Completing the first generation

The first generation of spacecraft consisted of relatively simple payloads in which simplicity, reliability, and, in the United States, suitability for small launch rocket weight-lifting capabilities took precedence. Those spacecraft carried a single primary

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scientific instrument, plus, in some cases, one or a few secondary instruments and engineering sensors. Sputnik 1, Explorers I through V, Vanguards I and II, and Pioneers 3 and 4 were clearly in this category.

Vanguard II The Vanguard program continued to move forward. After some addi­tional disappointing launch failures, a successful launch on 17 February 1959 placed 21 pound Vanguard II into a durable orbit. It contained a single active scientific in­strument array—a pair of optical cloud cover scanners provided by the U. S. Army Signal Corps Research and Development Laboratory at Monmouth, New Jersey, un­der William (Bill) G. Stroud’s leadership. It depended on the satellite’s spin as it advanced in its orbit to trace a raster pattern that could be processed to provide a pic­ture of the Earth. Although the instrument operated perfectly throughout its operating lifetime, its success was marred by the fact that the satellite was nudged following separation from its third rocket stage, causing the satellite to wobble. Thus, the cloud cover instrument traced a much more complex path over the Earth’s surface, making it next to impossible to assemble coherent pictures.

Vanguard II also supported a secondary objective. Its clean, spherical shape, com­bined with the Vanguard tracking and orbit determination capabilities, permitted accurate measurements of satellite drag and therefore upper atmospheric density as a function of altitude, latitude, season, and solar activity. Among other things, Vanguard II showed that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated in the region where the Earth’s upper atmosphere gradually fades into space.

SCORE The SCORE project initiated the field of satellite radio communications. The acronym stood for Signal Communication by Orbiting Relay Equipment. It was a program supported by the Advanced Research Projects Agency, with the payload supplied by the U. S. Army Research and Development Laboratory at Fort Monmouth, New Jersey. The payload consisted of a communications repeater, augmented by an onboard tape recorder that was capable of recording and delayed playback of voice messages. Launched on 18 December 1958, it broadcast the famous “Christmas mes­sage” by U. S. President Dwight D. Eisenhower. With an operating lifetime of 12 days, the communications objectives were completely met, including the demonstration of both real-time and delayed transmission from one ground station to another.

Probably more significantly, it met a major U. S. geopolitical objective. Launched only 19 days after the first fully successful test flight of an Atlas ICBM, and result­ing in the placement of the complete 8700 pound Atlas main stage and its payload in orbit, it represented an impressive new U. S. launch capability. Although billed as a peaceful scientific mission, SCORE demonstrated for the entire world that the United States was also finally capable of delivering nuclear payloads anywhere on Earth.

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The similarities between the SCORE and the earlier USSR Sputnik 1 achievements are striking. Sputnik 1 was launched only 44 days after the Soviets achieved their first fully successful test flight of an ICBM. Its declared scientific objective was, also, communications. But its main purpose was to demonstrate to the world a long-range strategic rocket launching capability. Thus, the two projects had similar objectives, and both placed impressive weights in orbit—over 14,000 pounds (rocket plus detached payload) for Sputnik and 8700 pounds (rocket plus integrated payload) for SCORE. In terms of implied nuclear capabilities, the two were about equal. The U. S. nuclear devices were physically smaller and lighter than their USSR counterparts, and could, therefore, be launched with smaller launch vehicles.

The main distinction between the two programs was that the Soviets were able to demonstrate their capability fully 14 months before the United States was able to do so.

The race to the Moon As soon as the first satellite was launched, mankind’s ev­erlasting fascination with the Moon kicked in. In the thoughts of some, orbiting the Earth was only a prelude to the much more exciting prospect of flight to the Moon. Both the Soviets and the Americans quickly set their sights on that goal.

Lunar missions introduced a new set of technical challenges. Not only must the rockets push the spacecraft to an initial speed of about 18,000 miles per hour to get them into Earth orbit, but they must speed beyond that to an initial velocity of about 25,000 miles per hour to escape most of the Earth’s gravitational pull and reach the neighborhood of the Moon. In addition, they require far more accuracy in initial aiming and in on-course trajectory control. Communication and tracking also presented new challenges because of the much greater transmission distances.

