Category Dreams, Technology, and Scientific Discovery

Frank McDonald was born in Columbus, Georgia, on 28 May 1925. He did his undergraduate work at The Citadel and Duke University. In July 1948, just as he was completing work on his bachelor’s degree and looking forward to his graduate studies, the discovery of heavy nuclei in the primary cosmic rays that was mentioned above was announced by Phyllis Freier, Edward Lofgren, Edward (Ed) P. Ney, and Frank Oppenheimer at the University of Minnesota13 and, independently, by Bernard Peters and Helmut L. Bradt at the University of Rochester. That event sparked Frank’s interest in cosmic ray research, and he decided to join the University of Minnesota group.14

For his master’s degree, received in 1951 under the tutelage of Phyllis Freier and Ed Ney, he spent many hours peering through a microscope at cosmic ray tracks in nuclear emulsions spread on glass plates. Through that experience, he developed an uncommonly keen understanding of cosmic ray interactions as they traversed matter. For his Ph. D. degree, he developed and flew a Wilson cloud chamber. That chamber employed a particle telescope consisting of GM counters and a sodium iodide (Na-I) scintillation detector. Whenever the telescope indicated the presence of helium and heavier nuclei, it triggered the cloud chamber expansion, thus permitting the study of the composition and energies of those particles.

Frank joined the Iowa Physics Department as a research associate in September 1953, while still completing a few odds and ends dealing with his Ph. D. dissertation at Minnesota.

He received that degree in 1955 and was appointed assistant professor at Iowa in 1956.

Frank left the University of Iowa in 1959 to play a key role in establishing the space research program in the fledgling NASA. As a member of the initial complement in what became the GSFC at Greenbelt, Maryland, he established the Fields and Particles Branch and its early research program. He moved through a number of positions at Goddard during the next 23 years, ending that period with his service as chief of the High Energy Astrophysics Laboratory. From 1982 to 1987, he served as chief scientist at NASA Headquarters, while simultaneously holding a position as a part-time professor at the University of Maryland in College Park. He returned to Goddard as its associate director and chief scientist in 1987, and served for a time in 1989 as senior policy analyst in the Office of Science and Technology Policy in the Executive Office of the president.

Frank very successfully combined senior-level executive management with his own re­search. Even while serving as the NASA chief scientist, he continued with his personal research program. Having served as principal investigator on 15 NASA space missions, as of 2007, he was still actively interpreting data from the Voyager Deep Space Missions and Inter­planetary Monitoring Platform (IMP) 8 at the Institute for Physics, Science, and Technology at the University of Maryland.

Frank’s first goal upon arriving at Iowa was to continue his investigation of the higher-charged component (charge greater than two) of the primary cosmic rays. He immediately started the development of a new particle telescope for improved measurements of the charge and energy spectra of those heavier primary cosmic rays. It featured a combination of a thin-lucite Cerenkov detector and a three-GM counter array. That arrangement provided better discrimination between the nuclei of different energies and charges than had been provided by previous instruments. The detectors displayed their data on cathode ray tubes in the flight gondolas that were,

CHAPTER 2 • THE EARLY YEARS 35

in turn, photographed by special cameras that Frank designed. I assembled many of Frank’s new electronic circuits as part of my early work at Iowa during the 1953-1954 period.

Frank made his shakedown balloon flight in early 1954 at Goodfellow Air Force Base (AFB) at San Angelo, Texas, only five months after he started this new project. After that initial test, the next step was an expedition to Goodfellow AFB in January

1955 as part of a major two-week international balloon field project. Iowa instruments were carried on 4 of the 13 balloon flights made during that expedition.15 Iowa participants, in addition to McDonald, were William (Bill) R. Webber, Jason Ellis (not to be confused with Robert Ellis, mentioned earlier), Hugh R. Anderson, and Belle Fourche. Cosmic ray instruments from the universities of Chicago and Minnesota and photographic plates from several European universities were also flown on some of the flights.

The balloons, 120 foot diameter Skyhooks, carried more than 100 pounds of instruments per flight. General Mills again furnished the balloons and conducted the launch operations. After floating at altitudes of up to 18 miles, for an average of seven hours, they landed from 50 to 100 miles from the launch site. They were followed in flight by light airplanes and trucks and were assisted by visual sightings from the ground and radio signals to facilitate recovery of the instruments as soon as possible after they landed. Early recovery was not always possible, as the chase parties sometimes had to break off their pursuit because of bad weather and darkness. In most cases, however, instruments were eventually recovered, some of them after they were found by farmers or others at the landing sites.

After that field trip, Frank developed an improved instrument that added a Na-I scintillation detector in a telescope arrangement. The combination of Cerenkov and scintillation detectors provided an improved measurement of the energy and charge for nucleons in certain ranges. The first flight of his new instrument was made from Minneapolis on 7 July 1955, and additional flights followed during the next four years.

Concurrently, Bill Weber developed a Cerenkov-GM counter combination to ex­tend the information on charge composition at low latitudes. He flew it in Texas in

1956 and used those data for his Ph. D. thesis.

Frank McDonald, Bill Webber, Kinsey Anderson, Robert Johnson, and Larry Cahill spent six weeks in February and March 1957 on the island of Guam as partici­pants in an ONR – and AEC-sponsored Equatorial Expedition. The balloon experi­menters, Frank, Bill, and Kinsey, were able to loft only three of their balloon payloads because of strong local trade winds, but they still obtained some useful equatorial data.

Frank and Bill formed a close collaboration during that 1953-1959 period that was the start of an especially durable and fruitful association that has lasted until the present

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(2010). Their first joint paper, published in 1959, used the proton data from a number of Frank’s Cerenkov-scintillation detector flights. Ultimately, the pair launched some 22 Skyhook balloon flights. Other joint papers through the years dealt with various aspects of cosmic ray work, including some on charge composition. The instruments gave excellent energy measurements in the range 300-800 MeV per nucleon and complete charge resolution at the higher end of that energy range. The extended program yielded more precise hydrogen and helium energy spectra, their long – and short-term modulation, geomagnetic cutoffs, and the first electronic measurements of lithium (Li), beryllium (Be), boron (B), and heavier elements.

I especially treasure my long-standing and close personal relationship with Frank. His keen understanding of physics and the processes involved in observing cosmic rays was particularly outstanding and personally helpful. He was able to conceptualize and carry out experiments over the years that have added substantially to our understanding of space particle physics. His accomplishments in cosmic ray physics, combined with his outstanding management abilities, made him one of the truly outstanding contributors to the blossoming of space physics during the second half of the twentieth century.

Long before the president’s U. S. satellite commitment in 1955, many researchers had been turning over in their minds ideas for scientific investigations that might be conducted with such carriers. As related in Chapter 3, Van Allen prepared an outline for a cosmic ray experiment in an Earth satellite as early as 1 November 1954, after learning of the army’s thinking about a satellite launcher.2 His objectives, which remained substantially unchanged throughout the subsequently evolving satel­lite program, were “to measure total cosmic ray intensity above the atmosphere as a function of geomagnetic latitude, and to measure fluctuations in such intensity and their correlation with solar activity.” The general description of the basic apparatus, too, remained unchanged, i. e., a “single Geiger-counter, necessary auxiliary circuits, radio telemetering transmitter and antenna.”

