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Part of American Mars Expeditions Family
Credit: NASA
American manned Mars lander. Study 1991. The reference Mars Excursion vehicle (MEV) was a manned lander that could transport a crew of four to the surface.

Status: Study 1991.

It consisted of a surface-stay habitat module (roughly Space Station Freedom-module size), an airlock, 5 metric tons of surface-science payload, a cryogenic ascent propulsion system with four engines and bus structure, and the ascent vehicle (MAV).

The MAV ascent vehicle consisted of a short-duration crew cab and a cryogenic ascent propulsion system with two engines. All propellant tanks were mass-balanced around their maneuver CMs so that no lateral CM shifting occurs. The entire MEV was packaged in a rigid, truncated-hyperboloidal aerobrake with L/D = 0.5, to which it was attached at eight points (four bus-frame corners and four landing-gear footpads). The aerobrake was fitted with doors, which opened to allow the descent engines to extend and ignite prior to aerobrake separation (allowing full benefit of the brake's drag). The brake was then jettisoned as the landing gear extends prior to terminal approach and hovering touchdown.

Dominant configuration constraints for the MEV were as follows:

  • Payload manifesting
  • Surface access
  • Contiguous crew volumes
  • Short vehicle stack
  • Engine-out capabilities
  • On-orbit assembly

Payload manifesting was mainly a proximity and mass balance issue. The surface habitat and airlock, which were the bulk (80%) of the payload, required access to the ascent crew cab and the surface, as well as being mass balanced for proper flight. The science payload required surface access for ease of unloading. Docking was facilitated by placing the crew cab high in the vehicle stack. The flight deck window was located to provide viewing of the surface for landing as well as to the upper hatch for docking. Keeping crew volumes contiguous allowed access during flight for check-out procedures and simulation training. The vehicle stuck was kept as short as possible for aerobrake wake protection, which tended to conflict with having the center of mass (CM) as high as possible, desirable for a small engine gimbal-angle to provide minimal steering loss in an engine-out scenario. A high CM within a short stack was accomplished by placing the dense ascent LOX high in the configuration. Finally, although the dominant constraints for the MEV derived from its performance at Mars, consideration had been given to its earth-to-orbit launch. It was configured to be launched in a few, large, pre-integrated systems for on-orbit assembly. For example, the ascent vehicle could be launched intact in a 10 m diameter shroud, while the descent structure could be launched in 2 sections for fairly simple on-orbit assembly and integration.

The MEV for the cryogenic/aerobrake mission had a total mass of 84,349 kg with the breakdown was as follows:

  • Mars capture and descent aerobrake, 15,138 kg
  • MEV Ascent stage, 22,754 kg
  • MEV Descent stage, 21,457 kg
  • Surface cargo, 25,000 kg

The MEV for the NTR, NEP, and SEP missions (no aerobraking into Mars orbit required) had a total mass of 73,118 kg with the breakdown was as follows:

  • Mars descent aerobrake, 7,000 kg
  • MEV Ascent stage, 22,464 kg
  • MEV Descent stage, 18,659 kg
  • Surface cargo, 25,000 kg

Family: Mars lander. Country: USA. Spacecraft: STCAEM Cryogenic Aerobrake, STCAEM NEP, STCAEM SEP, STCAEM NTR. Agency: NASA, Boeing. Bibliography: 1985.

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