North American Aviation's 1965 Plan to Rescue Apollo Astronauts Stranded in Lunar Orbit

Apollo 15 Command and Service Module Endeavour in lunar orbit. The drum-shaped portion is the Service Module and the conical portion is the Command Module. Note the Service Propulsion System rocket engine bell at upper left and the extended probe docking unit at lower right. Image credit: NASA.

North American Aviation (NAA) became the prime contractor for the Apollo Command and Service Module (CSM) spacecraft on 28 November 1961. In July of the following year, the company received the unwelcome news that its spacecraft would not land on the Moon. NASA had favored the Lunar-Orbit Rendezvous (LOR) mode for carrying out Apollo landings over Direct-Ascent or Earth-Orbit Rendezvous, both of which would have seen the CSM reach the lunar surface.

LOR made the CSM a lunar orbiter and spawned a new spacecraft: the Lunar Excursion Module (LEM) lander. The LEM, later redesignated the Lunar Module (LM - pronounced "lem"), would transport two astronauts from the CSM in lunar orbit to a landing site on the Moon's surface and back again. The LEM comprised a descent stage with landing legs and a throttleable rocket engine and an ascent stage with a pressurized crew cabin, flight controls, a rocket engine, and a concave drogue docking unit on its roof.

LOR meant that NASA needed to develop the technologies and techniques of rendezvous and docking in lunar orbit. The LEM ascent stage would use the descent stage as a launch pad and climb to a low lunar orbit. The CSM would then move in, extend the active probe docking unit on its nose, and dock with the passive drogue on the LEM.

After the LEM crew transferred back to the CSM, the ascent stage would be cast off. The CSM would subsequently ignite its large Service Propulsion System (SPS) main engine to escape lunar orbit and begin the fall back to Earth.

This image of the Apollo 16 Lunar Module Orion shows clearly the separation plane between the descent and ascent stages. The former has legs, a ladder, and is covered with black paint and gold-colored multilayer blankets for thermal control; the latter is silver and black and has four attitude-control thruster quads (two are readily visible), a crew hatch (square with rounded corners), and a pair of triangular windows. Image credit: NASA. 

In December 1965, NAA's engineers briefed the NASA Headquarters Office of Manned Space Flight (OMSF) and Bellcomm, the space agency's Apollo planning contractor, on results of a preliminary feasibility study of a one-person CSM mission to rescue Apollo astronauts stranded in lunar orbit. The NAA engineers did not describe specific lunar-orbit rescue scenarios, though the CSM modifications they outlined offer clues about the types of rescue missions they envisioned.

The most important piece of rescue hardware they proposed was a special docking adapter ring installed on the rescue CSM's nose. Either an active probe or an active drogue could be mounted on the ring, so the rescue CSM could dock with either a LEM or a CSM. The lone rescue CSM astronaut could reconfigure the docking unit during the flight from the Earth to the Moon; this would permit adaptation to changing circumstances in lunar orbit.

NAA anticipated that a lunar-orbit rescue might require spacewalks, so provided the rescue CSM pilot with a tether and a life-support umbilical extension, a cold gas-propelled hand-held maneuvering device, and a protective "meteoroid garment" of the type Apollo astronauts would wear over their suits on the lunar surface. In addition, the rescue CSM would carry an Expandable Structures Space Rescue System (ESSRS) device. ESSRS was an inflatable "pole" meant to serve as a handrail for astronauts spacewalking between two spacecraft.

Other rescue CSM modifications would include new crew couches to accommodate up to four astronauts, a fourth umbilical so that all could link their suits to the rescue CSM's life support system, added breathing oxygen, a dish-shaped LEM docking radar antenna on an extendable boom, and new rendezvous and docking computer software. Modifications and additions would add a total of 445 pounds to the rescue CSM's weight. Removal of science equipment and other systems not required to rescue and return to Earth a crew stranded in lunar orbit would, however, reduce the rescue CSM's weight by 415 pounds, for a net weight gain of only 30 pounds.

Rescue CSMs would be advanced Block II spacecraft of the type earmarked for Apollo lunar missions. In late 1965, NAA expected to build a total of six Block I and Block II CSMs per year beginning in late 1966. Block I CSMs would be used in Apollo testing and Apollo Extension System (AES) Earth-orbital missions. AES, a proposed program intended to apply Apollo hardware to new missions, became a predecessor to the Apollo Applications Program, which subsequently evolved into the Earth-orbital Skylab Program. In the event, only Block II CSMs carried astronauts; work on Block I CSMs ceased following the deadly AS-204 (Apollo 1) fire of 27 January 1967.

NAA offered two plans for providing rescue CSMs for the Apollo Program. The first, Rescue Vehicle Program "A," would see CSM-110 and CSM-113 converted into rescue CSMs; that is, diverted from lunar exploration missions. They would be flight-ready in early 1969 and mid-1969, respectively. Starting in mid-1970, one of the lunar CSMs NAA produced annually would be built as a rescue CSM; the first of these would be designated CSM-119.

