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SP-4206 Stages to Saturn

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[347] Vehicle AS-501, the first Saturn V, lifted off from Launch Complex 39 at the Kennedy Space Center on 9 November 1967. After several weeks of trial and error, the launch capped a countdown that experienced no serious holds or delays. The prime mission objectives for the Apollo 4 launch vehicle were to verify the first "all up" test of the Saturn V, including all three stages and the instrument unit. The mission objectives also emphasized the qualification of Launch Complex 39 and its ground support equipment, as well as the first orbital reignition of the S-IVB third stage as configured for the Saturn V. The launch of Apollo 4 included a number of "firsts." For TV viewers, the most visible events were the ignition and liftoff of the vehicle itself, the word from Mission Control in Houston that the spacecraft had entered its simulated lunar trajectory, and the successful reentry and splashdown of the command module. However, as mission director William C. Schneider remarked, these events represented only the tip of the iceberg. "Most of the things we were proving were below the surface," he explained, "not readily apparent to public view."¹

Before an airplane entered operational service, hundreds or even thousands of hours of flight testing proved its air worthiness. For each Apollo-Saturn launch, every component aboard the vehicle was making its first and last flight. For this reason, the weeks, months, and years of ground testing were necessary, and for this reason, the vast array of telemetry was necessary to evaluate the performance of parts and systems that could never be flown again or even recovered for postflight analysis.

[348] The AS-501 flight had tremendous significance. It was not only the first Saturn V but it also tested several major systems for the first time in an "all-up" configuration. As one observer described it, "The all-up concept is, in essence, a calculated gamble, a leap-frogging philosophy which advocates compression of a number of lunar landing preliminaries into one flight. It balances the uncertainties of a number of first-time operations against a `confidence factor' based on the degree of the equipment reliability achieved through the most exhaustive ground-test program in aerospace history." If NASA had followed prior custom, the S-IC first stage might have been launched by itself, testing the concept of the five clustered F-1 engines, each of which had a thrust nearly equal to that of the entire first stage of the Saturn IB. Then a two-stage vehicle would be launched to try out the clustered J-2 engines of the liquid-hydrogen-fueled S-II second stage. Next the three-stage booster would be launched, and finally the entire Apollo-Saturn vehicle including the CSM. This program would have entailed four separate flights, 12 months extra for preflight preparations, and analysis of postflight data for each launch-all this running into hundreds of millions of dollars.²

The concept of the all-up launch did not originate with von Braun or with MSFC, but came from the experience of George E. Mueller, who took up his new duties as Director of the Office of Manned Space Flight for NASA on 3 September 1963. When Mueller took office, NASA was faced with extreme budgetary pressures. The request submitted originally to President Kennedy had totaled $5.75 billion. In the hectic months following Kennedy's assassination, President Johnson had a very short time for making a multitude of decisions and experienced heavy pressure from Congress to reduce federal expenditures. One influential senator, not a friend of the space program, informed the President that unless NASA expenditures were kept under $5 billion for the next year, Johnson would lose the senator's vote for the tax bill-and the President wanted that bill very much. These financial pressures on the Johnson administration constitute one reason for all-up testing. As James Webb recalled, "Under these circumstances, NASA made a complete reevaluation of its plans for the NASA program and decided to revise it, going to the very advanced and, to some, risky approach of the `all-up systems test' procedure for the Saturn V-Apollo combination." It seemed to be the only way to achieve the lunar landing within the decade. Moreover, it imposed a stronger discipline on the contractors and on NASA itself. Even so, Webb admitted, "It was a very bold move."³

Obviously, budgetary constraints played a large role in the all-up decision. On the other hand, this procedure also matched Mueller's background in rocket development and testing. Before joining NASA, Mueller had been with the Space Technology Laboratories in Redondo, [349] California, where he had been in charge of a number of technical operations for various Air Force missile programs. These included the Thor, Atlas, Titan, and Minuteman ballistic missiles. The all-up concept had been introduced in the development of the Titan II missile and was being written into the development plan for the Minuteman ICBM.⁴

In the fall of 1963, the flight-test sequence for the Saturn launch vehicles was based on a plan issued by Brainerd Holmes, Mueller's predecessor. The Holmes plan reflected the conservative philosophy of the Marshall Space Flight Center, which tested new vehicles step by step. In the case of the Saturn IB, for example, the plan called for two launches, one in August 1965 with both stages live but still utilizing a guidance system from the Saturn I. The second Saturn IB would be launched late in 1965 with the same configuration, and the operational Saturn IB with a prototype instrument unit was not to be flown until January 1966. The same plan called for the first Saturn V launch in March 1966, with a live first stage, inert second and third stages, and a prototype instrument unit. The second Saturn V launch, scheduled for July 1966, was to have live first and second stages, an inert third stage, and a prototype instrument unit. As Mueller settled into his new job, he came to the conclusion that the financial consequences and the time consumption of the step-by-step approach simply could not meet the national goal of a lunar landing by the end of the decade. "It was pretty clear," Mueller said, "that there was no way of getting from where we were to where we wanted to be unless we did some drastically different things, one of which was all-up testing."⁵

It did not take Mueller long to act. On 1 November 1963, in office less than a month, Mueller dispatched a priority teletype to the directors of the Manned Spacecraft Center, Houston; Launch Operations Center, Cocoa Beach, Florida; and Marshall Space Flight Center, Huntsville: "Subject: Revised manned spaceflight schedule. Recent schedule and budget reviews have resulted in a deletion of the Saturn I manned flight program and realignment of schedules and flight mission assignments on the Saturn IB and Saturn V programs." The teletype directed that the first Saturn IB flight, SA-201, and the first Saturn V flight, AS-501, should comprise all live stages, and both should carry complete spacecraft. Mueller also indicated that he wanted the first manned Saturn IB flight to be AS-203. For Saturn V, he wanted the first manned flight to be AS-503. In other words, Mueller was suggesting that the first manned flights in each series occur on the third launch, instead of the seventh. Mueller asked for responses to his proposed schedule by 11 November and concluded with the comment, "My goal is to have an official schedule reflecting the philosophy outlined here by November 25, 1963."⁶ The arrival of Mueller's teletype at Huntsville caused a furor comparable only to the debate on Earth orbit rendezvous versus lunar orbit rendezvous (EOR-LOR).

[350] The first occasion for von Braun to discuss the message with his top staff occurred on Monday, 4 November, at the staff luncheon. A lively and occasionally rancorous debate continued for the next several days. The Mueller idea went against the approach of the von Braun team, steeped in a step-by-step, conservative philosophy of flight testing. Before the V-2 was operational, dozens of test rounds had been fired; many remembered the numerous abortive launches suffered in the early development period of Redstone and Jupiter. The chance of failure on the inaugural Saturn V seemed too high, and the financial risk too great. As recalled by Bob Young, Chief of Industrial Operations at the time, the reaction among von Braun's senior technical staff was "one of shock and incredulity." The general reaction seemed to be, "It is simply not done that way." The meetings, and the debate, continued. Walter Haeussermann, for example, pointed out that it was difficult to predict the rate of success for an all-up launch. How was it possible, for instance, to assign the probability of success or failure for a first stage on the first flight? Other people groused about the limited time available, and there was continuing concern about the workability of liquid hydrogen-particularly in the S-II second stage with its cluster of five engines. There was still some question about the degree of readiness of the instrument unit. One individual close to the discussions at this time, Frank Williams, said that he could not remember anyone who thought it was a good idea or that it would work at all.

The initial consensus at MSFC was to oppose the all-up decision. Bob Young recollected that both von Braun and Rees were low keyed in voicing their doubts, but in the end they sided with Mueller. Rees, in retrospect, stressed the time element in particular. He pointed out that the original approach would have required reconfiguring the launch site for every launch. The time involved in this reworking would have made a landing on the moon within the decade very doubtful. Still, there was considerable ambivalence on the part of the senior staff at Marshall Space Flight Center. Dieter Grau seems to have summed up the situation most accurately. "I'm not aware," he wrote years later, "that a consensus was obtained on this subject in favor of the all-up concept, although I know that Dr. von Braun went on record for the Center supporting this concept eventually. Just as Dr. Mueller could not guarantee that this concept would succeed, the opponents could not guarantee that it would fail. Dr. Mueller wanted to eliminate the additional costs which a more cautious approach would have required and Dr. von Braun decided MSFC should share the risk with him." The decision was declared to be MSFC policy, even though doubts continued to be expressed by many at Huntsville.⁷ Without saying so, von Braun himself still harbored some concerns.

