Apollo Extension System Flight Mission Assignment Plan (1965)

NASA piloted spacecraft as conceived in 1964. The rockets at left are the Apollo-Saturn V, the Gemini-Titan, and the Mercury-Atlas. The spacecraft at right are the Apollo CSM/Apollo LEM, Gemini, and Mercury. At the time this was painted, only the one-man Mercury (lower right) had carried an astronaut into orbit. Note the round hatch on the front of the LEM ascent stage (upper right); a square hatch replaced this late in the year. Image credit: D. Meltzer, National Geographic Society/NASA.

On 30 January 1964, President Lyndon Baines Johnson asked NASA Administrator James Webb for a comprehensive list of candidate post-Apollo piloted space programs. At the time, NASA was between Project Mercury, its first piloted program, and Project Gemini, its second. The longest U.S. piloted mission at the time was Mercury-Atlas 9 (15-16 May 1963), which had lasted for 34 hours and 19 minutes. The space agency's top priority was to achieve the goal of a man on the Moon by the end of the 1960s decade.

Webb's response might have included a large Earth-orbiting space station, a lunar base, and a Mars expedition. NASA and its contractors had studied all three by 1964. Instead, his list included just one item: modification of Apollo Command and Service Module (CSM) and Lunar Excursion Module (LEM) spacecraft to provide Earth-orbital and lunar capabilities beyond those planned in the Apollo Program. Because its aim was to extend planned CSM and LEM capabilities, the proposed program was dubbed the Apollo Extension System (AES).

Using spacecraft derived from existing spacecraft to accomplish new missions was, of course, not a new idea. Gemini prime contractor McDonnell proposed a steady stream of Gemini-derived spacecraft beginning in 1962. Gemini had, in fact, started out as a Mercury derivative called "Mercury Mark II."

In 1963, CSM prime contractor North American Aviation (NAA) studied a six-man CSM derivative for delivering space station cargo and changing out station crews. That same year, LEM prime contractor Grumman studied a two-man LEM-derived reconnaissance spacecraft that could fly free of the CSM in lunar orbit, turn cameras toward the lunar surface, and dispense small landing probes.

NASA managers expected that, if all went well, they would have Apollo CSM and LEM spacecraft left over after they achieved Apollo's goal. Surplus Apollo lunar spacecraft would become available for AES missions.

At a press conference, Webb told reporters that he expected NASA's annual budget to climb to about $5.25 billion during Apollo and subsequently remain close to that amount. Funding freed up as Gemini and Apollo wound down would, like the surplus Apollo spacecraft, be shifted to AES, making no new infusion of funds necessary.

Though AES was generally ignored in the rush to develop approved programs like Gemini and Apollo, the proposed post-Apollo program had its critics. Some felt that it was not ambitious enough. The fact was, though, that NASA had enough to do in 1964-1965 without starting a new ambitious program.

Others believed that AES would do nothing in space that needed to be done. In testimony on the Fiscal Year 1966 NASA budget before the House Committee on Space and Astronautics on 18 February 1964, Associate Administrator for Manned Space Flight George Mueller sought to assure legislators that AES was not a "make-work" program. He explained that the Apollo-based program would enable NASA "to perform a number of useful missions. . .in an earlier time frame than might otherwise be expected."

On 29 January 1965, eighteen planners with Bellcomm, NASA's Washington, DC-based Apollo planning contractor, completed an interim report on their study of AES spacecraft and missions. Their eight-part report included a tentative Flight Mission Assignment Plan (FMAP).

In the FMAP, missions were assigned to specific months for planning purposes with the proviso that they would eventually be given precise dates determined by mission objectives, launch constraints, target lighting, and other factors. A chronological list of missions in the January 1965 AES FMAP can be found at the end of this post.

NASA had provided Bellcomm with a preliminary (hence vague) list of AES planning "ground rules" for its study. The first two ground rules taken together were clear: AES should not interfere with or compete with the Apollo Program.

NASA ground rules aimed to contain AES costs by placing restrictions on Apollo spacecraft modification. For example, they specified that CSMs and LEMs manufactured for AES missions were to be delivered to NASA configured for Apollo missions. Spacecraft modification and experiment installation for AES missions would occur outside the NAA and Grumman plants where the CSMs and LEMs were manufactured. In addition, no major facility construction or modification would be allowed; Apollo spacecraft would be converted into AES spacecraft inside buildings where Apollo spacecraft processing occurred.

NASA assured Bellcomm that eight Apollo spacecraft, along with six Saturn IB rockets and six Saturn V rockets, would be available for AES flights each year in the 1969-1971 period. The two-stage Saturn IB was designed for Apollo test missions in low-Earth orbit; the three-stage Saturn V, for boosting Apollo spacecraft to the Moon.

Bellcomm developed additional "guidelines" which it considered "not as firm" as the NASA-provided ground rules. For example, the Bellcomm team decided that all eighteen AES Saturn Vs launched in 1969-1971 should carry astronauts. Of the eighteen, six would launch crews to geosynchronous or polar Earth orbit and the rest would launch crews to the Moon.

The FMAP described 23 AES missions of three types - Earth orbital, lunar orbital, and lunar surface - spanning the period from March 1968 through December 1971. The team proposed eight mission classes within the framework of the three types. Earth-orbital missions included Earth-Oriented, Astronomy, Biomedical/Behavioral, and Operations/Technology classes. Lunar-orbital missions included Equatorial, Inclined, and Polar classes. Lunar-surface missions were of just one class: 14-Day Stays.

Mission difficulty would increase gradually and enough time would be allotted to enable data from one mission of a given class to be used to "optimize" the next mission of that class. Bellcomm cautioned that its list was not meant to include all possible classes, adding that the "catalog of suggested areas of investigation is expanding almost daily."

