The Apollo 13 Lunar Module functioned as a lifeboat to provide life support and propulsion to keep the crew alive for the trip home, when their CSM was disabled by an oxygen tank explosion en route to the Moon.

Soon after TLI, the SLA opened; the CSM performed a maneuver whereby it separated, turned around, came back to dock with the Lunar Module, and extracted it from the S-IVB.

During the flight to the Moon, the docking hatches were opened and the Lunar Module pilot entered the LM to power up temporarily and test all systems except propulsion.

After the command module pilot visually inspected the landing gear, the LM was withdrawn to a safe distance, then rotated until the descent engine was pointed forward into the direction of travel.

During final approach, the vehicle pitched over to a near-vertical position, allowing the crew to look forward and down to see the lunar surface for the first time.

At this point, manual control was enabled for the commander, who had enough propellant to hover for up to two minutes to survey where the computer was taking the craft and make any necessary corrections.

If necessary, landing could have been aborted at almost any time by jettisoning the descent stage and firing the ascent engine to climb back into orbit for an emergency return to the CSM.

[8] Communications were eventually deemed to be reliable enough to allow both crew members to walk on the surface, leaving the spacecraft to be only remotely attended by Mission Control.

Beginning with Apollo 14, extra LM propellant was made available for the powered descent and landing, by using the CSM engine to achieve the 50,000-foot (15 km) perilune.

[18] 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.

Power was initially to be produced by fuel cells built by Pratt and Whitney similar to the CSM, but in March 1965 these were discarded in favor of an all-battery design.

[25] 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.

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.

[26] LM-1 was built to make the first uncrewed flight for propulsion systems testing, launched into low Earth orbit atop a Saturn IB.

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.

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 47,400 feet (9.0 mi; 14.4 km) above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM.

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".

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.

[29] 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.

It contained its own ascent propulsion system (APS) engine and two hypergolic propellant tanks for return to lunar orbit and rendezvous with the Apollo command and service module.

[32] The return payload included the lunar rock and soil samples collected by the crew (as much as 238 pounds (108 kg) on Apollo 17), plus their exposed photographic film.

Its octagonal shape was supported by four folding landing gear legs, and contained a throttleable Descent Propulsion System (DPS) engine with four hypergolic propellant tanks.

A continuous-wave Doppler radar antenna was mounted by the engine heat shield on the bottom surface, to send altitude and rate of descent data to the guidance system and pilot display during the landing.

An external compartment on the right front panel carried a deployable S-band antenna which, when opened, looked like an inverted umbrella on a tripod.

[38] Compartments also contained replacement Portable Life Support System (PLSS) batteries and extra lithium hydroxide canisters to purge carbon dioxide from the LM.

This would have been launched on an uncrewed Saturn IB, and docked with a crewed command and service module, named the Apollo Telescope Mission (ATM).

[63] When Skylab changed to a "dry workshop" design pre-fabricated on the ground and launched on a Saturn V, the telescope was mounted on a hinged arm and controlled from inside the MDA.

In 2013, in the television show Arrested Development, a fictionalized version of Howard is depicted as having the Apollo 11 "LEM" in his office, which his character claims was used to fake the 1969 moon landing.