By 8 November, von Braun was ready with the interim response that Mueller had requested. "There is no fundamental reason why we cannot [351] fly 'all-up' on the first flight, von Braun wrote. Nevertheless, he urged the importance that a "fall back" position should also be maintained, if some problem developed in a technical area with scheduling or in funding before the launch of AS-501.⁸ Before sending the letter, however, von Braun called Mueller, read him the draft and discussed the various issues involved. He reminded Mueller that details were somewhat sketchy, because the program under discussion was a multibillion dollar program with dozens of contractors, and it was difficult to rethink such a radical change and reschedule everything in less than a week. Mueller acknowledged the tentative character of the discussion and was reassured by von Braun's description of Marshall's consensus. Stretching things a bit, von Braun told him, "Our development team here with whom we discussed everything in much detail is solidly behind the all-up flight concept."⁹

Although correspondence between Marshall and NASA Headquarters continued to endorse the all-up principle and in-house memorandums at Huntsville encouraged commitment to it, there was still some sniping from von Braun's senior management. When Mueller and Robert Seamans, NASA Associate Administrator, visited Marshall early in December 1963, the Saturn V Program Manager, Arthur Rudolph, raised the issue again. He steered Seamans over to a corner where a model of the Saturn V was standing next to a model of the Minuteman on the same scale and discoursed on the comparative simplicity of solid-propellant rockets as opposed to the complexity of liquid chemical rockets the size of the Saturn V. His doubts about the all-up concept were implicit. He paused dramatically, turned to Seamans and said, "Now really, Bob!" Seamans got the point. "I see what you mean, Arthur," he said. Encouraged, Rudolph buttonholed Mueller, drew him over to the same models and repeated his discourse about the relative merits and disadvantages of each. Mueller was unimpressed. "So what?" he responded.¹⁰ The planning for the all-up flight of AS-501 continued. In the spring of 1964, following a visit to Marshall, Dr. Golovin reported to General Sam Phillips at Headquarters that the all-up concept was being supported with enthusiasm by MSFC management.¹¹

From the time of Mueller's all-up teletype of 1 November 1963, it was four years, one week, and one day until the launch of AS-501. The interim was filled with exhaustive research and development of Saturn V systems, subsystems, and components. At Kennedy Space Center, a parallel effort involved the construction and verification of Launch Complex 39. Prior to the arrival of the AS-501 vehicle, the facilities had received a comprehensive checkout using an interim Saturn V facilities [352] test vehicle, called 500-F. Saturn 500-F was rolled out on 25 May 1966, followed by exhaustive testing and development of procedures at Cape Kennedy.¹²

This preliminary experience provided invaluable information prior to the first operational launch of AS-501. Nevertheless, NASA management realized that the launch of the live vehicle would provide significant additional information for future Saturn V operations. For AS-501, therefore, additional plans were made for extraordinarily detailed experience reports. According to the instructions issued by General Phillips,

It is important that accurate, comprehensive records are obtained of failure, delays, holds, and scrubs for each pre-launch test and launch attempt on flight hardware, GSE [ground-support equipment], software, launch instrumentation, facilities, control centers, or MSFN [Manned Space Flight Network] which are involved in the final countdown from T-4 days to T-0. Data should be recorded for all failures, delays, holds and scrubs even though the time sequence or length of the pre-launch test in process at the time of the failure may not have been affected.¹³

In the meantime, Saturn V stages began arriving at KSC. All did not go well. Problems with hardware caused considerable delays and postponement of the launch date. In March 1967, an agenda for a briefing on AS-501, to be attended by General Phillips, included mention of 1200 problems resulting in 32 discrepancy reports. The memo to Phillips indicated that work teams had divided the problems into four separate categories and planned to work them off at an intensive rate of 80 per day. A typical problem was the discovery of an errant bolt in one of the F-1 engines and the requirement to see how it got there to make sure that nothing similar would happen again.¹⁴ Then in June 1967, after the AS-501 vehicle had already been stacked, it was necessary to take it down. On the West Coast, North American Rockwell had discovered some 80 weld flaws in the S-II second stage, designated S-II-6; it developed that S-II-1, already sitting in the AS-501 stack, had similar flaws. This costly delay nearly escalated when Boeing decided to follow up on its own stage, the S-IC, and discovered similar difficulties. Subsequent tests gave the S-IC-1 a clean bill of health, but not without a flurry of concern for the status of AS-501. Late in the month, NASA Headquarters issued a special directive calling for better management of the hardware changes on the AS-501 vehicle. In an attempt to keep the launch schedule on an even track, the teletype message warned, "It is essential that change traffic of all types be reduced to only those changes which are mandatory for safety or mission success."¹⁵ Finally, having overcome these and other numerous difficulties, AS-501 was "rolled out" on 26 August 1967.¹⁶

The teething troubles of AS-501 were not over, however, even after the vehicle reached the launch pad. Numerous preliminary test operations exposed a host of potential complications.¹⁷

[353] The countdown demonstration test (CDDT) on AS-501 brought out additional difficulties which, as Program Manager Rudolph admitted, "caused numerous holds, delays, crew fatigue, scrubs, and recycles." Three recycles were required and instead of about one week, three weeks were needed to complete the test. Everything, Rudolph said, encountered difficulties-the Saturn V, the spacecraft, the launch facility, everything. Rudolph contended, however, that he was not surprised. It was, after all, the first time that a multitude of components were integrated into a "super system." On the first stage, for example, a number of the propellant valves opened simultaneously instead of in sequence as had been intended. On the second stage, items within the S-II were damaged by filling the LOX tanks too rapidly. In the third stage, cable connections were shorted as a result of the accumulation of moisture in the environment of the launch site. The instrument unit had difficulty in the environmental control system designed to keep the electronics in black boxes cool during operation of the vehicle. In the ground support equipment, a malfunction prevented proper pressure in the helium bottles, and the ground computer's problems included "intermittent operation due to design deficiencies, loose connections, electronic component failures, and insufficient maintenance."¹⁸

International prestige, as well as millions of dollars, were riding on the mission of AS-501. At NASA Headquarters, the Public Affairs Office was apparently feeling increasingly uncomfortable about questions from the press concerning the condition of AS-501. Would it ever fly, or not? Late in October, the head of the Public Affairs Office, Julian Scheer, met with Administrator Webb and representatives of the Office of Manned Space Flight in a heated conference that ended with Webb announcing that when he wanted the launch date announced, Webb would say so.¹⁹ Finally, the date was set for 7 November 1967. Then, less than a week before liftoff, on 2 November, MSFC started worrying about leaks in the seal rings of LOX fill and drain valves caused by aging of the Teflon over the long time that AS-501 had been on the launch pad. Concern was expressed about the batteries of the S-II stage for the same reason. Although these and other problems were subsequently solved, it put the count approximately 40 hours behind the detailed work plan leading to a launch on 7 November. General Phillips resolutely rescheduled the launch of Apollo 4 to 9 November at 7 a.m. EST.²⁰

Summing up the troublesome and erratic prelaunch experience with AS-501, Rudolph ticked off the lessons learned. The prolonged holds and recycling of the count wore out critical components with short lifetimes. For this reason, continuously updated logistical plans had to be prepared. Rudolph asserted that production components in many cases did not live up to the standards attributed to them by the qualification test program. He warned that the suppliers had to maintain much stricter [354] manufacturing control and quality control to prevent degradation of such equipment. A number of problems resulted from the first-time conditions at Cape Kennedy. Work crews had to redesign many items "on the spot" while constrained by complicated procedural changes under pressure of the countdown. To launch successfully, concluded Rudolph, it was necessary to plan built-in holds, not only to replace components but also to prevent fatigue of the crews.²¹

These behind-the-scenes struggles heightened the drama of the launch of Apollo 4; the media, in the meantime, were attempting to convey to the American public something of the complexities of the Saturn V vehicle. Trying to find familiar examples with which to compare the Saturn V, the press corps and public relations offices came up with mountains of Saturn esoterica.

Because of its size and astronomical statistics, the F-1 engine received a good deal of mention in the press. The engine burned 145 000 liters (40 000 gallons) of propellant per minute, the equivalent of three metric tons of propellant per second. The cluster of five F-1 engines, which put out 33.4 million newtons (7.5 million pounds) of thrust, performed their operation for only 150 seconds, although each of the engines was tested for an average of 650 seconds of static firing before a launch. NASA also figured in a lifetime factor of 1400 seconds as a confidence factor for each engine. The only limiting factor was therefore the amount of propellant that could be crammed into the S-IC first stage.