Information about first Soviet attempts at flights to the Moon is sparse because of their initial practice of outright denial of unsuccessful attempts. Information published in later years indicates that the Soviet program for lunar flights was actually formally approved as early as March 1958. Although the Miami Herald reported on 4 August 1958 that the Soviets had tried and failed to launch a rocket to the moon on 1 May,1 no other evidence can be found that they attempted a deep space launch that early. The first substantiated Moon attempt was made by the Soviets on 25 June 1958 with an SL-3 (A-1) rocket (derived from the SL-1 [A] rocket that had launched the first three Sputniks). That attempt failed.2

The U. S. Thor-Able 1 mission (sometimes referred to as Pioneer 0) was launched on 17 August 1958. The vehicle was a Thor Intermediate-Range Ballistic Missile, topped by a modified Vanguard third-stage solid rocket. On that attempt, the first-stage rocket exploded 77 seconds after liftoff, probably due to a failed turbopump bearing.

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I was at Cape Canaveral preparing for our Explorer V launch at that time and witnessed the Thor-Able attempt. My journal reads:

Well, the moon attempt was a failure. After 77 seconds it blew. I saw it from Hangar S, five miles away, Bill Whelpley from one half mile (RIG [Radio Inertial Guidance] site). Bill said after it climbed 300 or 400 feet, a small fireball appeared for three seconds about the diameter of the second stage, at the point where stages one and two join. I didn’t see this from Hangar S, and to me it appeared to climb normally until 77 seconds, when two white puffs of smoke were seen in quick succession. Following the first one, several small pieces were thrown off.

It looked like it might have been an engine explosion.

The beaches were lined for the shot. It is surely a shame it failed, because now USSR will have another chance to beat us.3

The instrument complement on this 83 pound payload consisted of a nonlinear search coil magnetometer provided by the Space Technology Laboratories Inc. (STL) to measure the Earth’s magnetic field and determine whether the Moon had such a field. The STL also provided a microphone assembly to detect micrometeorites. The Naval Ordinance Test Station provided an image-scanning infrared television system to take low-resolution images as the craft approached the Moon.

Thor-Able 1 marked the entry of an important new organization on the U. S. space scene. In September 1953, Simon Ramo and Dean Wooldridge had formed the Ramo-Wooldridge Corporation to work directly with the U. S. Air Force on problems of system engineering, including development of the Atlas Intercontinental Ballistic Missile (ICBM). Adolf (Dolf) Thiel, one of the original group of German rocket experts brought to the United States following World War II, joined them in 1955. The Ramo-Wooldridge Corporation was renamed STL in December 1958. That orga­nization (later spun off to form Thompson Ramo Wooldridge and, later still, simply TRW) was responsible for a long string of space missions during the 1950s, 1960s, and 1970s, of which Thor-Able 1 was the first. TRW has remained a prolific contractor for NASA and military space efforts.

The Soviets followed with another failed attempt on 23 September. That Luna 1958A launch vehicle structure failed after 92 seconds of flight, and the vehicle exploded. It is believed that that spacecraft weighed about 800 pounds and carried an instrument complement somewhat like the later successful Luna 1.4

The United States achieved a modest space first by sending a craft well beyond low Earth orbit for the first time. Under the banner of the newly formed NASA, the Air Force launched Pioneer 1 on 11 October 1958, again with their Thor-Able launcher (Figure 14.1). Although Pioneer 1 failed to achieve its primary objective of reaching the Moon due to a programming error in the upper stage, it did travel out to a distance of about 70,000 miles from the Earth.

CHAPTER 14 • EXTENDING THE TOEHOLD IN SPACE FIGURE 14.1 Artist’s drawing of the Pioneer 1 spacecraft, pictured with its final-stage rockets firing at the left. The spacecraft was about 30 inches in diameter and length and weighed about 83 pounds. (Courtesy of U. S. Air Force.)

Pioneer 1 looked much like the earlier Pioneer 0, except for the addition of one new instrument. Time had permitted the development and addition of a chamber to measure total ionization as the probe moved through the radiation zone.

The ionization chamber experiment was a cooperative effort between scientists at STL and Carl McIlwain at Iowa. The STL experimenters, Alan (Al) Rosen, Charles (Chuck) P. Sonett, and Paul J. Coleman Jr., carried the primary responsibility for preparing the instrument, while Carl specified the characteristics of the chamber and participated in its preparation, calibration, and data interpretation.

