Moonport: A History of Apollo Launch Facilities and Operations|
Testing the Booster (SA-2 - SA-4)
After the launch of the first Saturn rocket on 27 October 1961, the rest of the research and development schedule went like clockwork. The nine remaining launches of the Saturn I program (April 1962-July 1965) set a record for consistent performance while receiving a minimum of recognition. The launches coincided with America's first successes in manned spaceflight and all eyes were on the astronauts. When one of them was cradled out into space in a Mercury shot, the nation paused to participate by television in the liftoff, flight, and recovery.
While no human passengers lent drama to the Saturn I flights, Saturn team members had much to be proud of. The ten launches proved the clustered booster concept, the hydrogen-propelled upper stage, and the Cape's ground facilities. In 1964, in what was to become a historic collaboration, the Saturn rocket and Apollo vehicle were mated for the first time, with both SA-6 and SA-7 flying an Apollo "boilerplate" model.* The last three Saturn vehicles carried Pegasus, a satellite flown in low earth-orbit to detect meteoroids. Although Marshall Space Flight Center engineers introduced new features in every Saturn I launch, the tests came off without a major failure. The confidence gained from these successes was Saturn I's great contribution to the Apollo program.
SA-2 (25 April 1962)
The second Saturn I, vehicle SA-2, arrived at Cape Canaveral on 27 February 1962. Launch preparations took 58 days. Although there were no serious delays, daily status reports revealed many minor problems:
A leak has been detected between the injector and the LOX [liquid oxygen] dome on Engine Position No. 4... Discussions concerning this matter are being held with Rocketdyne and Propulsion and Vehicle Engineering Laboratory personnel.
Attempts to correct the LOX dome leak, reported yesterday, have failed to remedy the problem. Further discussions are now in progress, to determine whether to buy the "as is" condition or change the engine. A change in the overall schedule will result if the engine has to be changed.
Discussion between Propulsion and Vehicle Engineering Laboratory, Rocketdyne, and LOD has resulted in a decision to launch without replacement on engine, Position 4.
Minor difficulties exist in the guidance sub-system; these are under investigation. No interference was noted during the RF [radio frequency] test.
The service structure was removed from around the vehicle; alignment and RF checks were made and the structure replaced around the vehicle. Minor difficulties were encountered with structure operations.
Two strain gauges have been found to be damaged (LOX stud and truss member). Attempts will be made to repair the truss member gauge.
The manhole cover on the top of the S-V-D was found damaged yesterday. A replacement cover has been received from MSFC, which will be installed this afternoon.
A modification to the fuel density and fuel level sensing lines has been completed.
Fuel loading test in the manual mode is in progress. . . . During preparations for the fueling test, a leak was detected in the fuel level computer. The computer was removed and sent to the lab for repair . . . . An effort was made to get a spare computer from MSFC. A second computer was sent down by plane Saturday evening [7 April] . . . . It developed that the second computer was not in a sufficient state to be properly calibrated prior to today's operation. Therefore, the primary effort Sunday night was directed toward readying the original computer for the test today.
LOX tanking test was postponed one day after difficulties developed in the electrical tanking computer circuit. Attempts are being made to isolate and correct the problem area. The one day delay . . . will not affect the overall schedule. If the test can be satisfactorily performed tomorrow, we will be back on the original schedule by [16 April].
The fuel loading computer has been repaired and functionally checked satisfactorily.
A potential problem area exists with respect to three hydraulic systems. If it should be declared by Propulsion and Vehicle Engineering, Astrionics and Quality Laboratories that the three systems must be checked, the launch date [25 April] cannot be met.1
Marshall engineers had made one significant change in the SA-2 booster design, placing additional baffles in the propellant tanks to prevent a recurrence of the sloshing experienced in the latter part of the SA-1 flight. The countdown on 25 April went smoothly; the only hold came when a ship strayed into the flight safety zone, 96 kilometers downrange. The successful flight was terminated with a dramatic experiment. When SA-2 reached an altitude of 105 kilometers, launch officials triggered the command destruct button. Project "High Water" released 86,000 kilograms of water from the dummy upper stages, giving scientists a view of a large disturbance in the upper regions of the atmosphere. A massive ice cloud rose 56 kilometers higher in a spectacular climax.2
SA-3 (16 November 1962)
A tropical storm greeted the SA-3 vehicle's arrival at the Launch Operations Center on 19 September 1962. Three days of rain and high winds delayed erection of the booster, and conditions were still unfavorable when the launch team resumed work on the 21st. Aeronautical Radio Incorporated engineers, hired by NASA to review Saturn operations, reported: "The erection operation was safely performed but is rather hazardous, with technical personnel climbing around on top of the horizontal booster to install hoisting equipment. This operation was performed on the slick plastic covering of the S-1 stage in a wind of up to [37 kilometers per hour]." The Aeronautical Radio team considered the preparation prior to stage erection (removing the end ring segments) "a relatively slow, inefficient, and dangerous operation, with a considerable amount of trial and error," and recommended more familiarity with the instruction handbooks. During the eight-week checkout, the Washington, D.C., firm found other shortcomings such as "the use of metallic hammers to urge recalcitrant components into place." The observers noted that proper tools were not always handy, "and expediency sometimes prevailed." They concluded, however, that the "efficiency and dedication" of Hans Gruene's Launch Vehicle Operations Division** was instrumental in the success of the Saturn test.3
SA-3 lifted from Cape Canaveral on 16 November 1962. Debus asked von Braun not to invite outside visitors, as the United States armed services were still on alert for the Cuban missile crisis. The rocket incorporated a number of important new features. The first two Saturns had used 281,000 kilograms of propellant, about 83% of the booster's capacity. Marshall, wanting information for the new Saturn IB program, flew SA-3 with a full propellant load to test the effects of a lower acceleration and a longer firststage flight. The flight also tested the retrorockets that would separate the two live stages on SA-5, the first launch of the upcoming block II series. SA-3 flew three other important prototypes: the ST-124 stabilized platform, a pulse code modulated data link, and an ultrahigh-frequency link. The stabilized platform was a vital part of the Saturn guidance and control system, containing gyroscopes and accelerometers that fed error information to the control computers, which provided steering signals to the gimballed engines. The data link's importance lay in its ability to transmit digital data, a vital ingredient in plans for automation of checkout and launch procedures. The ultrahigh-frequency link would be used to transmit measurements, such as vibration data, that could not be handled effectively on lower frequencies.4
SA-4 (28 March 1963)
SA-4 ready for launch from LC-34, March 1963.