The first stage boasted its own set of gargantuan statistics. Its girth was ample enough to allow three big moving vans to drive, side by side, into the first stage tank. The LOX tank of the first stage held enough liquid oxygen to fill at least 34 railroad tank cars (or 54, depending on which handout was read). To get the fuel from the tanks to the engines, the pumps on the S-IC first stage worked with the force of 30 diesel locomotives, and some of the fuel lines and associated valves were big enough for a man to crawl through. Fully fueled and running, the S-IC first stage turned out the equivalent of 119 million kilowatts (160 million horsepower)-twice as much power as all the rivers and streams of America running through hydroelectric turbines at the same time.

In trying to visualize the size of the Saturn V rocket, writers most frequently compared it in height to a 36-story building, or noted that it towered well above the Statue of Liberty, and weighed 13 times as much. A public relations pamphlet issued by North American Rockwell included the information that "6 200 000 lbs. is over 3000 tons; a good-sized Navy destroyer is only 2200 tons. Which gives you a fair idea of how much weight will have to be lifted off the ground before the Apollo spacecraft can be boosted into orbit, then shot almost 11 400 statute miles out into space and intricately maneuvered during the Apollo 4 flight." In terms of space payload capability, a writer for Fortune magazine pointed out that the Saturn V could lift "1500 Sputniks on a single launch, or [355] 9000 copies of Explorer I, this country's first satellite, or 42 manned Gemini spacecraft."

To make the most of the first Saturn V flight, data collection was also geared up to astronomical capabilities. During the Mercury test program, for example, data were received on the ground at a rate that would fill a standard printed page every second. The Apollo-Saturn vehicle was designed to relay some 300 pages of data in one second. The research, design, manufacturing, test, and preparation leading to the moment when the rocket was poised for its leap into space had required the services of over 300 000 scientists, engineers, technicians, and craftsmen, representing over 20 000 companies. The estimated cost for the AS-501 vehicle was $135 million for the rocket and $45 million for the spacecraft.²²

The enormity of the effort involved in the Apollo-Saturn program and the trials and tribulations of getting the AS-501 countdown to work provided an additional dramatic background for the final preparations. The inherent risks of the all-up concept seemed to multiply the chances for total failure. The electric tension of the atmosphere heightened perceptibly with the influx of VIPs. Congressional figures, the diplomatic corps and other foreign visitors, industry executives, and NASA managers began arriving at the Cape. Late in the afternoon of 6 November, von Braun left Huntsville in NASA's Gulfstream No. 3. After arrival at Patrick Air Force Base, von Braun was scheduled for an exclusive executive dinner and conference. The next day, Tuesday, 7 November, included further executive sessions with the Office of Manned Space Flight and other contractor personnel. Early in the morning of 8 November 1967, the final 24-hour countdown period for AS-501 began. The day included a major press conference at the Vertical Assembly Building, and, late in the evening, a dinner for top-level NASA personnel and industry representatives.

At dusk on 8 November, the silhouette of AS-501 faded with the setting sun, but as darkness descended over the Atlantic, Apollo 4 reappeared as a shining white pillar swathed in floodlights on Pad 39. The towering vehicle made a dramatic focal point for the pressures that mounted during the night. The count continued through programmed holds, then through a spate of minor difficulties as the clocks ticked away the minutes and seconds to the scheduled launch time, seven o'clock in the morning of 9 November.

At only one second past the appointed hour, the Saturn V lifted off the pad, its engine exhaust emitting plumes of stabbing red fire, lighting up the low-lying Cape landscape-an exceedingly dramatic scene in the....

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		Top left, the first flight-ready Saturn V, AS-501, is rolled out of the Vehicle Assembly Building at KSC on 20 August 1967. Above, the AS-501 stands for weeks on the pad at Launch Complex 39, bedeviled by minor problems. Then (left) on 9 November 1967, it lifts off to a perfect flight; the "all-up" concept has been vindicated.

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[357] ....half-light of dawn. The spectacular flames, billowing exhaust clouds, and the rolling thunder of the engines stunned the onlookers. Dr. William Donn, of Columbia University's Lamont Geological Observatory, at Palisades, New York, reported that the only man-made sounds that exceeded the liftoff noise of the Saturn V were nuclear explosions and added that the only natural sound on record that exceeded the noise of the Saturn V engines was the fall of the Great Siberian Meteorite in 1883. Five and a half kilometers away, in the studio trailer of the Columbia Broadcasting System, the commentary of CBS correspondent Walter Cronkite was all but drowned out by the thunder of Saturn's engines, and Cronkite himself was subjected to a shower of debris shaken loose from the walls and ceiling of his broadcasting booth.²³

The all-up concept was undeniably successful. With AS-501 up, von Braun could finally admit his lingering doubts about it. He turned to Rudolph in the firing room at Kennedy Space Center, and told him that he thought such a completely flawless three-stage flight would never have been possible on the first try.²⁴ During a postlaunch press conference von Braun said, "No single event since the formation of the Marshall Center in 1960 equals today's launch in significance [and] I regard this happy day as one of the three or four highlights of my professional life-to be surpassed only by the manned lunar landing."²⁵

The flight of Apollo 4 was a success on all accounts. In W. C. Schneider's first teletyped 24-hour report, the opening sentence told the story: "The Apollo 4 mission was successfully accomplished on 9 November 1967." Talking to reporters later, he called AS-501 a bench mark to aim for in succeeding flights. Apollo 4 would be "a tough act to follow."²⁶

The flight marked the initial flight testing of the S-IC and S-II stages; the S-IVB was essentially the same as that used in the Saturn IB launches. The first-stage S-IC performed with the accuracy anticipated by launch officials. A timer cut off the center F-1 engine at 135.5 seconds into the flight, and the outboard engines cut off at LOX depletion in 150.8 seconds, when the vehicle had recorded 9660 kilometers per hour at an altitude of 61.6 kilometers. The separation of the first stage took place only 1.2 seconds off the predicted time lines, and the cameras aboard the S-II showed a clean separation of the stages. Other major systems of the S-IC, including the pneumatic control pressure system, pressurization, and propellant utilization, performed within acceptable ranges. On the S-II second stage, the cluster of five J-2 liquid-hydrogen engines achieved perfect sequencing for engine start and burn. Two slight variations were observed by ground controllers: engine-start bottle pressures were somewhat higher than predicted, and the temperatures of the thrust chamber jackets increased at rates higher than predicted. Neither of these minor anomalies exceeded the operational limits of the Saturn V; all other systems performed normally. Cutoff for the S-II occurred at 519.8 seconds, about 3.5 seconds later than indicated on the [358] mission control sheets. The troublesome external insulation on the liquid-hydrogen tank of the S-II stage survived the countdown and launch with no recorded failures.

Variations in the S-IVB third-stage performance were greater than those of the lower stages. In achieving orbit, the guidance control system ended the first third-stage burn a few seconds beyond the predicted shutdown point, when the stage achieved a speed exceeding 27 000 kilometers per hour at an altitude of 192 kilometers. Prior to the restart sequence, after two revolutions in Earth orbit, telemetry received at Cape Kennedy indicated that the liquid-hydrogen ullage pressure was somewhat below the anticipated minimum and that the status of the helium repressurization spheres was below normal for S-IVB restart preparations. Mission personnel decided that the engine could be reignited in spite of the deficiencies, and the third stage respond successfully. The instrument unit (IU) ended the second burn several seconds short of the expected duration, reacting to the earlier extended burn of the S-II stage, made at higher thrust levels of the J-2 five-engine cluster, which enabled the third stage to make its mission profile with less burn time required. The IU operated exceptionally well with only 40 questionable measurements and single pair of confirmed failures out of about 2862 measurements made during the Saturn V portion of the mission.²⁷

Behind the primary mission objectives, NASA personnel closely monitored many individual items of flight hardware. Of singular importance was the experience of coordinating the platoons of NASA and contractor personnel during the long months of prelaunch operations. Even as the painstaking procedure of checking out each stage and every item in the stage progressed, launch engineers were evaluating the procedures themselves on this first Saturn V mission. The mobile launch concept was only one example. Planned and orchestrated to reduce the time the vehicle remained on the launch pad and exposed to the effects of corrosion, dust, and weather, the concept required that the Saturn V be assembled and checked out inside the huge VAB. With the huge vehicle complete, the plan called for mobility to reposition the complete vehicle on the launch pad, 5.5 kilometers distant. This meant the use of the crawler, bearing the combined launcher and vehicle out to the pad. The launch itself the holddown arms for the first time. Not only did the arms stabilize the vehicle during rollout to the pad and keep the vehicle in place during the long countdown, but they also held down the straining vehicle after ignition until computers verified satisfactory operation of the engines and signaled release of the rocket. The strain was so intense that the mobile launcher was actually stretched about 20 centimeters.

