A total of 12 lunar landing missions would be conducted between 1969 and 1976, the final two being dual-launch missions with the Apollo crews landing on the lunar surface near a previously-landed payload lander. The supplies, lunar flying vehicles, and rovers delivered by the separate lander would allow two-week explorations of the lunar surface. This was the final iteration of the AES Lunar Base before further Saturn V production was cancelled.
Phase 1: 1969-1971: This "Apollo Phase" commenced with the first lunar landing and continued for four missions, or until sufficient experience had been achieved to allow the next phase to commence. Using standard Apollo hardware, missions would evolve from 22 hours and 2 EVA'S on the lunar surface to the full Apollo LM capability of 36 hours and 3 or 4 EVA's. Landing sites were all in the equatorial "Apollo zone" of the moon. Manual maneuvering of the LM to the landing point, used to avoid hazards in mission 1, would be used in succeeding missions to get close to interesting features such as fresh craters or ridges. Sampling and ALSEP deployment were prime science objectives. Simple orbital experiments would be conducted, such as multi-spectral photography with Hasselblad cameras. Mission spacing was increased to six months to allow sufficient feedback and to avoid using an undesirably excessive number of spacecraft in the Apollo phase. As actual flown by NASA, these missions corresponded to Apollo 11 to 14.
Phase 2: 1972 to 1973: This Lunar Exploration Phase would commence about two years after Apollo and consisted of four flights of the Extended LM (ELM), a modification of basic Apollo LM hardware. This assumed a decision was made to proceed with the ELM immediately after the first Apollo success and the prior completion of all engineering design. ELM missions extended lunar stay time to 3 or 4 days with landed payloads approaching 450 kg. Advanced ALSEP's and mobility devices would consume a major portion of this payload. Return of samples collected in geologic contexts remained a prime objective. Landing sites would be selected from available Lunar Orbiter photography but relaxation of the free-return constraint would open up sites outside the Apollo zone. A specific mission would be targeted to a specific site. Several launch opportunities to a given site could be provided by either varying translunar flight time or by waiting in lunar orbit. Orbital remote sensing experiments would also conducted, including infrared and metric photography. This scenario corresponded to Apollo 15 to 17 as flown.
Phase 3: 1974: A single Lunar Orbital Survey Mission was indicated after the Lunar Surface Exploration phase and would be the end of the initial buy of Apollo spacecraft. This 28-day lunar polar orbit mission would be flown after the Apollo's and ELM's, in order to have several "ground-truth" sites and to allow prior "feasibility" experiments to be flown. This positioning would make use of an augmented CSM that was expected to be developed for earth-orbital use under the Apollo Applications Program. It would occur before the next phase since it was felt that NASA did not have the necessary data upon which to pick sites for dual missions. A subsatellite would be deployed in orbit for magnetic, gravity , and X-ray sensing. In reality most of the Apollo Applications Program was cancelled (except Skylab and Apollo ASTP) and this mission was never flown.
Phase 4: 1975-1976: This Lunar Surface Rendezvous and Exploration Phase nominally consisted of two dual-launch missions, although it was expected the program would continue on a build-up to a lunar base. A Lunar Payload Module (LPM - essentially the LM Truck of earlier studies) would be delivered by an unmanned cargo carrier to the surface and provide a rendezvous target for a manned ELM that would arrive up to 3 months later . The LPM's 3620 kg payload included one or more mobility devices, advanced science stations, and consumables for ELM stay time extension to about two weeks. Deciphering of the interrelationships of several lunar features, conduct of "traverse" geophysics, and utilization of preliminary sample analysis in-situ were new scientific features of the mission.
A pacing item in dual missions was payload development. To be ready for a mid-70's launch, such payloads had to be defined by the end of 1968, and science systems concepts studied with regard to feasibility and preliminary design. The technique of the unmanned landing had to be developed. The possibility of augmentation of the LM and Saturn V in the next production lots used for these missions had to be considered and might be mandatory if the ELM concept did not have sufficient margins.
The dual missions had greater weight capability and longer stay time. The issue of precision landing was considered a major risk factor. The LPM had to land unmanned and the LM crew had land close enough to work with both vehicles on the surface on foot. If the unmanned vehicle landed first it would need a CEP of about 100 m for efficiency. The manned vehicle would land as close to it as possible using manual landing procedures (in fact his proved to be no problem, as Apollo 12 proved in the second lunar landing when it touched down within easy walking distance of Surveyor 3).
A number of schemes were suggested to achieve a CEP of 100 m for the unmanned landing, of which TV guidance with man in the loop appeared the most promising. A less promising alternative was to have the manned vehicle land first and then "talk down" the unmanned vehicle, which would have been stored in orbit.
Crew Size: 2.