The chamber, produced by Nicholas Anton and his engineers at the Anton Elec­tronics Laboratories under Carl’s guidance, consisted of an aluminum-walled vessel with a volume of about 2.5 cubic inches. It was initially filled with pure argon to a pressure of about 193 pounds per square inch. The design of the electronics that followed the chamber was based on the circuit that Carl had developed for the scintillation counters in Explorers IV and V Its most noteworthy feature was a log­arithmic response that provided measurements over a huge dynamic range so that it could determine the radiation dosage both in the midst of, and outside, the radiation zone.

The chambers were carefully calibrated before launch with a Cobalt-60 radioactive source at the Radiology Department of the University of California, Los Angeles

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Medical Center. It was determined later, however, that the Pioneer 1 flight chamber had had a slow leak, and that by the time of the flight, the pressure had dropped to about 22 pounds per square inch, with a concomitant reduction in its sensitivity. A correction for that change, as well as corrections for other instrumental errors and temperature effects, was used for all work on the data.

For the first 17 minutes of the Pioneer 1 flight, the telemetering system was dedicated to monitoring vehicle performance. Then the scientific instruments were turned on so that useful research data began when the spacecraft was about 2200 miles from the Earth’s surface, and at about 32 degrees north latitude and 30 degrees west longitude. Data recovery continued until the spacecraft reached about 22,400 miles height at about 6 degrees north latitude and 0 degrees longitude. Unfortunately, scientific data were not recovered during the rest of the flight, including the return trajectory.

Analysis of the Pioneer 1 ion chamber data provided several significant results. (1) It verified by direct measurement the extent of the region of high-intensity radiation that had been inferred earlier from the lower-altitude Explorer I, III, and IV data. (2) Throughout the altitude range from about 2500 miles to 15,000 miles from the Earth’s surface (to 4.8 Earth radii from the Earth’s center), the level of ionizing radiation remained in excess of two roentgens per hour. (3) When the spacecraft was outward bound at about 20 degrees north latitude, peaks of the radiation belt intensity occurred at heights of about 6600 and 7400 miles (2.6 and 3.4 Earth radii from the Earth center). The maximum level of radiation at those locations was about 10 roentgens per hour. Results from later flights showed that the second peak was accurately correlated with the center of the outer radiation belt.5

The Soviets tried again with Luna B on 12 October 1958, just a few hours after the Pioneer 1 launch. Although details of its payload are also not known, it is presumed that it was essentially the same as Luna 1958A. The rocket exploded 104 seconds into the flight.

The United States tried again on 8 November with Pioneer 2, a craft that was gen­erally similar to Pioneer 1, but with the addition of a proportional counter telescope by John Simpson’s group at the University of Chicago. Another rocket failure—the third stage separated from the second and failed to ignite, and the spacecraft fell back to Earth over northwest Africa. Carl McIlwain’s ion chamber did, however, provide useful information. Correlation with the Explorer IV data showed that the counting rate at about 1000 miles height was relatively independent of longitude, but strongly dependent on geomagnetic latitude, thus supporting the model of the trapping region that had evolved by that time. In addition, use of the ion chamber data and the data from the proportional counter telescope showed that the trapped

CHAPTER 14 • EXTENDING THE TOEHOLD IN SPACE FIGURE 14.2 Louis Frank (left) and James Van Allen in the process of calibrating the GM coun­ters on the Pioneer 3 flight instrument. An X-ray source is behind the white circle under Van Allen’s right elbow. The payload was moved along the rails to vary its distance from the source. (Courtesy of the Department of Physics and Astronomy Van Allen Collection, The University of Iowa, Iowa City, Iowa.)

particles were a combination of electrons and protons, rather than high-energy elec­trons alone.

And another try by the Soviets on 4 December: Luna C. The payload, too, is presumed to have been a copy of Lunas A and B. The rocket exploded after 245 seconds of flight.

A very productive partial success was finally achieved two days later with the NASA – Army launch of 13 pound Pioneer 3 on 6 December 1958. It was the first attempt with the Juno II launch vehicle developed by the Huntsville group. That vehicle substituted a larger Jupiter rocket for the Redstone booster that had been used in the earlier Jupiter C-Juno I configuration for Explorers I, II, III, IV, and V

The form of the payload was a cone attached to a short cylindrical section, with an overall height of about 24 inches and a cylinder diameter of about 10 inches, as seen in Figure 14.2. It was developed primarily by the Jet Propulsion Laboratory (JPL) with two main objectives. One was to demonstrate a close flyby of the Moon. Two

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photocells were set to trigger by the light of the Moon when the probe was about 20,000 miles distant, to serve as tangible proof of the accomplishment.

