NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Apollo 16 Lunar Module /ALSEP



The Apollo 16 lunar module (LM) "Orion" was the fifth crewed vehicle to land on the Moon. It carried two astronauts, Commander John W. Young and LM pilot Charles M. Duke Jr., the ninth and tenth 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 the physical properties of the lunar regolith, the solar wind composition experiment which collected samples of solar wind for return to Earth, a cosmic-ray detector to measure heavy cosmic rays, a far-ultraviolet camera for lyman-alpha astronomical observations, and a portable surface magnetometer to study local magnetic sources.

Mission Profile

The LM separated from the Command/Service Module (CSM) at 18:08:00 UT on 20 April 1972 and landed at 02:23:35 UT on 21 April (9:23:35 p.m. EST, 20 April) in the Descartes highland region just north of the crater Dolland at 8.9730 S latitude, 15.5002 E longitude (IAU Mean Earth Polar Axis coordinate system). Young and Duke made three moonwalk extra-vehicular activities (EVAs) totaling 20 hours, 14 minutes. During this time they covered 27 km and collected 95.71 kg of rock and soil samples, stopping at 11 sites. The LRV was used during EVAs to extend the range of manned lunar exploration. The first EVA was on 21 April from 16:47:38 UT to 23:58:40 UT, during which the astronauts set up the ALSEP, deployed the LRV, and explored surrounding craters in a 4.2 km traverse. During ALSEP set up Young tripped on the cable to the heat flow experiment and broke it, rendering the instrument inoperable. During the second EVA on 22 April from 16:33:35 UT to 23:56:44 UT the astronauts explored a ridge and mountain slope during a 11.1 km traverse and on the third, of 11.4 km, on 23 April from 15:25:28 UT to 21:05:31 UT they travelled to North Ray Crater. During all these EVAs the astronauts collected samples and took photographs. The LM lifted off from the Moon on 24 April at 01:25:48 UT after 71 hours, 2 minutes on the lunar surface. After docking with the CSM (piloted by Thomas K. Mattingly 2nd) at 03:35:18 UT, the LM was jettisoned into lunar orbit at 20:54:12 UT on 24 April. Loss of attitude control on the LM made the planned impact near the Apollo 16 site impossible, so it was left in lunar orbit with an estimated life of 1 year.

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 16445 kg was the total mass of the LM ascent and descent stages including propellants (fuel and oxidizer). The dry mass of the ascent stage was 2385 kg and it held 2378 kg of propellant. The descent stage dry mass (including stowed surface equipment) was 2810 kg and 8872 kg of propellant were onboard initially. 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 tranceivers 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.

Apollo Lunar Surface Experiments Package (ALSEP)

The Apollo Lunar Surface Experiments Package (ALSEP) consisted of a set of scientific instruments emplaced at the landing site by the astronauts. The instruments were arrayed around a central station and connected by cables which supplied power to run the instruments and communications so data collected by the experiments could be relayed to Earth. The central station was a 25 kg box with a stowed volume of 34,800 cubic cm. Thermal control was achieved by passive elements (insulation, reflectors, thermal coatings) as well as power dissipation resistors and heaters. Communications with Earth were achieved through a 58 cm long, 3.8 cm diameter modified axial-helical antenna mounted on top of the central station and pointed towards Earth by the astronauts. Transmitters, receivers, data processors and multiplexers were housed within the central station. Data collected from the instruments were converted into a telemetry format and transmitted to Earth. The ALSEP system and instruments were controlled by commands from Earth. The uplink frequency for all Apollo mission ALSEP's was 2119 MHz, the downlink frequency for the Apollo 16 ALSEP was 2276.0 MHz.

Radioisotope Thermoelectric Generator (RTG)

The SNAP-27 model RTG produced the power to run the ALSEP operations. The generator consisted of a 46 cm high central cylinder and eight radiating rectangular fins with a total tip-to-tip diameter of 40 cm. The central cylinder had a thinner concentric inner cylinder inside, and the two cylinders were attached along their surfaces by 442 spring-loaded lead-telluride thermoelectric couples mounted radially along the length of the cylinders. The generator assembly had a total mass of 17 kg. The power source was an approximately 4 kg fuel capsule in the shape of a long rod which contained plutonium-238 and was placed in the inner cylinder of the RTG by the astronauts on deployment. Plutonium-238 decays with a half-life of 89.6 years and produces heat. This heat would conduct from the inner cylinder to the outer via the thermocouples which would convert the heat directly to electrical power. Excess heat on the outer cylinder would be radiated to space by the fins. The RTG produced approximately 70 W DC at 16 V. (63.5 W after one year.) The electricity was routed through a cable to a power conditioning unit and a power distribution unit in the central station to supply the correct voltage and power to each instrument.

ALSEP Scientific Instruments

All ALSEP instruments were deployed on the surface by the astronauts and attached to the central station by cables. The Apollo 16 ALSEP instruments consisted of: (1) a passive seismometer, designed to measure seismic activity and physical properties of the lunar crust and interior; (2) an active seismometer to study the physical properties of lunar surface and subsurface materials and the structure of the local near-surface layers; (3) a lunar surface magnetometer (LSM), designed to measure the magnetic field at the lunar surface; and (4) a heat flow experiment, designed to measure the rate of heat loss from the lunar interior and the thermal properties of lunar material. The central station, located at 8.9754 S latitude, 15.4981 E longitude, was turned on at 19:38 UT on 21 April 1972 and shut down along with the other ALSEP stations on 30 September 1977.

Alternate Names

  • 06005
  • ALSEP 16
  • Apollo 16 LM/ALSEP
  • Apollo 16 Lunar Surface Experiments Package
  • Apollo 16C
  • Apollo16ALSEP
  • LEM 16
  • LM-11
  • Orion
  • Rover 16

Facts in Brief

Launch Date: 1972-04-16
Launch Vehicle: Saturn 5
Launch Site: Cape Canaveral, United States
Mass: 16445 kg

Funding Agencies

  • NASA-Office of Space Science (United States)
  • NASA-Office of Manned Space Flight (United States)


  • Planetary Science
  • Space Physics
  • Human Crew
  • Astronomy

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. Floyd I. RobersonProgram ManagerNASA Headquarters
Mr. Wilbert F. EichelmanProject ManagerNASA Johnson Space Center
Dr. John B. HanleyProgram ScientistNASA Headquarters

Selected References

  • Apollo 16 preliminary science report, NASA, SP-315, Wash., D.C., 1972.
  • Davies, M. E., and T. R. Colvin, Lunar coordinates in the regions of the Apollo landers, J. Geophys. Res., 105, No. E8, 20277-20280, Aug. 2000.
Diagram of Apollo 11 Lunar Module

Diagram of the Apollo Lunar Module. (Courtesy of NASA History Office.)

Other Sources of Apollo 16 Information at NSSDCA

Apollo 16 Command Module
Apollo 16 Subsatellite
Apollo Lunar Roving Vehicle
Apollo 16 Page

Other Sources of Apollo Information at NSSDCA

Apollo landing sites and ALSEP and LRRR locations - and information on the modified DMA/603 control network
Apollo Page
Lunar Science Page

Related Information at NSSDCA

Moon Page

[] NASA Logo -