Agency in Huntsville, Alabama.25 That was to permit their group to move forward with the off-the-record development of a scientifically useful satellite for the Jupiter C launch vehicle. That preliminary work laid the foundation for the shift of our instrument from Vanguard to the Jupiter C launch vehicle following the Sputnik 1 launch, as related in Chapters 7 and 8.

June 1957 We were tremendously excited on 6 May, when the first aluminum prototype satellite shell arrived.26 Wayne Graves and I immediately tried fitting our evolving prototype instrument package into the satellite, as shown in Figure 5.7. To our considerable relief and elation, it fit perfectly!

PACKAGE

SEPARATION DEVICE

FIGURE 5.6 Drawing of the Vanguard cosmic ray satellite as of April 1957. The central cylin­der with the stack of decks is the instrument package that we were assembling at Iowa. The shell, antennas, and internal structure were developed and produced by NRL.

We were working toward an all-up vibration test on 15 June. The test was actually conducted on 27 May. As that date approached, Wayne Graves, Riley Newman, our other student helpers, and I worked feverishly into the late evenings to ensure that the tests would be as comprehensive as possible. It became clear, however, that the instrument package would still be incomplete. Nevertheless, I still hoped to prove the physical design of the overall package and the operational viability of a major portion of the electronics. One of the most pressing specific objectives was to make a full and meaningful test of the tape recorder, including its control, recording, and playback capabilities.

Arriving in Washington, D. C., on Sunday, 23 June, hand carrying my instrument package in its wooden carrying case, my ever-present toolbox, and a kit of supplies, I began the next morning with some of the final preparations of our prototype (PT2) on a bench in the NRL facilities.

By Wednesday evening, with the vibration test set for the following morning, I still had to complete the master interconnecting wiring harness and to verify that the fully assembled package was operating properly. In my hotel room, at its small writing

desk, with my soldering iron plugged into a nearby convenience outlet, and with the test equipment, hand tools, kit of wire, and other supplies that I had carried from Iowa, I worked on that final wiring late into the night. At about 2:00 on Thursday morning, it was done. The package as it existed at that time included the fully operational transmitter, modulator, subcarrier oscillator, calibration system, binary counters, and battery stacks. The receiver was included but not working, apparently due to a transmitter interference problem that would have to be worked out with the NRL engineers. Provisional tuning fork timing and recorder stepping circuitry would also be replaced by improved designs.

After a few hours’ sleep, I drove to NRL in south D. C. on the morning of 27 June to help in setting up for the vibration tests. The NRL teams had also been working hard—by the time I arrived, they had completed the assembly of the satellite shell, the interior instrument support structure, and the jigs for physically mounting the satellite on the vibration table. We inserted my instrument package into the shell, connected

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the radio frequency harness to the antennas, activated the instrument, verified its operation, closed the access port, and mounted the fully assembled package on the vibration table.

Four series of design-level verification tests were planned at progressively higher vibrational levels.27 Each series consisted of three runs, first with vibration along the thrust axis (vertical), second with vibration perpendicular to the thrust axis (horizon­tal), and third, also with vibration perpendicular to the thrust axis, but 90 degrees from the previous tests. All runs were to be of four minutes’ duration, with vibrational ac­celeration within the frequency band 10 to 2000 cycles per second. The levels were to be at 15,20,25, and 30g along the thrust axis and at 10,15,20, and 25 g along the two transverse axes.

During the first run, with vibration along the thrust axis at 15 g, the calibration relay contact bounced, but it operated satisfactorily after the run. During the second run, with vibration horizontal at 10 g, the calibration relay operated properly but was intermittent after the run. The run along the other horizontal axis was satisfactory. The second series of three runs, at 20 g vertical and 15 g horizontal, was satisfactory.

It was when we began the third series that we ran into serious trouble. Following the initial run along the vertical axis at 25 g, we discovered a loose screw and locknut inside the shell. Since that threatened the mechanical integrity of the entire assembly, we immediately stopped the tests. I discovered that the GM counter was hot to the touch and, upon checking further, found that an abnormally high current was being drawn from the batteries powering its high-voltage power supply.

Thus, the test results were mixed, requiring a return to the design laboratories at both NRL and Iowa City. They would have to address the problems with the satellite shell and internal structure, and I would have to tend to the GM counter and relay problems.

Upon further checking the instrument package back in Iowa, I discovered a small crack in the GM counter’s ceramic insulator. It had allowed some of the internal gas to escape, causing it to arc and fail.

The 700 volts required to operate the GM counter presented a special problem. That voltage can be easily managed at sea level pressure where even a small air gap provides adequate insulation. However, as the air pressure is reduced, some electrons can pass across the gap, and a phenomenon called corona discharge begins to occur. That results in a high current flowing between the conductors, effectively shorting out the GM detector. The net result of that process is interference with the operation of the counter, overheating of components, and, eventually, destruction of the power supply.

The original design called for the Vanguard cosmic ray instrument to be sealed in an airtight container. As long as normal atmospheric pressure was maintained

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within that container, the corona discharge would not occur. However, we wanted to protect against the possibility that the container might leak. That required sealing all conductors carrying high voltage with some type of solid insulating material. However, the epoxy that we tried constrained movement of the base of the counter where its insulating terminal and seal were located. Vibration flexed the assembly enough to crack the epoxy and insulating terminal. That allowed some of the counter’s gas to escape.

It was clear that I had to improve the high-voltage insulation. That problem con­tinued to plague me in one form or another throughout the next 18 months, including during my later work at JPL.

Despite that result, I was optimistic, as my package’s overall mechanical design seemed to be sound. Other than the problems with the relay and counter, operation was satisfactory for all of the package’s electronic components and circuits, and the electromechanical tape recorder operated satisfactorily both during and after the tests.

