RAND's Apollo backup plan (1965)

George Mueller left private industry to become NASA's 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 September 28, 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 carry out its first manned moon landing in late 1971.

Mueller took drastic action. When he came on board, the Apollo flight-test plan was based on incremental testing, which meant that untried rocket stages would launch only dummy stages and dummy spacecraft. On October 29, 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 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.

Many believed that NASA should have backup plans in case the Saturn V or Apollo spacecraft suffered development problems. Eighteen months after Mueller's announcement, E. Harris and J. Brom, engineers with The RAND Corporation think tank, proposed one such backup 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 in time as being safe for 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 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 on top of a two-stage Saturn IB rocket (bottom image above). The ferry CSM would carry a special drogue docking unit for docking with the unmanned lunar mission CSM's probe docking unit. The only new system required for the backup plan, the special drogue would need about one year and "perhaps several million dollars" to develop.

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 the mission would occur as in NASA's Apollo plan. The astronauts would restart the S-IVB stage to leave Earth orbit for the moon. After S-IVB 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 segmented SLA would separate, revealing the LM, then the CSM would dock to the top of the LM and detach it from the spent S-IVB.

The RAND engineers declined to recommend whether the unmanned Saturn V or the manned Saturn IB should be launched first. They noted that hydrogen fuel in the Saturn V S-IVB stage would boil and escape at a rate of 700 pounds per hour; it would thus need to restart within 4.5 hours of reaching parking orbit if it were to retain enough to place the CSM and LM on course for the moon. Deletion of the 2900-pound LES would, they wrote, make the unmanned Saturn V that much lighter, so its S-IVB would reach parking orbit with enough extra propellants to loiter there for nearly 10 hours. Extending the loiter time further would require a complex and costly S-IVB redesign.

Launching the crew first would avoid the S-IVB loiter-time constraint. Harris and Brom noted that, though the Apollo lunar mission would last only seven to 10 days, NASA planned a 14-day Earth-orbital Gemini mission to certify that astronauts could withstand long space flights. This meant that the ferry CSM crew would be able to wait for from four to seven days in Earth orbit for the unmanned Saturn V. Harris and Brom recommended that, if the unmanned Saturn V became delayed so that the astronauts waiting in orbit would be unable to accomplish a lunar mission and return to Earth within 14 days of entering space, then they should carry out a backup Earth-orbital mission in the ferry CSM.

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 November 9, 1967. In keeping with Mueller's 1963 directive, it included complete S-IC, S-II, and S-IVB stages, plus a CSM with LES (top image above). Because LM development had hit snags, a dummy LM rode inside its SLA. The eight-hour Earth-orbital mission was an unqualified success.

Apollo 6 (image below) was, however, another story. On April 4, 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 shaking knocked pieces off the SLA and damaged one of the S-II's five engines. Following S-II ignition, the engine underperformed and shut down prematurely, then a control logic flaw caused a healthy engine to shut down. The remaining three S-II engines burned for a minute longer than planned to make up for the lost engines. The S-IVB's single engine then burned for 30 seconds longer than planned to reach a lopsided Earth orbit. Two orbits later, it failed to restart.

The pogo 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 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. The giant rocket performed flawlessly, placing the Apollo 8 CSM on course for lunar orbit on December 21, 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.