Details of the envisioned technical implementation, however, changed dramatically between that earliest outline and the instrument that we began developing a little more than a year later. Van Allen based his early proposal on the use of vacuum tube circuitry, as transistors were not yet available except as purely experimental devices. His proposal did not even mention them. Furthermore, he believed that a transmitter radiating five watts would be necessary for reception at 1500 miles. Those factors combined to focus most of the rest of his discussion upon power supplies to provide the relatively high energy level needed for extended operation. He listed possibilities for the power source as (1) dry batteries, (2) lead storage batteries, (3) Yardney silver cells, (4) hydrogen and oxygen heat of combustion (now known as fuel cells), (5) red fuming nitric acid and aniline heat of combustion, (6) gasoline and oxygen heat of combustion, and (7) solar power. Van Allen narrowed his focus, in that proposal, to the use of a generator driven by a gas turbine fueled by nitric acid and aniline.

The president’s announcement added a sense of reality to the experimenters’ as­pirations, and Van Allen quickly prepared an updated and more complete version of his proposal.3 That one, titled “Proposal for Cosmic Ray Observations in Earth Satel­lites,” reflected some of the new technological developments. On 28 September 1955, less than two months after the president’s commitment, he submitted that new version to Joseph Kaplan, chairman of the U. S. National Committee for the International Geophysical Year (IGY).4

Despite Van Allen’s heavy workload in heading the university’s Physics Depart­ment, it is clear that Van Allen’s thinking and energies were sharply focused on the coming IGY satellite program.

As mentioned earlier, in late January 1956, the Upper Atmosphere Rocket Research Panel, under his chairmanship, held a meeting on the University of Michigan’s Ann Arbor campus to hear and discuss serious satellite research proposals. Among the 38

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT 127

papers presented there, Van Allen delivered two containing three specific proposals. His first paper, “Cosmic-Ray Observations in Earth Satellites,” actually contained two separate proposals, the first of which expanded upon his September 1955 proposal.5 It called for the use of a single Geiger-MUller (GM) counter or scintillation detector for a first-time study of the cosmic ray intensity above the appreciable atmosphere on a comprehensive geographical and temporal basis. Specific objectives were listed as “determination of the effective geomagnetic field; the magnetic rigidity spectrum of the primary radiation; time variations of intensity and their correlations with solar and magnetic observations and with the observed intensity of secondaries observed in ground stations; and cosmic-ray albedo of the atmosphere.” He also envisioned that those data would be especially valuable in helping to interpret the observations from the extensive array of cosmic ray ground stations that were being established.

In that proposal, Van Allen included an extended discussion of the effect of limited data recovery by various hypothetical networks of ground receiving stations. Conspic­uously, he did not mention onboard storage, although he and I had seriously discussed that possibility well before the meeting. But our thinking about onboard storage was still evolving at the time of the meeting, and we didn’t add that feature until a little later. That proposal, with the addition of the onboard data storage, was accepted in June 1956 for development.

The second part of Van Allen’s first paper was for the use of a Cerenkov detector to study the relative abundance of heavy nuclei in the primary cosmic radiation. That proposal was soon dropped from further early flight consideration because it could not be accommodated within the severe limitations on instrument weight imposed by the Vanguard launcher. Although not pursued in the initial satellite program, its scientific objectives were eventually achieved by other groups using later satellites.

Van’s second Ann Arbor paper (his third proposal), “Study of the Arrival of Auroral Radiations,” proposed a further study of the auroral soft radiation that had been discovered from the data from the Iowa rockoon flights.6 That proposal also had to be set aside for then, primarily because it required a much higher orbital inclination than was envisioned for Vanguard. Most of the objectives of that second proposal were also achieved with later spacecraft instruments.

Ernst Stuhlinger’s graduate-level training began in 1932 in physics and mathematics at Hans Geiger’s institute at the University at Tubingen, Germany. There he worked under Geiger’s tutelage on developing charged particle detectors and applying them to cosmic ray research. For his Ph. D. dissertation, Stuhlinger developed a variation of Geiger’s counter that was sensitive enough to operate in the proportional region for incident electrons. Stuhlinger used his counter to determine the specific ionization of electrons in cosmic ray showers produced in the upper atmosphere. His postgraduate work included applying his experience with nuclear detectors to helping to clarify the possibilities for building energy-producing uranium reactors in Werner Heisenberg’s laboratory in Berlin.

Ernst’s work in pre-WWII Germany put him in a position, much later, to assist in getting Van Allen’s cosmic ray instruments aboard the early Explorer satellites. There were never many engaged in nuclear physics and cosmic ray research prior to WWII. Those few indi­viduals formed a closely knit community that often transcended national boundaries and the turmoil of the times. During his work in Geiger’s and Heisenberg’s laboratories, Stuhlinger became aware of the work of many of those coworkers. Among them was a young post­graduate researcher in the United States—James A. Van Allen. Some of Van Allen’s early published papers dealt with deuteron-deuteron reactions and the detection of high-energy protons in the presence of fast neutrons. That, of course, was closely related to the work that Ernst was doing in Berlin. Although Stuhlinger kept track of Van Allen’s work in those early days, there was no direct contact between them until much later, when Stuhlinger began working in the United States after WWII.

The rise of Nazism and WWII interrupted Stuhlinger’s nuclear science research in Berlin. Following the German invasion of Russia and eventual setbacks on that front, the demand for additional military manpower for the German Army became overwhelming. In the fall of 1941, Stuhlinger was drafted and sent to the Russian front as a private first class. By early 1943, it was decided that there was a greater need for his physics background, and he was reassigned from the Stalingrad battlefront to the rocket development endeavor at Peenemunde. He remained with the rocket group until the end of the war, with his primary work being helping in the development of the guidance and control system for the A-4 (V-2) rocket.

Stuhlinger was among the group of German scientists who were brought to the United States in 1945 as a part of Operation Paperclip, the U. S. operation to collect components and technology needed to assemble and test V-2 rockets following the German surrender. The captured hardware was accompanied by extensive documentation and more than 100 of the senior scientists and engineers who had participated in the rocket development. Those individuals were very helpful in assembling and firing the captured V-2 rockets in Texas and otherwise assisting in jump-starting the burgeoning U. S. rocket development efforts.

The German group, led by Wernher von Braun and including Stuhlinger as chief scientist, was taken first to Fort Bliss near El Paso, Texas. Many of them moved in 1950 to the

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Redstone Arsenal near Huntsville, Alabama. That organization was later reorganized to form the ABMA and, after NASA was formed in 1958, the Marshall Space Flight Center.

Stuhlinger figured prominently in the space program at Huntsville, beginning with plan­ning for Orbiter, the Jupiter C program, and for use of the Juno vehicles for launching Explorers I, II, III, IV, V Beacon 1, Pioneers 3 and 4, Payload 16, Explorer 7, and Payload S-46. In succeeding years, he was active with numerous additional space flights, including lunar exploration flights, the Apollo telescope mount flown on Skylab, the High Energy Astronomy Observatory, various Space Telescope missions, and scientific payloads for the Space Shuttle.

Von Braun, as the director of a large military research and development organization, always had some independent flexibility to conduct limited feasibility studies in areas of high technological interest. After the Vanguard decision in August 1955, he drew upon a special fund earmarked for general research related to the advancement of the art of rocketry for further Orbiter-related studies. Thus, by the time Huntsville was directly ordered to stop all further satellite work in June 1957, theoretical work had been conducted on four capabilities needed to advance from the nose cone-testing Jupiter C RTV to the eventual satellite launcher. They were as follows:

• A new attitude control system to turn and orient the upper portion of the Jupiter C rocket cluster after the end of main-stage engine burning and separation of the forward section from the booster. That had to be done in such a way that the forward section would be exactly horizontal when it reached the apex of the upper-stage cluster flight trajectory.

