''''

FROM A-4 TO EXPLORERI

Seventh International History of Astronautics Symposium 24th International Astronautical Congress Baku, USSR October 8, 1973

Memoir Paper by '. 'J • Dr. Kurt H. Debus Director John F. Kennedy Space Center National Aeronautics and Sp~ce Administration EXPLORERI

Even as the successful flight te::ting of continued, and while Army pursu ed studies of longer-range missiles, the deYelopment team opened discussion:: ,\ith other Government and scientifi c group:: conc erning the :;ame goal we reached for at Peenemuende onlv to be sidetrack ed for a decade bv the a"ful realitv of war. " · In June, 195-1-Dr. von Braun ,i:;ited the :\aval Research Office in "\\"ashington , D.C. where he adYanced a proposal to utilize the Red:;tone as boo ster for a four-stage configuration that could carry a fo-e-pound into circular orbit 300 kilometers (186 miles) abo,-e Earth. He recommended small. solid motors known as Loki for the upper stages since they were arnilable and could supply the required thrust. With the help of the :\a,-y Office and the Jet Propulsion Laboratory of the California Institute of Techno logy. a joint proposal was developed titl ed "A \lin imum Satellite Yehicle Ba;,ed r pon Compon ents Available from \Lissile Development of the Army Ordnanc e Corps." The document was trans mitted to the Department of Defense January 20, 1955. Five days later. President Dwight D. Eisenhower announced that the United States would launch a small Earth satellite a:: a contribution to the Inter­ national Geophysical Year. But the joint Army-JPL-Naval Research Project was not selecte d. Inst ead. the choice went to the Naval Re::earch Laboratory's project which would utilize the Yiking rocket and new stages to carry an eight-pound, spherical orbiter. Our satellite hopes were put aside. However, th e har dware and the conce pt could be usefully applied for other pu rp oses. The staging idea and study work performe d by ABMA and the Jet Propulsio n Labor atory for "Pro ject Orbiter" became the basis for the Jupite r Composit e Reentry Test Vehicle, or Jupi ter C, which I mentioned earlier. This was the carrier to test th e ablative type, fiberglass nose con e adopt ed for the Jupit er IRBM missile. You will recall that I reported thre e Jupiter C launches from Cape Canaveral in 1956 and 1957, the last of which demon strat ed that the scale model con e survived reentry heating of 2000 degrees Fahrenheit. The same configuration, with the addition of a fourth stage, had a satellite capability. But with the successful 1957 test, th e remaining Jupiter C vehicles were placed in storag e. The achieved a dramati c "first" October 4, .1957, by placing in orbit. This technological feat had profound impact within the United States. As one possible consequence the

42 tER I Department of Defen:,e instructed AB\IA to prepare for a satellite launch attempt but to stand by awaiting an effort by the Yanguard Project. Early the next month the t:3:3R launched an e,-en heaYier spacecraft "ith the dog. Laika. as passenger. On '.',/owmber 8, �sting of Redstone continued, 195 7'. Defense transmitted specific instrnctions to the Agency to of longer-range missiles, the modify two Jupiter C ,-ehicles and attempt to launch a satellite by ,ns \\ith other Government and �larch. 1958. The task was accomplished 8-1 days later. (Fi 1re 20) '8.rne goal we reached for at [!t rd for a decade bv the a,\ful

ited the :\aval Research Office meed a proposal to utilize the configuration that could carry bit 300 kilometers (186 miles) ll. wlid motors known as Loki a,-ailable and could supply the the :\an- Office and the Jet •rnia Institute of Teclmology. '·A \linimum Satellite Vehicle from \lissile Development of document was transmitted to - 20, 1955. Five days later. ounced that the United States as a contribution to the Inter­ int Armv-JPL-Naval Research the choi�e went to the '.\aYal >ject which would utilize the rry an eight-pound, spherical

