Mars orbit rendezvous (MOR) is a concept for space travel, where a spacecraft takes off from Mars (a martian ascent stage) and does a rendezvous in Mars orbit with another spacecraft.[1] Applied to a Mars sample return or manned mission to Mars, it allows much less weight to be sent to the surface and back into orbit, because the fuel needed to travel back to Earth is not landed on the planet.[1] It can also be used for a Mars sample return.[2] [3] NASA developed designs for a combination of a mars lander, surface habitat, and ascent vehicle called a Mars Excursion Module (MEM) in the 1960s for its human mars mission plans.
MOR is analogous to Lunar orbit rendezvous (LOR) used on the United States NASA Apollo program missions to Earth's moon during 1969 to 1972 (as opposed to Earth orbit rendezvous(EOR) or Direct ascent).[1]
Another variation is a Mars flyby rendezvous, where the mother ship (such as a Mars cycler) does not enter orbit.[4] Mars flyby rendezvous was evaluated at NASA's Manned Spaceflight Center in the 1960s.[4]
Another variation is that the ascent stage comes from one of the Mars moons, in the case of an expedition to Phobos or Deimos.