The mission also tested the gimbal capability of the engines. The vehicle had to make a roll maneuver around its vertical axis after launch and pitch into an inclined northeasterly trajectory after climbing away [359] from the launch pad. Before ignition of the J-2 engines of the second stage, mission personnel closely watched the second-stage ullage maneuver. Following separation of the first and second stages, the nearly weightless propellants tended to surge forward, climbing the propellant tank walls as acceleration decreased. Unless the propellants were settled once more against the propellant line inlets to the engines, no second-stage ignition could occur. So the eight ullage rockets had to fire first, accelerating the stage and forcing the propellants into place. The system worked, and the five J-2 engines burned as expected. The emergency launch escape tower jettisoned perfectly, and the third stage performed like the veteran it was. The IU for the Saturn V functioned just as planned, and reignition of the S-IVB third stage represented another crucial test: the second burn would supply the acceleration required for the translunar trajectory.

The S-IVB reignition had appeared to be a particularly difficult sequence. The behavior of hydrogen in orbit was a problem, and the restart sequence depended on especially designed, complex equipment. After its first burn, cutoff, and three-hour coast through space, the J-2 had to be reconditioned to cryogenic temperatures before the final restart sequence began. To purge the engine of contaminants remaining after the first burn, an automatic sequence initiated a helium purge, and a gaseous hydrogen start tank was refilled by a tap line from the stage's hydrogen tanks. Valves opened to permit liquid hydrogen and oxygen to trickle through the engine and cool down its parts to the requisite cryogenic temperatures. During an ullage maneuver to seat the propellants for entry into the pumps, an automatic sequence ran a final check on temperatures, pressure levels, and other engine conditions to verify the readiness of the engine and propellant systems. When the IU received positive indication on all the numerous readings required, it triggered the final start sequence for reignition. Apollo 4 proved the restart capability, and the second burn put the spacecraft into a very high elliptical orbit, reaching more than 16 000 kilometers from Earth. With its mission complete, the S-IVB separated from the spacecraft, which performed its own programmed burns and maneuvers before CSM-CM separation and CM reentry.²⁸

Following the months of doubts and problems created by the rocky research and development of the S-II second stage, the disastrous fire at Cape Kennedy early in 1967, and the troublesome experiences with the countdown demonstration tests of the AS-501 vehicle late in 1967, the flawless mission of Apollo 4 elated the entire NASA organization; everyone looked ahead with buoyant spirits. Returning to Huntsville, von Braun received a call from Brainerd Holmes on 15 November. "Congratulations! That was such a remarkable achievement with Saturn V. I was very excited about it," Brainerd exclaimed. Von Braun warmly responded that it showed the spacecraft to be in better shape than many [360] people had thought following the fire and redesign and added that it performed magnificently during reentry.²⁹

NASA management shared its elation with the Apollo-Saturn contractors as well. In a letter to Bill Allen, president of the Boeing Company, George Mueller pointed with pleasure to the success of the all-up concept, and continued in glowing terms about the success of the industry-government team. The mission of Apollo 4, Mueller emphasized, was a true landmark, ".... a very large step forward. It is, in my view, the most significant single milestone of the Apollo-Saturn program." Urging continued dedication to the task ahead, Mueller closed with the remark that it was possible to fulfill the national commitment of landing Americans on the moon and returning them safely to Earth within the decade.³⁰

In the meantime, planning continued for the flight of the second Saturn V mission, to be known as AS-502, or Apollo 6. In the aftermath of the AS-501 flight, NASA planners were optimistic in planning for the next two missions, both of which were to be unmanned. General Phillips advised NASA center directors that if AS-502 was successful, AS-503 would become the first Saturn V manned mission. Thus, AS-502 served as an all-important dress rehearsal for the first manned flight.³¹

The general euphoria was badly worn by the problem-prone mission of AS-502. Nothing had indicated the impending series of trials ahead. After a satisfactory countdown, AS-502 blasted off from Launch Complex 39 on schedule, early in the morning of 4 April 1968. The first thing to go awry was the S-IC first stage, which developed longitudinal oscillations of five cycles per second during the last moments of the first-stage burn. These oscillations, known as the "Pogo effect," had occurred on the first Saturn V, but their magnitude on AS-502 became alarming. "The second Saturn V's takeoff at the Cape was faultless," von Braun recalled. "For two minutes everything looked like a repeat of the first Saturn V's textbook performance. Then a feeling of apprehension rolled through the launch control center when, around the 125th second, telemetered signals from accelerometers indicated an apparently mild Pogo vibration." The lengthwise oscillation lasted less than 10 seconds.

After the moments of concern about the first-stage Pogo readings, launch personnel felt better about the stage separation and ignition of the five J-2 engines on the S-II second stage. After burning 4.5 minutes, however, the number two engine began to develop unwholesome problems. The engine began to falter; it lost thrust and then shut down. No more than a second later, the number three engine suddenly shut off as well. To compensate for the loss of 40 percent of its thrust, the IU steered [361] the faltering second stage into a recomputed trajectory to reach the programmed altitude for third-stage separation. After some overtime firing, the S-II finally shut down its three remaining engines and fell back from the S-IVB. The third stage fired up normally, and the S-IVB, IU, and payload finally made it into an Earth parking orbit, although a somewhat lopsided one. After two orbits, the bird received a command for the third stage to reignite. Nothing happened. The J-2 engine just would not restart, despite repeated efforts. Salvaging all that was available from the flight, mission controllers succeeded in separating the CSM from the malfunctioning third stage, got a couple of burns out of the service module engine to get the command module into better position for the reentry tests, and finally brought the CM through reentry and splashdown to verify the heat shield.

"Had the flight been manned, the astronauts would have returned safely," von Braun emphasized afterward, "but the flight clearly left a lot to be desired. With three engines out, we just cannot go to the Moon."

In the aftermath of the marginal flight of AS-502, teams went to work to find answers to the problems. Pogo had been encountered previously in Titan-Gemini and other launch vehicles, and a fix was likely in the future. However, the J-2 engine failures involved a problem of unknown origins and causes, indicating the need for some intensive sleuthing.

Armed with reams of reports and telemetry data from the AS-502 flight, the J-2 problem team assembled, including engineers from MSFC and Rocketdyne. The record of temperature readings from thermocouples in the S-II tail section provided the tipoff, beginning at the 70th second of flight, when investigators discovered telltale indications of a flow of cold gas. Such a phenomenon could only come from a leak of liquid-hydrogen fuel, and the leak was located in the upper regions of the number two engine. Even more conclusive was the coincidence of increased cold flow from about the 110th second on, when ground controllers first noticed the falter of thrust. Clinching the theory of a fuel leak, the J-2 team found indication that a split second before the number two engine shutdown, hot gas had erupted in the area of the leak. The only theory to explain a hot gas eruption, followed by engine shutdown, was the failure of the J-2 igniter line in the upper part of the engine.

These data allowed the J-2 group to reconstruct the sequence of the failure. The leaking fuel line, leading to the igniter, sprayed the upper engine section with liquid hydrogen, even though some fuel continued through the line and the engine kept burning. Finally, the line broke completely, and fiery, high-pressure gas from the combustion chamber backed up and spurted through the rupture. Combustion chamber pressure began to fall off, so that the low-thrust sensing equipment triggered a sequence to shut down the engine by closing the fuel and oxidizer valves. The electrical sequence to close number two LOX valve [362] went erroneously to number three. Closing the fuel valve for engine number two and the LOX valve for engine number three shut down both engines. Telemetry from the J-2 engine on the third stage told the same story as engine number two of the second stage: a failed igniter line. The S-IVB had arrived in orbit before the failure was complete, but could not restart the engine.

The MSFC and Rocketdyne investigation team now knew how the engines and igniter fuel lines failed, but no one could say why. Engineers set up special test stands to wring out the fuel lines again. The tests began by subjecting the igniter fuel lines to successively higher pressures, flow rates, and vibration, surpassing the extremes that might reasonably be encountered during a mission. The lines survived the punishment. Next, the investigators checked into the possibility of resonance failures, concentrating on the bellows sections in the lines. The accordionlike sections, located near either end of the line, were intended to provide flexibility for expansion and contraction, and engineers wondered if some flow rates could induce "buzzing" in the bellow-a phenomenon that, if sufficiently severe, could cause metal fatigue and failure. There was buzzing, but the lines held. Finally, Rocketdyne technicians decided to test the lines in a vacuum chamber, in close simulation of the environment where failure occurred. Eight lines were set up for test in a vacuum chamber, and engineers began to pump liquid hydrogen through them at operational rates and pressures. Before 100 seconds elapsed, each of the eight lines broke; each time, the failure occurred in one of the bellows sections. By using motion picture coverage acquired during repeated vacuum chamber tests, Rocketdyne finally could explain the failures.

