LEM
(Lunar Excursion Module)
A
spacecraft that carries astronauts from the command module to the
surface of the moon and back Common clues: Moon vehicle,
briefly; Moon lander; The Eagle, e.g.; Apollo component, for
short; NASA vehicle; Moon-landing transport Crossword
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2 times a year News: Flags
from Apollo moon-landing still standing, photos reveal Video:
The
Eagle Has Landed
The
Apollo Lunar Module was the lander portion of the Apollo
spacecraft built for the US Apollo program to achieve the transit
from Moon orbit to the surface and back. The module was also
known as the LM from the manufacturer designation (yet pronounced
"LEM" from NASA's early name for it, Lunar Excursion
Module).
Apollo
16 on lunar surface
The
module was designed to carry two crew in a 6.65 m³ space.
The total module was 6.4 m high and 4.3 m across, resting on four
legs. It consisted of two stages - a descent stage and a module
and ascent stage. The total mass of the module was 15,264 kg with
the majority of that (10,334 kg) in the descent stage.
The
Apollo Lunar Module came into being because NASA chose to reach
the moon via a lunar orbit rendezvous (LOR) instead of a direct
ascent or Earth orbit rendezvous (EOR). Both a direct ascent and
an EOR would have involved the entire Apollo spacecraft landing
on the moon; once the decision had been made to proceed using
LOR, it became necessary to produce a separate craft capable of
reaching the lunar surface.
The
LM contract was given to Grumman Aircraft Engineering and a
number of subcontractors. Grumman had begun lunar orbit
rendezvous studies in late 1960 and again in 1962. In July 1962
eleven firms were invited to submit proposals for the LM. Nine
did so in September, and Grumman was awarded the contract that
same month. The contract cost was expected to be around $350
million. There were initially four major subcontractors - Bell
Aerosystems (ascent engine), Hamilton Standard (environmental
control systems), Marquardt (reaction control system) and
Rocketdyne (descent engine).
The
primary guidance, navigation and control system (PGNCS) on the LM
was developed by the MIT Instrumentation Laboratory. The Apollo
Guidance Computer was manufactured by Raytheon. A similar
guidance system was used in the Command Module. A backup
navigation tool, the Abort Guidance System (AGS), was developed
by TRW.
To
learn lunar landing techniques, astronauts practiced in the Lunar
Landing Research Vehicle (LLRV), a flying vehicle that simulated
the Lunar Module on earth.
Configuration
freeze did not start until April 1963 when the ascent and descent
engine design was decided. In addition to Rocketdyne a parallel
program for the descent engine was ordered from Space Technology
Laboratories in July 1963, and by January 1965 the Rocketdyne
contract was cancelled. As the program continued there were
numerous redesigns to save weight (including 'Operation Scrape'),
improve safety, and fix problems. For example initially the
module was to be powered by fuel cells, built by Pratt and
Whitney but in March 1965 they were paid off in favor of an all
battery design.
The
first LM flight was on January 22, 1968 when the unmanned LM-1
was launched on a Saturn IB for testing of propulsion systems in
orbit. The next LM flight was aboard Apollo 9 using LM-3 on March
3, 1969 as a manned flight (McDivitt, Scott and Schweickart) to
test a number of systems in Earth orbit including LM and CSM crew
transit, LM propulsion, separation and docking. Apollo 10, which
launched on May 18, 1969, was another series of tests, this time
in lunar orbit with the LM separating and descending to within 10
km of the surface. From the successful tests the LM successfully
descended and ascended from the lunar surface with Apollo 11.
This
article is licensed under the GNU
Free Documentation License.
It uses material from the Wikipedia
article "Apollo Lunar Module".
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