24 August 2015

What If Apollo Astronauts Could Not Ride the Saturn V Rocket? (1965)

Image credit: NASA
George Mueller left private industry to become NASA's new Associate Administrator for Manned Space Flight in September 1963. He immediately asked John Disher and Adelbert Tischler, two veteran NASA engineers not directly involved in Apollo, for an independent assessment of the moon program. On 28 September, they told Mueller that it could not achieve President Kennedy's goal of a man on the moon by 1970. They estimated that NASA might be able to carry out its first manned moon landing in late 1971.

Mueller took drastic action. When he joined NASA, the Apollo flight-test plan was based on the philosophy of incremental testing, which meant that untried rocket stages would launch only dummy stages and dummy spacecraft. On 29 October 1963, Mueller informed his senior managers that Apollo test flights would henceforth use complete systems. Mueller's directive meant that, when the Saturn V S-IC first stage flew for the first time, it would be as part of a complete 363-foot-tall three-stage Saturn V. The new "all-up" approach would, it was hoped, slash the number of test flights needed before the Saturn V could launch astronauts to the moon.

George Mueller. Image credit: NASA
All-up Saturn V testing, today hailed as a visionary and heroic step, made many Apollo engineers nervous. The Saturn V was the largest rocket ever developed. It had engines of unprecedented scale and power: the F-1 engines in the 33-foot-diameter S-IC first stage, which burned RP-1 kerosene fuel and liquid oxygen, remain today the largest ever flown. The J-2 engines in the top two stages, the 33-foot-diameter S-II second stage and the 22-foot-diameter S-IVB stage, gulped down temperamental liquid hydrogen and liquid oxygen propellants. Cautious engineers could see many opportunities for trouble, and they were aware that problems they could not foresee might be the most difficult to solve. Many believed that NASA should have in place backup plans in case the Saturn V suffered development delays.

Eighteen months after Mueller's announcement, E. Harris and J. Brom, engineers with The RAND Corporation think tank, proposed one such back-up plan. Their brief report, originally classified "Secret," looked at how NASA might accomplish a manned moon landing by 1970 if the Saturn V could not be certified as safe enough to launch astronauts.

Harris and Brom's backup plan would see the Apollo Saturn V lift off without astronauts on board. It would expend its S-IC first stage and S-II second stage in turn, then its S-IVB third stage would place itself plus unmanned Apollo Command and Service Module (CSM) and Lunar Module (LM) spacecraft into parking orbit about the Earth. Because it would carry no crew, the CSM would need no Launch Escape System (LES) tower on its nose.

The astronauts would reach Earth orbit separately in a ferry CSM launched atop a two-stage Saturn IB rocket. The ferry CSM would carry a special drogue docking unit on its nose for linking up with the unmanned CSM's nose-mounted probe docking unit. The special drogue, the only new system required for RAND's backup plan, would need about one year and "perhaps several million dollars" to develop.

The top of the Apollo 13 Lunar Module Aquarius. The red arrow points to the concave drogue docking unit. Image credit: NASA
The astronauts would dock with and transfer to the lunar mission CSM in Earth orbit, then would cast off the ferry CSM. The remainder of their mission would occur as in NASA's Apollo plan (image at top of post). The astronauts would restart the S-IVB stage to perform Trans-Lunar Injection (that is, to leave Earth orbit for the moon). After S-IVB stage shutdown, they would detach the CSM from the Spacecraft Launch Adapter (SLA) shroud that linked the bottom of the CSM to the top of the S-IVB. The SLA, made up of four segments, would peel back and separate, revealing the LM. The CSM would then dock with the drogue docking unit on top of the LM and pull the moon lander free of the spent S-IVB stage.

The RAND engineers declined to recommend whether the unmanned Saturn V or the manned Saturn IB should be launched first. They noted that liquid hydrogen fuel in the Saturn V's S-IVB stage would boil and escape at a rate of 700 pounds per hour; the stage would thus need to be restarted within 4.5 hours of reaching parking orbit if it were to retain enough propellants for Trans-Lunar Injection. They noted that deletion of the 2900-pound LES would make the unmanned Saturn V that much lighter, so its S-IVB stage could be loaded with an extra 2900 pounds of liquid hydrogen; that is, enough to permit it to loiter in low-Earth orbit for nearly 10 hours. Extending the loiter time further would demand a complex and costly S-IVB stage redesign.

Launching the crew first would avoid the S-IVB stage loiter-time constraint. Harris and Brom noted that, though the Apollo lunar mission was scheduled to last only from seven to 10 days, NASA planned a 14-day Earth-orbital Gemini mission by the end of 1965 to certify that astronauts could withstand long space flights. Assuming that the Gemini flight confirmed that humans could endure 14 days in weightlessness, then the ferry CSM crew could in theory wait for from four to seven days for the unmanned Saturn V to join them in Earth orbit. Harris and Brom recommended that, if the unmanned Saturn V became delayed so that the astronauts waiting in orbit could not accomplish a lunar mission and return to Earth within 14 days of first reaching space, then they should carry out an unspecified backup Earth-orbital mission in the ferry CSM so that their flight would not be wasted.