The Bellcomm engineers expected that, when AES began to fly modified Apollo spacecraft, the program would need one derivative of the Apollo CSM and three Apollo LEM derivatives. The CSM derivative was the Extended CSM (XCSM), the AES workhorse spacecraft. The XCSM would be capable of operating for up to 45 days in space without resupply. Bellcomm saw the XCSM as a "general purpose spacecraft" able to support any AES mission without additional modifications.

Bellcomm noted that design of workable LEM derivatives was problematic. The LEM was evolving rapidly in 1964-1965. In addition, the LEM was inherently more specialized and had more limited design margins than the CSM. Bellcomm described a LEM-Lab, LEM-Shelter, and LEM-Taxi in its January 1965 report, but cautioned that all three derivatives needed more study. Though they put a brave face on it, the Bellcomm engineers were clearly not confident that LEM hardware could be adapted to support all the missions they described.

LEM-Lab with legless descent stage from an October 1965 Grumman study document. The two large structures on either side of the ascent stage are components of a large-format stereo camera. The image at left depicts the LEM-Lab within the segmented Spacecraft Launch Adapter (SLA) shroud. The position of the CSM engine bell within the SLA relative to the top of the LEM-Lab is indicated as an outline. Image credit: Grumman Aircraft Engineering Company.

LEM-Lab without descent stage as depicted in the 1965 Grumman study document. Image credit: Grumman Aircraft Engineering Company. 

The LEM-Lab would have two forms: "ascent-stage-alone" and "ascent-stage-with-descent-stage." Both would depend entirely on the docked XCSM for life support and electricity. In the ascent-stage-with-descent-stage case, the LEM descent engine would augment XCSM propulsion but not attitude control; ascent-stage-alone would rely entirely on the XCSM for propulsion and attitude control. In the text that follows, LEM-Labs are ascent-stage-alone unless otherwise indicated.

At the time the Bellcomm engineers completed their interim study, the LEM ascent stage was expected to include 180 cubic feet of free pressurized volume. To form the LEM-Lab, most LEM ascent stage systems would be stripped out to free up an additional 60 cubic feet of pressurized volume for instruments and experiments in the LEM pressure vessel.

The LEM-Shelter would reach lunar orbit docked to a piloted Apollo CSM, land on the Moon automatically, hibernate on the surface for several months, then provide a two-man crew arriving in a LEM-Taxi with living quarters and exploration equipment for a 14-day lunar surface stay. The LEM-Taxi would be outwardly almost identical to the Apollo LEM, but could be placed in hibernation on the lunar surface for 14 days.

In an attempt to avoid interference with Apollo missions, the Bellcomm engineers built its AES FMAP around an "unofficial" Apollo schedule that saw the first unpiloted Apollo Saturn IB rocket test in January 1966. Bellcomm designated the test SA-201. Two additional Saturn IB test flights would occur, then astronauts would ride to Earth orbit in an Apollo CSM  for the first time atop a Saturn IB in October 1966. Bellcomm called the flight SA-204.

The FMAP also included nine "unassigned" missions for which Saturn rockets were expected to be manufactured, but which would, based on NASA's ground rules, have no Apollo spacecraft to launch. These brought the potential AES mission total to 32.

The first unassigned flight, SA-208, might occur as early as November 1967. Bellcomm explained that the SA-208 Saturn IB might remain in the Apollo Program or might be used to launch a "cislunar" version of the Pegasus micrometeoroid-detection satellite in the AES Program. At the time Bellcomm conducted its study, NASA had on its launch docket for 1965 three Pegasus launches. The first reached orbit less than a month (16 February 1965) after the Bellcomm team completed its AES report.

The next unassigned flight was SA-212 in December 1968. The Bellcomm engineers saw it as another candidate cislunar Pegasus mission. It would be the first cislunar Pegasus mission if SA-208 stayed in the Apollo Program. Other unassigned missions were SA-216 (July 1969), SA-217 (September 1969), SA-220 (April 1970), SA-222 (July 1970), SA-223 (September 1970), SA-224 (November 1970), SA-225 (January 1971), and SA-226 (March 1971).

The original Apollo "buy" included 12 Saturn IB rockets and 15 Saturn V rockets, which meant that SA-212 would be the last flight of an Apollo Saturn IB rocket. NASA would need to order new rockets in 1966 if six Saturn IBs and six Saturn Vs were to be available per year in 1969, 1970, and 1971.

The Bellcomm engineers included five Saturn IB-Centaur upper stage missions in the AES FMAP because Saturn IB-Centaur was nominally under AES management at the time they completed their study. They did not, however, see them as AES missions; they were included for planning purposes. All would carry as payloads automated Voyager Mars/Venus exploration spacecraft (see "More Information" below).

The first Saturn IB-Centaur mission, designated SA-210, would be a Voyager test. It would depart Cape Kennedy in June 1968. The first operational Voyager missions (SA-213/SA-214) would launch to Mars in February/March 1969. A second Voyager pair (SA-227/SA-228) was scheduled for Mars launch in May/June 1971.

The first piloted flight of the AES program would be SA-209 in March 1968. The mission to near-equatorial low-Earth orbit would include two or three astronauts, an unmodified Apollo CSM, and an unmodified Apollo LEM ascent stage with no descent stage. The mission would last from 10 to 14 days. Its crew would focus on engineering experiments, such as pumping propellants in weightlessness and performing spacewalks to test new tools. SA-209 was the first mission in the AES Operations/Technology class.

The first unpiloted Saturn V test (SA-501) would take place as part of the Apollo Program in January 1967. On its third flight (SA-503) in October 1967, the Saturn V would launch its first Apollo crew to Earth orbit.

