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Apollo Extension System Flight Mission Assignment Plan (1965) (1)
David S. F. Portree  on 10/31/2019


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.

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Odp: [SHB] Apollo Extension System Flight Mission Assignment Plan (1965)
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Apollo Extension System Flight Mission Assignment Plan (1965) (2)


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)

1/66 - SA-201 - Apollo
4/66 - SA-202 - Apollo
7/66 - SA-203 - Apollo
10/66 - SA-204 - Apollo, CSM test
1/67 - SA-205 - Apollo, CSM/LEM test
1/67 - SA-501 - Apollo
4/67 - SA-206 - Apollo
5/67 - SA-502 - Apollo
7/67 - SA-207 - Apollo
10/67 - SA-503 - Apollo
11/67 - SA-208 - Apollo or AES, unassigned
2/68 - SA-504 - Apollo
3/68 - SA-209 - AES, Apollo CSM/Apollo LEM ascent stage
5/68 - SA-505 - Apollo
6/68 - SA-210 - Voyager, Saturn IB/Centaur
8/68 - SA-506 - Apollo, lunar landing 1
9/68 - SA-211 - AES, XCSM/LEM-Lab
11/68 - SA-507 - Apollo, lunar landing (SA-506 backup), or AES, Apollo CSM/Apollo LEM
12/68 - SA-212 - AES, unassigned
1/69 - SA-213 - Voyager, Saturn IB/Centaur
2/69 - SA-508 - Apollo, lunar landing 2
2/69 - SA-214 - Voyager, Saturn IB/Centaur
4/69 - SA-509 - AES, Apollo CSM/Apollo LEM ascent stage
5/69 - SA-215 - AES, Apollo CSM/Apollo LEM ascent stage
6/69 - SA-510 - Apollo, lunar landing 3
7/69 - SA-216 - AES, unassigned
8/69 - SA-511 - AES, XCSM/LEM-Lab/descent stage
9/69 - SA-217 - AES, unassigned
10/69 - SA-512 - Apollo, lunar landing 4
12/69 - SA-513 - AES, Apollo CSM/Apollo LEM ascent stage
12/69 - SA-218 - AES, XCSM/LEM-Lab
1/70 - SA-219 - AES, XCSM/LEM-Lab
2/70 - SA-514 - AES, Apollo CSM/LEM-Shelter
4/70 - SA-220 - AES, unassigned
4/70 - SA-515 - AES, XCSM/LEM-Taxi
5/70 - SA-221 - AES, XCSM/LEM-Lab
6/70 - SA-516 - AES, XCSM/LEM-Lab
7/70 - SA-222 - AES, unassigned
8/70 - SA-517 - AES, XCSM/LEM-Lab/descent stage
9/70 - SA-223 - AES, unassigned
10/70 - SA-518 - AES, XCSM/LEM-Lab
11/70 - SA-224 - AES, unassigned
12/70 - SA-519 - AES, Apollo CSM/LEM-Shelter
1/71 - SA-225 - AES, unassigned
2/71 - SA-520 - AES, XCSM/LEM-Taxi
3/71 - SA-226 - AES, unassigned
4/71 - SA-521 - AES, XCSM/LEM-Lab
5/71 - SA-227 - Voyager, Saturn IB-Centaur
6/71 - SA-228 - Voyager, Saturn IB-Centaur
6/71 - SA-522 - AES, XCSM/LEM-Lab/descent stage
8/71 - SA-523 - AES, XCSM/LEM-Lab
9/71 - SA-229 - AES, XCSM/LEM-Lab
10/71 - SA-524 - AES, Apollo CSM/LEM-Shelter
10/71 - SA-230 - AES, XCSM/LEM-Lab
12/71 - SA-525 - AES, XCSM/LEM-Taxi

Sources

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.
 
Source: http://spaceflighthistory.blogspot.com/2019/10/apollo-extension-system-flight-mission.html