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. 62,000 bytes. 583 x 475 pixels.

Gemini was extensively redesigned for the MOL Manned Orbiting Laboratory program. The resulting Gemini B, although externally similar, was essentially a completely new spacecraft. 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.

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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. 56,000 bytes. 597 x 475 pixels.

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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 reentries from polar orbit, the heat shield was increased in diameter, so that it actually stuck out a bit from the base of the reentry vehicle.
• The OAMS maneuvering thrusters of the NASA Gemini were deleted; spacecraft orientation in orbit was handled by the forward RCS thrusters.
• The number of solid propellant retrofire motors was increased from four to six. These served double-duty: for deorbit of the Gemini B and as abort rockets for separation of the Gemini from the enormous Titan 3M in case of launch vehicle failure.

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  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 reentry, providng the validity of the rather scary concept... Credit: © Peter Bednar. 39,000 bytes. 571 x 471 pixels.

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Unit Price $ : 13.00 million. Craft.Crew Size: 2. Orbital Storage: 30.00 days. Total Length: 4.9 m. Maximum Diameter: 3.0 m. Total Habitable Volume: 2.55 m3. Total Mass: 3,851 kg. Primary Engine Thrust: 72 kgf. Main Engine Propellants: N2O4/MMH. Main Engine Isp: 273 sec. Electrical System: Batteries.

The first unmanned Gemini-B/Titan 3M qualification flight was planned for late 1970 at the time the program was cancelled.

The second unmanned Gemini-B/Titan 3M qualification flight would have taken place in 1971 and set the stage for the first manned mission in 1971.

• 137 - Peebles, Curtis, Spaceflight, "The Manned Orbiting Laboratory", Part 1; Part 2 in 1980, Volume 22, page 248.