The first Apollo lunar landing attempt would occur during mission SA-506 in August 1968. If it was successful, then its backup mission (SA-507) might become the first Saturn V-launched AES mission in November 1968. The AES SA-507 mission would see unmodified Apollo CSM and Apollo LEM spacecraft launched to geosynchronous or polar Earth orbit for from 10 to 14 days. Because SA-507 reassignment was tentative, Bellcomm did not specify the mission's class.

If SA-507 stayed within the Apollo Program, then the first AES Saturn V flight (SA-509) would take place in April 1969. Two or three men, an unmodified Apollo CSM, and an unmodified Apollo LEM ascent stage would be launched to geosynchronous Earth orbit for a 10-to-14-day "subsystems development" (Operations/Technology class) mission in preparation for SA-211.

SA-211 in September 1968 would see the first flight of the XCSM and LEM-Lab. The three-man flight in near-equatorial low-Earth orbit, scheduled to last for from 30 to 45 days, would emphasize biomedical/behavioral experiments and would test lunar survey instruments ahead of mission SA-511.

Bellcomm explained that all AES missions would include a biomedical/behavioral component, and all Biomedical/Behavioral-class missions would include at least one other activity. It noted also that AES missions that studied the effects of long-duration spaceflight on astronauts were the most important for future NASA piloted programs.

The Bellcomm engineers might have transferred all Apollo hardware to AES after SA-506 or SA-507 - whichever mission became the first successful Apollo lunar landing mission - but they opted instead to schedule SA-508, SA-510, and SA-512 as Apollo lunar landing missions in February, June, and October 1969. Sandwiched between the February and June Apollo flights, the team scheduled SA-215, an Earth-orbital Apollo CSM/Apollo LEM ascent stage mission intended to test Earth survey instruments (Earth-Oriented class). Between the June and October flights, it scheduled SA-511 (August 1969), the first AES Lunar Orbital Survey mission.

During SA-511, three astronauts would image the Moon from near-equatorial lunar orbit using instruments mounted in a LEM-Lab with a descent stage. The descent stage would help the SA-511 XCSM/LEM-Lab stack maneuver so that it could pass over important lunar surface targets. Bellcomm envisioned that the SA-511 LEM-Lab might release small lunar probes derived from planned Surveyor robotic landers. The mission would last about 35 days, of which about 30 days would be spent in lunar orbit.

In December 1969, a pair of AES missions would lift off, but only one would conclude. SA-513 (Apollo CSM/Apollo LEM ascent stage) was an Operations/Technology-class subsystems development mission like SA-509. It would include three astronauts and operate for from 10 to 14 days in polar Earth orbit. SA-218, on the other hand, would continue - and greatly extend - the biomedical research SA-211 began.

The SA-218 crew would attempt to remain in space for from 60 to 90 days on board an XCSM/LEM-Lab in near-equatorial Earth orbit. They would take an occasional break from gathering data on their own reactions to long-duration spaceflight by testing a "zero-g lab."

In January 1970, NASA would launch SA-219, a three-man XCSM/LEM-Lab mission meant to rendezvous with and resupply SA-218. The Bellcomm team provided little information on how resupply would take place. The SA-218 crew would not return to Earth until March (for the 60-day mission) or April (for the 90-day mission).

Just as SA-218/SA-219 would support a giant leap in space biomedical knowledge, so would SA-514/SA-515 support a giant leap in lunar knowledge. Launched in February 1970 with a crew of two or three, it would see an Apollo CSM transport a LEM-Shelter to the Moon. After insertion into lunar orbit, the LEM-Shelter would separate from the CSM without a crew on board, land automatically at a complex exploration site, and put itself into hibernation.

LEM-Shelter as depicted in the 1965 Grumman study document. Note the rover at right shown in stowed and deployment positions. To the left of the descent stage engine bell, a deep drill is shown in deployed position. Image credit; Grumman Aircraft Engineering Company.
Stylized depiction of the LEM as envisioned in 1964. This image can stand in for the 1964 LEM-Taxi; outwardly, the Apollo LEM and the LEM-Taxi designs were very similar. Image credit: NASA

In April 1970, SA-515 would reach lunar orbit. The mission would use the last of the 15 Saturn V rockets ordered for Project Apollo. Its payload would comprise an XCSM, LEM-Taxi, and a crew of three.

Two men would descend to a landing near the LEM-Shelter in the LEM-Taxi, then would put the LEM-Taxi in hibernation and transfer to the LEM-Shelter. The LEM-Shelter would carry a small rover, enabling longer geologic traverses than could be achieved during Apollo missions (at the time Bellcomm performed its study, no Apollo mission was expected to carry a rover).

The LEM Shelter would include analysis equipment to enable the astronauts to decide which geologic samples should be returned to Earth (Bellcomm assumed that the astronauts would collect more samples than the LEM-Taxi could carry to lunar orbit, so some form of "discrimination" would be required). After 14 days on the Moon, they would abandon the LEM-Shelter, revive the LEM-Taxi, and return to the XCSM in lunar orbit in the LEM-Taxi ascent stage. Mission duration would total about 20 days.

Bellcomm noted that astronauts living in the LEM-Shelter for 14 days stood a 28% chance of exceeding their allowed mission radiation dose. Passing the limit would force them to terminate their surface mission early. Beefing up radiation protection would dramatically increase LEM-Shelter weight. They determined that, combined with other modifications required for months-long hibernation and a 14-day surface stay - for example, replacement of Apollo LEM batteries with fuel cells and insulated tanks containing cryogenic liquid oxygen/liquid hydrogen fuel cell reactants - the LEM-Shelter might put on so much weight that its landing legs would collapse (unless, of course, they were also modified).

