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Lunar orbit rendezvous
Lunar orbit rendezvous (LOR) is a process for landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a lunar lander travel to lunar orbit. The lunar lander then independently descends to the surface of the Moon, while the main spacecraft remains in lunar orbit. After completion of the mission there, the lander returns to lunar orbit to rendezvous and re-dock with the main spacecraft, then is discarded after transfer of crew and payload. Only the main spacecraft returns to Earth.
Lunar orbit rendezvous was first proposed in 1919 by Ukrainian engineer Yuri Kondratyuk, as the most economical way of sending a human on a round-trip journey to the Moon.
The most famous example involved Project Apollo's command and service module (CSM) and lunar module (LM), where they were both sent to a translunar flight in a single rocket stack. However, variants where the landers and main spacecraft travel separately, such as the lunar landing plans proposed for Shuttle-Derived Heavy Lift Launch Vehicle, Golden Spike and the 2029/2030 Chinese crewed effort, are also considered to be lunar orbit rendezvous.
The main advantage of LOR is the spacecraft payload saving, due to the fact that the propellant necessary to return from lunar orbit back to Earth need not be carried as dead weight down to the Moon and back into lunar orbit. This has a multiplicative effect, because each pound of "dead weight" propellant used later has to be propelled by more propellant sooner, and also because increased propellant requires increased tankage weight. The resultant weight increase would also require more thrust for lunar landing, which means larger and heavier engines.
Another advantage is that the lunar lander can be designed for just that purpose, rather than requiring the main spacecraft to also be made suitable for a lunar landing. Finally, the second set of life support systems that the lunar lander requires can serve as a backup for the systems in the main spacecraft; this redundancy saved the crew of Apollo 13 when their command module's systems failed.
Lunar-orbit rendezvous was considered risky in 1962, because space rendezvous had not been achieved, even in Earth orbit. If the LM could not reach the CSM, two astronauts would be stranded with no way to get back to Earth or survive re-entry into the atmosphere. Rendezvous was successfully demonstrated in 1965 and 1966 on six Project Gemini missions with the aid of radar and on-board computers. It was also successfully done each of the eight times it was tried on Apollo missions.
When the Apollo Moon landing program was started in 1961, it was assumed that the three-man command and service module combination (CSM) would be used for takeoff from the lunar surface, and return to Earth. It would therefore have to be landed on the Moon by a larger rocket stage with landing gear legs, resulting in a very large spacecraft (in excess of 100,000 pounds (45,000 kg)) to be sent to the Moon.
If this were done by direct ascent (on a single launch vehicle), the rocket required would have to be extremely large, in the Nova class. The alternative to this would have been Earth orbit rendezvous, in which two or more rockets in the Saturn class would launch parts of the complete spacecraft, which would rendezvous in Earth orbit before departing for the Moon. This would possibly include a separately launched Earth departure stage, or require on-orbit refueling of the empty departure stage.
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Lunar orbit rendezvous AI simulator
(@Lunar orbit rendezvous_simulator)
Lunar orbit rendezvous
Lunar orbit rendezvous (LOR) is a process for landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a lunar lander travel to lunar orbit. The lunar lander then independently descends to the surface of the Moon, while the main spacecraft remains in lunar orbit. After completion of the mission there, the lander returns to lunar orbit to rendezvous and re-dock with the main spacecraft, then is discarded after transfer of crew and payload. Only the main spacecraft returns to Earth.
Lunar orbit rendezvous was first proposed in 1919 by Ukrainian engineer Yuri Kondratyuk, as the most economical way of sending a human on a round-trip journey to the Moon.
The most famous example involved Project Apollo's command and service module (CSM) and lunar module (LM), where they were both sent to a translunar flight in a single rocket stack. However, variants where the landers and main spacecraft travel separately, such as the lunar landing plans proposed for Shuttle-Derived Heavy Lift Launch Vehicle, Golden Spike and the 2029/2030 Chinese crewed effort, are also considered to be lunar orbit rendezvous.
The main advantage of LOR is the spacecraft payload saving, due to the fact that the propellant necessary to return from lunar orbit back to Earth need not be carried as dead weight down to the Moon and back into lunar orbit. This has a multiplicative effect, because each pound of "dead weight" propellant used later has to be propelled by more propellant sooner, and also because increased propellant requires increased tankage weight. The resultant weight increase would also require more thrust for lunar landing, which means larger and heavier engines.
Another advantage is that the lunar lander can be designed for just that purpose, rather than requiring the main spacecraft to also be made suitable for a lunar landing. Finally, the second set of life support systems that the lunar lander requires can serve as a backup for the systems in the main spacecraft; this redundancy saved the crew of Apollo 13 when their command module's systems failed.
Lunar-orbit rendezvous was considered risky in 1962, because space rendezvous had not been achieved, even in Earth orbit. If the LM could not reach the CSM, two astronauts would be stranded with no way to get back to Earth or survive re-entry into the atmosphere. Rendezvous was successfully demonstrated in 1965 and 1966 on six Project Gemini missions with the aid of radar and on-board computers. It was also successfully done each of the eight times it was tried on Apollo missions.
When the Apollo Moon landing program was started in 1961, it was assumed that the three-man command and service module combination (CSM) would be used for takeoff from the lunar surface, and return to Earth. It would therefore have to be landed on the Moon by a larger rocket stage with landing gear legs, resulting in a very large spacecraft (in excess of 100,000 pounds (45,000 kg)) to be sent to the Moon.
If this were done by direct ascent (on a single launch vehicle), the rocket required would have to be extremely large, in the Nova class. The alternative to this would have been Earth orbit rendezvous, in which two or more rockets in the Saturn class would launch parts of the complete spacecraft, which would rendezvous in Earth orbit before departing for the Moon. This would possibly include a separately launched Earth departure stage, or require on-orbit refueling of the empty departure stage.