The second objective was to make radiation measurements throughout the flight to further substantiate and map the newly discovered high-intensity radiation around the Earth. Van Allen served as the principal investigator for that experiment, which employed a pair of Geiger-Miiller (GM) counters sized to measure the full intensity of the high-intensity radiation. He, aided by rising undergraduate student Louis (Lou) Frank, calibrated the payload’s detectors in the Iowa laboratory, using a variety of radiation sources, as shown in Figure 14.2.

That attempt with the new launcher also failed to reach the Moon. Early depletion of propellant caused the first-stage engine to shut down 3.7 seconds early. Although that prevented the vehicle from reaching escape velocity, the craft did climb to a height of over 66,000 miles before falling back to Earth.

Although the flight fell short of its first objective, it met the second one splendidly. In fact, its failure to reach escape velocity, with the instrument falling back to Earth, provided a second pass through the region of high-intensity radiation. While the outbound trajectory passed through the heart of what came to be referred to as the outer belt, it only grazed the core of the inner belt. But the return trajectory passed through the central cores of both belts and proved beyond any possible doubt the presence of two distinctly different regions, as seen later in Figure 14.4.6

The two GM counters in Pioneer 3 had distinctly different characteristics. The first was an Anton type 302 counter similar to the one used in Explorer IV It was followed by a very wide dynamic range scaler and filter arrangement first suggested by this author in April 1958.7 Although the Explorer IV schedule had been too tight for me to develop that circuit at the time, JPL engineers developed it for Pioneers 3 and 4. It had the feature that multiple scaling factors of 512, 8192, and 131,072 could be telemetered over a single channel.8 That wide dynamic range permitted the instrument to track a variation of over 2000 to 1 in counting rate during its transit through the region of high-intensity radiation.

The second GM counter was a much smaller one, specially built for this mission by the Anton Electronic Laboratories as their type 213. Its effective size was about one-tenth that of the 302 counter, and its primary purpose in Pioneer 3 was to serve as an ambiguity resolver for the 302 counter.

The Soviets finally approached the Moon on 2 January 1959 in spectacular fashion. Using a redesigned R-7 launch vehicle, their spacecraft (variously referred to as the First Cosmic Rocket, Mechta, Dream, Luna 1, or Lunik 1) was intended to impact the Moon, although that was not admitted by the Soviets until much later. A malfunction in the ground-based control system caused an error in the rocket’s

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burn time. Although missing its primary objective, it passed within 3700 miles of the Moon’s surface and became the first man-made object to escape from Earth orbit to take up its own orbit around the Sun. That orbit lies between the orbits of Earth and Mars, where, barring collision with some other object, it will dwell for the ages to come.

Luna 1, weighing nearly 800 pounds, carried an impressive array of instruments. They included GM counters, scintillation counters, a Cerenkov detector, a magne­tometer, a micrometeorite detector, and traps for detecting low energy protons. The data provided new information on the Earth’s trapped radiation, showed that the Moon did not have a substantial magnetic field, and made the first direct observations and measurements of the solar wind, a strong flow of ionized plasma emanating from the Sun.

While outbound, at a distance of about 74,000 miles from the Earth, the spacecraft released a cloud of sodium gas, creating an orange vapor trail. That cloud was easily visible from the neighborhood of the Indian Ocean, and accomplished two purposes. It provided a visible confirmation of the vehicle’s trajectory and served as an experiment on the behavior of gas in the vacuum of outer space.

The spacecraft also contained a number of medallions for dispersal around the point of intended lunar impact to perpetually mark the feat.

The U. S. Pioneer 4, launched on 3 March 1959, followed Luna 1 to the general neighborhood of the Moon. It passed about 37,000 miles from the Moon and entered its own independent orbit around the Sun. The records generally refer to it as a successful mission, even if it did not pass close enough to the Moon to trigger its photoelectric sensor. The significance of the accomplishment suffered somewhat by being greatly overshadowed by the Luna 1 flight two months earlier. The Pioneer 4 spacecraft weighed only one-sixtieth the weight of Luna 1 and passed the Moon at about 10 times the distance.

The Pioneer 4 spacecraft was similar to Pioneer 3—its only difference was the inclusion of additional shielding around the type 213 GM counter to provide bet­ter information about the penetrating ability of the charged particles. Van Allen’s set of objectives for that flight included a resurvey of the intensity structure of the Earth’s radiation zones, an examination of temporal changes that might have oc­curred since the Pioneer 3 flight, a rough further determination of the composition and spectral character of the radiation, and a look in interplanetary space for re­gions of plasma that might contain particles energetic enough to trigger the GM counters.

