Encyclopedia Astronautica
Gemini B RM

Gemini B Hatch
View of Gemini B hatch in heat shield, as seen from the interior. Compare it with the equivalent hatch in the Soviet TKS manned spacecraft.
Credit: © Peter Bednar
Manned Orbiting Laboratory, Final Design
Credit: © Mark Wade
Gemini B
Gemini B cross-section
Credit: McDonnell Douglas
Gemini B Panel
Gemini B control panel, as would be used in the MOL project, showing numerous changes from NASA Gemini.
Credit: Glen Swanson
Gemini B Interior
View of Gemini B control panel. The panel differs substantially from that of NASA's Gemini spacecraft for the MOL mission.
Credit: © Peter Bednar
Gemini B Hatch
View of Gemini B hatch in heat shield. A prototype was tested on the reflight of Gemini 2; it melted shut during re-entry, providing the validity of the rather scary concept...
Credit: © Peter Bednar
American manned spacecraft. Cancelled 1969. Gemini was extensively redesigned for the MOL Manned Orbiting Laboratory program. The resulting Gemini B, although externally similar, was essentially a completely new spacecraft. Reentry capsule.

Gemini B was not designed to fly separately, but rather was launched with the crew aboard attached to the manned orbiting laboratory. After reaching orbit, the crew would shut down the capsules systems and put them into hibernation. They would crawl through an 0.635 m diameter hatch in the heat shield, leading to a tunnel that accessed the MOL itself. After thirty days of operations, the crew would return to the Gemini B, separate from the MOL, and reenter the atmosphere. Gemini B had only 14 hours of 'loiter capability' for autonomous operations after separation from the MOL.

Many changes were made from the original NASA Gemini, including:

  • Internal systems were containerized and designed for long term orbital storage
  • The cockpit layout was completely redesigned and new instruments were developed
  • The cant of the ejection seats were changed in order to make room for the hatch in the heat shield between the crew's shoulders
  • After the Apollo fire, cabin atmosphere was changed to Helium-Oxygen in place of pure oxygen. At launch, the crew breathed pure oxygen in their suits while the cabin was filled with pure helium. During ascent, oxygen from the suits slowly brought the cabin atmosphere up to the helium-oxygen content of the station itself.
  • In order to handle higher energy re-entries from polar orbit, the heat shield was increased in diameter, so that it actually stuck out a bit from the base of the re-entry vehicle.
  • The OAMS maneuvering thrusters of the NASA Gemini were deleted. Spacecraft orientation in orbit was handled by the forward RCS thrusters.

Gemini B would have been flown alone, without an active MOL, unmanned, in two qualification test launches of the Titan 3M booster prior to the first manned MOL flight.


Crew Size: 2. Orbital Storage: 40 days. Habitable Volume: 2.55 m3. Structure: 638 kg (1,406 lb). Heat shield: 144 kg (317 lb). Reaction Control System: 133 kg (293 lb). Recovery Equipment: 98 kg (216 lb). Navigation Equipment: 63 kg (138 lb). Telemetry Equipment: 51 kg (112 lb). Electrical Equipment: 126 kg (277 lb). Communications Systems: 26 kg (57 lb). Crew Seats and Provisions: 426 kg (939 lb). Crew: 144 kg (317 lb). Miscellaneous Contingency: 100 kg (220 lb). RCS Fine No x Thrust: 16 x 98 N. RCS specific imulse: 283 sec. RCS total impulse: 90 kgf-sec. Electric System: 4.00 kWh. Battery: 180.00 Ah.

AKA: Reentry Module.
Gross mass: 1,983 kg (4,371 lb).
Unfuelled mass: 1,950 kg (4,290 lb).
Height: 3.35 m (10.99 ft).
Diameter: 2.32 m (7.61 ft).
Specific impulse: 283 s.

More... - Chronology...

Associated Countries
Associated Spacecraft
  • MOL American manned space station. Cancelled 1969. MOL (Manned Orbiting Laboratory) was the US Air Force's manned space project after Dynasoar was cancelled, until it in turn was cancelled in 1969. The earth orbit station used a helium-oxygen atmosphere. More...

See also
Associated Launch Vehicles
  • Titan American orbital launch vehicle. The Titan launch vehicle family was developed by the United States Air Force to meet its medium lift requirements in the 1960's. The designs finally put into production were derived from the Titan II ICBM. Titan outlived the competing NASA Saturn I launch vehicle and the Space Shuttle for military launches. It was finally replaced by the USAF's EELV boosters, the Atlas V and Delta IV. Although conceived as a low-cost, quick-reaction system, Titan was not successful as a commercial launch vehicle. Air Force requirements growth over the years drove its costs up - the Ariane using similar technology provided lower-cost access to space. More...

Associated Manufacturers and Agencies
  • USAF American agency overseeing development of rockets and spacecraft. United States Air Force, USA. More...
  • McDonnell American manufacturer of spacecraft. McDonnell, St Louis, USA. More...

Associated Propellants
  • N2O4/MMH Nitrogen tetroxide became the storable liquid propellant of choice from the late 1950's. Monomethylhydrazine (CH3NHNH2) is a storable liquid fuel that found favour in the United States for use in orbital spacecraft engines. Its advantages in comparison to UDMH are higher density and slightly higher performance. More...

  • Peebles, Curtis, "The Manned Orbiting Laboratory", Spaceflight, Part 1; Part 2 in 1980, Volume 22, page 248.
  • NASA Report, Gemini B - Air Force Gemini, Web Address when accessed: here.

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