SA-221 (May 1970) was a three-man, 30-to-45-day XCSM/LEM-Lab mission in near-equatorial low-Earth orbit dedicated to meteorology, agricultural remote sensing, and oceanography, placing it in the Earth-Oriented mission class. The Bellcomm engineers stressed that astronauts on board would serve as "trained observers" and "data filters," functions that automated satellites were unable to perform. The following month, SA-516 (XCSM/LEM Lab, 30-45 days, geosynchronous orbit) would test an astronomy payload.

SA-517 (August 1970), the second Lunar Orbital Survey mission, would see an XCSM/LEM-Lab/descent stage stack enter an orbit inclined steeply relative to the lunar equator, enabling it to pass over a larger portion of the lunar surface than its predecessor SA-511. SA-518 in October 1970, an XCSM/LEM-Lab, would survey the Earth from polar orbit using instruments tested during SA-215. SA-519 (December 1970) would round out the year by delivering a LEM-Shelter to a new complex landing site on the Moon.

The first mission of the AES program's last year would be the February 1971 SA-520 LEM-Taxi mission to the LEM-Shelter delivered during SA-519. Next up would be Earth-Oriented SA-521 (April 1971), which would see three astronauts in an XCSM/LEM-Lab study meteorology and oceanography from geosynchronous orbit for up to 45 days. Bellcomm noted that AES meteorological studies might lead to an "economical" weather satellite system or even "eventual control of the weather."

In June 1971, NASA would launch to lunar polar orbit SA-522 (XCSM/LEM-Lab/descent stage), the third and final AES Lunar Orbital Survey Mission. In polar orbit, the spacecraft would pass over the lunar polars on every orbit and fly over the entire lunar surface in daylight over a period of about a month.

SA-523 (XCSM/LEM-Lab) would be a long-duration Earth-orbital astronomy mission with a substantial biomedical/behavioral component (August 1971). SA-229 (XCSM/LEM-Lab) would rendezvous with and resupply SA-523 in September 1971.

SA-524 (October 1971) would deliver to the Moon the third and last LEM-Shelter of Bellcomm's AES FMAP. The same month, SA-230 (XCSM/LEM-Lab) would rendezvous with and resupply the ongoing SA-523 mission in Earth orbit. The final scheduled AES FMAP mission, SA-525 in December 1971, would see astronauts in a LEM-Taxi descend from an XCSM in lunar orbit to land near the SA-524 LEM-Shelter for 14 days of exploration.

The Bellcomm engineers argued that AES could accomplish many more types of missions if NASA's ground rules were relaxed. They suggested, for example, that another LEM derivative, the LEM-Truck, be developed to deliver large lunar surface payloads, such as more capable rovers, to the surface of the Moon in the period after 1971. The LEM-Truck would enable planners to abandon entirely the restrictive confines of the LEM ascent stage, permitting maximum exploitation of descent stage payload capacity. Grumman had studied the LEM-Truck since 1962.

The LEM-Truck was a LEM descent stage that included ascent stage systems required for landing on the Moon. Cargo would replace the LEM ascent stage. The image shows cargo volume available atop the LEM-Truck. Image credit: Grumman Aircraft Engineering Company.

In March 1965, against a backdrop of budget hearings in Congress, President Johnson made a surprise visit to NASA Headquarters. He received a briefing on Mariner IV, which had left Earth for Mars on 28 November 1964. Along with Vice President Hubert Humphrey's visit to Cape Kennedy a few days earlier, this was widely seen as a show of support for programs in the Fiscal Year 1966 NASA budget, including AES.

In August 1965, with the Fiscal Year 1966 budget in effect since 1 July, George Mueller established the Saturn/Apollo Applications Office at NASA Headquarters. The following month, AES became the Apollo Applications Program (AAP). The name changes signalled that NASA managers had learned an important lesson during the Fiscal Year 1966 budget cycle; that extending Apollo had less appeal than applying Apollo to new tasks with benefits for people on Earth.

Webb and Mueller remained outwardly enthusiastic about minimally modified Apollo spacecraft and long-duration missions; during August 1965 visits to the NASA Manned Spacecraft Center (MSC) in Houston, Texas, for example, Webb reiterated that AAP should use "off-the-shelf" spacecraft with minimal modifications. Mueller, for his part, raised the possibility of a 135-day XCSM/LEM-Lab AES Earth-orbital mission in a 27 August 1965 letter to MSC director Robert Gilruth.

Bellcomm, Grumman, and NASA in-house studies had, however, by August 1965 raised questions about the practicality of using modified Apollo spacecraft for long-duration flights. On 20 August 1965, NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama, home of the Saturn rocket family, began an in-depth in-house study of an orbital "workshop" based on the 21.7-foot-diameter S-IVB stage. The S-IVB was the second stage of the Saturn IB and the third stage of the Saturn V.

At the end of November, MSFC planners briefed Mueller on their results as part of the lead-up to NASA's Fiscal Year 1967 budget request. On 1 December 1965, Mueller gave MSFC director Wernher von Braun authority to establish the S-IVB Workshop Project Office.