• Development of a way to determine the exact moment that the forward section reached its apex. The upper-stage rockets would have to be fired at just that instant.

• Working out the celestial mechanics, orbital parameters, acceptable launch times, and injection conditions for the satellite.

• Development of a satellite payload. Von Braun and Stuhlinger insisted from the beginning that any satellite had to be scientifically useful. The satellite would need to accommodate appropriate detectors, a data transmitter, tracking equipment, antennas, and batteries.

After the unambiguous command to stop further satellite development, von Braun no longer considered it prudent to continue use of that source of discretionary funding for this purpose. Even then, however, a number of the Huntsville technical staff enthusiastically continued the work on their own, often during evenings in their homes. Fred Digesu and Hans H. Hosenthein worked out the theory for the attitude control system. Ernst Stuhlinger developed an “apex predictor” to accomplish the second task. Task 3, orbital considerations, was addressed collectively by individuals in Helmut Hoelzer’s Computation Laboratory, Ernst Stuhlinger’s Research Projects Office, and

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Ernst D. Geissler’s Aeroballistics Laboratory. Charles A. Lundquist developed a method for computing the satellite’s orbit based on a limited number of observations from the ground. Josef Boehm, Helmut Pfaff, and their staffs produced designs for the satellite, as described below, as well as designs for mechanical components of the attitude control system.

Admittedly, the distinction between private and official work during that period sometimes became a little blurred. It should be appreciatively acknowledged that Redstone Arsenal commander general Holger N. Toftoy and, succeeding him, ABMA commander general Medaris, “always turned very generously the other way when they visited a laboratory and spotted on one of the drawing boards a sketch that looked suspiciously like a little satellite.”27

A discussion of Stuhlinger’s apex predictor illustrates the character of one of those behind-the-scenes efforts. It was essential that the firing of the solid fuel stages should be initiated at just the right moment. Basic data to assist in that process were available from a variety of radio, Doppler, and radar measurements. The challenge was to pull all of the information together, and to use it in a systematic way to determine the instant when the cluster of upper stages should be fired.

Some of the basic apex prediction concepts were tested during the first Jupiter C reentry test on 20 September 1956. The written plan for that exercise included the statement, “The three proposed methods to determine the apex of a missile. . . will be tested for the first time in Missile #27 [Missile # 27 was the internal identification nomenclature for the first nose cone reentry test vehicle]. Although that missile does not represent an exact duplication of Missile #29 [the vehicle quietly set aside for the first satellite launch], a number of valuable data regarding feasibility and proper functioning of apex determination methods will be obtained. Also, human operators will have the opportunity to familiarize themselves with their tasks. It is anticipated that more practice runs of this kind will be made before the firing of Missile #29.”28 The three methods referred to above were the Radar Method, the Dovap (Doppler, velocity, and position) Method, and a Back-up Method. The plan went on to describe the backup method.

A third and independent method to estimate the expected apex time has been prepared in the following way: velocity signals from the missile fixed gyro-accelerometer, as received by the telemeter ground station, will be directed through a relay circuit to the operator of the apex computer. The signals are recorded by a Brush recorder, together with a time base. They are entered into a time-velocity diagram, which contains, as a reference, the standard time-velocity diagram. The amount of deviation between the two curves is quickly estimated and entered into another diagram, which gives the apex time variation as a function of the velocity deviation.29

That document stated that no great accuracy should be expected from the backup method; it was being implemented in case the other two methods should fail. The

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backup method used an approach in which the information was assimilated and combined in a manual process employing prepared charts and other graphical aids. Although it did not use any special equipment, it tested the basic approach envisioned for the satellite launches.

Based on the results from the September 1956 flight, Ernst Stuhlinger developed a form of analog computer to simplify the human operator’s task and to make it more precise. The development of that computer, the apex predictor, was described by Ernst Stuhlinger in the following way:

An electro-mechanical analog computer, called “Apex Predictor,” was developed at Stuh – linger’s Research Projects Office, and built largely at home in his garage, with some help from Wilhelm Angele’s Precision Shop in the Science and Engineering Directorate (because the satellite project did not have an official standing at the Army Ballistic Missile Agency at that time, such work could not be carried out as a normal ABMA activity).30

The apex predictor was built well before the first satellite launch and was tested extensively so that it would be ready if needed for that purpose. It was operated in parallel with other methods during the test of a Chrysler Corporation production Redstone rocket in July 1957 (Missile 37), for the fully successful Jupiter C nose cone reentry test in August (Missile 40), and for another Chrysler Redstone on 2 October (Missile 39).31

Ernst informed me recently that two identical apex predictors were assembled in 1957. Both were used for the Jupiter C launches, one as primary and the other as a backup. Those instruments were lost following the launches, but Ernst built a full-size working replica in his garage during the 1990s.32

The fourth task at Huntsville was to design a satellite that could be launched atop the Jupiter C rocket. The general form of such a payload had been under consideration for some time. Ernst Stuhlinger has recounted that, as early as 1952, as he and von Braun were discussing the prospects for eventually using their Redstone rocket to launch a satellite, Von Braun expressed his belief that they should have a “real, honest-to – goodness scientist” involved in their little unofficial satellite project. “I’m sure you know a scientist somewhere who would fill the bill, possibly in the Nobel Prize class, willing to work with us and to put some instruments on our satellite.” Being fully aware of Van Allen’s work as related earlier, Stuhlinger was ready with his reply: “Yes, of course, I will talk to Dr. Van Allen.”33

As the behind-the-scenes Jupiter C satellite effort progressed during 1956 and 1957, ABMA engineers continued to design the satellite under Ernst Stuhlinger’s general oversight. Josef Boehm and his group of design engineers carried that effort forward at the working level.

The JPL engineers participated actively in that work, with their primary focus being the inclusion of their Microlock system. A key meeting of the ABMA and JPL engineers to plan details of the satellite was held in December 1956. After early 1957,

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we at the University of Iowa also worked closely with the ABMA and JPL groups to add our cosmic ray instrument to the evolving satellite design, as detailed later.

The culmination of that ABMA-centered, three-party collaboration was a rather complete top-level paper satellite design by the end of July 1957, shown here as Figure 7.1.34

At the Jet Propulsion Laboratory The basis for the ABMA-JPL collaboration had a long-standing background. Through their work on the guidance and control systems for Corporal and other rocket programs, JPL developed an early capability in elec­tronics design. Their interest in electronics was additionally stimulated in late 1954, when the Redstone Arsenal and NRL groups sent their Orbiter proposal to them for comment. JPL immediately became an enthusiastic supporter and participant in the Orbiter work. That involvement made them a bona fide partner in early satellite planning and whetted their appetite for further satellite work.

I turned toward home. I was anxious to stop in Iowa City, where I looked forward to comparing notes with Van Allen, helping with the preparations for processing the flight data, and making further arrangements for the upcoming launch of the much more complex Deal II instrument. I also took that opportunity to check our home on Rochester Avenue and to look in on my parents and three sisters. My journal account of that visit reads:

Arrived in Iowa City Sunday afternoon 2:05. There [were] dad and a few reporters [to greet me at the airplane]. We went to the farm (viaNona’s & Ivan’s [my sister and brother-in-law’s] new farm) where I took a nap. After supper at the Ox Yoke [a restaurant in nearby Amana, Iowa], Van Allen, Ray, Casper [sic: Kasper], Cahill, and McDonald came to the farm where we discussed data, data reduction, etc.