. However, the hardware and FIGURE 20 ed for other purposes. The t nder heavy pressure, the Yanguard team tried to launch med bv ABMA and the Jet December 8, 1957. The vehicle broke up on the pad. We were )rbiter'' became the basis for ehicle, or Jupiter C, which I then negotiating with the Atlantic \fissile Range for a launch ier to test the ablative type, opportunity January 29, 1958. RS 29, as the booster was identi­ Jupiter IRBM missile. You fied, was taken out of storage. It had been static tested the last �iter C launches from Cape week of October, 1956. of which demonstrated that As previously mentioned in connection with the Jupiter pro­ ry heating of 2000 degrees ject, this version of Redstone carried longer propellant tanks for with the addition of a fourth Hydyne, which yielded 15 percent higher than rith the successful 1957 test, alcohol, and liquid oxygen. These changes boosted Redstone's >laced in storage. thrust from the nominal 334,000 to 370,000 newtons (75,000 to 83,000 pounds) and extended burning time from 121 to 155 1tic "first" October 4, ,1957, seconds. In tum, that required adding another hydrogen pe:roxide mological feat had profound tank to keep the turbo pump operating longer. The elongated ne possible consequence the booster was made possible because the upper Jupiter C high speed

43 ,,tages weighed much less th�n the 3.130 kilogram:3 (6,900 pounds) stages to the booster. The bolts were warhead of the tactical Redstone. released the springs which imparted a The booster was 13.87 meters (-15.52 feet) long with an instru­ cmps (2.6 fps) to the compartment a.i ment compartment 3.17 meters (10.39 feet) in length. The spin disconnect couplings simultaneously n cluster was 3.69 meters (12.12 feet) long so that overall, the between the compartment and first stag, vehicle measured 20. 7-1 meters (68.03 feet) and had a diameter of The stainless steel compartment sh 178 centimeters (5 feet. 10 inches). Liftoff weight was 28.834 num oxide stripes which served as 1 kilograms (63,568 pounds). At booster cutoff, 990 kilometers Doppler tracking, and radio c�mm�d. (535 nautical miles) from the pad. the upper portion separated '.'lo access hatch was proVIded m th from the first stage weighed -1.573 kilograms (10.082 pounds). entire outer shell had to be removed to The second stage cut off at 2,222 kilometers (1,200 nautical same difficultY in access arrangement, miles) out while the third stage increa:,ed the range to 2.895 kilo­ was to crop up again many times ?�er meters (1,563 nautical miles). (Figure 21) acceptable in a quick response militar project one could accept. such penal�· pounds of metal in the mterest of me The attitude control system had to partment and upper stages exac�y hori Each of the air nozzles could deliver ma of 22 newtons (five pounds). A sm sprocket wheel which regulated the wheel engaged the teeth of a push-pull 1 As it moved right or left, more or le! Th.is afforded proportional control wh of one-tenth degree in rocking and otl How to make th.is control system tions was one of the most difficult pri vacuum, ewn at \·ery low rates of a.ii supersonic. Th.is tended to cause an S­ AB�lA �lechanical Laboratory found curve. Four of the double nozzle air the instrument compartment, two f, maneuvers. Roll control signals were J in the form of differential signals. Directly above the control device ta.ining the· second and third stages an� the satellite. The second stage conSI FIGURE 21 down Sergeant solid propellant rock( were three more of these rockets CODI Atop the tank section was the compartment which housed fourth stage motor had a slightly diffe guidance and control equipment for the booster and a spatial The tub, fabricated in the ABMA attitude control system which aligned the compartment and for­ grooved bosses top and bottom to su ward stages horizontally at apex of the trajectory. Air nozzles second stage cluster. Th.is provided integral to the attitude control system were spaced around the second stage ring could make lateral 1 bottom of the compartment. Six explosive bolts, each surrounded out contacting the tub shell,. The by a preloaded coil spring joined the compartment and upper third stage clearance relative to th