That Monday, 1 July 1957, marked the official beginning of the IGY. Many individuals in the United States were working hard to make sure that we could launch a satellite during the next 18 months.

August 1957 Another vibration test at NRL was due in mid-August. We set about to put the prototype instrument package, referred to by then as PT3, in what we hoped would be its completed form. On 19 August, I boarded the plane for Washington, again hand carrying the prototype unit. After several days of work to install the instrument package in the satellite shell and set it up for the test, the all-important vibration test was made on 22 August.

The problem with the GM counter had not been solved. I had encapsulated the entire end of the GM counter and its mounting flange in a block of solid epoxy. Sometime during the second test, arcing again occurred. It caused the recorder tape to be nearly blank, even though the recorder operated perfectly throughout the test. The blank tape was a result of the method of encoding the data. Blank recordings were to be seen later after the successful Explorer I and III launches, when the pulse rate from the counter was very high for a different reason. That is a story of its own, as related in Chapter 12.

We continued with more of the vibration tests. In addition to the GM counter problem, several problems were again encountered with the satellite structure. Shortly before the final run, we noticed that the top of the satellite shell was deformed, and upon opening it, we found that our instrument package had broken entirely away from its supporting structure. Although it had been bouncing around for the last bit of the test, slamming against the top of the satellite shell to dent it, there was no apparent damage to our instrument. Thus, I was pleased with the instrument design

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and construction, including the fact that the tape recorder had behaved as planned. I returned home the next day.

Careful examination of the GM counter back in Iowa City revealed that the latest encapsulation technique still did not cure the problem. Although the block of epoxy firmly anchored the ceramic insulator, the swaying of the rest of the counter relative to its mounting flange again cracked its insulator. After that test, I worked out a variation of the encapsulating and mounting arrangement that permitted the counter and its insulator to move in unison without damage.

After those tests, NRL was under even greater pressure to improve the design of the satellite internal structure. At Iowa, in addition to further work on insulating the GM counter, I needed to make a number of additional changes to clean up our design and make its operation more dependable.

But first, I wanted a break. During the last week in August 1957, I left the frenetic pace at the laboratory for some rest and recreation with my much-neglected family. We had discovered the attractions of family camping vacations during two trial camping trips during the preceding summer. A short stay at Devils Lake, Minnesota, for our first introduction to tent camping was followed two months later by tent camping along the way as we drove west to visit Rosalie’s family in Seattle. Those were highly satisfying experiences and showed us that camping (true camping, in a tent) provided a complete break from the pressures of work and home, a valuable collective family experience, a close contact with nature, the thrills of encountering new horizons, and an inexpensive way to take extended vacations.

We were so excited by those early camping experiences that we decided to under­take our first extended pure-camping trip. That last week in August, Rosalie and I took preschool-aged Barbara and Sharon on a six day canoe-camping trip. This was in the Boundary Waters Canoe Area in the Quetico-Superior Parks in northern Minnesota and southwestern Ontario. Driving through Ely, Minnesota, to the end of the road, we rented a canoe at the southern end of Moose Lake. From there we canoed and portaged across Moose, New Found, and Ensign lakes and passed onto Bass Lake, where we found an isolated, small island that served as our home for the next four days.

We were amazed by the diminution of human presence that resulted from the portages. Moose Lake, accessible by road at its south end, and New Found Lake, directly connected with Moose Lake, were crowded along their lengths with canoes, sailboats, and speeding motorboats. After a short portage of about 25 rods, on Ensign Lake, we encountered only three canoes (one with a small outboard motor) during the time it took to traverse it. The portage to Bass Lake was 53 rods, enough to cut the average traffic density to only three canoe parties per day (none with motors).

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In addition to the absence of people, the seclusion of the island in Bass Lake had additional advantages—fewer bears and mosquitoes. We all had a great time with the routine of camp life, hiking, fishing, very brief dips in the frigid lake, sitting around the campfire, and restful sleep. We started as camping novices but ended with enough confidence to undertake many camps throughout the United States during the entire period that the children remained at home. Even after the children left, Ros and I continued our camping forays for many more years.

We returned much revitalized to our home on Rochester Avenue on Saturday, 31 August. After a Sunday to reestablish our usual home routine, Rosalie began arranging for another important family milestone, Barbara’s entry into kindergarten. And I went back to the laboratory.

October 1957 I looked forward to the push to deliver our prototype instrument package for what we hoped would be its final acceptance tests. As indicated earlier, that was already running several months late, partly because of the immensity of our task in completing the instrument, but also because of delays at the NRL in completing the final satellite shells, antennas, separation mechanisms, receivers, and transmitters. Both NRL and we were saved from major embarrassment, however, by the fact that the launch vehicle development was lagging substantially. Nevertheless, we all felt tremendous pressure.

During the summer, my only enrollment for university credit had been in research, and my work on satellite development easily fulfilled that requirement. In September, I felt that I had to continue pushing toward my degree with my course work and signed up for Theoretical Optical Physics and Quantum Mechanics, two very challenging courses. It turned out that they had to be dropped later when our program was shifted to the Jupiter C launch vehicle.

During the following weeks, I busied myself on many final details. My first sub­stantial task was to process and analyze the data that had been recorded during the recent vibration tests at NRL. I continued with temperature and vacuum tests of the recording and playback amplifiers and worked on final assembly of the full instrument stack.

I also hurried to make another change in the tape recorder. I had a growing uneasiness about the Mark III tape-advancing ratchet drive. By good fortune, Frank McDonald brought a newly available component to my attention—a solenoid that was designed at G. H. Leland Inc. to rotate wafer switches. I quickly adapted that device, resulting in the final Mark IV recorder, as seen in Figure 5.8. That final version of the tape-advance drive was fully balanced for steady state rotation, translational acceleration, shock, and vibration, and it operated dependably throughout the rest of the developmental program, and, eventually, in orbit.