SA-4 set records for the shortest launch checkout (54 days) and the longest countdown holds (120 minutes) of the block I series. At T-100 minutes on launch day, test conductor Robert Moser called a 20-minute hold while the launch team adjusted the yaw alignment of the ST-90 gyro guidance platform. Readings from a ground theodolite showed that the platform was not properly aligned on the launch azimuth. An operator oriented the Watts theodolite on a geodetic survey line and then turned the head of the instrument to the launch vehicle. The alignment prism in the ST-90 platform reflected a light directed from the theodolite. If the platform was aligned properly, the reflection from the prism appeared in the center of the theodolite's scope. In this case, the problem was with the theodolite and not the gyro platform.
The final hold came at T-19 minutes as a result of a LOX bubbling test. Andrew Pickett's propulsion group performed the test late in the countdown to verify the flow of helium to the LOX suction ducts of the eight engines. The decreasing temperature of the LOX indicated a proper flow of helium, but the propulsion panel did not register a signal that the LOX bubbling valve was open. Without the signal the terminal sequencer would shut down. Pickett's team, along with Isom Rigell's electrical engineers, improvised a bypass for the valve signal on the sequencer. The propulsion team assured a proper LOX temperature for the Saturn and then initiated the bypass manually as the sequencer brought the vehicle to liftoff.5
In SA-4's most important test, officials deliberately shut down the number 5 engine 100 seconds after liftoff. Booster systems rerouted propellants to the seven other engines. Contrary to some predictions, the shutdown engine remained intact and the imbalance of hot gases on the engine compartment heat shield had no ill effect. The SA-4 vehicle simulated all block II protuberances on the dummy second stage, e.g., fairings and vent ducts, to determine the aerodynamic effects of a live second stage. Block II antenna designs were also flown. The SA-4 vehicle employed a new radar altimeter and two experimental accelerometers for pitch and yaw measurements. After the successful flight, the von Braun team in Huntsville looked confidently toward two-stage missions.6
Pad damage from the first four launches did not surpass expectations. Restoration cost an average $200,000 and took one month. LVOD officials were particularly interested in assaying pad damage after the launch of SA-3. One of the mission's goals was to determine the effect on the pad of an increased propellant load with the consequent slow acceleration and longer exposure to rocket exhaust. The damage was comparable to the first two launches. The only effect readily attributable to the slower acceleration was increased damage to the pedestal water deluge system (the torus ring) and a warping of the flame deflector.7
The LOX fill mast at the base of the rocket had to be replaced after each launch. The 21-meter cable mast assembly extending up alongside the rocket also crumpled during each of the first two launches. After watching the long aluminum fixture collapse the second time, officials replaced it with an umbilical swing arm. The Huntsville engineers converted a swing arm intended for the SA-5 launch and shipped it to the Cape in early August. At LC-34, Consolidated Steel and Ets-Hokin-Galvin began work on the new umbilical tower two weeks after the SA-2 shot.# The swing arm, mounted in August, suffered very little damage in the SA-3 launch.8
* Boilerplate means a full-scale model of a flight vehicle flown on research and development missions, without some or all of the internal systems.
** See chap. 7. From 1 July 1962 to 24 April 1963, LVOD was a division of MSFC. Since Debus and Gruene served as Director and Deputy Director of both the Launch Operations Center and LVOD, this was an administrative distinction with little or no bearing on launch activities.
# Saturn construction became rather complicated at times. LOD personnel observed that the column splices connecting the new construction to the existing 8-meter base were not consistent with Maurice Connell & Associates design drawings. In a letter to the Corps of Engineers, Debus stated, "Upon investigation, it appears as though the Jacksonville District Office had instituted changes in the original design without the concurrence of LOD, who has the design responsibility." The fabricator of the first phase steel had apparently erred in the column's angle of slope. The Corps solution, using one-inch diameter interference body bolts, was satisfactory; but the construction teams were using one-inch high-tension bolts, which had only two-thirds the necessary strength. Debus requested that the Corps get LOD's approval in future modifications.