The Apollo Lunar Module (written 'LM' but pronounced 'LEM' from its former name of Lunar Excursion Module) is the part of the Apollo spacecraft that left an orbit around the moon, landed, and then ascended back into orbit. The LM was built by Grumman Aircraft Engineering Corporation for the Apollo program.
There are two parts to the LM (shown in their joined configuration here). The lower part of the vehicle (known as the descent stage) contains the descent engine, used to slow the LM down so that the moon's gravity could pull it to the surface. The landing legs contained large pads to prevent the vehicle from sinking into the moon's soft surface and to stabilize the platform which would later become the launch pad for the ascent back into orbit.
The upper portion (known as the ascent stage) held the two astronauts in a 6 meter square crew compartment. This part also had a rocket motor, which when fired launched the ascent stage back into the moon's orbit, leaving the descent stage on the moon. This small module met up with the Command Module (CM), which remained in lunar orbit while the LM was on the surface.
There were 16 LMs built for the Apollo program; LM-2, 9 and 13 are on displays in museums (reportedly so are parts from LM-14). Of the LMs that were launched, many were destroyed when they were discarded into the earth's atmosphere or deliberately crashed back into the lunar surface. All of the LM descent stages that were used in moon landings are still on the surface of the moon.
The lower portion contained a ladder that extended to the upper module. This is the ladder you see in the video shown of Neil Armstrong's historic first step of the moon. Note that the ladder did not extend to the ground, but was a least a meter off the surface. In his bulky spacesuit that severely restricted normal motion, that was a giant leap from the last rung to the surface.
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Author(s): Leonard Churchill (2007 January 17)