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I was in the final stages of making the conversion to the Mark IV recorder when the Soviets orbited Sputnik 1 on 4 October 1957. I continued with that task for a short time, even after I began talking to JPL and Vanguard program officials and engineers about shifting our instrument from the Vanguard to the Jupiter C launch vehicle. The final solenoids and ratchets were prepared in the University of Iowa instrument shop but were fitted onto the flight units at JPL after I arrived there.

In mid-September, Kittl at the Signal Corps Engineering Laboratories reported on the results of their efforts to design a good high-voltage power supply to drive the GM counter. Superior to my design, it was immediately adopted for inclusion in our package. They delivered a working unit near the end of September, and then collected and pretested kits of parts, which we assembled on our circuit boards. Through that arrangement, I developed great admiration for the highly competent engineers at the Signal Corps Engineering Laboratories. The ones with whom I worked most directly were, in addition to Kittl, Paul Rappaport and George Hunrath.

I completed my preparations for the next vibration test a little ahead of schedule, so that I could attend the CSAGI Conference on Rockets and Satellites in Washington,

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D. C., during the week of 30 September through 5 October 1957. The story of the astonishing announcement of the Soviet launch of Sputnik 1 during that conference, and of its impact on the University of Iowa satellite experiment, is related in the next chapter.

ith the launch of Sputnik 1 on 4 October 1957, all reservations about the use of military hardware for launching a U. S. satellite evaporated. After all, the Soviets had just used a military rocket for that purpose. Their satellite was flying over many nations of the world, with no one objecting to any violation of their air space sovereignty. Von Braun, Pickering, Van Allen, and their collaborators had been dreaming of this opportunity.

As related in the last chapter, the essential elements of a satellite-launching version of the Jupiter C launch vehicle had been quietly evolving. Two satellite designs, both containing the State University of Iowa (SUI) cosmic ray instrument, were also well advanced. The Army Ballistic Missile Agency (ABMA)-Jet Propulsion Laboratory (JPL)-SUI version existed as a paper design, while the (still externally unknown) JPL design had already edged into the prototype hardware stage.

A word about Deal, the name coined at JPL for this satellite project. The most likely account of its origin is that the term surfaced well before Sputnik, while the Reentry Test Vehicle (RTV) was being developed and tested. A number of the JPL scientists, including Jack Froehlich, Henry Richter, Leonard R. Piasecki, Al E. Wolf, and John G. Small, were avid gin rummy players. They played during aircraft flights, in motels, in conference rooms, and wherever else they found themselves with free time. One account says that immediately after the first successful firing of the RTV-Jupiter C in 1956, they were ready with their cards, and one of them called out, “Deal!”1

A second version of the story attributed the Deal name directly to Jack Froehlich. A formidable poker player, he is claimed to have bestowed the name after the first Sputnik launch with the remark, “When a big pot is won, the winner sits around and cracks bad jokes and the loser cries ‘Deal’!”2

213

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Whatever account is true, the word Deal became a byword around JPL and was adopted as the internal pet name for the satellite project. The name was solidly established well before I arrived in Pasadena in November 1957, and persisted for a long time. The JPL even printed a set of playing cards that featured a drawing of Explorer I and the name “Deal” on their backs (Figure 8.1).

The Deal designation is used in this book for satellite work that occurred before the individual Explorer launches. Explorer names are used for events occurring after their respective launches.

A satellite launch operation was (and remains today) a carefully choreographed ballet, with dozens of key performers and hundreds of supporting personnel. The common

media portrayal of countdowns, with their final “three-two-one” and terse “liftoff,” is the climax of an extremely long and arduous process. Each tiny action is minutely defined, timed, and documented ahead of time, and many detailed lists of steps (countdown lists) are assembled and pretested. Each such list terminates in a go/no – go decision, and all lists are linked to form the whole. For the Deal II launch there were, in addition to the master countdown conducted by the launch director in the blockhouse, separate countdowns for activating the blockhouse, activating the launch pad, activating each of the rocket subsystems, fueling, and so on. Closer to my own area of activity, there were countdowns for the final preparation of the satellite instrument package, for attaching it to the final rocket stage, for activating the backup Spare Payload in case it was needed at the last moment, for readying the Microlock ground station, for activating the interrogation ground transmitter, and so on. Just one, the countdown list for preparing the payload for its mating to the final rocket stage, occupied a number of pages.

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For rocket launches until the time of the later, much more massive Saturn 5 Moon rockets, the launch activities were centered in blockhouses near the pads. Those were an outgrowth of simple barriers used during the 1920s, 1930s, and 1940s to protect launch crews from possible explosions and other mishaps. The blockhouse used for the Jupiter C launches was representative of those employed during that period. It was located only a few hundred feet from the launch pad so that the two sites could be coupled through conduits and tunnels by hundreds of wires carrying power, control, and monitoring signals.

The blockhouse was dome shaped, with a very thick concrete and earth-covered shell to protect against direct impacts of wayward rockets. It was sealed against liquids and fumes in case the rocket’s load of fuel should spill on its top and ignite. Massive blast doors were sealed before liftoff, and the heating and air-conditioning systems were closed off from the outside world. The entire complex was switched over to internal electrical power generators to guard against failure of the main Cape Canaveral power or severance of the supply lines. The blockhouse was as nearly self-sufficient as it was possible to make it.

As the director of Von Braun’s Launch Operations Laboratory at Cape Canaveral, Kurt Debus served as the launch director for ABMA launches during that period. For the Deal II launch, he was at his usual station in the blockhouse, where he could have eye contact with all of the senior engineers at their separate launch consoles. He was one of the few who could actually see the rocket through one of the periscopes that poked through the roof of the blockhouse. For this launch, Von Braun was at his favorite blockhouse observation post, with his own periscope. I was located in the rear of the blockhouse at a rack of equipment that received and displayed the signals as they were received from the satellite payload. We were all able to switch our earphones between several special telephone and intercom circuits. One permitted those of us monitoring the instrument to talk to crews at the Microlock receiving station in its trailer some distance away, to the RIG site where the command transmitter was located, and to other locations. A narrator kept all apprised of progress via a public address system.