The igniter fuel lines were installed on the engine with protective metal braid around the bellows section. When tested in a chamber that was not in a vacuum condition, the surrounding air was liquefied by the extremely cold liquid hydrogen flowing through the lines and was trapped between the bellows and the protective metal braid. This condition clamped subsequent vibration in the fuel line. When tested in the vacuum chamber, where the environment simulated the conditions of space, there was no liquefied air to dampen the destructive resonance. A redesigned igniter fuel line eliminated the bellows sections, replacing them with bends in the line to allow for expansion and contraction during the mission.

Concurrent with the J-2 failure investigation, a Pogo task force, with representatives from MSFC and other NASA agencies, the contractors, industry, and universities, analyzed the first-stage F-1 engines and the overall Saturn V vehicle. The Pogo phenomenon, they reported, originated from two sources. While F-1 engines burned, the thrust chamber and combustion chamber of each engine developed a natural vibration of some 5.5 hertz. Further, the whole vehicle vibrated in flight with a [363] varying frequency that peaked at 5.25 hertz around 125 seconds into the flight. When the engine frequency closely matched the structural frequency, Pogo vibrations appeared up and down the entire vehicle. The vibration was not in itself destructive, but it did increase the stresses on the vehicle and the astronaut crew, because the lighter spacecraft, perched at the tip of the tall rocket, was buffeted more than the engines at the bottom. The team investigating Pogo concluded that they should "detune" the engine frequencies away from those of the structural frequencies.

The group explored a number of possible fixes before settling on pneumatic "shock absorbers" in the LOX lines leading to each of the five F-1 engines in the first stage. The so-called shock absorbers made use of cavities in the LOX line prevalve assembly. The prevalve assembly contained a bulging casting in the LOX line to accommodate the movement of a big valve that opened or closed the LOX line. During engine operation, with the valve in the open position, liquid oxygen filled the casting's cavity to about half its volume. Engineers tapped the first stage's ample helium supply (used to pressurize the fuel tank), and filled the remainder of the valve cavity with helium gas. The helium gas in the cavity acted as a shock absorber by clamping the engine pulsations into the LOX lines and into the vehicle structure.

At Mississippi Test Facility, engineers successfully demonstrated the two fixes during August 1968, with test firing of the S-IC first stage equipped with the Pogo suppression equipment on the F-1 engines, and the S-II second stage with the redesigned igniter fuel lines on the J-2 engines. The demonstration cleared the way for a manned launch of AS-503, as Apollo 8. The AS-503 was planned to place the manned CSM in a low Earth orbit. If the interim Apollo 7 mission, boosted by a Saturn IB, verified the redesigned CSM and its new safety features, then the Saturn V-Apollo 8 mission could be revised boldly. "There is even a remote possibility of a spectacular swing around the Moon by the manned spacecraft," von Braun said in the autumn, a little over a month before the scheduled launch. "That a mission as bold as the last is even considered, for the first Saturn V to be manned, bespeaks planners' confidence that all about it has been set aright."³²

In many respects, the momentous mission of Apollo 11 in 1969, which put Armstrong, Aldrin, and Collins on their way to the first manned landing on the moon, has obscured the importance of the first manned Apollo-Saturn mission, that of Apollo 8, or AS-503. The decision to man AS-503 was a significant step forward, in some respects [364] comparable to the decision to make AS-501 the first all-up configuration. The decision to send it around the moon was even more significant.

Back in June 1967, a NASA memorandum was issued warning against the tendency by NASA employees and others "to create overly optimistic impressions of NASA's capability for early achievement of such key milestones as Apollo long duration manned missions, manned Saturn V missions, and the lunar landing mission." The memorandum observed that AS-503 had a low probability of being the first Saturn V manned mission and that even AS-504 had only a moderate probability of being manned.³³ If AS-504 were manned, it would be a low-Earth-orbit flight. At the same time, some executives at NASA Headquarters were suggesting the possibility of at least a lunar orbital manned mission by the third manned Saturn V.³⁴ By September 1967, Robert R. Gilruth at Houston was advocating "four, or perhaps even five, basic manned mission types. . .before lunar landing capability is achieved. One of these mission types is a lunar orbit mission." At the same time, Gilruth strongly advocated a third unmanned launch of the Saturn V vehicle to "help assure launch vehicle maturity prior to manning." Gilruth noted that "the probability of landing on the moon before 1970 is not high."³⁵

The manning of AS-503 became an even more touchy question following the difficulties of AS-502 in the spring of 1968. A prerequisite to a manned mission for 503 was a design certification review, but as von Braun pointed out to Mueller, too many people at Marshall were still working on the data received from the troublesome AS-502 mission. Mueller was anxious to get a commitment before he appeared before Congress on 23 April to testify on NASA plans, but von Braun pleaded for more time-two or three weeks. Mueller finally agreed.³⁶ On 24 April, Phillips said that he was recommending preparation of AS-503 for manned flight with an option to revert to the unmanned configuration if necessary. However, difficulties uncovered by AS-502 continued to plague the question of a manned or unmanned mission on AS-503. On 29 April, Arthur Rudolph, the manager of the Saturn V Program Office, advised Phillips that the continuing problems with AS-502 anomalies still did not allow him to make a firm recommendation for a Saturn V payload of 45 000 kilograms or more, which Phillips had requested by 30 April 1968.³⁷ Nevertheless, preparations for launching AS-503 either in the manned or the unmanned configuration necessarily continued.³⁸

NASA planners had wanted to use AS-503 to fly the complete Apollo-Saturn configured for the lunar landing mission. This plan presumed an Earth-orbital flight, testing both the command module and the lunar module in the flight mode and using them both to perform maneuvers that would simulate the operations in the lunar environment as closely as possible. During late spring and early summer of 1968, work on the lunar module fell behind. By August, General Phillips glumly concluded that the original mission for AS-503 could not be flown until.....

.....early 1969. With only 18 months to get to the moon before the decade ended, the schedule slippage of Apollo 8 was extremely serious.

But George Low, the spacecraft manager at Houston, came up with what Phillips called a "daring idea." Low proposed to skip the Earth-[366] orbital test phase and postpone lunar module trials until the next Apollo-Saturn after AS-503. In the meantime, Low argued, go ahead and send a crew in the command and service modules to the moon. After all, the spacecraft hardware assigned to the launch had been built to specifications for actual mission hardware. Use it. A hastily convened session of the Apollo management team brought key people flying into Marshall Space Flight Center, centrally located to the other major Apollo operations at Headquarters, KSC, and Houston. The preliminary three-hour session ended on a distinctly up-beat note. More study was required, but a circumlunar flight for Apollo 8 looked quite feasible. Back in Washington, Phillips explained the plan to Thomas O. Paine, Acting Administrator while James Webb was attending a space conference in Vienna. Paine was not so sure. "We'll have a hell of a time selling it to Mueller and Webb," he warned Phillips.³⁹

Not until early fall were NASA planners ready to decide on manning AS-503 or to confirm the prospects of a lunar orbital mission. On 19 September 1968, the Office of Manned Space Flight made an intensive review of each problem uncovered by AS-502, examining the solutions and scrutinizing test procedures and results. In a long memorandum reviewing these aspects, George Mueller recommended to Acting Administrator Paine that AS-503 should be manned. On 11 November 1968, Mueller further recommended to Paine that AS-503 also circumnavigate the moon. Paine's reply to Mueller on 18 November 1968 made it official: AS-503 would leave the lunar module behind, but go for a manned lunar orbit.⁴⁰