… Monday morning [I] was on his radio program, then with reporters. Then to Iowa City & Physics Dept., Ray’s in evening. Next day was spent primarily taking care of per­sonal matters—check house, make arrangements to sublet it to Boleys [former neighbors at Finkbine Park], etc. Evening at Cahills for dinner, then Rays.18

CHAPTER 9 • THE BIRTH OF EXPLORER I

Van Allen had arrived back from Washington on Saturday evening, just ahead of me. Among the extensive coverage in the Sunday edition of the Cedar Rapids Gazette was the following article19:

VAN ALLEN, LUDWIG RETURN TO IOWA

The Iowa City Press Citizen carried an extended article20:

S. U.I. PHYSICISTS TELL OF TENSION,

JOY AS SATELLITE LAUNCHED

Even the Van Allen dog was included in the publicity. An article in the Cedar Rapids Gazette read:

No Space Trip For Van Allen’s Dog, Family Says

Dr. James Van Allen, leader in space physics, recently touched off a domestic tempest when he jokingly offered his dog for outer space.

“Our children have been threatening him ever since,” says his attractive wife Abigail. “It looks like Domino is safe.” Domino is the Van Allen’s 8-year-old Cocker.21

JPL director Pickering also returned home that Sunday. A newspaper reporter who interviewed him upon his arrival at the Los Angeles Airport wrote:

Pickering’s arrival was something in the nature of a conqueror’s triumphal return home, but he brushed aside plaudits to extend credit to fellow scientists working at the Jet Propulsion Laboratory for their “team” contributions.

Two of these fellow workers reached Los Angeles from Cape Canaveral, Florida,

10 minutes after Dr. Pickering’s arrival and joined him on the airport ramp for a group inter­view. They were Dr. Al Hibbs, 34-year-old chief of research analysis at the Caltech lab, and Dr. H. J. Stewart, 36, chief of the center’s liquid propulsion systems division. Also at the airport as head of a welcoming delegation was I. E. Newlan, supervisor of technical reports at the Pasadena school.22

Newspaper articles were rife with reports of new space projects planned, hoped for, and dreamed of. Typical of the more interesting statements was Pickering’s prediction that man-carrying Earth satellites might be launched into outer space within five years and that landings on the Moon and Mars were “possible” within the foreseeable future.

Even before Van Allen arrived home on Saturday evening, his wife, Abigail, had received a telegram from the White House in Washington:

The President and Mrs. Eisenhower hope you can come to dinner at the White House on Tuesday, February 4th, at 8 o’clock. White tie. Please wire reply.23

That started a scramble in the Van Allen household. Abby’s first reaction was, “What will I wear?” She did not have anything appropriate for a formal state dinner. Friends, relatives, and neighbors all rushed to offer their best gowns and accessories,

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and she was able to assemble an appropriate outfit. The Van Allen couple left Iowa City on Monday afternoon for the grand event.

The local papers carried extensive coverage of the state dinner and of the Van Allens’ excitement in participating in such a magnificent event.24

On Wednesday, we learned of the failure of the second Vanguard satellite launch attempt. The rocket had lifted off at 2:33 AM EST that morning. About 60 seconds after liftoff, at about 20,000 feet height, it tilted due to a problem in the guidance and control system, cracked in two, and was additionally destroyed by the range safety officer.

It was indeed painful to hear of the continuing terribly bad luck of the Vanguard program. I thought of Marty Votaw and Roger Easton, who had been so helpful to me a few days earlier, and of the anguish they and their colleagues must have felt as their program suffered another major setback.

My postlaunch stop in Iowa was short. The first Explorer I tapes were expected to arrive from the ground receiving stations within the next few days. By Wednesday morning, I had ensured that the data-processing equipment was in order, and Ernie Ray was poised to take charge of the data reduction activities. I stopped at the university’s television laboratory to tape an interview. At noon, Dad took me to his Lions Club meeting, and then to the Iowa City Airport to catch the United Airlines flight for California. At the steps of the ramp leading to the airplane’s door, I paused to talk to Van and Abbie, who were just then returning from the previous evening’s White House dinner. [3]

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and evening in trying to lip-sync film footage of me. He worked for a company hired by JPL to produce the film X Minus 80 Days, a documentary describing the Deal program. They had filmed a series of interviews with a number of us at JPL earlier. Synchronizing my voice and lip movement had proven unusually difficult because, apparently, I move my lips very little when I speak.

The JPL managers were eager to release the film during the great excitement immediately following the launch, so the film producers were rushing to complete their work. Just that evening, they had assembled the first full version, and they planned to take it to JPL the next morning for its first exposure there.

Being very proud of their work, the film editor was anxious to show it off. As soon as we completed our coffee, he took the four of us to his company’s nearby studio, where we felt like movie moguls as we previewed the film in the luxurious comfort of the heavily cushioned seats in their viewing room.

The film aired on the following Tuesday evening on three Los Angeles television channels.

ithout a doubt, the most momentous event during this period of early space exploration was the discovery, from the data obtained from Explorers I and III, of what we dubbed initially as simply the high-intensity radiation. It has come to be known commonly as the Van Allen Radiation Belts. This discovery was a serendipi­tous event. The original purpose of the experiment had been for a rather straightfor­ward extension of the cosmic ray research that had been under way for many years. That objective was immediately overshadowed when the new discovery thrust itself upon us.

There have been many accounts of the discovery, some of them misleading, incom­plete, or contradictory. In the interest of historical accuracy, there is heavy reliance in this work on primary documentation, that is, material that was written by direct participants at the time of the activity. Those include a variety of archival materials, personal files, and many papers and other published and unpublished accounts.1,2’3’4 There was secondary dependence on the recollections of direct participants, including a number of unpublished exchanges.5

It should be noted that there is a relative lack of primary documentation for one key period—much of the month of April 1958. Laboratory notebooks and personal journals of the four major participants, Van Allen, McIlwain, Ray, and this author, are strangely deficient. It was a time of unusually intense activity—all of us were so completely absorbed in following up on the exciting new findings, that our normal habits for record keeping appear to have been set aside for a while.

Van Allen, the principal investigator and intimately involved in all aspects of the project, was an unusually meticulous record keeper, and he retained his many journals, diaries, notebooks, day-to-day notes, calendars, meeting files, travel records, letters,

319

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and so on. As mentioned earlier, they reside now, along with complete cataloging, as a professionally maintained collection by the Department of Special Collections in the University of Iowa Libraries.

I was responsible for the cosmic ray instrument development, for our field activi­ties, and for designing, setting up, and running the University of Iowa data-processing facilities. Although participating at times in the data analysis effort, much of my atten­tion was directed to the instrumentation, operational, and data-processing activities. My work is also thoroughly documented. It includes extensive personal journals, notebooks, calendars, meeting files, travel records, photographs, sample data records, letters, and so on. Arrangements have also been made to preserve most of my materials as another special collection in the University of Iowa Libraries.

Carl McIlwain concentrated on developing a thorough understanding of the behav­ior of Geiger counters in the presence of intense radiation and on working with Ernie and Van in pondering, unraveling, and describing the new phenomenon. Carl’s record keeping was intermediate in scope. His records, combined with his keen recollection of events that took place during the 1950s, have been instrumental in resolving some of the conflicting details. Discussions are under way about also placing Carl’s records in the University of Iowa Libraries.

Ernie Ray took charge of the initial processing and plotting of the Explorer I and III flight data at Iowa City. He was an enthusiastic participant, throughout the period, in developing an understanding of the physical processes being observed. Ernie’s record keeping was nonexistent—his shirt pocket served as his file cabinet. Having died in 1989, his personal memories can no longer help us. His contributions to this account are based primarily on the recollections of his wife, Mary, some of his data plots, and a few short notes.