44 45 10 pounds) stages to the booster. The bolts were triggered electrically and released the springs which imparted a velocity increment of 79 cmps (2.6 fps) to the compartment and forward stages. Quick an instru­ disconnect couplings simultaneously released cabling and tubing The spin between the compartment and first stage. ·erall, the ameter of The stainless steel compartment shell was coated with alumi­ � �8.834 num oxide stripes which served as antennas for telemetering, ilometers Doppler tracking, and radio command. ;eparated �o acce� hatch was provided in the compartment, hence the pounds). entire outer shell had to be removed to reach the equipment. The nautical same difficulty in access arrangements for checkout and testing 895 kilo- was to crop up again many times over the years. It would be un­ acceptable in a quick response military rocket, but in a research project one could accept such penalty in order to &ffe additional pounds of metal in the interest of increasing payload capability. The attih1de control system had to align the instrument com­ partment and upper stages exactly horizontal ,\;th Earth's surface. Each of the air nozzles could deliver maximum thrust. right or left, of 22 newtons (five pounds). A small electric motor drove a sprocket wheel which regulated the air flow. The cogs of the wheel engaged the teeth of a push-pull needle driYen by the motor. As it mowd right or left, more or less air entered either nozzle. This afforded proportional control which operated to an accuracy of one-tenth degree in rocking and other analog pre-flight testing. How.. to make this control system linear under ,·acuum condi­ tions was one of the most difficult problems we encountered. In vacuum, even at very low rates of air flow, the result would be supersonic. This tended to causean S-shaped response curve. The AB�IA .'.\lechanical Laboratory found a way to straighten out the curve. Four of the double nozzle air flow units were attached to the instrument compartment, two for pitch and two for yaw maneuvers. Roll control signals were fed to all four electromotors in the form of differential signals. Directlv above the control devices sat an aluminum tub con­ taining the· second and third stages and the fourth stage which was the satellite. The second stage consisted of a ring of 11 scaled down Sergeant solid propellant rockets. Nested within the ring were three more of these rockets comprising the third stage. The housed fourth stage motor had a slightly different propellant. (Figure 22) spatial The tub, fabricated in the ABMA shops, had matching sets of nd for- grooved bos...;;es top and bottom to support and guide lugs on the 10zzles second stage cluster. This provided a zero length support. The nd the second stage ring could make lateral moves of sevet"al inches: with­ iunded out contacting the tub shell,. The same arrangement apphed to upper third stage clearance relative to the second stage. Finally, the

45 FIGURE 22 fourth 5tage "ith the satellite attached to its front bulkhead rested in a coincal holder attached to the forward end of the third 5tacre. The Jet Propul:;:ion Laboratory packaged the5e stage5 and the satel-"' lite. A cortical stool 5Upported two heavy ball bearings which allowed the tub to 5pin. Two electric motors installed under the stool turned the tub by means of sprocket type rubber belts similar to those employed in motorcycles. _-\ spin test facility was built to check out the tub and its stages for static and dynamic balance. During the te5t electric motors droYe the tub which was encased in a cage suspended on four rods within a frame. Anv mass imbalance caused the inner cage to vibrate within the frame. The amplitude and pattern of ,ibration could be measured by stroboscope which pinpointed locations where balance weights should be attached. The same technique is used in industry to balance gyros and fly wheels. Late in countdown, the tub would be spun up to 550 revolu­ tions per minute. Seventy seconds after liftoff, a governor con­ trolled by tape program inside the instrument compartment changed the regulator setting from 550 to 650 rpm. At ll5 seconds of flight the rate increased to 750 rpm: This acceleration was calculated to prevent resonance between spm frequency of the high speed stages and the bending frequency of the Redstone booster which became lighter as propellant was consumed. The maximum spin rate of 750 rpm was attained 20 seconds prior to propellant cutoff and did not change during the coast to apex. It was essential to maintain that rate when the second stage fired.