Unlike the Deal I situation, I was fully integrated into the prelaunch activities for Deal II. Of course, the JPL payload manager had the overall responsibility for the satellite payload, but I was directly involved in all decisions dealing with the performance of the cosmic ray instrument. I monitored every step of the payload assembly and checkout, performed numerous counting rate checks, and read and evaluated the many tape recordings of our instrument’s signals.

My journal entry at 4:20 AM on 5 March 1958 stated:

Have the [blockhouse] equipment turned on. Payload activation in 40 minutes. Sky is light cloudy and broken—rather high. This is the day for which I have been working since January

CHAPTER 10 • DEAL II AND EXPLORERS II AND III 275

1956. If successful, this is to provide my Ph. D. dissertation. I’ll have to give that payload a

goodbye pat.10

There were some difficulties during the countdown. At a check at X – 300 minutes, the onboard tape recorder double-stepped. That is, for each drive pulse, the recorder tape advanced two steps. All later operation was normal in that regard.

The most serious problem was the difficulty in commanding playback of the tape recorder during the final countdown. When spin-up of the upper rocket stages was started at X – 11 minutes, the recorder operated normally. But when the spin rate reached 550 rpm, we were unable to command playback. The launch director interrupted the spin-up, slowed the rotating tub, and then had its rate increased gradually. Playback was successful at 450 rpm but not at 500.

All of that occurred within the final few minutes of the countdown, while the rocket sat there fully fueled and ready to go. The pressure for a final go/no – go decision was intense, as further delay would have meant canceling the launch for that evening and recycling for the following day or later. While we held up the launch for 18 minutes, the payload manager, other payload engineers, and I had a lively discussion and concluded that the problem was with the on – pad commanding link, not with the recorder itself. Specifically, we believed that there was a problem with the grounding path for the interrogating signal and that operation would be normal once the rocket was free of the cluttered pad environment. I gave my go-ahead based on that assessment, and the countdown continued.

The official launch time was 1:28 PM EST on Wednesday, 5 March 1958. At my post in the blockhouse, I monitored the signal from the cosmic ray counter until it faded out downrange.

Later analyses indicated that the firing of stages one, two, and three were all nor­mal. However, the fourth stage apparently failed to ignite, for reasons that were never completely determined, and the launch attempt failed. The satellite pay­load plummeted into the Atlantic Ocean about 1900 miles downrange from Cape Canaveral.11

As the payload passed over the island of Antigua, British West Indies, that station attempted to interrogate the onboard tape recorder to reset the tape to its starting point in preparation for the first orbit. That interrogation attempt failed to elicit a response. We were never able to ascertain whether that was because of a failure of the onboard instrument, a problem with the ground station, or the result of some catastrophic failure of the final rocket stage.

Even though it did not go into orbit, the payload received an Explorer II designation.

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The earlier rockoon expeditions actually provided a first hint of high-intensity trapped radiation, as described earlier. A few days after Explorer I was launched, we re­ceived another, more substantive indication. The scientists at the Jet Propulsion Laboratory (JPL), primarily Conway Snyder and Phyllis Buwalda, were carefully checking the quality of the initial data. As quickly as possible, they gathered the verbal comments from the station operators and took a look at the data tapes as they arrived to determine the condition of the orbiting instruments and to mea­sure the satellite internal temperatures. In the process, they observed on 5 February that the Geiger-Muller (GM) counter rates appeared at a few times to be zero. Conway immediately notified Bill Pickering, who in turn called Van Allen, start­ing the conversation along the lines, “I have bad news for you. Conway Snyder has looked at the data, and there are no counts. Your instrument appears to have failed.”

Van Allen told me recently that he was noncommittal during that conversation. He had considerable confidence in our instrument and was greatly concerned that premature interpretations of the data might be problematic.13

His reservations and concerns must have been apparent to Pickering, because when I returned to Pasadena the next day, a memorandum lay on my desk that had been issued by Deal’s project director, Jack Froehlich. That terse memo emphatically

CHAPTER 12 • DISCOVERY OF THE TRAPPED RADIATION 325

reinforced the earlier-stated data release policy. It declared, “The two experiments on Deal I, the cosmic ray experiment and the micrometeorite experiment, are the responsibility of the State University of Iowa and the [Air Force Cambridge Research Center] respectively. No member of this Laboratory is authorized to comment on any result of these experiments. Please bear this in mind in all conversations either public or private.”14

We now know that the zero apparent counting rate from that pass was a direct ob­servation of the Earth’s zone of intense radiation. We did not arrive at that conclusion, though, until much more work had been completed with the data from Explorers I and III.

Results related to the Argus experiment were released in two phases: an early Top Secret exchange within a small circle of appropriately cleared individuals, followed later by an unclassified public release. The initial discussions were to help determine the effectiveness of the nuclear detonations in injecting electrons into the Earth’s magnetic field. That was, after all, the primary purpose of the Argus exercise. Although a broad assortment of rocket, aircraft, and ground measurements was made, it was the results from Explorer IV that were the most eagerly awaited.

Classified early discussions As mentioned before, there were four fairly high alti­tude nuclear detonations before the first Argus test. The first was Operation Teapot’s high-altitude shot at about eight miles height in April 1955 to investigate atmospheric effects. Obviously, it was too low to figure in the trapped radiation study. Operation Hardtack I, consisting of 35 tests, was conducted between 28 April and 18 August 1958. Although most of the Hardtack I tests were conducted near the surface or un­derwater at Bikini Atoll and Eniwetok Island in the central Pacific Ocean, three were designed especially to investigate effects within the high atmosphere.