One important additional contribution of the Pioneer flights was to shake down and quantify the performance of the Microlock tracking and telemetry system developed

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by JPL. That system, using the 85 foot antenna dish at Goldstone Lake in California, turned out to be capable of recovering the signal from the miniscule transmitter on the 13 pound Pioneer 4 to a distance of over 400,000 miles. Even there, transmission apparently stopped only because of the expected exhaustion of the probe’s batteries. That telemetry system was a precursor to the wonderful capability that JPL has steadily improved and used over the years for tracking and recovering the data from a long progression of deep space excursions.

The Pioneer 4 scientific productivity was marred slightly by two factors. The largest of the three scaling factor taps for the 302 GM counter was lost due, apparently, to a major physical shock during the burning of one of the rockets. The performance of the other two taps was normal. Second, telemetry data were lost for about half a minute, just as the probe was passing through the core of the outer radiation zone, that is, between about 2.5 and 4.5 Earth radii.

The Soviets made another attempt to impact the Moon on 18 June 1959, but the vehicle’s guidance system failed.

Finally, following a 12 September launch, the Soviets succeeded in making the first physical contact with the Moon. After a 33.5 hour flight, Luna 2 impacted at a point west of Mare Serenitatis. To mark the event, two small spheres with their surfaces covered with stainless steel pentagonal elements were ejected and exploded shortly before spacecraft impact, to disperse the pendants around the impact site. The pendants were emblazoned with the USSR Coat of Arms and the Cyrillic letters CCCP. Some 30 minutes after the spacecraft impacted, the third rocket stage also struck the Moon. Another device on that rocket—a capsule filled with liquid and with suitably engraved aluminum strips—marked its impact site.

Luna 2, shown in Figure 14.3, weighed an impressive 860 pounds. It included six GM counters, three scintillation counters, two Cerenkov detectors, a magnetometer, micrometeorite detectors, four low-energy ion traps, and the equipment for generating a sodium cloud. As in the case of Luna 1, a bright orange sodium cloud was produced en route.

Several of the scientific instruments were reconfigured from the Luna 1 arrange­ment to take advantage of new scientific information then accumulating. The three – axis fluxgate magnetometer’s dynamic range was adjusted to provide greater measure­ment accuracy as it approached the Moon. Counter sizes and shielding were adjusted. The ion traps were arranged in a different configuration.

Luna 2 provided a wealth of new information on the particles and fields around the Earth, in interplanetary space, and near the Moon.9 One of its most notable achievements was the confirmation and further delineation of the solar wind by the ion traps designed by Konstantin Gringauz. Its magnetometer placed a very low limit on

CHAPTER 14 • EXTENDING THE TOEHOLD IN SPACE FIGURE 14.3 Luna 2, with its magnetometer sensor on the upper boom and four antenna rods clearly visible. Various scientific sensors are arrayed around the outer surface. (Courtesy of the National Aeronautics and Space Administration.)

the strength of the magnetic field near the lunar surface—it is essentially nonexistent. The radiation detectors confirmed the broad structure of the outer radiation belt, as it had been revealed by Pioneer 3. The diversity of detectors added valuable new information about the composition of the outer belt.

On 4 October 1959, the second anniversary of their first Sputnik launch, the Soviets achieved another spectacular first with Luna 3. It took the first pictures of the back side of the Moon.

The Luna 3 craft employed a completely new design. In addition to its primary moon-imaging instruments, it included scientific instruments for measuring cosmic rays, other charged particles, and micrometeorites. Unfortunately, very few results from those auxiliary instruments can be found—the pictures of the Moon’s far side completely dominated the postflight public and scientific releases. The fact that the flight did not contribute substantially to the early radiation belt studies is also likely due to its being launched over the North Pole, so its trajectory carried it north of most of the Earth’s radiation belt structure.

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With the aggregation of data from Sputniks 2 and 3, Explorers I, III, IV, and 6, Lunas 1 and 2, and Pioneers 1,3, and 4, a quite clear picture of the Earth’s radiation belts was emerging. The collective set of lunar probes during the closing years of the 1950s was especially important in delineating the belts’ overall structure and composition. Figure 14.4 shows the approximate relationship between the trajectories of deep space probes Pioneers 1,3, and 4 and Lunas 1 and 2 and the locations of the two belts.