Apollo and AES Flights in the January 1965 AES FMAP (includes Voyager)
  1. 1/66 - SA-201 - Apollo
  2. 4/66 - SA-202 - Apollo
  3. 7/66 - SA-203 - Apollo
  4. 10/66 - SA-204 - Apollo, CSM test
  5. 1/67 - SA-205 - Apollo, CSM/LEM test
  6. 1/67 - SA-501 - Apollo
  7. 4/67 - SA-206 - Apollo
  8. 5/67 - SA-502 - Apollo
  9. 7/67 - SA-207 - Apollo
  10. 10/67 - SA-503 - Apollo
  11. 11/67 - SA-208 - Apollo or AES, unassigned
  12. 2/68 - SA-504 - Apollo
  13. 3/68 - SA-209 - AES, Apollo CSM/Apollo LEM ascent stage
  14. 5/68 - SA-505 - Apollo
  15. 6/68 - SA-210 - Voyager, Saturn IB/Centaur
  16. 8/68 - SA-506 - Apollo, lunar landing 1
  17. 9/68 - SA-211 - AES, XCSM/LEM-Lab
  18. 11/68 - SA-507 - Apollo, lunar landing (SA-506 backup), or AES, Apollo CSM/Apollo LEM
  19. 12/68 - SA-212 - AES, unassigned
  20. 1/69 - SA-213 - Voyager, Saturn IB/Centaur
  21. 2/69 - SA-508 - Apollo, lunar landing 2
  22. 2/69 - SA-214 - Voyager, Saturn IB/Centaur
  23. 4/69 - SA-509 - AES, Apollo CSM/Apollo LEM ascent stage
  24. 5/69 - SA-215 - AES, Apollo CSM/Apollo LEM ascent stage
  25. 6/69 - SA-510 - Apollo, lunar landing 3
  26. 7/69 - SA-216 - AES, unassigned
  27. 8/69 - SA-511 - AES, XCSM/LEM-Lab/descent stage
  28. 9/69 - SA-217 - AES, unassigned
  29. 10/69 - SA-512 - Apollo, lunar landing 4
  30. 12/69 - SA-513 - AES, Apollo CSM/Apollo LEM ascent stage
  31. 12/69 - SA-218 - AES, XCSM/LEM-Lab
  32. 1/70 - SA-219 - AES, XCSM/LEM-Lab
  33. 2/70 - SA-514 - AES, Apollo CSM/LEM-Shelter
  34. 4/70 - SA-220 - AES, unassigned
  35. 4/70 - SA-515 - AES, XCSM/LEM-Taxi
  36. 5/70 - SA-221 - AES, XCSM/LEM-Lab
  37. 6/70 - SA-516 - AES, XCSM/LEM-Lab
  38. 7/70 - SA-222 - AES, unassigned
  39. 8/70 - SA-517 - AES, XCSM/LEM-Lab/descent stage
  40. 9/70 - SA-223 - AES, unassigned
  41. 10/70 - SA-518 - AES, XCSM/LEM-Lab
  42. 11/70 - SA-224 - AES, unassigned
  43. 12/70 - SA-519 - AES, Apollo CSM/LEM-Shelter
  44. 1/71 - SA-225 - AES, unassigned
  45. 2/71 - SA-520 - AES, XCSM/LEM-Taxi
  46. 3/71 - SA-226 - AES, unassigned
  47. 4/71 - SA-521 - AES, XCSM/LEM-Lab
  48. 5/71 - SA-227 - Voyager, Saturn IB-Centaur
  49. 6/71 - SA-228 - Voyager, Saturn IB-Centaur
  50. 6/71 - SA-522 - AES, XCSM/LEM-Lab/descent stage
  51. 8/71 - SA-523 - AES, XCSM/LEM-Lab
  52. 9/71 - SA-229 - AES, XCSM/LEM-Lab
  53. 10/71 - SA-524 - AES, Apollo CSM/LEM-Shelter
  54. 10/71 - SA-230 - AES, XCSM/LEM-Lab
  55. 12/71 - SA-525 - AES, XCSM/LEM-Taxi

Final Technical Presentation: Modified Apollo Logistics Spacecraft, Contract NAS 9-1506, North American Aviation, Inc., Space and Information Systems Division, November 1963.

Study of LEM for Lunar Orbital Reconnaissance, ASR 323D-1, Grumman Aircraft Engineering Company, 23 September 1963.

"LBJ Wants Post-Apollo Plans," H. Taylor, Missiles and Rockets, 4 May 1964, p. 12.

"Interim Report for AES Flight Mission Assignment Plan - Part I: Summary," Bellcomm TM-65-1011-7, T. Powers, 29 January 1965.

"Interim Report for AES Flight Mission Assignment Plan - Part III: Extended CSM Spacecraft," Bellcomm TM-65-1011-2, K. Martersteck, 29 January 1965.

"Interim Report for AES Flight Mission Assignment Plan - Part IV: LEM Derivatives," Bellcomm TM-65-1011-3, J. Waldo, 29 January 1965.

"Interim Report for AES Flight Mission Assignment Plan - Part VII: Scheduling Constraints and Alternative Schedules," Bellcomm TM-65-1011-6, P. Gunther, 29 January 1965.

"Top-Level Space Support," W. Coughlin, Missiles and Rockets, 8 March 1965, p. 46.

"NASA to Decide Key AES Issues in June," W. Normyle, Aviation Week & Space Technology, 24 May 1965, pp. 16-17.

LEM Utilization Study for Apollo Extension System Missions, Final Report - Volume I: Summary, Design 378, Grumman Aircraft Engineering Company, 15 October 1965.

Skylab: A Chronology, R. Newkirk and Ivan Ertel with Courtney Brooks, NASA, 1977, pp. pp. 28-29, 35-43, 47-55.

More Information

Space Station Resupply: The 1963 Plan to Turn the Apollo Spacecraft into a Space Freighter - NAA's plan for a six-man crew rotation/logistics resupply spacecraft for a revolving artificial-gravity space station.

The First Voyager (1967) - The name Voyager was first applied to a planned series of advanced Mars/Venus spacecraft JPL hoped to build and fly in the 1970s.

Riccioli Outpost (1990)

The red oval at left marks Riccioli crater, Paul Lowman's candidate site for a lunar geology/astronomy outpost. The crater is approximately round, but appears foreshortened because it is near the lunar limb. Image credit: NASA
NASA held a workshop in August 1990 to examine candidate lunar base sites as part of the Space Exploration Initiative (SEI). U.S. President George H. W. Bush had announced SEI on 20 July 1989, the 20th anniversary of the Apollo 11 Moon landing. SEI aimed to return American astronauts to the Moon to stay and to carry out the first piloted Mars expedition. For most of its first year, SEI lacked a timetable, though in November 1989, The 90-Day Study, NASA's initial SEI blueprint, scheduled the return to the Moon for as early as 2001. On 11 May 1990, Bush called for American astronauts on Mars by 2019.