The first of those, Yucca on 28 April 1958, was a balloon-lofted detonation at only about 16 miles altitude, again, too low to be useful in looking for Argus-like effects. The other two, launched by Redstone rockets to a much higher altitude from a pad on Johnston Atoll, were Teak on 1 August 1958 (48 miles high) and Orange on 12 August 1958 (27 miles). Those bursts produced effects widely seen on the ground. The Teak event was observed by a group of New Zealanders at the Apia Observatory in Samoa as a flat, horizontal arc of bright violet rays in their western sky. The display lasted about 14 minutes, shrinking and gradually changing in color to red and finally to green. Fourteen days later, they saw similar results from the Orange blast. For that one, they reported that 10 minutes after the initial flash, the sky looked like a dawn on an overcast morning. The New Zealanders quickly connected the observations with the hydrogen bomb explosions above Johnston Atoll, located over 2000 miles to their north.

The Teak flash, being the higher of the two, was clearly seen from Hawaii, some 800 miles to its northeast. Even though the actual burst was below the horizon from

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Hawaii, the flash in the sky was bright enough to be seen, and the fireball rising above the horizon was photographed. The event also produced a magnetic storm that resulted in radio blackouts that persisted for nine hours in Australia and at least two hours in Hawaii. This was a result, primarily, of the introduction of a large amount of fission debris into the ionosphere, which prevented the normal reflection of radio waves back to the Earth.

The Orange shot, being at a somewhat lower altitude, was seen in Hawaii, but it did not have as much effect on communications.

Explorer IV was in orbit at the times of the Teak and Orange blasts. Despite the high yields of those blasts (3.8 megatons), they produced only small increases in the population of trapped particles at the satellite altitudes. Furthermore, since the blasts were low enough that atmospheric absorption played a major role, the effects persisted for only a few days.26

The three Argus blasts were made at much higher altitudes and in the region over the South Atlantic where the asymmetry of the Earth’s magnetic field causes the trapping region to dip to its lowest height.

Very pronounced effects from the blasts were seen by the Explorer IV instruments, as well by instruments on the ground, aircraft, and rockets. Qualitative and quantitative results from interpretation of the satellite data were provided by our Iowa group to the other Argus Project participants as quickly as they became available. It was eventually deduced that about 3 percent of the electrons from the blasts were injected into durably trapped trajectories. The mean lifetime of the artificially produced shells was about three weeks from the first two of the Argus blasts and about a month for the third. The four detectors on the satellite also revealed that the physical nature of the artificially created shells was substantially different from that of the naturally occurring belts, thus dispelling all previous thoughts that the natural belts might have been created by Soviet high-altitude nuclear detonations.

Still under a strict secrecy umbrella, a 10 day workshop on the interpretation of all Argus observations was conducted at the Lawrence Livermore Radiation Laboratory in February 1959. Van Allen and Carl McIlwain attended from Iowa. At that workshop, many of the general principles of geomagnetic trapping were substantially clarified.

But a puzzle remained. Why did the thin shells of trapped electrons produced by the blasts remain so thin over time? The Earth’s actual magnetic field differs from the shape of a dipole field that might be produced by a simple bar magnet. That was initially expected to result in a radial spreading of the thin shells.

Theoretical physicist Theodore (Ted) G. Northrup at the LLNL, at the urging of Edward Teller, had been working on the problem of longitudinal drift of charged particles in the Earth’s magnetic field. He had found an important key, a so-called longitudinal invariant. At the workshop, he described his work at an impromptu

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seminar for Van Allen, McIlwain, and several others. That train of discussion led to several theorems that greatly simplified the problem of particle drift. Among other things, it clarified the question of radial dispersion of the electron shell.27

Following the workshop, McIlwain devised a way of mapping the trapped radiation that greatly simplified the process of working with the data. It reduced the usual three-dimensional coordinate system used to describe the magnetic field to a two­dimensional one. That two-dimensional system became known as McIlwain’s B, L coordinate system, where B (in gauss) represents the magnitude of the magnetic field at any point in space, and L (in Earth radii) is a parameter that is approximately constant along the specific line of force that passes through that point.

The nuclear bursts had, in effect, provided markers on magnetic shells that permit­ted the rigorous testing of Carl’s system. In that manner, Explorer IV provided a firm observational basis for the B, L coordinate system. That system, and variations of it, has been used ever since in the study of magnetic trapping in the neighborhood of celestial bodies.

It should be noted that the possibility of electronic devices being damaged by nuclear detonations well above the atmosphere was later fully validated. Operation Starfish Prime, conducted by the United States on 9 July 1962, included the detonation of a W49 thermonuclear warhead about 250 miles above Johnston Atoll in the Pacific Ocean. The burst produced an equivalent yield of 1.4 megatons of TNT. It resulted in immediate damage to three low-orbit Earth satellites and damage to a number of others over a period of several weeks.

In addition, it produced major ground effects at Hawaii andNew Zealand, including interference with radios and television sets, the fusing of 300 streetlights on Oahu, the setting off of at least 100 burglar alarms, and the failure of a microwave repeating station on Kauai that cut off telephone service with the other Hawaiian islands.