Upon Van Allen’s return to Iowa City on Friday, 2 May, he, Carl, and I met to plan our work. Additional personnel would be needed, and more student helpers were quickly identified. Arrangements were made with Stuhlinger for ABMA to send engineers to help us on short-term staffing loans. In addition, Huntsville would detail an engineer to our laboratory to help us over a longer term. Importantly, in the process of helping us, those engineers would learn what they needed to know for testing our satellite payloads and integrating them into the launch assemblies at Huntsville.

Our work progressed at breakneck speed. Carl concentrated on developing the new scintillator counters. One was for measuring the average current (representing total integrated energy) over a very wide intensity range, while the other included a pulse

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height discriminator to provide information on the particle energy spectrum. One of my early tasks was to develop a faster scaling circuit that would work with GM counters (Anton type 302) having a smaller cross section than the earlier Explorer units by a factor of about 100 times. The scintillation counters and faster GM counters represented the first configuration explicitly designed to follow up on the new radiation belt discovery by making measurements to much higher intensities than had been possible with the earlier Explorers.

Within several days, we had detailed the final detector configuration, and I sent that to Ernst Stuhlinger at Huntsville.15 Within several more days, engineers began arriving from Huntsville. Hermann Wagner was the first—in short order, we were visited by specialists in structures, electronics, environmental testing, and payload checkout, and H. Burke arrived to help us over a longer period.

Relating the details of the many activities that took place during the next weeks would be a book in itself. As already stated, the ABMA at Huntsville carried the primary mission responsibility. I worked extensively with Ernst Stuhlinger, Joseph Boehm, and Charles Lundquist in coordinating many of the programmatic issues. The working-level contacts that I remember with special fondness include (in alphabetical order) Tomas (Tom) A. Barr, H. Burke, George Campbell, Charles Chambers, Harold Donnelly, James Warren Harper, Gerhard Heller, Hans Kampmeier, Samuel (Sam) Stevens (Huntsville’s payload manager), Arthur (Art) Thompson, Willis Underwood, and Hermann Wagner.

I served as SUI’s project manager, overall system designer, coordinator, and equip­ment and supplies procurer. By mid-project, William (Bill) Whelpley, a young engi­neering student, had become my right arm, taking responsibility, among other things, for a substantial portion of the field activities. He continued his work in the laboratory for a number of years, becoming a very competent satellite designer in his own right.

Carl McIlwain carried the full responsibility for the new scintillation counters (Figure 13.1), with Ernie Ray working with him from time to time. Carl was also assisted by Dale (Pete) Chinburg, who prepared his numerous drawings. Pete also remained with the Iowa group for a number of years, where he served primarily as a payload coordinator and manager.

Wayne Graves continued his earlier assignment from Collins Radio in Cedar Rapids, providing very skillful help with the electronics design and construc­tion and with GM counter calibration. Charles Cook, Riley Newman, and Chris Richards provided additional laboratory assistance. Drafting support was provided by Mr. Schnerre.

The JPL provided the low-power transmitters, subcarrier oscillators, antenna gaps, and outer shells with their temperature-control coatings. In addition to working with

CHAPTER 1 3

director Bill Pickering, chief scientist Eb Rechtin, and senior engineer Henry Richter, I worked at various times on this project with Walt Downhower, Karl W. Linnes, Phil D. Potter, Lee Randolph, Fred Riddle, and Al Wolfe.

The NRL in Washington provided the high-power transmitter. My primary interface there was with my good friend Marty Votaw.

The U. S. Signal Research and Development Laboratory at Fort Monmouth, New Jersey, provided the battery packs through their contract with the Mallory Battery Company. My primary contacts there were Hans Ziegler and A. Legath.

During the instrument development, Pentagon brass and other officials showed up at the physics building from time to time. They returned home incredulous:

Visitors to the University of Iowa during the spring and summer of 1958 were astonished to find that a crucial part of this massive undertaking had been entrusted to two graduate students, and two part-time professors working in a small, crowded basement laboratory of the 1909 physics building. But we knew our business and were in no way intimidated by representatives of huge federal agencies.16

Despite the secrecy, we could build all of the equipment in the open, since the satellite and its instrumentation served officially as an International Geophysical Year (IGY) program to extend our investigation of the natural radiation discovered by Explorers I and III. Only the second mission to study the nuclear blasts was held in strict confidence by a small group of us who were building the instrument. In fact, only Van Allen and McIlwain had access to the full range of details. My knowledge

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was limited to a basic understanding of the mission and to details necessary to build the instrumented satellite, test it, and interface it with the launch vehicle.

The Argus Project was helped immeasurably by the assignment of a very high mil­itary priority that helped to cut through the red tape and delivery delays. Specifically, it enjoyed a DX-A2 designation, where the DX rating was the highest Department of Defense priority, and A2 designated missile-related contracts. Its high priority enabled us to obtain materials that existed anywhere in the national manufacturing, warehous­ing, and delivery chain, regardless of who may have ordered them. Our procurement of a complete vibration test system illustrates the benefit of that arrangement. It was a large aggregate of electronic and electromechanical assemblies capable of vibra­tion testing our satellite. It included four racks and a console filled with electronics equipment, plus a vibration exciter on which the equipment to be tested was mounted. Those systems were normally produced at the factory only upon receipt of concrete orders, so that the normal delivery time was substantial. We ordered one in late May, and it was delivered and placed in operation in about six weeks. In order to accomplish that, a system that was being built for another customer was intercepted and delivered to us. That system, shown later in the lower left corner of Figure 15.2c, turned out to be operational too late to help much with the Argus Project, so the Explorer IV and V vibration testing was conducted at Huntsville. Our vibration test system was used extensively over time on later projects.

We had a substantial body of experience with most of the circuits and components used in Explorer IV, as they were similar to those in the earlier Explorers. Carl McIlwain’s new detectors, however, introduced a completely new element. During their environmental testing, failures occurred with a calibration relay and with the Radio Corporation of America (RCA) type 6199 photomultiplier tubes. A summary of the problems on 25 June 1958 indicated that the relay problem had been satisfactorily resolved. Although RCA had made some improvements in the tubes, a complete redesign was not possible. The launches would have to proceed with somewhat less than full confidence in them.

Specifically, after the initial tests, their failure rate was determined to be about 25 percent. The late June report summarized the situation, as it had evolved by that time, by stating that the tube was not designed for the rocket launch environment, that no other suitable tube was available, and that there was no time for complete redesign of the tube’s construction. The RCA was able, however, to make some minor changes, and Carl made an improvement in the exterior mounting arrange­ment to further isolate the tube from payload vibration. In addition, the vibration test levels were somewhat reduced. Because of the urgency of the mission, the decision was made to launch the payloads with an estimated failure rate still at about 5 percent. Fortunately, Explorers IV and V were launched without instrument failure.

The photomultiplier tube evolving from that design effort served for a number of years as the standard for similar rocket and spacecraft detectors.

On 5 May, Stuhlinger called a planning meeting at Huntsville. Neither Van Allen nor I could go because of the press of our work in Iowa City, but we participated via a telephone conference call. Many issues involving receiving stations, orbital computation, payload weight, and the assignment of responsibilities for providing the various components were worked out. That meeting was followed by another on 10 May, which I did attend. Engineers were there from ABMA, JPL, and the Signal Corps Engineering Laboratory in New Jersey, while NRL participants joined us via telephone. During that meeting, a more detailed delivery schedule was established. It was tied to the requirement that we have our satellite in orbit before the first Argus high-altitude nuclear detonation, then scheduled to occur on 31 July.