One candidate lunar base site was 156-kilometer-wide Riccioli crater. Riccioli is located southwest of Oceanus Procellarum, near the edge of the Moon's disk as viewed from Earth, just west of prominent dark-floored Grimaldi basin. Named by 17th-century astronomer-priest Giovanni Battista Riccioli for himself, the crater includes slumped crust blocks (graben) overlain with ejecta from the impact that blasted out the nearby multi-ringed Orientale basin, the youngest large basin on the Moon.

Heavily degraded Riccioli crater. The red oval marks a possible outpost site on the interior uplift. Light-colored ejecta from Mare Orientale (out of shot to the lower left) is discernible over much of the crater. Image credit: NASA
Riccioli's ancient, complex geology and its position near the Moon's equator and western limb had drawn the gaze of geologist Paul Lowman. At the August 1990 workshop, he advocated for the crater's irregular interior uplift as the site for a geoscience outpost and astronomical observatory. In places, the interior uplift stands more than 800 meters above the crater floor.

Paul Lowman. Image credit: NASA
NASA put Lowman on its payroll in 1959. By some accounts, he was the agency's first geologist. He worked at NASA Headquarters in Washington, DC, then moved to the newly built NASA Goddard Space Flight Center in Greenbelt, Maryland, a Washington suburb. He trained Mercury, Gemini, and Apollo astronauts to identify and photograph Earth's geologic features from Earth orbit and participated in the development of Apollo lunar geology experiments. He wrote about future lunar mining as a member of the interagency Working Group on Extraterrestrial Resources; he also took part in an internal NASA study of a temporary lunar outpost based on Lunar Module spacecraft and other Apollo technology.

After Apollo, Lowman participated in Skylab Earth observation experiments and the Landsat Program. The Earth-orbiting Landsat automated satellites sought resources and monitored the environment on Earth.

Lowman assumed that geologist-astronauts at Riccioli outpost would have at their disposal several rovers equipped as campers. He planned three traverses within Riccioli, each about 100 kilometers long with multiple stops. The traverses would each last several days.

Traverse 1 would begin with a sample stop just outside the outpost's front door. Lowman believed that the Riccioli interior uplift might include some of the oldest lunar crust. From there, the geologist-astronauts would drive across the dark mare to sample light plains material — probable ejecta from the Orientale basin — on Riccioli's northeast rim. The Orientale ejecta, he asserted, could contain pieces of mantle material from deep within the Moon.

Lowman's Traverse 2 would explore criss-cross grabens and rilles (canyons) in search of recent volcanism. Lowman hoped that the explorers might uncover water-rich minerals they could mine.

During Traverse 3, they would sample craters with dark haloes along the Riccioli southeast rim about 50 kilometers from the outpost. Lowman believed that the dark haloes could be signs of relatively recent volcanism; that the craters they surround could be volcanic vents and the haloes erupted volcanic material. Alternately, the impacts that blasted out the craters might have exposed ancient dark deposits buried beneath Orientale basin ejecta.

Lowman expected that geologist-astronauts would build on the exploration experience they gained in Riccioli crater to rove beyond its degraded walls. Riccioli is located in the Moon's "wild west," a region of complex geology that even today is in many ways mysterious. Lowman named as geologic exploration targets within a few hundred kilometers of Riccioli the ring mountains and small mare plains of Mare Orientale; the Reiner Gamma swirls, a prominent magnetic anomaly; the Marius Hills volcanic complex, an Apollo candidate landing site; and bright Aristarchus crater.

Astronomers based at near-equatorial Riccioli outpost could, Lowman added, observe nearly the entire celestial sphere every month. He suggested that the generally level Riccioli crater floor could provide a stable platform for groups of sensitive astronomical instruments that had to be kept carefully aligned to function properly. A cluster of carefully aligned small telescopes, for example, could act as a single large telescope.

Riccioli crater's near-limb location meant that Earth would stand low in the eastern sky; low enough that at some locations the crater rim and central uplift could hide the home planet from view. Radio telescopes built out of sight of Earth could, he explained, operate without interference from terrestrial artificial and natural radio sources.

Lowman revealed a playful side when he proposed that Riccioli outpost include a bright strobe light. This could be activated when the Moon was at first-quarter phase, when it stands high and half-lit immediately after sunset for observers on Earth. The Sun would not yet have risen at Riccioli crater, so the blinking strobe would stand out against the dark part of the first-quarter lunar disk.

SEI excited scientists, engineers, and space enthusiasts, but it never gained much traction with Congress and the wider public. Because of this, it ended soon after President Bush left the Oval Office in January 1993. NASA, meanwhile, turned its efforts toward building the International Space Station in low-Earth orbit in cooperation with its long-time International Partners and Russia.

Lowman, for his part, never stopped advocating for a lunar outpost, and Riccioli crater remained his favorite candidate site. In 1996, taking into account new miniaturized space technology and capable robots, he proposed a mostly automated astronomy outpost in Riccioli crater built up using small, cheap automated landers. Lowman passed away a week after his 80th birthday on 29 September 2011.