Nobody wanted a repeat of the worrisome AS-502 mission, and so the Apollo 8 launch vehicle received an exceedingly thorough going over before launch day. Several months before the scheduled launch, even before the official decision to man AS-503, Dieter Grau, Chief of Marshall's Quality and Reliability Operations, sat through a two-day meeting when all the major contractors discussed the action items for Apollo 8/AS-503. The participants seemed to be approaching a consensus that the vehicle was ready to go. Having lived and worked closely with the vehicle and its various components for months, however, Grau did not have a good feeling in his bones that all was well. In the face of the growing consensus, Grau took a position of caution. As Grau recalled, von Braun sensed his reticence and asked what more should be done. Grau wanted the opportunity to do one more complete check and von Braun gave it to him. Personnel in Grau's laboratories went over the AS-503 vehicle again, rechecking subsystems, interfaces, and drawings to make sure everything was all right. Sure enough, numerous little mistakes and potential problems were uncovered. "We went through the vehicle from top to bottom;" Grau said. "I think that was kind of a life saver. We found so many things which needed to be corrected and improved." After these extra weeks of checking and rechecking, Grau [367] and his people in the Quality and Reliability Laboratory finally gave the green light for the launch of Apollo 8.⁴¹

"Wet" and "dry" countdown demonstration tests began for AS-503 on 5 December 1968, and concluded by 11 December, clearing the way for the final countdown for launch, which began four days later. As the launch countdown proceeded, the final Pogo suppression test took place on the S-IC-8 stage at Mississippi Test Facility during a 125-second static-firing test on 18 December. On the same day, MSFC engineers finished a series of tests on the S-IVB battleship unit to verify the redesigned fuel lines. The program included three hot tests, from 4 December to 14 December, ranging from about 122 seconds to 435 seconds. The last of the miscellaneous component tests was completed on 18 December, with Apollo 8 poised on its pad, only three days away from launch.

For the premier launch of a manned Saturn V, NASA prepared a special VIP list. The fortunate individuals on the list received an invitation in attractively engraved and ornate script: "You are cordially invited to attend the departure of the United States Spaceship Apollo VIII on its voyage around the moon departing from Launch Complex 39A, Kennedy Space Center, with the launch window commencing at 7 A.M. on December 21, 1968." The formal card was signed "The Apollo VIII Crew" and included the notation, "RSVP."

With the primary objectives to verify the manned spacecraft, support systems, and lunar orbit rendezvous procedures, Apollo 8 lifted off from KSC at 7:51 a.m. EST, on 21 December, 1968, crowed by Frank Borman, commander; James A. Lovell, Jr., command module pilot; and William A. Anders, lunar module pilot. In contrast to its predecessor, AS-503 performed without a hitch. The telemetry readings from the S-IC indicated that the Pogo suppression system worked as planned, and no longitudinal vibrations were reported. Staging of the first and second stages went smoothly, followed by the staging of the S-II and S-IVB near the top of the launch trajectory. The S-IVB, IU, and spacecraft went into Earth parking orbit 11.5 minutes after launch. During the second orbit, the S-IVB stage reignited, boosting the vehicle into translunar trajectory at over 38 600 kilometers per hour. After separation of the spacecraft, ....

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[368] ....the spent third stage was directed into a trajectory for solar orbit and Saturn V's job was done. At 3:29 p.m. EST, on Monday, 23 December 1968, Apollo 8 crossed the dividing line that separates the Earth's gravitational sphere of influence from that of the moon, propelling men beyond control by Earth for the first time in history.

On Christmas Eve, Apollo 8 slipped behind the moon, and the three crewmen became the first to see the far side. The last TV transmissions of the day were verses from the first chapter of Genesis, read by the astronauts. From earlier transmissions, the vivid image of the emerald, brown, and cloud-wreathed Earth-rise above the barren gray surface of the moon gave the broadcast unusual drama. Some 400 000 kilometers away in space, the passengers in Apollo 8 beamed a special message: "Good night, good luck, a Merry Christmas and God bless all of you-all of you on the good Earth." On Christmas Day, the spacecraft's main engine fired a three-minute burst to push Apollo 8 out of lunar orbit and into trajectory for return to Earth. Swaying under its parachutes, the command module carrying the three crewmen settled safely into the Pacific late in the morning of 27 December.⁴²

A preliminary review of AS-503 data confirmed the faultless performance of the Saturn V launch vehicle. The fix for Pogo problems had worked; the J-2 engines of the S-II and S-IVB stages had worked; the modified igniter lines had worked. The Saturn V was in good shape for the next two flights leading up to "the big one"-the moon landing, less than seven months away.

As the next Saturn V in the series, the AS-504 vehicle for Apollo 9 comprised the first complete Apollo-Saturn configuration, with the lunar module aboard. Manned by astronauts James A. McDivitt, David R. Scott, and Russell L. Schweickart, Apollo 9 rose from KSC's Launch Complex 39A on 3 March 1969, for a low-Earth-orbit flight to check out docking of the CSM and LM in space. After the launch had been postponed for three days because of minor illness among the crew, the mission proceeded smoothly. All launch vehicle stages performed normally, with S-IVB reignition taking place after the CSM-LM docking maneuver and removal of the LM from the spacecraft-lunar-module adapter (SLA). With the S-IVB in an Earth-escape trajectory, mission control officials were unable to perform third-stage propellant dumps. The remainder of the mission proceeded with great success, including firing of the LM engines for descent and ascent maneuvers, transfer of two of the crew (McDivitt and Schweickart) to the LM and back again, a "space walk" by Schweickart, and splashdown on 13 March.

Apollo 10, launched on 18 May 1969, again carried the full Apollo-Saturn configuration with the Saturn V launch vehicle AS-505. After the second burn of the S-IVB to place the S-IVB, IU, and spacecraft into translunar trajectory, T. P. Stafford, J. W. Young, and E. A. Cernan completed the docking maneuver, shown live on commercial television for [369] the first time. The third-stage propellant dump came off normally, and the S-IVB went into an Earth-escape trajectory. The spacecraft continued toward the moon and entered into a low, circular lunar orbit. Stafford and Cernan undocked the LM and flew even closer to the lunar surface, testing the descent stage, which was jettisoned before the ascent stage rendezvoused with the CSM. The mission demonstrated the lunar orbit rendezvous technique and verified LM operations in the lunar environment, along with Apollo mission guidance, control, radar, TV transmission, and other mission systems. The crew completed the eight-day flight with splashdown in the mid-Pacific on 26 May 1969.⁴³

Meanwhile, the Saturn V vehicle AS-506 neared its special date in history, when Apollo 11 lifted off to carry three astronauts to a landing on the moon.

By the time of Apollo 11 (AS-506), the Saturn V launch vehicle had been considerably eclipsed in the public eye. Although television coverage and still photography inevitably portrayed the towering white rocket, the attention of the press and pubic was primarily fastened on the crew itself. Commander Neil A. Armstrong, command module pilot Michael Collins, and lunar module pilot Edwin E. Aldrin, Jr., spent the last few days prior to the flight in the fish bowl of public attention. It was symptomatic that the standard chronology of such aerospace events, Astronautics and Aeronautics, 1969, in recapitulating the mission of Apollo 11 devoted only a few lines to the Saturn V launch vehicle. The stars of the show were the crew, the spacecraft, and the spiderlike lunar module to land Armstrong and Aldrin on the surface of the moon. Understandably, the crew members themselves gave most of their thought and attention to the details of the spacecraft and the details of the lunar mission, leaving the care and feeding of the launch vehicle to the technicians from Marshall and their contractors.

This is not to say that the astronauts had no thoughts whatsoever about the vehicle. Early on the morning of 16 July 1969, riding in the van on the way to the launch pad, Michael Collins was struck again by the enormity of the vehicle that was to carry them aloft:

Last night the Saturn V looked very graceful, suspended by a cross fire of search lights which made it sparkle like a delicate opal and silver necklace against the black sky. Today it is a machine again solid and businesslike, and big. Over three times as tall as a Gemini-Titan, taller than a football field set on end, as tall as the tallest redwood, it is truly a monster.⁴⁴

AS-506 lifted off at 9:32 a.m. EDT, 16 July 1969. The number of observers around the launch site was conservatively estimated at a million, including 200 congressmen, 60 ambassadors, 19 governors, 40 mayors, and other public figures. Vice-President Spiro T. Agnew and former President and Mrs. Lyndon B. Johnson were there. Live television coverage of the liftoff was beamed to 33 countries on six continents [370] and watched by an estimated 25 million TV viewers in the United States alone. Radio commentary was heard by additional millions around the world.⁴⁵

Inside the spacecraft, Collins was very much aware of the gimbaling of the F-1 engines below, separated from the command module by the length of a football field. Watching prior Saturn launches, he had been impressed by the rigid and stately progress of the rocket off the pad. From the inside, the ride was jiggly and caused a kind of twittering feeling because of the gimbaling engines. There was not as much noise as Collins had expected, although it probably would have been difficult to communicate without the intercom. The Saturn ride, he reported, was a bit softer than the ride he had experienced in the Titan-Gemini launches. During the boost phase, the crew watched the gimbaling rates of the F-1 engines to make sure that no dangerous deviations from the course occurred, the flow rates of the propellants, and the thrust levels of the rocket engines. The first 10 seconds of the liftoff concerned the astronauts somewhat because the Saturn V rose so close to the umbilical tower. After that point, the crew relaxed a bit, and the noise and motion of the rapidly climbing rocket abated. Collins noted to himself that all the lights and dials indicated no problems. "All three of us are very quiet-none of us seems to feel any jubilation at having left the earth, only a heightened awareness of what lies ahead."⁴⁶

During the long months of astronaut training, the emphasis had been on operations and control of the spacecraft. It had not been necessary for the crew members to become experts on each of the booster stages. Still, because the Saturn V was going to be the prime mover of the mission, the crew picked up odds and ends of information and formed an opinion about it.