During the preparations for the Explorer IV and V launches, we employed light military and chartered civil aircraft to shuttle personnel and equipment between Iowa City, Huntsville, and Washington, D. C. The schedule was too pressing for us to wait for commercial flights. At least 15 of those special flights were made.

On 7 June, Carl McIlwain and I packaged our prototype Explorer IV instrument assembly (Figure 13.2) and carried it via an Army Twin-Beech aircraft to Huntsville, where we test-fitted it into the outer satellite shell and began the process of balancing and aligning it. Two days later, Carl returned to Iowa City, where he prepared and sent

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some repair parts to me. I returned to Iowa City with ABMA’s George Campbell and Willis Underwood to make a new circuit board on 14 June, and five days later, I flew again to Huntsville with the result. On 21 June, it was back to Iowa City to work on the flight units.

About three weeks later, on 2 July, Bill Whelpley flew to Huntsville with our first flight unit for an extended stay to help with the testing. The next week saw the rapid shuttling of the flight payloads between Iowa City, Huntsville, and Washington. Flight Payload 1 moved from Huntsville back to Iowa City for transmitter rework, back to Huntsville, thence to NRL in Washington, and finally back to Huntsville. Payload 2 also made a trip to NRL for transmitter modification.

On 9 July, I left again for Huntsville to deliver the third flight unit and to remain for a week for extended testing. The rest of my family drove to Huntsville in our personal car to join me. While in Huntsville, we were the guests of gracious hosts George Campbell and his family.

We had a particularly rough night on 11 July, when we repaired a vacuum problem in flight unit 1 and were finally able to run a satisfactory vacuum test on it. Antenna matching problems with that flight unit were also resolved during the night, and we corrected a problem with the high-power transmitter in flight unit 2 and passed a vibration test with it.

And so it continued during the next days. I finally had a much welcomed short break on 16 July, when I drove our family to Cape Canaveral for the launch. I remember having great fun with Rosalie, Barbara, Sharon, and baby George during the drive with group singing, including many spontaneous variations on “Purple People Eater.”

Bill Whelpley remained at Huntsville to continue the testing on flight units, and Carl McIlwain soon joined me at the Cape. The pace there was just as hectic as it had been at Huntsville. During the next few days, I completed the final inspection and calibration of flight unit 1 and worked with the ABMA, NRL, JPL, and Cape personnel on fitting the payload to the launch vehicle, balance tests, and radio frequency testing and calibration. Other activities, such as working out the countdown procedures and checking ground receiving station readiness, occupied the remaining time leading up to launch.

We soon began concentrating on the final preparations of the most promising of the flight payloads. On 22 July, we completed the last radio frequency interference tests with it mounted on the launching vehicle, as it stood upright in the gantry.

Two incidents remain vivid in my memory that emphasize the informality of that early space flight era. A day or two before the Explorer IV launch, I was called to a meeting with Major General Donald N. Yates, Commander of the Air Force’s Atlantic Missile Range. He had the ultimate responsibility for flight safety. As mentioned earlier, an orbital inclination of 51 degrees had been chosen, compared with 33

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 373

degrees for Explorers I, II, and III. Those earlier launches involved aiming the rockets slightly south of due east from Florida, where their flight paths were well clear of any substantial landmasses. On the other hand, Explorers IV and V in order to achieve the desired higher inclination, had to be aimed northeast, with their paths passing just off the U. S. East Coast. In fact, the swath that included their intended paths, widened by allowances for reasonable aiming errors, included possible passage over the east coast of Newfoundland.

General Yates wanted to be assured that the flight would be reasonably safe. This was the easiest argument that I ever had to make, as he was just as eager to launch as we were. All I had to do was to mutter a few words about the low population density on its expected course and the improbability of hitting any populated areas if the vehicle should happen to stray, and he quickly said, “Let’s go.”

I especially marvel at the second incident. On 23 August, I performed a careful inspection of the number one flight unit being readied for the Explorer V launch. I found that many of the wires in a bundle of interconnecting wires were nearly broken off where they were soldered to the terminals.

Teflon insulation for electronic circuit wire had just made its appearance. The coating process had still not been perfected for copper, although it was well understood for silver. So the hookup wires that we selected were made up of many fine silver strands. The main problem with that was that the silver strands broke easily when flexed repeatedly. To compensate for that, the manufacturer included a stainless steel strand in the center of the bundle. The stainless steel strand provided strength, while the silver strands provided high electrical conductivity.

Our chosen flight instrument had been reworked so much that the silver strands in many of the interconnecting wires had broken, leaving only the single stainless steel strand intact. That, of course, could not be permitted for the flight. I did the thing that I thought most reasonable under the circumstances: I plugged in my soldering iron and went to work on reconnecting the entire main wiring harness, containing dozens of individual soldered connections.

Under the operating procedures of even those early times, that kind of rework would not have been attempted that late in the launching process. The launch would have been delayed, the repairs made, and a number of the electrical and environmental tests repeated to make sure that the work had been done properly. In this instance, though, time would not permit the standard procedures because of the inflexible Argus schedule. I felt comfortable in undertaking the rework, since I had personally installed the wiring harnesses in the first place.

The Huntsville engineers, I discovered later, were horrified. While I was soldering away, a number of them quietly retreated to a nearby trailer-workshop to discuss the situation. After a lengthy debate, and in consideration of the extremely tight schedule, they decided to let “that crazy Iowa student” proceed with the repairs. I completed

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the work in short order, and we proceeded with the remaining preparations as though nothing unusual had happened.

The repair worked perfectly.

With the experience that everyone had gained with the earlier Explorer launches, the countdown procedures had become very well established. We even had a written procedure in case the payload instrument should malfunction during the countdown. It spelled out the precise conditions that would call for either a hold or postponement. Interestingly, my copy was hand annotated “hide,” probably indicating that we did not want to reveal anything to the public other than full confidence in success.

The countdown began early in the morning of 26 July. The launch was completely normal, and Explorer IV was successfully in orbit later that day.

The satellite’s initially computed orbit ranged from 164 miles at perigee to 1381 miles at apogee, with an inclination relative to the Earth’s equator of 50.1 degrees. The initial orbital period was 110.1 minutes. Because of the rather low perigee, it decayed from its orbit and reentered the Earth’s atmosphere a little more than a year later.

With its attached final rocket stage, Explorer IV was, like the earlier Explorers, 80 inches in length and 6 inches in diameter. The total weight placed in orbit was 38.43 pounds, of which 18.26 pounds was the instrument, 7.50 pounds was the shell, and 12.67 pounds was the exhausted final rocket stage. The increased payload weight and higher orbital inclination were made possible by an upgrading by JPL of the high-speed rocket stages. [10]

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the NRL engineers checked the transmitter and found problems, and a replacement transmitter was flown from Washington and installed. Flight Payload 1 was chosen as the best-performing instrument.

The launch countdown began at 5:30 PM on 23 August, and ignition occurred early the next morning, but with a hugely disappointing result. The final rocket stage failed to ignite, and Explorer V ended up somewhere at the bottom of the Atlantic Ocean.

The day after the Explorer V launch attempt, I detoured to Huntsville for discus­sions about the IGY Heavy Payload, and two days later, I eagerly rejoined our group in Iowa City.

James Van Allen was a truly remarkable teacher, working in a gentle but persistent way. His most powerful tool was his use of the carefully phrased question. It invariably caused us students to go away and think critically about the issue and to come up with our own solutions. If we made wrong assumptions or arrived at wrong conclusions, he would gently steer us in the right direction.