NASA officials did not take up the Harris and Brom proposal, though for a time in 1968 they might have wished that they had. The first unmanned Saturn V test flight, Apollo 4, lifted off on 9 November 1967. In keeping with Mueller's 1963 directive, it included complete S-IC, S-II, and S-IVB stages, plus a CSM with LES. Because LM development had hit snags, a dummy LM rode inside its SLA. The eight-hour Earth-orbital mission was an unqualified success.

Troubled flight: Apollo 6 unmanned Saturn V test, 4 April 1968. Image credit: NASA
Apollo 6 was, however, another story. On 4 April 1968, two minutes into its unmanned flight, the second Saturn V to fly began to shake back and forth along its long axis. Dubbed "pogo" by engineers, the violent oscillations tore pieces off the SLA and damaged one of the S-II's five J-2 engines. Following S-II ignition, the engine under-performed and shut down prematurely, then a control logic flaw caused a healthy S-II engine to shut down. The remaining three S-II engines burned for a minute longer than planned to compensate for the two failed engines. The S-IVB's single J-2 engine then burned for 30 seconds longer than planned to reach a lopsided Earth orbit. Two orbits later, the engine refused to restart.

The pogo oscillations might have injured astronauts; the S-IVB failure would certainly have scrubbed their flight to the moon. Post-flight analysis showed, however, that the pogo and engine failures had relatively simple fixes. After intense internal debate, NASA decided in October 1968 that the third Saturn V should launch Apollo 8 astronauts Frank Borman, James Lovell, and William Anders to the moon. The giant rocket performed flawlessly, placing the Apollo 8 CSM on course for lunar orbit on 21 December 1968.


"Apollo Launch-Vehicle Man-Rating: Some Considerations and an Alternative Contingency Plan (U)," Memorandum RM-4489-NASA, E. D. Harris and J. R. Brom, The RAND Corporation, May 1965

The Apollo Spacecraft: A Chronology, Volume II, NASA SP-4009,  Mary Louise Morse & Jean Kernahan Bays, NASA Scientific and Technical Information Office, 1973, pp. 104-106

Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, NASA SP-4206, Roger Bilstein, NASA, 1980, pp. 347-363

Apollo: The Race to the Moon, Charles Murray & Catherine Bly Cox, Simon & Schuster, 1989, pp. 153-162

More Information

What If Apollo Astronauts Became Marooned in Lunar Orbit? (1968)

What If an Apollo Lunar Module Ran Low on Fuel and Aborted Its Moon Landing? (1966)

What If An Apollo Saturn Rocket Exploded on the Launch Pad? (1965)


  1. Why send up an unmanned CSM, when they were going to launch a manned one separately? Was it just that the Saturn V was big enough to launch the whole stack, so they might as well use it?

    1. Two reasons I can think of: You still need to have a TEI burn to leave Earth orbit. The only vehicle on hand to do that is the S-IVB that goes up on the Saturn V. How could you mate it up with the manned CSM? Oh, I suppose you could just stick a faring on top of the LEM and have that detach on reaching orbit, and have the manned CSM dock with the LEM, but hold off on extraction until after the burn. But I think that would pose some engineering issues that would have to be sorted out. Far easier to simply use the architecture you already have.

      The other problem is that the Saturn IB didn't have enough delta V to launch a fully fueled Apollo CSM. All five Apollo CSM's launched on the IB were short-fueled. That's really the killer factor here.

    2. That's right, the idea was to assume that the basic Apollo LOR plan would work and if the Saturn V couldn't be man-rated, adopt the backup plan. Of course, the S-IVB would have to work, but getting one stage to work would be a smaller problem than getting the whole Saturn V to work in concert.


  2. Very interesting post; this is the American version of the podsadka scheme minus the EVA.

    There's a very good operational reason for launching the Saturn IB first...if the Saturn IB suffers a launch failure the expensive Saturn V is still on the ground and that hardware can be used for the next mission.

    1. I think they were less concerned about Saturn IB problems since they'd already been flying Saturn Is by the time Mueller came on board. The conduct of that test program, plus Centaur troubles (Centaur was seen as the pathfinder for U.S. use of cryogenic propellants) was one reason Mueller sought to adopt the "all-up" scenario. From a managerial/bureaucratic standpoint, it was easier to build the big rocket and hammer out the problems than to build each stage and hammer out the problems. Too many second stage failures, say, might create and fuel opposition to the program so that work was abandoned ahead of a big investment in the third stage.


  3. I don't suppose anyone has the NASA technical note or procedures document where the contingency EVA, in case of LM failure to dock with the CSM after ascent from the lunar surface, is detailed? We all know about it but I can't easily find the actual procedures.

  4. I know I don't. The only thing I can suggest is a look at the Apollo 9 press kit, which should be online. That was meant to rehearse contigency EVA between the LM and CSM, though in fact that was not carried out.


    1. Many thanks but I managed to find it through some links at the ALSJ. This Apollo 11 flight plan lists contingency EVAs, including the Extravehicular Transfer (EVT) procedures.


      There were also some images of the Apollo 17 ce cards, which were auctioned off:




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