46 Another factor had to be considered. The constant spin rate was governor-controlled and this imposed rnrying loads on the electric motors. These loads exerted a reaction torque on the instrument compartment attached to the tub. In coast flight the torqu e had to be compensated by air nozzles of the attitude con­ trol system. Without this damp ening, the compartment would acquir e a spin with resulting gimbal Jock and spilling of the gyro­ scopes. So there had to be sufficient thrust in the air nozzle system to cope with these forces. The attitud e control system must tilt the spinning cluster and instrument compartment, e5sentially a non-rotating mass with a large gyro on its nose. During tilting , the gyro would cause pre­ cession forces. In order to tilt in the pitch direction. therefore, air was expelled out of the nozzles which pointed in the yaw direction. Thus the preces5ion force was applied to tilt in the pitch direction. Incidentally, this was worked out in analog sim­ ulation. \lounted on top of the second stage was a conical structure that contained a timer and batteries for igniting the third and fourth stages as well as supporting the fourth stage motor. The motor was identical in configuration with the other solid propellant stages, but used a propellant of improved performance with a nozzle exit diameter a little smaller to allow adequate launch clearance. The newer type propellant placed the lowest require­ ment on its physical properties because it spun on its own axis and kept radial loads to a minimum. The stage was 117 centimeters ( 46 inches) long with diameter of 15 centimeters (six inches). The satellite was rigidly attached to the bulkhead of this motor through an insulating ring which formed an antenna gap for one of two radio transmitters. The second transmitter operated across a similar gap between the cylindrical port and nose cone of the satellite. After burnout the empty stage weighed 5. 75 kilograms (12.67 pounds) while the instrument compartment, 86 centimeters (34 inches) long, weighed 8.22 kilograms (18.13 pounds). Hence the total weight in orbit was 13.97 kilograms (30.80 pounds). Josef Boehm of ABMA had designed the cylindrical satellite several years earlier. JPL packed the instruments. Dr. William H. Pickering, the JPL Director, represented the project as official interface with the National Academy of Sciences which supervised U.S. participation in the International Geophysical Year. The cylindrical shape was not suited to some Vanguard Project experi­ ments designed for a spherical orbiter. But there was room for the cosmic radiation experiment of Dr. of the State University of Iowa, who built his equipment around the Geiger­ Mueller counter. The Air Force Cambridge Research Center pro-

47 vided ano ther experiment designed to measure micrometeroid impacts . During the planning for the ill-fated Project Orbiter, ABMA had developed computer programs which were now brought into play to me.u,-ure atmospher ic densities, the oblateness of Earth and high altitude ionization. The collection of this data relied, in part, upon the Vanguard tracking network which supported the project. JPL treated the exterior of the satellite so that heat absorbed from solar radiation and reflected from Earth, plus heat generated within the spacecraft would balance heat radiated by the satellite to space. This maintained temperature ranges within the payload in which electronic components could function. SensitiYe com­ ponents were also thermally insulated. As it deYeloped, the temperature ranged between 43 and 104 degrees Fahrenheit. Two minimal weight transistorized radio transmitters were carried in the spacecraft. The low power device radiated lOmw while the other radiated 60mw. The latter signal could be heard by sensitive amateur receivers but the low power transmission could be tracked only by the more sophisticated, narrow band microlock and minitrack receivers. In addition to pro,iding a tracking signal, which was the primary function, the transmitters also telemetered scientific data including the temperature mea­ surements, cosmic ray intensities and micrometeroid impacts. (Figure 23)