As far as Collins was concerned, the Saturn V vehicle itself had been the largest question mark in the Apollo-Saturn program. If there had been trouble with the command module or with the lunar excursion module, it would have been possible to have found a fix on it in a matter of months. If one of the huge, complex, Saturn V's had blown up, however, during one of the R&D launches, for example, then several years would have been required to have made a fix. According to Collins, "the Saturn V loomed in our minds as being the biggest single unknown factor in the whole lunar landing program." Now, as the Apollo 11 vehicle soared upward, consuming tons of propellants in the S-IC booster, the next concern was the S-II boost phase. "Staging, it is called, and it's always a bit of a shock, as one set of engines shuts down and another five spring into action in their place," Collins explained. "We are jerked forward against our straps, then lowered gently again as the second stage begins its journey. This is the stage which whisperers have told us to distrust, the stage of the brittle aluminum, but it seems to be holding together, and besides, it's smooth as glass, as quiet and serene as any rocket ride can [371] be." Although Collins and others had the feeling that the S-II was probably going to be the weakest link in the chain of the three stages of the Saturn V, Collins had been very much encouraged with the fervor of workers at North American Rockwell. He was impressed by their hard work and impressed by the way they caught up with the time lags in the S-II program. Still, all that talk about brittle aluminum and cracks in the S-II tankage left a few nagging thoughts. The S-II performed beautifully, however, leading up to the end of its boost phase and the staging of the S-IVB.

Nine minutes into the mission, the second stage shut down, and the crew waited, weightless, for the ignition and acceleration of the S-IVB third stage. Although third-stage ignition occurred on schedule, the momentary wait seemed interminable to the expectant astronauts. When the S-IVB ignited, the acceleration softly pushed the crew back into their contoured seats. The third stage, as Collins described it, had "a character all its own," with more crispness and rattles than the second stage. After 11 minutes and 42 seconds, the S-IVB single J-2 engine completed its first burn and switched itself off. The astronauts were in orbit, gently restrained by the couch straps, with a stunning view of the world through the spacecraft windows.⁴⁷

Over Australia the crew received word that they were "go" for the translunar injection (TLI) to boost the spacecraft out of Earth parking orbit into the trajectory to take it to the moon. This procedure required a second burn of the S-IVB. As the spacecraft swept out over the Pacific Ocean, the Saturn prepared to pump hydrogen and oxygen to the J-2 engine and meticulously dictated the orientation of the spacecraft by computers. The crew had no control over the vehicle at this point and were merely observers of the flickering lights on the panel indicating that the Saturn was counting itself down to ignition. When the J-2 finally started up, Neil Armstrong emitted a heartfelt "whew." Collins felt both relief and tension that they were on their way to the moon, one more hurdle behind them, as long as the S-IVB continued to burn. "If it shuts down prematurely," Collins speculated, "we will be in deep yogurt," ending up in a kind of odd-ball trajectory that would take some fancy computations on the part of Houston and the crew members to get back on track and set up for a reentry to Earth. Collins was amazed to see flashes and sparks of light, evidence of the thrusting engine mounted on the tail of the vehicle 33 meters below him. Abruptly a sudden lurch, like the shifting of gears, indicated that the Saturn had gone into a programmed shift in the ratio of fuel to oxidizer flowing to the engine. "Marvelous machine!" Collins thought to himself. "It's pushing us back into our seats with almost the same force we are accustomed to on earth (one G), although it feels like more than that. It's still not smooth, 'just a little tiny bit rattly,' says Buzz, but it's getting the job done and our computer is spewing out numbers which are very close to perfection." [372] The shaking was more noticeable in the final moments of the ride, but ended with a good shutdown of the engine. "Hey, Houston, Apollo 11. That Saturn gave us a magnificent ride," Armstrong exclaimed.⁴⁸

On 20 July, as the spacecraft passed around the far side of the moon, Armstrong and Aldrin separated the lunar module from the command and service modules and began their descent for the lunar landing, leaving Collins in a station-keeping orbit above. During the final approach, the crew realized that the lunar module was headed toward a large, inhospitable crater filled with boulders. Taking over manual control of the descent rate and horizontal velocity, Armstrong steered toward a landing site several kilometers away from the original target area. At 4:18 p.m. EDT, the lunar module touched down. Armstrong reported to Earth: "Houston, Tranquility Base here-the Eagle has landed." With obvious relief, Mission Control in Houston called back: "Roger, Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We are breathing again. Thanks a lot." Television cameras attached to the lunar module were oriented to catch Armstrong as he crawled out of the spacecraft. At 10:56 p.m. EDT, Armstrong stood on the lunar surface. "That's one small step for man-one giant leap for mankind."

Armstrong was joined by Aldrin several minutes later, and the two men carried out a brief ceremony, unveiling a plaque fixed on one of the LM struts ("Here men from the planet earth first set foot on the moon July 1969, A.D. We came in peace for all mankind."), and set up a small U.S. flag. During their stay on the moon, Armstrong and Aldrin deployed a series of scientific experiments and picked up assorted surface material and chunks of rock, along with two core samples, all totaling about 24 kilograms. Their tasks accomplished, the pair of astronauts took off in the LM early in the afternoon of 21 July. Following the rendezvous in lunar orbit, Armstrong and Aldrin joined Collins in the CSM. The LM ascent stage was jettisoned, and a CSM engine burn on 22 July put them on a trajectory back to Earth. The command module made its programmed separation from the service module on the morning of 24 July 1969, and Apollo 11 splashed down in the middle of the Pacific, only 24 kilometers from the recovery ship U.S.S. Hornet, at 12:51 p.m. EDT. The first moon mission was over.⁴⁹

Although other major launch vehicles, including the Saturn I, required a number of development flights, no major redesign efforts were required for the Saturn V. Even Apollo 6, the troublesome AS-502 vehicle, had required only moderate design changes to eliminate the Pogo difficulties and the problem with the J-2 engine igniter lines. This ....

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		Apollo 11 reaches the thin air on the edge of space (above, left); in the control room, NASA leaders (above, right to left) Charles W. Mathews, Wernher von Braun, George E. Mueller, and Samuel C. Phillips celebrate the orbiting of Apollo 11; left, Astronaut Edwin E. Aldrin, Jr., is photographed by fellow astronaut Neil A. Armstrong as he prepares to take his first step onto the lunar surface; below, left to right, George M. Low, Samuel C. Phillips, Thomas 0. Paine, and Robert R. Gilruth admire the first box of lunar samples to be returned to Earth.
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[374] ...observation is not to say that there were no variations among vehicles or changes from one vehicle to the next. Adjustments were made in timing, sequences, propellant flow rates, mission parameters, trajectories. There was continued modification and refinement in the course of the program. Each mission also produced a list of malfunctions, anomalies, and significant deviations that required certain configuration or operational changes. Engines and other equipment were constantly submitted to fine tuning to ensure and enhance their proper operation in flight. It is interesting to note, for example, that the thrust of individual engines varied even within a vehicle and from one mission to another, as technicians continued to adjust and change their operational characteristics.⁵⁰

