, the key engineer behind the adoption of
lunar orbit rendezvous mission logistics. The Lunar Module (originally designated the Lunar Excursion Module, known by the
acronym LEM) was designed after NASA
chose to reach the Moon via
Lunar Orbit Rendezvous (LOR) instead of the
direct ascent or
Earth Orbit Rendezvous (EOR) methods. Both direct ascent and EOR would have involved landing a much heavier, complete Apollo spacecraft 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 and ascending back to lunar orbit.
Contract letting and construction location In July 1962, eleven firms were invited to submit proposals for the LEM. Nine companies responded in September, answering 20 questions posed by the NASA RFP in a 60-page limited technical proposal.
Grumman was awarded the contract officially on November 7, 1962. Grumman had begun lunar orbit rendezvous studies in the late 1950s and again in 1961. 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) was developed by the
MIT Instrumentation Laboratory; the
Apollo Guidance Computer was manufactured by
Raytheon (a similar guidance system being used in the
command module). A backup navigation tool, the
Abort Guidance System (AGS), was developed by
TRW. The landing gear was manufactured by
Héroux. The Apollo Lunar Module was assembled in a Grumman factory in
Bethpage, New York.
Design phase 's
Apollo 5 information film reel focused on the Apollo Lunar Module. The Apollo Lunar Module was chiefly designed by Grumman aerospace engineer
Thomas J. Kelly. The first LEM design looked like a smaller version of the Apollo command and service module (a cone-shaped cabin atop a cylindrical propulsion section) with folding legs. The second design invoked the idea of a helicopter cockpit with large curved windows and seats to improve the astronauts' visibility for hover and landing. This also included a second, forward docking port, allowing the LEM crew to take an active role in docking with the CSM. As the program continued, there were numerous redesigns to save weight, improve safety, and fix problems. First to go were the heavy cockpit windows and the seats; the astronauts would stand while flying the LEM, supported by a cable and pulley system, with smaller triangular windows giving them sufficient visibility of the landing site. Later, the redundant forward docking port was removed, which meant the Command Pilot gave up active control of the docking to the Command Module Pilot; he could still see the approaching CSM through a small overhead window. Egress while wearing bulky extra-vehicular activity spacesuits was eased by a simpler forward hatch (). The configuration was frozen in April 1963, when the ascent and descent engine designs were decided. In addition to Rocketdyne, a parallel program for the descent engine The initial design had three landing legs, the lightest possible configuration. But as any particular leg would have to carry the weight of the vehicle if it landed at a significant angle, this was also the least stable configuration if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration, however, was too heavy and the designers compromised on four landing legs. In June 1966, the name was changed to Lunar Module (LM), eliminating the word
excursion. According to
George Low, Manager of the Apollo Spacecraft Program Office, this was because NASA was afraid that the word
excursion might lend a frivolous note to Apollo. Despite the name change, the astronauts and other NASA and Grumman personnel continued to pronounce the abbreviation as () instead of the letters "L-M".
Astronaut training (LLRV) during a test flight Comparing landing on the Moon to "a hovering operation",
Gus Grissom said in 1963 that although most early astronauts were fighter pilots, "now we're wondering if the pilot making this first moon landing shouldn't be a highly experienced helicopter pilot". To allow astronauts to learn lunar landing techniques, NASA contracted
Bell Aerosystems in 1964 to build the
Lunar Landing Research Vehicle (LLRV), which used a
gimbal-mounted vertical jet engine to counter five-sixths of its weight to simulate the Moon's gravity, in addition to its own hydrogen peroxide thrusters to simulate the LM's descent engine and attitude control. Successful testing of two LLRV prototypes at the
Dryden Flight Research Center led in 1966 to three production Lunar Landing Training Vehicles (LLTV) which along with the LLRV's were used to train the astronauts at the Houston Manned Spacecraft Center. This aircraft proved fairly dangerous to fly, as three of the five were destroyed in crashes. It was equipped with a rocket-powered ejection seat, so in each case the pilot survived, including the first man to walk on the Moon,
Neil Armstrong.
Development flights Lunar Module Test Article (LTA-2R) shortly before being mated with the SLA|250x250px LM-1 was built to make the first uncrewed flight for propulsion systems testing, launched into low Earth orbit atop a
Saturn IB. This was originally planned for April 1967, to be followed by the first crewed flight later that year. The LM's development problems had been underestimated, and LM-1's flight was delayed until January 22, 1968, as
Apollo 5. At that time, LM-2 was held in reserve in case the LM-1 flight failed, which did not happen. LM-3 now became the first crewed LM, again to be flown in low Earth orbit to test all the systems and practice the separation, rendezvous, and docking planned for
Apollo 8 in December 1968. Again, last-minute problems delayed its flight until
Apollo 9 on March 3, 1969. A second, higher Earth orbit crewed practice flight had been planned to follow LM-3, but this was cancelled to keep the program timeline on track.
Apollo 10 launched on May 18, 1969, using LM-4 for a "dress rehearsal" for the lunar landing, practicing all phases of the mission except powered descent initiation through takeoff. The LM descended to above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM.
Production flights in lunar orbit The first crewed lunar landing occurred on July 20, 1969, in the
Apollo 11 LM-5 Eagle. Four days later, the Apollo 11 crew in the
command module Columbia splashed down in the Pacific Ocean, completing
President John F. Kennedy's goal: "...before this decade is out, of landing a man on the Moon and returning him safely to the Earth". This was followed by landings by
Apollo 12 (LM-6
Intrepid) and
Apollo 14 (LM-8
Antares). In April 1970, the
Apollo 13 LM-7
Aquarius saved the lives of the three astronauts after an oxygen tank in the
service module ruptured, disabling the CSM.
Aquarius served as a "lifeboat" for the astronauts during their return to Earth. Its
descent stage engine was used to replace the crippled CSM Service Propulsion System engine, and its batteries supplied power for the trip home and recharged the Command Module's batteries critical for reentry. The astronauts splashed down safely in the
South Pacific Ocean on April 17, 1970. The LM's systems, designed to support two astronauts for 45 hours (including two depressurization and repressurization cycles, causing loss of oxygen supply), actually stretched to support three astronauts for 90 hours (without pressurization cycles and loss of oxygen). Hover times were maximized on the last four landing missions by using the Service Module engine to perform the initial descent orbit insertion burn 22 hours before the LM separated from the CSM, a practice begun on Apollo 14. This meant that the complete spacecraft, including the CSM, orbited the Moon with a perilune, enabling the LM to begin its powered descent from that altitude with a full load of descent stage propellant, leaving more reserve propellant for the final approach. The CSM would then raise its perilune back to the normal .
Extended J-class missions . The Extended Lunar Module (ELM) used on the final three
"J-class missions"—
Apollo 15,
16, and
17—was upgraded. The descent engine thrust was increased by the addition of a extension to the
engine bell, and the descent propellant tanks were enlarged. A waste storage tank was added to the descent stage, with plumbing from the ascent stage. These upgrades allowed stays of up to 75 hours on the Moon. The
Lunar Roving Vehicle was folded up and carried in Quadrant 1 of the descent stage. It was deployed by the astronauts after landing. ==Specifications==