FIGURE 23

48 It is necessary to explain the circumstances surrounding the launch in order to justify some rather unusual arrangements. The United States suffered a blow to national pride, at very least, by the stunning demonstration of Soviet competence. The subsequent Vanguard failure served to heighten the almost hysterical reaction in some quarters. Vanguard, of course. later succeeded in placing several in orbit. The adverse response was all the more j severe because Vanguard had been conducted as an "open" pro­ I gram with showers of publicity. So it was decided at the highest levels that Army would avoid any buildup of interest and expecta­ tionin connection with the launch. Resident newsmen in the Cape area were briefed bv the Air Force Commander on this and other launches on their p�omise not to relea_� the information until and if a missile engine was ignited. No fire. no story. But when fire appeared they were free to report what the�· saw from a vantage point inside the Cape or what they were told by a briefing officer or other source. "\re took extraordinary precautions. The Redstone booster arri,,ed by C-12-1 aircraft from Hunb,ille December 20, 1957 and was kept under guard in a Patrick Air Force Ba_;ae hangar during inspection and checkout. The JPL upper stages had been spin tested and awaited mating with the booster. On January 13, hea,ily shrouded, the rocket was trucked to Hangar D of the Cape Industrial A.rea for additional preparations. It was erected on the launch pad after dark January 2-1 - without benefit of searchlights. The gantry was moved into position, the spin cluster was installed, and canvas shrouds were draped from the senice structure to con­ ceal most of the space vehicle. Onl�- the lower tail section, which was the familiar Redstone, could be seen. The vehicle rested on a launch table open at the top to allow flame to pass and strike a conical deflector positioned under the engine which spread the jet horizontally. The pad crews exhibited some nervousness about some rumored toxic properties of UMDH, and speculated that this mysterious chemical would (a) burn flesh to the bone upon contact, (b) depriYe a man who inhaled the fumes of his reproductive potential. or (c) cause one's hair to fall out. In defiance of these rumored dangers, Isom Rigell, the chief engineer, walked to the pad during test, climbed down in the cable pit and examined the circuitry. He wanted to make sure that an electrical bus, if it failed to drop out as it should, could not inhibit launch. He still has hair. General Medaris flew in from Huntsville whilevon Braun went to Washington to await launch with Dr. Pickering and Dr. van Allen at the National Academy of Sciences. Wernher resented but obeyed the Army's order because he wanted to be at the Cape.

49 Telephone circuits were imtalled so that talkns in the blockhouse rectangular window:' looking out on the could report the countdown to the pres:;, 2,286 meters (7,500 of ignition, Moser suddenly called out feet) away, and to a distinguishedgroup in the Pentagon including deflection, shall I hold?" I had looked at Secretary of the Army Wilbur Brucker and the Chief of Staff, did not see anv motion. This had to be. General Maxwell Tavlor. only. I waved ·my hand to continue. The shrouds were to come down before we loaded the tanks. As we planned to do this on January 29, Lt. John L. �teisenheimer, the Range weather officer, reported that the jet stream which flows west to east aero&; the C nited States had unexpectedly moved southward across Florida. Wind Yelocities of 270 kmph (146 knots) and more were measured at altitude:; of 11,000 to 12,200 meters (36,000 to -10,000 feet). The shear gradient was too much for the Juno I configuration (Jupiter C became Juno I with the addition of the fourth stage), so we postponed the launch one day. The countdown began on the 30th while we kept in close touch with Weather. Before flowing liquid oxygen into the booster, it became clear that the jet stream had increased in velocity and so we postponed again. By this time, the press had carried some brief mention of a satellite launch attempt, and the anticipation was beginning to be felt elsewhere. Approximately 200 newsmen representing ·wire services, magazines, newspapers and radio gathered in the area to watch the launch under military e�ort at the press site. The window January 31 opened at 10:30 P.�1. and would close at 2: 30 A.l\I. It was necessary to launch during this inten'al in order to balance exposure of the satellite to sunlight and Earth shadow which would conserve battery power for the radio trans­ mitters. We picked up the count despite less than encouraging weather data. Lieutenant Meisenheimersaid we might experience local thunderstorms. He flew more balloons during the day at my request. Most of those close to the activity were pessimistic; however, the weather officer declared that he would stake his reputation on a forecast that the wind shear would drop to toler­ limits by liftoff time. I persuaded General Medaris to accept this and we proceeded. (Figure 24) Well before launch the blockhouse was filled to capacity by some 54 operational personnel plus General Medaris. Dr. Jack Froelich and Phil Tardani of JPL were there. As the countdown moved steadily onward, Robert Moser, the test conductor, called out status reports coming in from key positions. At T minus 20 minutes Albert Zeiler, in charge of fueling, came in from the pad .- area with his crew. The blockhouse door was sealed against the FIGURE 24. Pre-launch pad activitiei for toxic gases which would form at ignition. Dr. Gruene, my deputy; The successful launch placed the first U.S. sautr Albert Zeiler, General Medaris and I took positions at the small,

50 51 rectangular windows looking out on the ..-eh.icle. Within seconds of ignition, Moser suddenly called out "We have a jet vane deflection, shall I hold?" I had looked at the vane in question and did not see anv motion. This had to be, therefore, an indication only. I waved 'my hand to continue.