A Site Selection Strategy for a Lunar Outpost — Science and Operational Parameters: Determining the Impact of Science and Operational Parameters for Six Sites on the Moon by Simulating the Selection Process, Conclusions of a Workshop, 13-14 August 1990, Solar System Exploration Division, NASA Johnson Space Center, Houston, Texas, pp. 31-36

"Remembering Paul Lowman," Landsat Science (Accessed 9 October 2019)

"Paul Lowman: NASA's 76-Year-Old Maverick," NASA Goddard Space Flight Center, 11 September 2007 (Accessed 9 October 2019)

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Retrograde Module separation. Image credit: Jeff Bateman/David S. F. Portree
In June 1962, a little more than a year after President John F. Kennedy put the U.S. on course for the Moon, NASA's piloted spaceflight organizations agreed that Lunar Orbit Rendezvous (LOR) should be the Apollo lunar landing mission mode. LOR would employ two spacecraft: a Command and Service Module (CSM) for carrying three astronauts from Earth to lunar orbit and back again; and a Lunar Excursion Module (LEM) for landing two astronauts on the Moon and returning them to the CSM in lunar orbit. Both the CSM and the LEM would include two modules: the Command Module (CM) and Service Module (SM) in the case of the CSM, and the Descent Module and Ascent Module in the case of the LEM.

On 11 July 1962, NASA Administrator James Webb made public NASA's mode choice. He told a press conference that LOR Apollo would leave Earth on a Saturn C-5 (as the Saturn V rocket was known at the time) capable of launching 45 tons to the moon, and that the agency would also study a two-man Direct Ascent Apollo lunar landing mission launched on a Saturn C-5. In Direct Ascent, a single spacecraft would carry the astronauts from Earth to the lunar surface and back again.

NASA Administrator James Webb (left) explains NASA's decision to adopt LOR at a NASA Headquarters press conference on 11 July 1962. Seated beside Webb are (L to R) NASA human spaceflight officials Robert Seamans, Brainerd Holmes, and Joseph Shea. Image credit: NASA
Webb did not provide a justification for the two-man Direct Ascent study, though it soon became clear that it was a concession to Jerome Wiesner, chairman of the President's Science Advisory Council (PSAC). Wiesner, a Massachusetts Institute of Technology professor who had also served as PSAC chair for President Kennedy's predecessor, President Dwight Eisenhower, was not comfortable with LOR's complexity.

While NASA moved ahead with LOR, it also hired McDonnell Aircraft Company and TRW Space Technology Laboratories to study Wiesner's preferred mode. For McDonnell, manufacturer of the one-man Mercury and two-man Gemini spacecraft, the study had three aims.

McDonnell would develop a conceptual Direct Ascent Moonship design incorporating a two-man CM similar to the three-man North American Aviation (NAA) Apollo CM. When NAA contracted with NASA to build the Apollo CSM in November 1961, it had assumed that Apollo would use either Direct Ascent or Earth-Orbit Rendezvous. In both of those mission modes, the CSM would have had the honor of landing on the Moon. NAA did not welcome NASA's choice of LOR.

McDonnell would also look at using Gemini for the Direct Ascent Moon landing mission. At the time it conducted its study, Gemini's maiden flight was scheduled for launch in 1964. Known initially as "Mercury Mark II," the spacecraft, which was meant to reach Earth orbit atop a Titan II rocket, was meant to provide NASA with experience with spacewalks and rendezvous and docking ahead of Apollo.

From aft to front, the Gemini spacecraft consisted of the Adapter Module, the Service Module, and the CM. The Gemini CM, which measured 8.7 feet across its heatshield and weighed 5775 pounds, had two hatches (one per astronaut) with one forward-facing window each. Gemini could carry enough life support consumables and fuel cell reactants for a 14-day Earth-orbital mission.

Cutaway of a Gemini spacecraft. Image credit: NASA
Finally, McDonnell would determine modifications the two-man Apollo and Lunar Gemini spacecraft would need to serve as unpiloted "rescue" vehicles. NASA expected that a rescue lander, if one flew, would be landed without a crew at the target landing site ahead of the Direct Ascent mission crew's arrival.

The company proposed four two-man Direct Ascent Command Module designs. The company's conical two-man Apollo would measure 8.8 feet tall and 10.4 feet across its heat shield. (For comparison, the three-man Apollo was 10.6 feet tall and 12.8 feet across.) Interior volume would total 185 cubic feet, of which 73 cubic feet would be available for the crew.

The astronauts would enter and leave the module through a hatch with two windows located above the pilot's couch. A blow-out hatch with one window located above the co-pilot's couch would provide emergency egress. During Earth launch and reentry, lunar liftoff, and while sleeping on the Moon, the astronauts would recline in their couches facing the nose and main control panel. This would place the windows above and behind their heads.

During lunar landing, they would sit upright on their couch backs facing landing controls and view the Moon's surface through the windows. Following Earth atmosphere reentry, the two-man Apollo CM would lower to a gentle land landing on three 71-foot-diameter parachutes.

Lunar Gemini I modifications would include a beefed-up heat shield so that it could withstand reentry at lunar-return speed, improved radio systems for communication between Moon and Earth, lunar landing controls, and life support consumables stocks sufficient to support an eight-day lunar mission. The spacecraft would also include two systems for viewing of the lunar surface during landing. The right-side astronaut would recline in his couch normally (back toward heat shield and lunar surface) and deploy an external mirror for an "over-the-shoulder" surface view. The left-side astronaut would roll over in his couch and view the lunar surface directly through a transparent "viewing dome" built into his hatch. The Lunar Gemini I Command Module would weigh 6802 pounds.

Except for its Earth-landing system, Lunar Gemini II would closely resemble Lunar Gemini I. Until June 1964, NASA planned a land landing for its Earth-orbital Gemini spacecraft. The Gemini CM would deploy an steerable delta-winged paraglider during descent to Earth and glide to a touchdown on skids or wheels. McDonnell retained this system in its Lunar Gemini I design, but decided to trim weight from Lunar Gemini II by substituting a single 84-foot-diameter parachute and splashdown at sea.

