09 October 2015

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, 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 moon 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) moon 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 lunar surface and back again. The LEM was a two-part vehicle: it consisted of 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 foil for thermal control; the latter is silver and black and has attitude-control thruster quads (two of four are 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 Headuarters Office of Manned Space Flight (OMSF) and Bellcomm, Inc., NASA's Washington, DC-based 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 would be a special docking adapter ring 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 moonwalkers 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 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 mass by 415 pounds, for a net mass gain of only 30 pounds.

The rescue CSM would be an advanced Block II spacecraft akin to the Apollo lunar CSMs. 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 building the six rescue CSMs it expected would be needed for the Apollo Program. 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. (In actuality, CSM-110 became the Apollo 14 CSM Kitty Hawk, while CSM-113 was assigned to Apollo 16 and named Caspar.) Starting in mid-1970, one of the six CSMs NAA produced annually would be built as a rescue CSM; the first would be designated CSM-119. This, the company noted, would reduce the number of Block II CSMs available for lunar exploration.

Rescue Vehicle Program "B" would see NAA produce nine CSMs per year. The company's representatives told NASA that this 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 CSM 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 S-IVB third stage. In addition, the Boost Protective Cover which 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 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 the 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 disused 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 the 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 other complications. It might, for example, increase the rescue mission's duration. NAA calculated that the time needed to reach a stranded spacecraft 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 its launch geometry would ensure that its mission duration would not exceed 10 days.

The company found that, once the rescue CSM reached the moon's vicinity, ignition of its SPS main engine could place it in an elliptical "catch up" orbit around the moon; then, at apolune (lunar orbit high point), the pilot could ignite the SPS again to line up the rescue spacecraft's orbital plane with that of the stranded spacecraft. 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 its 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."

Program "A" rescue CSM 1 (CSM-110) would roll off the assembly line early in 1969, about three months after the first lunar CSM. Rescue CSM 2 (CSM-113) would become available in mid-1969, and rescue CSM 3 (CSM-119), would be ready in mid-1970.

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: 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 enhanced risks of a one-person mission to lunar orbit, nor the technical problems of running two lunar missions concurrently.

Perhaps because of these difficulties, NASA chose not to prepare for astronaut rescues 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 inhabited spacecraft to return from lunar orbit.


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


  1. VERY good read! I LOVE reading 'what could have beens' from the past.

    Since the kids only know the Shuttle and there is so much 'we didn't go junk' out there, I do a hands-on science event with kids on Apollo 11 (see my link here), where I take the kids thru the whole mission, using a 6' Saturn V I made myself; the typical Earth globe in a classroom (put it in one corner of a typical class and a 'Moon' in the opposite corner, it JUST happens to be the right 'real' distance between them!); a Command Module control panel (on cardboard printed out on 40ish pieces of paper) that I put across 2 student desks over 3 student chairs laid back on the floor, so they each get to feel what its like to be in the Command module on the way to the Moon! Kids have a blast and the others get to line their desks up like Mission Control and draw their own control panels!

    So stuff like you post is great!

    1. Tom:

      Hearing from folks like you makes my day. I do tours for individuals and groups who visit the Astrogeology Science Center at USGS Flagstaff. The kids are the best. What you've got there - it makes me think of a low-cost, portable Challenger Center! It also makes me think I haven't been imaginative enough when I've put up educational materials in our hallways.

      Glad you like my posts - coming from a highly enthusiastic, involved individual like yourself, it means a great deal.



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