FIGURE 24. Pre-launch pad activities for the Juno I/Explorer I mission. The successfullaunch placed the first U.S. satellite in Earth orbit.

SI The missile flamed into life at 10: 58 P.\I. Eastern time and aloncr wire at liftoff at a rate directly pr roared off into darkne:3:3. We clustered around the recorder panels the ;w;tch reached a stop. the ignition c watching the needles trace the trajectory and listening to the high­ mitted to the secondstage. pitched Dovap signal. JPL also built redundant �-stems into The vehicle lifted vertically. Whenburning time ended, it had assure ignition, the igniter was designed a moved into a trajectory inclined -10degrees to the horizon. We did in laboratory vacuum, then the rocket mo not use programmed cutoff but elected the depletion technique. atmospheric pressure before launch._ �I After 1-10 seconds of flight a probe was energized in each propel­ housed in a container capable of retamlll{ lant discharge line. The first probe to sense "no pressure" excited eYent of a motor seal leak. The signal 1 a relay which closed both main YalYes to the propellant tanks. command transmitter ";thin the instrun Cutoff actually occurred at 15 7 seconds, or two seconds later than teries in the guidance compartment wo expected. Five seconds later a timer ignitied the explosive b�lts. Increasing pre5.5l.U'e in the second stage e separa n, This delay permitted thrustto decay completely befo� _h? conical support oi the fourth stage. The otherwise residual thrust might shove the booster mto colliding eight seconds later. and eig�t seconds : ";th the upper assembly if separated at cutoff. Then t�e spatial fourth stage. -� ea h fired it _bro ·e sh attitude 5'-stem took oYer to align the upper stages durmg coast a....,sembh·. rele ,· o all back. until apex· was reached at about 40-1 seconds. In r�alitT. i !!VTOS The same which stabilized the rocket through booster Jet exact apex. · E.a. vanes up to c�toff now controlled the compressed � nozzles in seconds and the tail of the instrument compartment. The thrust imparted by and ignition o; this system tilted the cluster faster than the tilt of the trajectory, velocity incre which allowed time for residual attitude error to decay and thus stage c�toff. The gain the highest possible accur_acy in ali�ment. The comparativ�ly was onlv 0.81 crude cutoff technique made 1t 1mposS1ble before launch to predict still attained or .- the exact moment of apex, or to determinehow much horiz??tal separation of I-. travel might occur between takeoff I?oint �� apex. A�xiliary 403. 75 seconds. tracking had to be introduced to acqu rre additional data smce the after. assembly must be exactly horizontal over the local horizo . Only _ ? We had pro .-i by catching the apex moment and ensunng .accu�ate tub al�me?t could the upper stagesbe fired in the right direct10n to att n orbit. Stuhlinger coIDin.a.i:Ka::u i!,t;'.!:ir.Jcl � installed in the bl