The remaining six vehicles in the Apollo-Saturn program reflected this low-profile improvement and modification program. There were no major vehicle changes, and no catastrophic perturbations in the operational history of the Saturn V launch vehicles, although there were still dramatic moments and small problems that continued to crop up from time to time. The flight of Apollo 12 was electrifying, to say the least. Before it got away on 14 November 1969, the vehicle had been delayed by a liquid-hydrogen fuel tank leak, threatening to scrub the mission. When that problem was finally whipped, stormy weather on the morning of the launch portended additional delays. With a long string of successful flights behind them, however, NASA officials decided to go ahead and commit Apollo 12 in the midst of a heavy downpour. As it climbed away from the launch pad, AS-507 was lost to sight almost immediately as it vanished into the low-hanging cloud layer. Within seconds, spectators on the ground were startled to see parallel streaks of lightning flash out of the cloud back to the launch pad. Inside the spacecraft, Conrad exclaimed, "I don't know what happened here. We had everything in the world drop out." Astronauts Pete Conrad, Richard Gordon, and Alan Bean, inside the spacecraft, had seen a brilliant flash of light inside the spacecraft, and instantaneously, red and yellow warning lights all over the command module panels lit up like an electronic Christmas tree. Fuel cells stopped working, circuits went dead, and the electrically operated gyroscopic platform went tumbling out of control. The spacecraft and rocket had experienced a massive power failure. Fortunately, the emergency lasted only seconds, as backup power systems took over and the instrument unit of the Saturn V launch vehicle kept the rocket operating. As the huge Saturn continued to climb, technicians on the ground helped the astronauts weed out their problems, resetting circuits and making sure that operating systems had not been harmed by the sudden, unexplained electrical phenomenon. Apollo 12 went on to complete a successful mission, and NASA scientists explained later that Apollo had created its own lightning. During the rocket's passage through the rain clouds, static electricity built up during [375] its ascent through the cloud cover had suddenly discharged and knocked out the spacecraft's electrical systems in the process.⁵¹

The Apollo 12 mission survived the lightning charge for a number of reasons, but one significant factor was related to the ingrained conservatism at Huntsville in designing the rocket booster engines. During one early phase in planning the Apollo-Saturn vehicle, there had been considerable debate about designing spacecraft guidance and control systems to take charge of the entire launch vehicle, including the booster stages. Marshall had opposed the idea, arguing that the requirements of translunar guidance and control, lunar orbit control, lunar module rendezvous, and other jobs would be plenty for the spacecraft computer to handle. The peculiarities of the booster stages predicated quite dissimilar computer functions and schemes for guidance and control. Marshall finally won its case: the booster stages got their own guidance and control equipment, represented by the instrument unit. Besides, this approach provided redundancy, because the spacecraft got a separate system. An external umbilical connection between the command and service modules made the spacecraft guidance and control system vulnerable to the lighting charge. When the spacecraft gear was knocked out on Apollo 12, the booster guidance and control system, a separate piece of hardware, kept the vehicle operating and on course while the spacecraft electronics were reset and put back in operation. This vignette of Apollo-Saturn operational lore was a favorite of several MSFC managers.⁵²

Apollo 13 got off successfully on 11 April 1970. Because Thomas K. Mattingly II had failed to develop immunity after exposure to German measles, there was a last-minute substitution in the three-man crew, with John L. Swigert replacing him as command module pilot, joining Fred W. Haise, Jr., as lunar module pilot, and James A Lovell, Jr., as commander. The launch vehicle created some consternation among the mission officials monitoring AS-508 in flight, because the center engine of the S-II stage cut off 132 seconds too early, and the remaining four J-2 engines burned 34 seconds longer than predicted. This left the space vehicle with a lower velocity than planned. Therefore, the S-IVB had to burn nine seconds longer than predicted to achieve proper orbital insertion. This hiatus in the boost phase of the mission led to questions about adequate propellants remaining in the S-IVB for the translunar injection burn. Double- checked calculations indicated that there were adequate propellants, and the second S-IVB burn put Apollo 13 into trajectory toward the lunar surface. The remainder of the flight was normal until about 56 hours after liftoff, when Swigert tensely called back to Mission Control, "Hey, we've got a problem here." With sudden concern, ground controllers responded, "This is Houston, say again please." This time Lovell replied, "Houston, we've had a problem."

An explosion had occurred in the No. 2 oxygen tank of the service [376] module. As a result, all fuel-cell power was lost, as well as other CSM failures, including dangerously low oxygen supplies. Astronauts and mission controllers quickly agreed to abort the mission and concentrate on getting the three-man crew safely back home. Apollo 13 went into a "lifeboat mode" with emergency measures to stabilize the spacecraft environment and stretch the consummable items for life support as far as possible. Using the descent engine of the lunar module after completing a lunar flyby, Apollo 13 went into a return trajectory at a faster rate. Happily, the tense six-day mission ended successfully on 17 April, with splashdown in the Pacific Ocean. In the aftermath of the near disastrous flight of Apollo 13, NASA convened a special Apollo 13 review board. Working in high gear, the board's painstaking research pinpointed the problem as a pair of defective thermostatic switches that permitted dangerously high heat levels in a heater tube assembly associated with the oxygen tank equipment. The board stated that combustion probably occurred as the result of a short circuit from faulty wiring, resulting in a combustion in the oxygen tank. Following release of the board's report, there was extensive redesign of the oxygen tank, wiring, and related materials with a high combustion probability. There was an impact on the launch of Apollo 14, which was slipped to 31 January 1971.⁵³

An interesting sidelight of the flight of Apollo 14 involved the three-man crew, which included astronaut Alan B. Shepard, who had flown on the first U.S. suborbital launch in the Mercury program back in 1961. A decade later, Shepard was going to the moon. The countdown and launch of AS-509 proceeded according to the book, with the only delay caused by high overcast clouds and rain that postponed the ignition by 40 minutes and 3 seconds. Failure of a multiplexer in the instrument unit meant that some information on the condition of the vehicle during flight was lost, and there were some minor problems during the docking maneuver in orbit. Aside from that, Apollo 14 was a perfect mission.⁵⁴

The last three vehicles, AS-510 through AS-512, performed without a hitch. The payload, however, was continuously climbing. These last three launches included the lunar rover vehicle, which added almost 225 kilograms to the payload of the Saturn V. The rover turned out to be extremely significant, permitting astronauts to extend greatly the range of surface explorations and increasing their stay time.⁵⁵ The uprated engines of the Saturn V, which permitted it to boost this additional weight into orbit, turned out to be a function of thoughtful long-range planning by NASA engineers. In the evolution of rocket vehicles, the actual payload requirements almost always turned out to be greater than originally planned. As a result of bitter experience, engine designers kept in mind the likelihood that their creations would have to be uprated from time to time. In addition to this consideration, engine designers normally incorporated a certain degree of margin in setting up the specifications for engine development. If the specifications called for an engine of 4.5 [377] million newtons (1 million pounds) thrust, it might be designed for 5.3 million newtons (1.2 million pounds) thrust to be sure that the original specification line was met. With operational experience, it was then possible to uprate the engine by relatively minor changes-improving the turbopump and the tubing (to improve flow rates), adjusting the injector for better mixing (to get a higher percentage of the fuel burned and increase the specific impulse)-these all were contributing factors to the success of uprating the engines of the Saturn V vehicle. In this way, the Saturn V was able to absorb not only the increasing weight of the command and service modules early in the program, but the added weight of scientific equipment and other paraphernalia such as the rover in the later stages of the Apollo-Saturn program.⁵⁶

Saturn I and Saturn IB missions had been intended to clear the way for Saturn V launch vehicles. Normally, the worst difficulties would have shown up in the R&D flights of the former. Instead, one of the most baffling periods came early in the Saturn V flight series.

Saturn V development began auspiciously, with the calculated gamble on AS-501's "all-up" launch. The mission garnered precious time and raised confidence in the reliability of Saturn stages. The time and reliability factors seemed to slip away, however, with the perplexing flight of AS-502 and slipping schedules for the lunar module to be flown on AS-503. Recovering quickly, NASA and contractor personnel kept the momentum of Apollo-Saturn through diligent sleuthing to resolve the problems uncovered in AS-502 and responded flexibly to revise the....

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[378] ....probable mission of AS-503. In light of its uncertain background, the circumlunar flight of Apollo 8 was a triumph.

There were two more Saturn V launches, wringing out the last details of mission hardware, before AS-506 took a crew to the lunar surface and back. Apollo 11 was a textbook flight, carried out in an unprecedented public exposure of worldwide dimensions. From beginning to end, it was a spectacularly successful mission, a historic odyssey in the annals of human exploration. The remaining six missions in the Apollo program were completed with no major difficulties stemming from the launch vehicles. In retrospect, the conservative design inherent in the Saturn launch vehicles paid off. Saturn V not only carried a spacecraft and lunar module whose weight had spiraled upward from original guidelines, but accommodated additional equipment such as the lunar rover. The added payload capability of the Saturn V also permitted delivery of more scientific gear to the moon, enhancing the scientific results of the Apollo-Saturn missions.⁵⁷

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