Rescue Vehicle Program "B" would see NAA produce nine CSMs per year. The company's representatives told NASA that this approach would guarantee "non-interference with basic Apollo or AES." The first rescue CSM of Program "B," designated CSM R-1, would be ready for flight at the end of 1968, between AES CSM-109 and lunar CSM-110. Program "B" rescue CSMs R-2, R-3, and R-4 would be completed in mid-1969, early 1970, and late 1970, respectively.

NAA assumed that during every Apollo lunar mission a rescue CSM would stand by atop a three-stage Saturn V rocket on one of the two Launch Complex (LC) 39 pads at Kennedy Space Center (KSC), Florida. The lunar mission would launch from the other LC 39 pad.

The rescue CSM Saturn V would be outwardly nearly identical to the lunar mission Saturn V. The rescue rocket would, however, carry no LEM in the tapered Spacecraft Launch Adapter shroud that would link the aft end of the rescue CSM to the ring-shaped Instrument Unit atop the Saturn V S-IVB third stage. In addition, the Boost Protective Cover that protected the conical Command Module during the first part of ascent would need to be modified slightly to make room for the special docking ring.

On the launch pad, the Saturn V rocket bearing the rescue CSM would have appeared nearly identical to one bearing a lunar landing mission CSM Saturn V. The Boost Protective Cover, visible near the top of the image, would have had a slightly more bulbous nose. Internally, the most significant difference would have been the lack of a Lunar Module within the segmented Spacecraft Launch Adapter, the white tapered housing linking the bottom of the CSM to the ring-shaped Instrument Unit on top of the Saturn V S-IVB third stage. Image credit: NASA. 

The rescue CSM and Saturn V would stand by on the launch pad until the Apollo lunar landing mission CSM safely departed lunar orbit and began its fall back to Earth, then would be rolled back to KSC's cavernous Vertical Assembly Building for storage until the next Apollo lunar mission. A single rescue CSM could be prepared for flight three times and and mothballed twice; this meant that it could stand by during three lunar missions, then would need to be replaced.

NAA did not explain what would be done with unused rescue CSMs; presumably they would be scrapped, though perhaps some systems could be salvaged for use in other CSMs. Neither did the company explain what would happen to unused rescue Saturn V rockets.

The company assumed that in most cases the rescue CSM would launch immediately after NASA learned that a crew had become stranded in lunar orbit. Because it would not wait, in most cases it would not be able to rely on Earth launch geometry to help it to match orbits and carry out a rendezvous with the stranded spacecraft.

NAA determined that launching the rescue CSM immediately could create complications. It might, for example, increase the rescue mission's duration. NAA calculated that the time needed to reach a spacecraft stranded in lunar orbit and return to Earth could in fact exceed the Block II CSM's anticipated 240-hour (10-day) operational lifetime by up to 52 hours in the worst case. NAA recommended that NASA delay the rescue CSM's launch until launch geometry could ensure that its mission duration would not exceed 10 days.

When the rescue CSM reached the Moon's vicinity, it would ignite its SPS main engine to place itself into an elliptical "catch up" lunar orbit. At apolune (lunar orbit high point), the pilot could ignite the SPS again to line up the rescue CSM's orbital plane with that of the stranded CSM. At perilune (lunar orbit low point), the pilot would fire the SPS a third time to lower the rescue CSM's apolune, circularizing its orbit and placing it near the stranded spacecraft.

NAA estimated that Rescue Vehicle Program "A" would add a total of $86 million to the cost of the Apollo Program per year. An 18-month program of development and testing would cost $50 million, $6 million would pay for modifications to two Apollo lunar CSMs, and four new rescue CSMs would cost $38 million each. The company provided no cost estimate for its Rescue Vehicle Program "B."

The NAA engineers did not discuss how astronauts stranded in lunar orbit might eke out their limited supplies of consumables — for example, breathing oxygen — while they awaited rescue. This would be particularly worrisome in the case of a LEM stranded in lunar orbit by a catastrophic CSM failure, for at the time of the NAA study the LEM was expected to keep two astronauts alive for at most one or two days. Neither did they assess the risks of a one-person CSM mission to lunar orbit, nor the technical problems of running two lunar missions simultaneously.

Perhaps because of these difficulties, NASA chose not to make preparations for astronaut rescue in lunar orbit. This did not stop Bellcomm from considering the problems of lunar orbit survival three years later, in December 1968, shortly after the Apollo 8 CSM became the first piloted spacecraft to return from lunar orbit (see link under "More Information" below).

Source

4-Man Apollo Rescue Mission, AS65-36, M. W. Jack Bell, et al., North American Aviation, November 1965; presentation at NASA Headquarters, 13 December 1965.

More Information

What If a Crew Became Stranded On Board the Skylab Space Station (1972)

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

Space Race: The Notorious 1962 Proposal to Launch an Astronaut on a One-Way Trip to the Moon