After years of effort, NASA has finally chosen a pair of contractors to build replacements for the now-retired Space Shuttle to send Americans into Earth orbit and possibly beyond. Ironically, the craft being built by Space X and Boeing are capsule-based concepts not too dissimilar to the Apollo spacecraft retired by NASA four decades ago to make way for the Shuttle. The development of the newer crewed capsule designs in many ways mirrors the development of Apollo and they owe much to the test flights of the Apollo spacecraft first flown a half a century ago.

The first Apollo orbital test flight, called A-101, was successfully launched as part of the SA-6 Saturn I development flight on May 28, 1964 (see “The First Apollo Orbital Test Flight“). The objectives of the second test flight, A-102, were similar to those of its predecessor: demonstrate the compatibility between the Apollo spacecraft and Saturn I launch vehicle as well as verify the design of the Apollo during launch and ascent into orbit. This flight would also demonstrate a new mode of jettisoning the Apollo Launch Escape System (LES) during ascent after it was no longer needed.

Like the A-101 test flight, the Apollo Command/Service Module (CSM) payload for this flight consisted of a boilerplate spacecraft designated BP-15. Boilerplate models mimic the mass, shape and dynamic properties of flight models but otherwise only carry systems and instruments needed for the tests being conducted. Their low costs and adaptability make them ideal for early testing of a new spacecraft design. BP-15 was a 6.6 meter tall aluminum structure with a maximum diameter of 3.9 meters and total mass of 7,800 kilograms including 1,270 kilograms of strategically placed lead ballast. The exterior of the Command Module (CM) was covered with cork insulation to prevent overheating during ascent. The spacecraft was instrumented to acquire 133 measurements including heat rates, temperatures, aerodynamics, and static loads that were sent to the ground using three telemetry systems. Unlike BP-13 flown on the A-101 mission, one of the simulated attitude control engine “quads” on the CSM of BP-15 was also instrumented on this flight to gather information on heating and vibration loads to verify Apollo engineers’ estimates.

On top of BP-15 was the 7.7 meter tall LES that would be jettisoned during ascent employing not only the normal jettison motor but also a pitch motor for the first time to turn the LES safely out of the flight path of the ascending rocket. The ultimate goal of this flight was to place BP-15 into a 185 by 217-kilometer orbit that would approximate the parking orbit to be used by future Apollo lunar flights. Once in orbit, BP-15 and the S-IV second stage of the Saturn I launch vehicle would remain attached to each other just as they had in the previous flight. This satellite would have a total length of 24.4 meters and a dry mass of about 16,650 kilograms. Data were required to be collected for only a single orbit before the batteries were expected to be depleted and no recovery would be attempted. The low orbit was expected to decay in about three days with the spent stage and payload burning up during reentry.

The launch vehicle for the A-102 test flight was a Block II Saturn I designated SA-7. This was the seventh test flight of the Saturn I program and the third orbital flight. The Saturn I was developed for NASA at the Marshall Space Flight Center in Huntsville, Alabama by a team headed by famed German-American rocket pioneer, Wernher von Braun. SA-7 was the third flight of the improved Block II model of the Saturn I with a first stage, designated S-I, sporting eight uprated Rocketdyne H-1 engines generating 6,700 kN at liftoff. The second or S-IV stage of the Block II Saturn I employed six hydrogen-fueled Pratt & Whitney RL-10 engines to generate 400 kN of thrust. The SA-7 with its Apollo payload was 58 meters tall with a launch mass of 517 metric tons.

Several changes were made to the SA-7 based on experience with earlier flights to improve the performance and reliability of the rocket. This was the first Saturn I flight to rely on the new ST-124 guidance platform carried in the Instrument Unit between the top of the launch vehicle and the payload. This replaced the ST-90 system used on the previous two orbital flights. This was also the first Saturn I flight to employ upgraded Mark III H turbopumps in the first stage’s eight H-1 engines. The Mark III H included design changes to prevent the type of engine turbopump failure that occurred during the previous flight of SA-6. The venting system of the S-IV stage was also altered to minimize propulsive effects from the outgassing of leftover cryogenic propellants once in orbit in order to avoid increasing the spin rate of the stage and its attached payload. The SA-7 had 13 telemetry systems that gathered a total of 1,245 measurements of vehicle performance during flight. Combined with the data from BP-15, the A-102/SA-7 mission returned the largest number of telemetry measurements of any American launch up until that time.

After weeks of delays because of hardware issues and a pair of hurricanes, SA-7 carrying BP-15 successfully lifted off from Launch Pad 37B at the Cape Kennedy (which had been renamed in December 1963 in honor of the late President Kennedy) at 12:22:43 PM EDT on September 18, 1964. The first stage operated normally and shutdown less than a second later than planned 147 seconds after launch. Just 2.5 seconds later, the S-IV second stage ignited followed by the successful jettisoning of the LES 160 seconds into the flight. The six RL-10 engines of the S-IV stage shutdown just 1.3 second later than planned 621 seconds after launch. The S-IV stage and the attached BP-15, which had an orbital mass of 17,816 kilograms including the unused propellant, were now in a slightly higher than planned 212.7 by 226.5-kilometer orbit. Telemetry was received from the tracking transmitter on the Apollo until the batteries were exhausted during the fifth orbit. The silent satellite was then tracked by radar as its orbit decayed and finally fell to Earth over the Indian Ocean during the 59th orbit on September 22.

Despite some minor anomalies, all of the major test objectives of the SA-7 flight were met. One of the anomalies was bad data from the thermocouples used to gather heating data from the CSM attitude control quad but usable data could be gathered on subsequent test flights. There were also problems with the recovery of the eight film pods from cameras on the first stage that were suppose to document various operations especially those associated with stage separation. The film pods were supposed to be ejected 172 seconds after launch but they ended up parachuting farther downrange than the planned 850 kilometers and into the path of Hurricane Gladys preventing their recovery. Two months afterwards, a pair of barnacle-encrusted pods washed ashore with their precious cargo of film undamaged. With this successful flight and with only three more Saturn I test flights planned through mid-1965, the Saturn and Apollo programs were one step closer towards the eventual goal of sending Americans to the Moon.

Related Reading

“The First Apollo Orbital Test Flight”, Drew Ex Machina, May 28, 2014 [Post]

“The First Apollo-Little Joe II Launch”, Drew Ex Machina, May 13, 2014 [Post]

“The Coolest Rocket Ever”, Drew Ex Machina, March 30, 2014 [Post]

“A History of American Rocket Engine Development”, Drew Ex Machina, June 9, 2014 [Post]

General References

Roger E. Bilstein, Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, University Press of Florida, 2003

Alan Lawrie, Saturn I/IB – The Complete Manufacturing and Test Records, Apogee Books, 2008

Mary Louise Morse and Jean Kernahan Bays, The Apollo Spacecraft – A Chronology Volume II, SP-4009, NASA, 1973

“NASA to Launch Seventh Saturn I in Apollo Test”, Press Release 64-228, NASA, September 13, 1964