In addition to the three Argus and one Starfish detonations by the United States mentioned so far, the Soviets produced substantial effects somewhat later with three high-altitude detonations as part of their K Project. Shots K-3, K-4, and K-5 were conducted in October and November 1962. Although the blast yields were only about one-fourth that of Starfish, the tests were conducted above a populated land mass, so that the damage was apparently much greater than that caused by Starfish. The electromagnetic pulse from one of them (K-3, Soviet nuclear test number 184 on 22 October) reportedly fused 350 miles of overhead telephone lines with a measured current of 2500 amperes, induced an electrical current surge in a long underground power line that caused a fire in a power plant in the city of Karaganda, and shut down 620 miles of shallow-buried power cables between Astana and Almaty.28

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 383

Declassification Although the Argus Project was highly classified throughout its planning stage and during the first months after the nuclear detonations, that status could not be maintained indefinitely. A number of factors argued for early declassification. First was that the possibility of artificially injecting charged particles into the Earth’s magnetic field had already occurred to others. Second was that many effects of the high-altitude nuclear detonations were observable worldwide. Third was the probability that Soviet receiving stations were receiving the transmissions from Explorer IV and would be able to see effects of the nuclear blasts directly from that source.

A final factor was the fact that Explorer IV had been widely advertised as a component of the U. S. participation in the IGY, arranged to follow up on the radiation belt discovery. A very basic tenet of the IGY program was that all of its data would be released quickly for use by the entire research community. Although an attempt was made to argue that the IGY data policy did not apply to the Argus-related data, that distinction between the unclassified and classified missions was obviously thin and would be widely challenged.

To elaborate on several of those points, the idea of detonating a nuclear bomb in space as an experiment in electron trapping developed in the summer of 1958 com­pletely independently of the Argus Project, in a totally unclassified environment. Two researchers at the University of Minnesota, Edward Ney and Paul Kellogg, upon hearing of the Earth’s newly discovered trapped radiation in May 1958, suggested that a nuclear device might be detonated some 250 miles high near the southern auroral zone to see what effect it would have on the radiation belt. They figured that it might produce an effect in the Earth’s magnetic field that would “jar loose” trapped electrons, resulting in artificially created auroras in the north and south auroral zones. At the same time, they posited that particles produced by the bomb blast might be injected into the natural belt.

Those discussions took place in the absence of any knowledge by Ed and Paul of the Argus Project. When they first outlined their idea to friends in the Office of Naval Research in Washington, they received an unexpectedly cool reaction. Instead of greeting the suggestion as an interesting prospect for an IGY experiment, the Washington contacts asked that the pair not discuss their idea with anyone. The two drafted a letter to Herbert F. York, by then the chief scientist of the newly formed Advanced Research Projects Agency. They quickly learned that their letter would most likely be classified secret if sent. So they did not send it, but they decided to publish the idea in the British scientific journal Nature. When the Pentagon learned of that, their initial consternation changed to full-blown alarm. Ed and Paul were swayed to hold off on further discussions of their idea for a while. They kept the idea

OPENING SPACE RESEARCH

quiet until February 1959, when they finally published their idea in modified form in Nature a short time before the Argus Project was officially declassified.

The idea of injecting charged particles into the Earth’s magnetic field by nuclear detonations did, as it turned out, also occur independently to the Soviets. It is unknown when the idea first occurred to them—it might have been either before or after they learned of our discovery of the region of high-intensity radiation. The idea was certainly well established by 8 March 1959, when several Soviet scientists voiced their thoughts on the subject in a newspaper release.29 Their suspicion apparently resulted from their study of the widely reported visual and electromagnetic effects produced by the Teak and Orange nuclear bursts during the previous August. The article appeared well before the Argus Project was declassified.

The Soviets also had ample opportunity to see the results of the Argus tests by receiving the Explorer IV signals at their receiving stations. On one specific occasion, as Explorer IV was transiting one of the Argus-generated shells, it was easily within range of their Tashkent receiving station.

Walter S. Sullivan was a distinguished science reporter for the New York Times for many years. During the IGY, his primary assignment was to report on its activities. From that vantage point, he played a significant role in publicizing the Argus Project and its results.30

About the end of June 1958, Hanson W. Baldwin, military analyst for the Times, somehow learned of the Argus Project. In a private conversation, he told Sullivan of the plans, stating that he had obtained the information in a manner that placed no limit on its use. However, both had misgivings about releasing the information. Sullivan prepared a summary sheet containing many of the key points about the operation, including the location, height, and yield of the blasts. He carried that information to a friend who was centrally involved in the U. S. space program and knew of the Argus plans. That friend was both horrified and amused upon reading the summary. He told Sullivan, “I can’t tell you not to print it, but I can say this: If you do, the operation will never take place.”31

The next day, Sullivan received a call from the security chief in the Pentagon’s Advanced Research Project Agency, who pleaded with him not to publish the infor­mation. Sullivan and Baldwin agreed to hold the story under wraps until after the firing—they dutifully kept that secret for more than eight months.

Sullivan had been led to believe initially that the project would be declassified soon after the blasts occurred. As the months passed, however, and no announcement was forthcoming, he became apprehensive that he might be scooped on a very important story. After all, by then, literally thousands of individuals, including the many ship crew members who participated, were well aware of the tests. He also believed that the scientific brilliance of the experiment might be eclipsed by prolonged secrecy.

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With time, additional hints surfaced. On 28 November 1958, Christofilos presented his calculations on how an electron shield could be placed around the Earth at a meeting of the American Physical Society. To avoid a violation of security, he made no mention of atomic bombs as the source of the electrons but suggested that an electron accelerator in a satellite could provide them.

In a report released on 26 December 1958, Hugh Odishaw, executive director of the U. S. IGY program, called attention to some of the information then appearing in the news that suggested that the Teak and Orange blasts had caused widespread effects in and above the atmosphere.

The following day, Fred Singer presented a paper, “Artificial Modification of the Earth’s Radiation Belt,” at a session of the American Astronautical Society. In that paper, however, Fred made no direct reference to the Argus Project or its results.

During that same meeting, Van Allen described the unclassified findings from Explorer IV and Pioneer 3 that showed that there were two separate radiation belts. At a press conference following the presentation, Van Allen was asked a very pointed question by a Newsweek reporter, who wanted to know if the John­ston Atoll detonations (Teak and Orange) had produced any measurable effect in the Explorer IV data. Van Allen replied that the effect had not only been seen but was “tremendous.”