Many of us have expressed our admiration for Van Allen’s willingness to turn students loose on such important projects and to give us great freedom in carrying them forward. His guidance provided just the right amount of direction to advance our skills and understanding of the work, but at the same time to keep us from getting into too much trouble. Only with later widening experience did I come to appreciate the immensity of the risks he took with us.

Although we all made our individual contributions toward the State University of Iowa Physics Department’s rise to leadership in the new branch of research, it was Van who provided much of the vision, gained a major portion of the outside programmatic and financial support, and had the most to lose if we failed.

CHAPTER 16 • SOME PERSONAL REFLECTIONS 441

I visited with Van only a few weeks before he died, and we talked of many things. One of our topics was the discovery of the Van Allen Radiation Belts.

Van had posed a question to me a few months earlier: “Would we have discovered the radiation belts with Explorer I alone, if we had not had the onboard-recorded data from Explorer III?” We exchanged independent written responses before the visit. In his response, he asked further, “Would we have concluded that our detector on Explorer I was hopelessly erratic and despaired of getting any credible data? Or would we have persisted in reading and compiling the data, recognized the dead time problem, and made the radiation belt discovery? If so, how long would this process have taken?”

Van asserted that we would have organized enough Explorer I data so that we would have discovered the high intensity of geomagnetically trapped energetic particles, but he did not speculate further. My response was that we would have made the discovery, but that it would have taken longer. I further speculated that we would likely still have made the announcement before the Soviets, but posited that the trapped radiation announcement would have been less dramatic and have had less impact on jump­starting an energetic space research and exploration program.

He also asked during our visit, “Do you know that a detailed description of how the proximity fuse worked has never been written?” It is remarkable but typical that, even as he lay in his bed near the end of his life, his writing pad was on his bedside table, and he had begun drafting a paper on that subject.

Van was a truly remarkable person, and I was indeed fortunate to have had him as a mentor and friend

Meredith’s initial detection of the auroral soft radiation in 1953 led to vigorous follow­up work for a more discriminating examination of its latitude dependence, compo­sition, and directional characteristics. In addition to his early work on the balloon in­struments, as described in the preceding section, Frank McDonald joined in the effort to further define the new phenomenon. Over the winter 1953-1954, working with Mel Gottlieb and Bob Ellis, he developed two new rockoon instruments.16 I worked with them during most of May and June 1954 to build a set of flight instruments.

The first new rockoon instrument paired the same type of GM counter that had been used on the 1953 expedition (minimally shielded with 30 mg/cm2 in the counter wall, plus 160 mg/cm2 in the nose cone) with a second identical Geiger counter having additional shielding (150 mg of aluminum and lead). That instrument also included a photoelectric rocket-orientation indicator.

The second payload type was fundamentally new for the rockoons. Derived from the balloon instruments on which McDonald and Webber had been working, it employed a Na-I (thallium-doped) scintillation crystal mounted on a photomultiplier tube. That scintillation detector was mounted below a single thin-walled GM counter located in the nose of the rocket. The Geiger counter pulses gated the output of the scintillation detector. When both were triggered within a very short time, usually by a single particle traversing both of them, the amplitude of the scintillator detector pulse was

CHAPTER 2 • THE EARLY YEARS 37

telemetered. The raw Geiger counter pulse rate was also telemetered. Thus, the instrument was to provide information about particle type, energy, intensity, and direction of arrival.

The SUI 1954 field expedition contingent consisted of Frank McDonald (heading the team) and Bob Ellis. The NRL again fielded a team. They all left from Boston on 15 July on the USN icebreaker USS Atka.17

Two shakedown launch attempts on 16 July due east of Boston were spoiled by rocket ignition problems. So-called redesigned, greatly improved igniters had been shipped with the rockets, but, like the igniters on the 1953 expedition, they failed to fire the rockets at altitude. The team prepared a version of the Jones Igniter so resourcefully worked out during the 1953 expedition. That proved to be completely successful, and it was used throughout the rest of the expedition.

The third rocket in the series, with the improvised Jones Igniter, was launched three days later while they were still en route to their primary area of interest. Although the rocket ignited properly, that flight experienced a partial telemetry system failure and did not produce usable data.

The first fully successful flight (SUI flight 27) occurred off the northern tip of Labrador near 59 degree north geographic latitude, or at about 70 degrees north geomagnetic latitude. That, with 10 other launches, was clustered in and near the heart of the auroral zone during the short five-day period from 21 through 25 July 1954. Seven of those flights reached observational altitudes with operating instruments.

Ellis, Gottlieb, and Meredith reported later on the data from two of the successful flights of the paired GM counters. One of those flights, number 36, dramatically revealed the auroral soft radiation, as shown in Figure 2.7. The effect of the additional shielding of the second GM counter is clearly evident.18

The data from McDonald’s scintillation/GM detectors was, at first, puzzling.19 That question was partly resolved in 1954, and McDonald, Ellis, and Gottlieb reported that, of three successful flights of that instrument, two revealed the soft radiation.

The group’s experience with balloon-, rocket-, and rockoon-launched instruments put us in an excellent position to develop the new satellite instrument. We were well versed in building the types of electronic circuits that would be required, and we had learned how to build them ruggedly enough to withstand the stresses of rocket firing. Nevertheless, designing an instrument for a satellite added new dimensions. In my 26 April 1956 notebook entry, I listed the major problems foreseen in developing the

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Vanguard instrument. Foremost among them were (1) learning how to use transistors, (2) developing the in-orbit data storage system, and (3) miniaturization.7

The transition from the vacuum tubes that we had been using in our balloon and rocket instruments to transistors was essential in order to minimize the instrument’s size, weight, and power demand. I worked hard during the initial few months, and, indeed, throughout the entire developmental period, to build miniaturized circuits that would operate at the required low power levels and still be highly reliable over the expected range of operating conditions.

Before starting work on the satellite project, I had never even seen a transistor, let alone developed a circuit that used one, although I had been following their evolution through the engineering literature out of general curiosity. The very few existing books on transistors were not at all helpful. They focused on a network analysis approach to understanding the basic characteristics of the devices and were not useful in designing actual working circuits. I quickly abandoned any theoretical approach for designing circuits and adopted a much more pragmatic experimental approach. Starting with appropriate circuits from our vacuum tube experience, I substituted transistors, and then varied circuit topologies and component values until I obtained the results that I was seeking. That approach eventually gave me considerable insight into the internal workings of the new devices, and I soon developed the same intuitive familiarity with transistor circuit design that I had enjoyed with vacuum tube electronics.

Admittedly, that first U. S. satellite instrument appears trivially simple by the stan­dards of current massively dense fabrication technologies. Today, all of the Explorer III electronics circuits could be fabricated in one or a few very small silicon chips. But those technologies were not available in the 1950s, and we were pushing the then-available state of the art.

The second major challenge was in devising a suitable device for storing the data during each orbit, and for relaying them rapidly to the ground when the satellite passed over the ground stations. As already mentioned, Van Allen’s proposal for the cosmic ray experiment was such that data recovery over a broad range in geomagnetic latitude was essential. Both his late 1955 and early 1956 cosmic ray proposals focused on the use of networks of ground receiving stations for that purpose. Although he did mention the use of “a magnetic storage drum” in his second Ann Arbor paper dealing with the auroral soft radiation, he did not mention onboard storage in the cosmic ray proposal. That was in spite of the fact that, from the beginning of our discussions in the fall of 1955, he and I had talked about its desirability and some early ideas for achieving it. Certainly, from very early, he strongly favored an approach employing onboard storage because of its vastly greater data coverage, even though we knew that development of the in-flight hardware would be challenging.