52 53 along wire at liftoff at a rate directly proportional to time. When the s,\'itch reached a stop, the ignition command would be trans­ mitted to the second stage. JPL also built redundant systems into the cluster assembly. To assure ignition, the igniter was designed and tested to fire reliably in laboratory vacuum, then the rocket motors were sealed to retain atmospheric pressure before launch, and finally the igniter was housed in a container capable of retaining atmospheric pressure in event of a motor seal leak. The signal would be received in the command transmitter within the instrument compartment. Bat­ teries in the guidance compartment would energize the igniter. Increasing pressure in the second stage started a timer in the conical support of the fourth stage. The timer fired the third stage eight seconds later, and eight seconds after that, also fired the fourth stage. As each fired it broke shear pins holding it to the a...'-�mbly, releasingthe stage to fall back. In reality, it was planned to ignite the upper stages prior to exact apex. Each of the three upper stages would burn 5 to 6 seconds and there was that time interval between burnout of one and ignition of the next. By firing ahead of apex, the vertical velocity increment of the cluster would be exactly zero at fourth stage cutoff. The data indicated later that the angle of the cluster was only 0.81 degree off. We could have missed by 4 degrees and still attained orbit. First stage cutoff occurred at 156.71 seconds, separation of 162.31 seconds, and the second stage ignited at 403. 75 seconds. The satellite was injected into orbit shortly there­ after. We had provided more assurance. While Haeussermann and Stuhlinger commanded ignition by timer relay, a backup link was installed in the blockhouse where Henry Paul, an Army officer, watched the plus count, then tolled off "one thousand one, one thousand two," and pressed a button. Sufficient interval for this backup command had been calculated to assure that one trans­ mitter did not capture the command receiver and block out the other's signal. Still later, a third signal was transmitted by Kelly Fiorentino, one of our engineers, through a command system on San Salvador Island. We observed the staging sequence on the blockhouse recorders and then drove to the JPL offices in the Cape Industrial Area to await orbital confirmation. Dr. von Braun called from Washington and asked for news. General Medaris told him to keep the line open and "share a cup o coffee with us." We stood by until JPL acquired the signal by a Calli· ornia tracking station and confirmed that the satellite was a ery satisfactory orbit. The period was 114.78 minutes with anor

53 meters (225 miles). Secretary Brucker phoned congratulations to the ABMA team and told General Medaris the satellite was Explorer I. The Secretary and General Taylor had picked the name and kept it secret until then. We drove to Patrick Base theater about l A.M. for a press conference. As the group entered, the newsmen stood, cheered and applauded. Then we all awaited the official announcement from the White House which came soon after. One does not easily forget such a moment. Despite its limited capacity, Explorer carried the nation into the Space Age and returned important scientific data. Telemetry could be collected only during its pass over ground stations in Florida, Nigeria, Singapore, California and several locations along the 65 degree west meridian. Much of the orbit could not he observed and much of the data was lost. Nevertheless, the Van Allen experiment, which was set to bracket anticipated intensity of 30 to 40 cosmic ray counts per second, encountered densities above 966 kilometers (600 miles) altitude so intense as to saturate the instruments. It was concluded that the intensity was at least 1,000 times higher than expected. From this information. Dr. Van Allen mapped the radiation belts above Earth which carry his name. This became the major discovery of the IG Y. The Cambridge micrometeorite experiment determined that these particles offered no undue hazard to space ships hut also indicated that 1,814 metric tons (2,000 tons) of cosmic dust rain down on Earth annually. The temperature data showed that man could, by design, control temperature in a space vehicle. The density of air 200 to 300 kilometers (124 to 186 miles) from Earth was found to be 40 percent higher than expected. The Earth spheroid turned out to be one-half to I percent flatter than pre­ viously reckoned. Irregularities in the decrease of Explorer's velocity suggested the pressure of enormous air mountains at altitudes where these masses fluctuated constantly due to changing irradiation from the Sun. The satellite's lifetime was initially predicted at two or three years. Explort'r continued to revolve around Earth for 12 years and reentered March 31, 1970. Its signals ceased 63 days after launch due to battery depletion. As to the nation's reaction, this has been reported many times. In effect. it was the reverse of the state of shock induced by Sputnik. The ABMA team had made good its promise of three years earlier. For the former Peenemuende engineers, it was the long-awaited fulfillment of a dream. In retrospect, the group who came to the United States and chose citizenship in a new land became the nucleus around which

54 to a missile development organization grew up which carried two was large missile systems from design to deployment, advanced the the state of the art in all related fields, and laid the foundation for the heayv class boosters which would follow. (Figure 25) ress :red tent .sily 1 nto ....l !try 1 � in ong be Van sity ties rate �ast 'an his hat tlso FIGURE 25 ·ain nan fhe t.rth t.rth Jre­ er's at :mg

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