Sullivan grew increasingly agitated. After that meeting, he talked quietly with other individuals about releasing his story. Finally, on 2 February 1959, he was able to present his arguments to James R. Killian Jr., the special assistant for Science and Technology to President Dwight D. Eisenhower, telling him that he doubted that he could withhold publication of at least a limited account of Argus for much longer.

Killian’s response was that disclosure at that time might imperil the then ongoing Geneva talks on a nuclear weapons test suspension. He feared that the Soviets would be handed the argument that the only untrustworthy participant in the talks was the one that had sneaked off to fire atomic bombs far from its own shores. Sullivan continued to sit on his story.

In late February, a highly classified 10 day meeting was held at the Lawrence Livermore Radiation Laboratory to discuss Argus results, as mentioned earlier. It included an extended discussion of the need to keep the Argus program classified. The arguments were, at times, heated, with the one side saying that the tests were made at great public expense and that the United States should reap its strategic benefits for as long as possible. The counterargument, primarily by the participating scientists, was that they had been party to a magnificent physical experiment, of which their country should be proud.

Sullivan learned in mid-March that some plans for a limited disclosure were being made with at least some Pentagon backing. With that knowledge, and fearing that the

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movement might gather steam and leave the Times sitting in the dust, he escalated his arguments on 16 March to the top officers of his newspaper. He soon received agreement that he could proceed, but not if the White House called and argued that the story would do serious damage to the United States. To Sullivan’s great relief, that call never came.

Public announcements of Argus Results Walter Sullivan’s first account of the Argus Project appeared in the New York Times a few days later (on 19 March 1959) under the banner “U. S. Atom Blasts 300 Miles up Mar Radar, Snag Missile Plan; Called ‘Greatest Experiment.’” His account was released by wire before press time, and many other newspapers carried the news that morning.

One week after the Times story, James C. Hagerty, press secretary to the president, provided a press release that outlined the Argus experiment and its results in con­siderable detail, and he laid out plans for a major public symposium to discuss them further.

That White House press release, prepared jointly by the President’s Science Advi­sory Committee and the National Academy of Science’s IGY Committee, in addition to providing considerable information about the Argus concept and project, provided a broad outline of many of the experimental results:

A fascinating sequence of observations was obtained. The brilliant initial flash of the burst was succeeded by a fainter but persistent auroral luminescence in the atmosphere extending upwards and downwards along the magnetic line of force through the burst point. Almost simultaneously at the point where this line of force returns to the Earth’s atmosphere in the northern hemisphere—the so-called conjugate point—near the Azores Islands, a bright auroral glow appeared in the sky and was observed from aircraft previously stationed there in anticipation of the event, and the complex series of recordings began. For the first time in history measured geophysical phenomena on a world-wide scale were being related to a quantitatively known cause—namely, the injection into the Earth’s magnetic field of a known quantity of electrons of known energies at a known position and at a known time.

The diverse radiation instruments in Explorer IV recorded and reported to ground stations the absolute intensity and position of this shell of high energy electrons on its passes through the shell shortly after the bursts. The satellite continued to lace back and forth through the man-made shell of trapped radiation hour after hour and day after day. The physical shape and position of the shell were accurately plotted out and the decay of intensity was observed. Moreover, the angular distribution of the radiation shell of the Earth’s magnetic field was being plotted out for the first time by experimental means. In their helical excursions within this shell the trapped electrons were traveling vast distances and were following the magnetic field pattern out to altitudes of over 4,000 miles. The rate of decay of electron density as a function of altitude provided new information on the density of the remote upper atmosphere since atmospheric scattering was the dominant mechanism for loss of particles. Moreover, continuing observation of the thickness of the shell served to answer the vital question as to the rate of diffusion of trapped particles transverse to the shell. All of these matters were of essential importance in a thorough understanding of the dynamics of the natural radiation and were not the subject of direct study by means of the “labeled” electrons released from Argus I.

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V

Throughout the testing period the planned series of firings of high altitude sounding rockets was carried out with full success and with valuable results in the lower fringes of the trapping region.

Explorer IV continued to observe the artificially injected electrons from the Argus tests, making some 250 transits of the shell, until exhaustion of its batteries in latter September, though by that time the intensity had become barely observable above the background of natural radiation at the altitudes covered by the orbit of this satellite.

It appears likely, however, that the deep space probe Pioneer III detected a small residuum of the Argus effect at very high altitudes on December 6, 1958. But the effect appears to have become unobservable before the flight of Pioneer IV on March 3, 1959.

The site of the Argus tests was such as to place the artificially injected radiation shell in a region where the intensity of the natural radiation had a relative minimum. If the bursts had been produced at either higher or lower latitudes, the effects would have been much more difficult to detect, plot and follow reliably for long times after the blasts.

The immense body of observations has been under study and interpretation by a large number of persons for about seven months. Only now are satisfactory accounts becoming available from the participating scientists.32

The press release concluded with an announcement of the arrangements by the National Academy of Sciences for the presentation of Argus results in a special unclassified symposium at its annual meeting planned for 27-29 April 1959.

At Iowa City, while I focused primarily on preparing instruments for the next satel­lites, Van Allen and McIlwain were concentrating on writing up our Explorer IV results for the National Academy’s meeting. Our first unclassified report was soon ready.33 It began with a discussion of the background of the Argus Project, the role of Explorer IV, and the relationship between its orbit and the Argus electron shells. Figure 13.5 portrays the geometry, as shown in that paper. There would have been four intersections of each satellite orbit with the Argus shells, except for details of the geometry and data recovery. In the sample shown here, there were three full transits at positions B, C, and D. The intersection at position A did not provide a full transit because the Argus shell was at the same height as the satellite’s height (161 miles or 258 kilometers). There were other cases in which the Argus shell lay well below the satellite height at its time of closest approach. In other cases, the intersection occurred where there were no ground stations to receive the data. The actual numbers of useful full penetrations of the electron shells were 37, 39, and 88 for Argus I, II, and III, respectively.