Van Allen and I increased our efforts immediately following the Ann Arbor meeting to examine various options for the instrument configuration. We continued to keep

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT 129

both the no on-orbit storage and the data storage options open while I examined the feasibility of an onboard data recorder. By early May, I was convinced that in-orbit storage was technically achievable, and we committed ourselves to that approach.

As events unfolded, both configurations were ultimately employed, with Explorer I being made as simple as possible with no on-orbit storage. It was followed by the unsuccessful Explorer II and the fully successful Explorer III, both of which carried the onboard storage device. The presence of onboard storage in Explorer III proved to be a critical element in interpreting the unexpectedly high counting rates encountered by the pathfinder Explorer I and was, therefore, a major factor in the discovery of the Earth’s radiation belts.

I began my design effort by inventorying known options, including the counting of shaft rotations, accumulating charge on a capacitor, chains of bistable scalers, magnetic matrix (core) storage, dielectric matrix storage, magnetic and dielectric tape recording, magnetic and dielectric drum recording, magnetic wire recording, cathode ray tube storage, and mercury tank storage. The latter two were discarded outright. By 7 May, I had narrowed the viable possibilities to magnetic drum, magnetic tape, ferroelectric matrix, ferromagnetic matrix, and capacitor bank storage. Two days later, I decided to proceed with magnetic drum storage.

The data storage device eventually passed through four major design phases. The first model, Mark I, was the drum recorder. The Mark II, III, and IV models, all based on magnetic tape storage, incorporated a number of progressive improvements. Mark II used Mylar tape and a mechanical centrifugal governor for controlling the playback speed. For Mark III, metal tape, a magnetic field-eddy current speed control mechanism, and an improved tape advancing mechanism were substituted. The final Mark IV design incorporated a further-improved tape-advancing mechanism.

Today the circuitry on a small fraction of a square millimeter of a solid-state memory chip would provide the same functionality as the Explorer III tape recorder. But that was before the age of integrated circuits, and the only practicable approach was to develop an electromechanical device.

The third major challenge was in miniaturization. Because of the extreme constraints in satellite size and weight, we needed a much more compact method of assembling our electronic components than we had used for the vacuum tube circuits in the balloons and rockoons. Single – and dual-layer printed circuit boards were state of the art in 1956—the Naval Research Laboratory (NRL) and the Jet Propulsion Laboratory (JPL) engineers were using them routinely, and they looked promising for our work. However, there were no facilities for producing them in the Iowa City area. I purchased the necessary supplies, set up a trial printed circuit facility, and produced a few boards to check out the techniques.

Their quality was poor. I turned to an alternate process using terminals that were pressed, or swaged, into holes drilled in fiberglass circuit boards. The component

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leads and other interconnecting wires were wound around the heads of the terminals and soldered in place. Although inelegant, that approach proved to be rugged and reliable, and the circuit boards could be assembled wholly within our laboratory by student aides.

The Jet Propulsion Laboratory’s director, William H. Pickering, played a central role in reshaping the organization’s direction at the beginning of the Space Era. Born in New Zealand in 1910, William H. Pickering was attracted to CalTech by an uncle. There, he took his bachelor’s and master’s degrees in electrical engineering. He received his Ph. D. in physics in 1936 and stayed on as a faculty member in electrical engineering. His graduate and postgraduate work put him in touch with the work of CalTech’s Robert A. Millikan and Victor Neher, whose seminal work in cosmic ray research especially caught his interest.

In 1944, he began part-time work at CalTech’s JPL, organizing their electronics efforts to support their guided missile research and development. He became project manager for Corporal, the first operational missile that JPL developed. During Corporal testing at White

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Sands, Pickering became aware of the work of von Braun’s group on the V-2, and the two groups collaborated to launch a series of combined V-2-WAC Corporal two-stage vehicles known as the Bumper-WAC. One of its flights reached a record altitude of 244 miles in February 1949, becoming the first man-made object to reach extraterrestrial space.

During that period, Pickering broadened his interest in scientific research and its special demands on technology, including serving on several national committees that were active in charting upper atmospheric research. He shifted from part-time to full-time work at JPL in 1950. From then on, although retaining the rank of full professor on the campus, the JPL work took most of his attention. He took over as the JPL director in the fall of 1954.

In his discussions with California Institute of Technology president Lee DuBridge, the new director agreed that JPL should begin thinking of a shift away from classified missile development to something that was more compatible with the open research character of university research. The Sergeant missile program had been authorized shortly before Pick­ering’s assumption of the JPL leadership—he and DuBridge agreed that it would be their last army missile program.35

In September 1955, upon returning to Pasadena from Huntsville from the von Braun discussion following the Vanguard decision, Froehlich placed the remaining scaled-Sergeant rockets in a “long-term life test.” It was explained to me after I went to JPL much later, that, although the ABMA and JPL had been instructed from Wash­ington to stop all work on the remaining Jupiter C rockets, they did obtain permission to use them in “technology tests.” The tests were characterized tongue-in-cheek as “placing the spare rockets in storage at normal room temperature and pressure until destroyed.” Through that stratagem, the upper-stage rockets were preserved for later use in the satellite program.

From the time of the discussion at Huntsville in September 1955 through the time of the third RTV flight in September 1957, JPL carried the project responsibility for three major RTV tasks: (1) adaptation of the scaled-Sergeant rockets for that purpose, (2) development of the cluster arrangement to form the upper stages of the vehicle, and (3) development of a telemetry system for relaying flight performance data to the ground.

The first two tasks, adaptation of the scaled-Sergeant rockets and development of the upper stage cluster, required the combined efforts of teams of mechani­cal engineers, materials specialists, and propulsion experts. They configured the rocket’s thrust chamber and developed a suitable ignition mechanism. Under Geoffrey Robillard’s leadership, they loaded and fired enough test rockets to determine the op­timum fuel and chamber configurations and to establish the rocket’s reliability. As for the mechanical configuration of the cluster, under John Small’s leadership, they determined the number of stages required, made the weight analyses, designed the mechanical configuration, and performed mathematical analyses of the structural design and in-flight performance. As already stated, the work was done in such a way that a live fourth stage with its satellite payload could easily be added to the cluster.

CHAPTER 7 • THE U. S. SATELLITE COMPETITION 203

The third JPL area of responsibility was to develop a suitable tracking and data telemetry system to assist in obtaining engineering data from the RTV final stages. That might have been quite simple if the system were designed exclusively for that purpose. Those flights were of short duration, so long-lasting batteries were not nec­essary. The RTV rocket configuration had sufficient weight-carrying capability that more conventional flight components, including vacuum tubes, could have been used. The higher weight-carrying capability also meant that much higher-powered trans­mitters could be used, obviating the need for a supersensitive tracking and telemetry system.

However, from the very beginning, the JPL engineers wanted the system to be usable in a satellite. Initial ideas for what became the future Microlock system had been developed while JPL was designing the Corporal missile. When JPL was brought into the Orbiter program planning by the Huntsville and navy teams in the fall of 1954, the long-range possibilities for such a system became even clearer in their minds, and the Microlock system began to take more tangible form. A look at the Microlock development emphasizes the extent to which it was shaped by their dreams of space flight.

One of the leaders in the Microlock development was a new engineer, Henry L. Richter. He figured prominently in the application of that system to the satellite program and in the preparation of the Jupiter C satellite instruments.

Henry holds a special place in my memory as my primary contact and close friend during the five months that I was at JPL during late 1957 and early 1958.