Land landing in the Lunar Gemini II capsule would be not survivable; if emergency land landing became necessary, the astronauts would eject from the falling capsule after reentry and descend on personal parachutes. The Lunar Gemini II Command Module would weigh 6376 pounds.

Lunar Gemini II spacecraft configurations. Clockwise from lower left: Lunar Gemini II Command Module; Lunar Gemini II Command Module with Service Module, Terminal Landing Module, and Retrograde Module; top view of Lunar Gemini II Command Module with Service and Terminal Landing Modules; Lunar Gemini II Command, Service, and Terminal Descent Modules; and Lunar Gemini II Command and Service Modules. Image credit: Jeff Bateman/David S. F. Portree
Earth-orbital Gemini astronauts would rely on ejection seats for escape if their Titan II booster rocket malfunctioned. Lunar Gemini I and II would retain this system.

For its Lunar Gemini III design, McDonnell opted for a launch-escape tower similar to the one used on the Mercury capsule. In the event of a Titan II malfunction, the tower's solid-rocket motor would blast the Lunar Gemini III CM to safety. Couches with shock absorbers would replace the ejection seats, and three 71-foot-diameter parachutes would provide a slower, gentler descent than Lunar Gemini II's single parachute. These modifications would restore the land landing capability lost in Lunar Gemini II. All three Lunar Gemini versions could return up to 85 pounds of scientific equipment and lunar samples to Earth.

The Lunar Gemini III couches could be configured so that the astronauts could sit upright (feet toward heat shield) relative to the Moon's surface during lunar landing. New hatch windows would provide direct views of the lunar surface for both astronauts. The Lunar Gemini III CM would weigh 6453 pounds minus its launch escape tower.

McDonnell proposed that both the two-man Apollo and the Lunar Gemini CMs reach the Moon atop a stack of three propulsion/service modules. The cylindrical, 21.6-foot-diameter, 16.4-foot-tall Retrograde Module would weigh 26.9 tons with a full load (23.8 tons) of liquid hydrogen/liquid oxygen propellants. It would rest atop the Saturn C-5 rocket and its top would attach to the bottom of the Terminal Landing Module. The Retrograde Module would perform course corrections during flight to the moon, lunar orbit insertion, de-orbit, and descent to 6000 feet above the Moon, then would detach from the Terminal Landing Module and tumble away to crash on the surface (image at top of post).

Lunar Gemini II on the Moon. Image credit: Jeff Bateman/David S. F. Portree 
The Terminal Landing Module, which would perform descent to the lunar surface following Retrograde Module separation, would weigh three tons with a full load (1.7 tons) of ignite-on-contact hydrazine/nitrogen tetroxide propellants. It would measure 21.6 feet across its base, which would attach to the top of the Retrograde Module, and 19.3 feet across its top, which would attach to the bottom of the Service Module. It would measure only 6.5 feet tall; this low profile would keep the Direct Ascent lander's center of gravity near the surface, helping to ensure that it would not tip during landing on its four spindly legs.

The legs would fold against the Retrograde Module's sides under ejectable streamlined fairings during ascent through Earth's atmosphere. A compartment in the module's underside would hold 165 pounds of scientific gear for exploring the lunar surface.

The top of the Service Module would measure 10.4 feet across if attached to a two-man Apollo CM and 8.7 feet across if joined to a Lunar Gemini CM. It would stand 8.5 feet tall and measure 19.3 feet across its base, where it would attach to the top of the Terminal Landing Module. The Service Module would perform lunar liftoff and course corrections during the flight home to Earth. It would weigh 11.7 tons with a full load (9.7 tons) of hydrazine/nitrogen tetroxide propellants.

In addition to propulsion systems, the Service Module would carry 1148 pounds of CM support equipment, including Gemini fuel cells to provide electricity and drinking water, a surface-mounted radiator for cooling, life-support oxygen tanks, and two boom-mounted radio dish antennas.

The Lunar Gemini II Service Module rocket motor ignites, boosting the Command Module off the Moon. Image credit: Jeff Bateman/David S. F. Portree
McDonnell found that both the two-man Apollo and the Lunar Gemini could serve a rescue function. The automated rescue spacecraft might home in on a radio beacon mounted on a pre-landed automated Surveyor lander. It could remain dormant on the lunar surface for up to 30 days awaiting arrival of the crew. If the piloted Direct Ascent spacecraft became damaged during landing or malfunctioned after touchdown, the astronauts would walk to the rescue spacecraft and use it to return to Earth.

Rescue modifications would include a guidance system similar to that under development for the automated Surveyor lunar soft-lander; additional liquid oxygen/liquid hydrogen fuel cell reactants (5.7 pounds per day) for powering electric heaters in the Command Module during the 14-day lunar night; additional water (6.5 pounds per day) for evaporative cooling during the 14-day lunar day; and a propellant-saving Surveyor-type "direct descent" landing profile with no stop in lunar orbit before descent to the lunar surface.

NASA/PSAC differences over the Apollo mode choice became public midway through the two-man Direct Ascent study, when Wiesner and Webb argued in front of President Kennedy and reporters during a presidential tour of NASA Marshall Space Flight Center (11 September 1962). Soon after McDonnell submitted its report, NASA reaffirmed its decision to go with LOR (24 October 1962).

Webb threatened to resign if NASA's choice were overruled, and Wiesner, sensing that Kennedy would back his NASA Administrator, acquiesced. On 7 November, the agency finalized its LOR decision by awarding the contract to build the LEM to Grumman Aircraft Engineering Corporation in Bethpage, Long Island.


Direct Flight Apollo Study, Volume I: Two-Man Apollo Spacecraft and Volume II: Gemini Spacecraft Applications, McDonnell Aircraft Corporation, 31 October 1962

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