Encyclopedia Astronautica
1962.07.25 - Invitation to bid for the Apollo lunar excursion module

MSC invited 11 firms to submit research and development proposals for the lunar excursion module (LEM) for the manned lunar landing mission. The firms were Lockheed Aircraft Corporation, The Boeing Airplane Company, Northrop Corporation, Ling-Temco-Vought, Inc., Grumman Aircraft Engineering Corporation, Douglas Aircraft Company, General Dynamics Corporation, Republic Aviation Corporation, Martin- Marietta Company, North American Aviation, Inc., and McDonnell Aircraft Corporation.

The Statement of Work distributed to the prospective bidders described the contractor's responsibilities:

- Detail design and manufacture of the LEM and related test articles, mockups, and other hardware with the exception of certain government- furnished equipment [navigation and guidance system (excepting the rendezvous radar and radar altimeter), flight research and development instrumentation system, scientific instrumentation system, and certain components of the crew equipment system (space suits, portable life support systems, and personal radiation dosimeters.)]
- Integration of government-furnished equipment into the LEM; development of specifications for equipment performance, interfaces, and design environment; and maintenance of interface control documentation in a state of validity and concurrence.
- Detailed trajectory analysis from lunar orbit separation until lunar orbit rendezvous directly related to the contractor's area of responsibility.
- Specification of the mission environment on the lunar surface and assessment of the effects of the spacecraft adapter environment on the LEM.
- Detail design of the LEM-mounted equipment for repositioning and mating the LEM to the command module CM.
- Design of the LEM-mounted equipment within the overall specification of the Principal Contractor NAA.
- Determination of the desirability of checkout or operation of the LEM during the translunar period of the flight.
- Identification of crew tasks related to the LEM before and during separation, whether actually performed in the LEM or CM.
- Design and manufacture of the ground support equipment directly associated with the hardware for which the contractor was responsible and ensurance of compatibility of all ground support equipment involved with the LEM.
- Design and manufacture of certain LEM training equipment for flight or ground personnel as required by NASA.
- Prelaunch preparation and checkout of the LEM, working with the other contractors in the same manner as during systems testing.
- Coordination of all LEM activities with the overall spacecraft prelaunch requirements.
- Planning and implementation of a reliability and quality assurance program.
- Provision of adequate logistic support for the equipment furnished by the contractor.

The mockups to be delivered by the contractor would include but not be limited to:

- Complete LEM
- Cabin interior arrangement
- Cabin exterior equipment
- Docking system
- Environmental control system
- Crew support system
- Antenna radiation pattern
- Handling and transportation
- Module interface

Before the first translunar midcourse correction, the LEM would be transferred from its stowed position in the spacecraft adapter to a docked configuration with the command and service modules (CSM). At a later point in the mission, the two-man LEM crew would enter the LEM from the CSM by means of a hatch without being exposed to the environment of space. Another hatch would allow access to the LEM during countdown and egress into space while docked with the CSM.

The LEM systems were to operate at their normal design performance level for a mission of two days without resupply. Equipment normally operated in the pressurized LEM cabin environment would be designed to function for a minimum of two days in vacuum without failure. The LEM pressurization system would be capable of six complete cabin repressurizations and a continuous leak rate as high as 0.2 pound per hour. Provision would be made for a total of six recharges of the portable life support system which had a normal operating time without resupply of four hours. Under usual conditions in the LEM cabin, the crew would wear unpressurized space suits. Either crewman would be able, alone, to return the LEM to the CSM and successfully perform the rendezvous and docking maneuver. Of the overall crew safety goal of 0.999, the goal apportioned to the LEM was 0.995.

The LEM would be capable of independently performing the separation from the CSM, lunar descent, landing, ascent, rendezvous, and docking with the CSM. It would allow for crew exploration in the vicinity of lunar touchdown but would not be required to have lunar surface mobility.

Lunar landing would be attempted from a lunar orbit of 100 nautical miles. After separation, the LEM would transfer from the circular orbit to an equal-period elliptical orbit which would not intersect the lunar surface. The hovering, final touchdown maneuvers, and landing would be performed by the LEM from the elliptical orbit.

Normally there would not be a requirement to reposition the LEM attitude before lunar launch. To rendezvous and dock with the CSM, the LEM would transfer from an elliptical to a circular orbit after lunar launch.

The LEM would not be recoverable.

Included in the Statement of Work was a description of the major LEM systems:

Guidance and control system

The navigation and guidance system would provide steering and thrust control signals for the stabilization and control system, reaction control system, and the lunar excursion propulsion system. Its basic components were:

- Inertial measurement unit

- Optical measurement unit

- Range-drift measurement unit (reticle)

- Computer Power and servo assembly

- Control and display unit

- Displays and controls

- Cabling and junction box

- Chart book and star catalog

- Rendezvous radar and radar altimeter

The stabilization and control system would meet the attitude stabilization and maneuver control requirements and would include:

- Attitude reference

- Rate sensors

- Control electronics assembly

- Manual controls

- Displays

- Power supplies

Lunar excursion propulsion system

The system would use storable hypergolic bipropellants and a pressurized propellant feed system. Variable thrust would be required from a propulsion system to be designed.


The fuel would be monomethylhydrazine or a mixture of 50 percent hydrazine and 50 percent unsymmetrical dimethylhydrazine. Nitrogen tetroxide with nitrous oxide, added to depress the freezing point if necessary, would be used as oxidizer.

Reaction control system

The system comprised two independent, interconnectable, pulse- modulated subsystems, each capable of meeting the total torque and impulse requirements and providing two-directional control about all axes. The same propellant combination would be used as for the LEM propulsion system.

Lunar touchdown system

Attached to the LEM by hard points which would accommodate variations of landing gear geometrics, the system would have load distribution capabilities compatible with anticipated landing gear loads and would include meteoroid protection and radiation protection inherent in its structure, Normally, the system would be deployed from within the spacecraft but could be operated manually by the crew in spacesuits outside the spacecraft.

Crew systems

The flight Crew would consist of the Commander and Systems Engineer. The crew equipment system would include an adjustable seat for each crewman, restraint system for each seat, food and water, first aid equipment, space suits, portable life support systems for each crewman, and personal radiation dosimeters.

Environmental control system

The following conditions would be provided:

- Total cabin pressure: Oxygen, 5 +/_ 0.2 psia

- Relative humidity : 40 to 70 percent

- Carbon dioxide partial pressure (maximum): 7.6 mm Hg

- Temperature: 75 degrees ±5 degrees F

Electrical power system

Selection of the source was still to be made and would depend largely on the time contingency allowed for various mission events, especially during rendezvous maneuvers.

Instrumentation system

The operational instrumentation system would consist of a clock, tape recorder system, display and control system, sensors, calibration system, cameras, and telescope.

The flight research and development instrumentation system would be made up of telemetry systems (including transmitters), clock and tape recorder system, sensors and signal conditioning, calibration system, power supply, radar transponder, and antennas.

The scientific instrumentation system would comprise a lunar atmosphere analyzer, gravitometer, magnetometer, radiation spectrometer, specimen return container, rock and soil analysis equipment, seismographic equipment, and soil temperature instrument.

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