Data from a sample receiving station transit are shown in Figure 13.6. Note that the vertical axis is logarithmic, so the counting rate covers a huge range during the time of this pass. Proceeding from the left of the chart (at 6:00 AM), the satellite was descending from the intense inner natural radiation belt and moving northward. As it moved through about 22 degrees north latitude (at about 6:08, as indicated in the figure), the Argus shell produced the sharp spikes in counting rates from the

FIGURE 13.6 A plot of data from the two GM counters on Explorer IV, taken about 3.5 hours after the Argus I burst on 27 August 1958. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Libraries.)

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 389

two counters. By about 6:10, the satellite had passed north of the Argus shell and was in the slot between the two natural radiation belts for a few minutes, and then passed through the lower fringes of the outer natural belt to produce the broad peak seen between about 6:13 and 6:23. Comparable results were seen in all four satellite detectors for all three of the Argus bursts.

The special symposium in late April 1959 titled “Scientific Effects of Artificially Introduced Radiations at High Altitudes” addressed the full range of results from the grand experiment. Christofilos outlined its concepts, including an extended discussion of the theory of trapping. Additional theoretical information was provided by Jasper A. Welch Jr. and William A. Whitaker of the Air Force Special Weapons Center at Kirtland Air Force Base, New Mexico. Sounding Rocket results were provided by a group of authors led by Lew Allen of the Air Force Special Weapons Center. Optical and electromagnetic observations were described by Philip Newman of the Air Force Cambridge Research Center and Allen M. Peterson of the Stanford Research Institute.

Van Allen presented our paper with its huge body of satellite data. He provided a preamble and a short outline of the instruments and observations, and then presented arguments for the conclusion that the observed thin electron shells were, in fact, created by the Argus bursts, and that the natural belts were not the result of previous high-altitude nuclear detonations. Those key arguments were as follows:

(a) The observed energy spectrum and the nature of the radiation [in the shells] were found to be in essential agreement with those expected for the decay electrons from fission fragments.

(b) A peak with similar characteristics was found at every observed intersection of the orbit of the satellite with the appropriate magnetic shell, irrespective of latitude and longitude.

(c) The geometric thickness of the shell was similar to that of pretest estimates.

(d) The observed intensity of trapped electrons was in order-of-magnitude agreement with pretest estimates.

(e) The temporal decay of trapped intensity resembled pretest estimates.34

Our paper concluded with an extended discussion of the thickness of the Argus shells, their positions in space, their angular distributions, trapped lifetimes, injection efficiencies, and the distribution of the electron turning points.

After the examination of data from Pioneer 3 (launched earlier on 6 December 1958), the two-belt structure of the intense radiation zone was fully understood. That discovery had been published in Nature in February.35 The figure in that paper clearly

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INNER ZONE {NATURAL]

В ARGUS SHELL

C OUTER ZONE (NATURAL)

FIGURE 13.7 Copy of a figure presented at the April 1959 Symposium on Argus results. The re­lationship between the Earth, inner radiation zone, Argus shells, and outer radiation zones is shown to approximate scale. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Libraries.)

showed the two-belt structure and was adapted for our Argus paper by adding the location of the Argus shell, as shown in Figure 13.7.36

As was mentioned earlier, following our original announcement of the discovery of the radiation belts in May 1958, some on both sides of the cold war thought that the radiation might be residue from nuclear weapons testing already conducted above the atmosphere. The Americans thought the Soviets might have been responsible for them, and the Soviets suspected the Americans. Although the earliest satellites were able to map the extent of the belts, they provided only crude information about the particle composition and were not capable of demonstrating persuasively that the radiation was not man-made. It was not until the data were received from Explorer IV that the more qualitative and quantitative information permitted us to discriminate unambiguously between residue from nuclear detonations and the naturally occurring radiation.

Van Allen attended the Cosmic Ray Conference arranged by the International Union of Pure and Applied Physics in Moscow in July 1959. Although the Argus results had been declassified and presented orally in the United States before then, there had still been no published results available for the Soviet scientists to study. So at least some of the attending Soviets still believed that the radiation belts might have been man-made and that the United States was trying to conceal that information from them.37

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V

Everyone was edgy during those cold war years. A federal official, most likely an agent from the U. S. Central Intelligence Agency, visited Van Allen before his departure for that meeting, asking that he prepare a “trip report” upon his return covering 11 areas of interest. They wanted information on recent cosmic ray work, names of the institutions and individuals involved, individuals behaving secretively or evasively, copies of all materials distributed at the conference, and other subjects. It was only natural for Van Allen to assume that he would be similarly observed by Soviet agents during his stay in Moscow.

While at the Moscow conference, Van Allen outlined the Explorer IV and Argus findings essentially as he had presented them in his lecture at the U. S. National Academy’s symposium more than two months earlier. The Soviets were very interested in that information, and Academician Leonid Sedov gave him a spontaneous invitation to give a more detailed technical seminar at the USSR Academy of Sciences that evening. Van Allen was apprehensive about the invitation. It was not unknown in those days for visitors to the USSR to disappear. Van invited fellow U. S. conference attendees John A. Simpson of the University of Chicago and George W. Clark of MIT to accompany him, figuring that “if all three of us disappeared, someone would certainly investigate.”

At the Academy, Van Allen spoke, showed our slides, and engaged in lengthy discussions with his Soviet cosmic ray counterparts. It was only after their careful ex­amination of the Explorer IV and Pioneer 3 data that the Soviets were fully convinced that the natural radiation belts and the artificially generated shells were two markedly different phenomena.