Apollo 15 Lunar Module Instrument Host Overview ======================== The Apollo 15 lunar module (LM) 'Falcon' was the fourth crewed vehicle to land on the Moon. It carried two astronauts, David R. Scott and LM pilot James B. Irwin, the seventh and eighth men to walk on the Moon. The LM also carried a Lunar Roving Vehicle (LRV), an Apollo Lunar Surface Experiments Package (ALSEP) that contained scientific experiments to be deployed and left on the lunar surface, and other scientific and sample collection apparatus. The experiments performed on the Moon, in addition to the ALSEP suite, were geologic sample collection, surface photography, soil mechanics investigations to study physical properties of the lunar regolith, and the solar wind composition experiment which collected samples of solar wind particles for return to Earth. The LM separated from the Command and Service Module (CSM) at 18:13:30 UT and landed at 22:16:29 UT (6:16:29 p.m. EDT) on 30 July 1971 in the Mare Imbrium region at the foot of the Apennine mountain range at 26.1322 N latitude, 3.6339 E longitude (IAU Mean Earth Polar Axis coordinate system [Davies and Colvin, 2000]). Scott and Irwin made three moonwalk extra-vehicular activities (EVAs) totaling 18 hours, 35 minutes. During this time they covered 27.9 km and collected 77.31 kg of rock and soil samples. The LRV was used to explore regions within 5 km of the LM landing site. This was the first time a vehicle of this type had been used, and its performance on the lunar terrain was very successful. Two hours after landing the cabin was depressurized and Scott performed a standup EVA for 33 minutes, describing and photographing the surrounding terrain from the LM upper hatch. The first moonwalk EVA was on 31 July from 13:13:10 UT to 19:45:59 UT, during which time the LRV was unloaded, deployed, and driven. Photographs of the lunar surface were taken and geologic samples were collected from the LM site and during the three geological traverses. The traverse on the first EVA covered 10.3 km to the edge of Hadley Rille to Elbow Crater and near St. George Crater and back to the LM, where a core sample was taken from three meters below the surface. The ALSEP was deployed at the end of the traverse. On the second EVA, on 1 August from 11:48:48 UT to 19:01:02 UT, the LRV was driven on a 12.5 km traverse southeast along the base of the Apennine Mountains near Index, Arbeit, Crescent, Dune, and Spur craters and back to the ALSEP site. On the third EVA on 2 August from 08:52:14 UT to 13:42:04 UT the LRV was driven a total of 5.1 km west to Scarp Crater and northwest along the edge of Hadley Rille and back east across the mare. After the final EVA Scott performed a televised demonstration of a hammer and feather falling at the same rate in the lunar vacuum. The astronauts also left a plaque and small figure on the surface in memory of all fourteen American and Soviet space explorers who had died during the two nation's space programs. The LM lifted off the Moon on 2 August at 17:11:22 UT after 66 hours, 55 minutes on the lunar surface. After docking with the CSM (piloted by Alfred M. Worden) at 19:09:47 UT, the LM was jettisoned on 3 August at 01:04:14 UT and impacted on the Moon 2 hours later (03:03:37.0 UT) at 26.36 N, 0.25 E, 93 km west of the Apollo 15 ALSEP site, with an estimated impact velocity of 1.7 km/s at an angle of about 3.2 degrees from horizontal. Lunar Module Spacecraft and Subsystems -------------------------------------- The lunar module was a two-stage vehicle designed for space operations near and on the Moon. The spacecraft mass of 16,434 kg was the mass of the LM including astronauts, expendables, and approximately 12,000 kg of propellants. The fully fueled mass of the ascent stage was about 4971 kg and the descent stage 11,463 kg. The ascent and descent stages of the LM operated as a unit until staging, when the ascent stage functioned as a single spacecraft for rendezvous and docking with the command and service module (CSM). The descent stage comprised the lower part of the spacecraft and was an octagonal prism 4.2 meters across and 1.7 m thick. Four landing legs with round footpads were mounted on the sides of the descent stage and held the bottom of the stage 1.5 m above the surface. The distance between the ends of the footpads on opposite landing legs was 9.4 m. One of the legs had a small astronaut egress platform and ladder. A one meter long conical descent engine skirt protruded from the bottom of the stage. The descent stage contained the landing rocket, two tanks of aerozine 50 fuel, two tanks of nitrogen tetroxide oxidizer, water, oxygen and helium tanks and storage space for the lunar equipment and experiments, and in the case of Apollo 15, 16, and 17, the lunar rover. The descent stage served as a platform for launching the ascent stage and was left behind on the Moon. The ascent stage was an irregularly shaped unit approximately 2.8 m high and 4.0 by 4.3 meters in width mounted on top of the descent stage. The ascent stage housed the astronauts in a pressurized crew compartment with a volume of 6.65 cubic meters. There was an ingress-egress hatch in one side and a docking hatch for connecting to the CSM on top. Also mounted along the top were a parabolic rendezvous radar antenna, a steerable parabolic S-band antenna, and 2 in-flight VHF antennas. Two triangular windows were above and to either side of the egress hatch and four thrust chamber assemblies were mounted around the sides. At the base of the assembly was the ascent engine. The stage also contained an aerozine 50 fuel and an oxidizer tank, and helium, liquid oxygen, gaseous oxygen, and reaction control fuel tanks. There were no seats in the LM. A control console was mounted in the front of the crew compartment above the ingress-egress hatch and between the windows and two more control panels mounted on the side walls. The ascent stage was launched from the Moon at the end of lunar surface operations and returned the astronauts to the CSM. The descent engine was a deep-throttling ablative rocket with a maximum thrust of about 45,000 N mounted on a gimbal ring in the center of the descent stage. The ascent engine was a fixed, constant-thrust rocket with a thrust of about 15,000 N. Maneuvering was achieved via the reaction control system, which consisted of the four thrust modules, each one composed of four 450 N thrust chambers and nozzles pointing in different directions. Telemetry, TV, voice, and range communications with Earth were all via the S-band antenna. VHF was used for communications between the astronauts and the LM, and the LM and orbiting CSM. There were redundant transceivers and equipment for both S-band and VHF. An environmental control system recycled oxygen and maintained temperature in the electronics and cabin. Power was provided by 6 silver-zinc batteries. Guidance and navigation control were provided by a radar ranging system, an inertial measurement unit consisting of gyroscopes and accelerometers, and the Apollo guidance computer (AGC). Updates to the AGC in the LM were relayed by voice, then typed into the computer by an astronaut. Scientific Experiments ---------------------- The following scientific experiments were performed on board or at the Apollo 15 Lunar Module: - Handheld Photography documented the deployment of experiments, augmented crew observations and descriptions of the lunar traverses, and recorded the effects of the interaction between Apollo equipment and the lunar surface. - The Soil Mechanics Experiment studied the properties of the lunar soil. - The Solar Wind Composition Experiment collected samples of the solar wind for analysis on Earth. - The S-Band Transponder Experiment measured the lunar gravitational field by observing the dynamical motion of the spacecraft in free fall orbits to provide information about the distribution of lunar mass. For more information about the lunar module and its experiments, see the Apollo 15 Preliminary Science Report (1972). References ========== Apollo 15 Preliminary Science Report, NASA SP-289, published by NASA, Washington, D.C., 1972. Davies, M.E., and T.R. Colvin, Lunar coordinates in the regions of the Apollo landers, Journal of Geophysical Research, Volume 105, Issue E8, pages 20,227-20,280, 2000.