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Gemini preflight
Gemini preflight - Gemini spacecraft being prepared in the shop.

Credit: NASA. 42,452 bytes. 395 x 480 pixels.

Manufacturer's Designation: McDonnell-Douglas. Class: Manned. Type: Spacecraft. Nation: USA. Agency: NASA. Manufacturer: McDonnell-Douglas.

It was obvious to NASA that there was a big gap of three to four years between the last Mercury flight and the first scheduled Apollo flight. There would therefore be no experience in the US in understanding the problems of orbital manoeuvring, rendezvous, docking, lifting re-entry, and space walking before the Apollo flights, which required all of these to be successfully accomplished to complete the lunar landing mission.

Gemini began as Mercury Mark II to fill this gap. The concept was to enlarge the Mercury capsule's basic design to accommodate two crew, provide it with orbital manoeuvring capability, use existing boosters to launch it and an existing upper rocket stage as a docking target. The latest aircraft engineering was exploited , resulting in a modularised design that provided easy access to and changeout of equipment mounted external to the crew's pressure vessel.

In many ways the Gemini design was ahead of that of the Apollo, since the project began two years later . The crew station layout was similar to that of the latest military fighters; the capsule was equipped with ejection seats, inertial navigation, the pilot's traditional 8-ball attitude display, and radar. The escape tower used for Mercury was deleted; the propellants used in the Titan II launch vehicle, while toxic, corrosive, poisonous, and self-igniting, did not explode in the manner of the Atlas or Saturn LOX/Kerosene combination. The ejection seats served as the crew escape method in the lower atmosphere, just as in a high-performance aircraft. The seats were also needed for the original landing mode, which involved deployment of a huge inflated Rogallo wing (ancestor of today's hang gliders) with a piloted landing on skids at Edwards Dry Lake. In the event, the wing could not be made to deploy reliably before flights began, so the capsule made a parachute-borne water landing, much to the astronauts' chagrin.

All around the Gemini was considered the ultimate 'pilot's spacecraft', and it was also popular with engineers because of its extremely light weight. The capsule allowed recover of a crew of two for only 50% more than the Mercury capsule weight, and half of the weight per crew member of the Apollo design. The penalty was obvious - it was christened the 'Gusmobile' since diminutive Gus Grissom was the only astronaut who was said to be able to fit into it. The crew member was crammed in, shoulder to shoulder with his partner, his helmet literally scrunched against the hatch, which could be opened for space walks. With the crew unable to fully stretch out unless an EVA was scheduled, living in the capsule was literally painful on the long missions (Gemini 5 and 7). Getting back into the seat and getting the hatch closed in an inflated suit in zero gravity was problematic and would have been impossible if the spacewalking astronaut was incapacitated in even a minor way.

Early on it was proposed that the Gemini could be used for manned circumlunar or lunar missions at a fraction of the cost and much earlier than Apollo. Truth be told, a Gemini launched atop a Titan 3E or Saturn IVB Centaur could have accomplished a circumlunar flight as early as 1966 and, using earth orbit rendezvous techniques, a landing at least a year before Apollo. But the capsule, while perhaps suited as a ferry vehicle to space stations, would have been quite marginal for the lunar mission due to the cramped accommodation. But mainly NASA was fully committed to the Apollo program, which was grounded on a minimum three man crew and minimum 10,000 pound command module weight.

Gemini6 in orbitGemini6 in orbit - Gemini6 in orbit view e

Credit: NASA. 13,559 bytes. 260 x 247 pixels.

At a cost of 5% of the Apollo project, NASA staged twelve flights, ten of them manned, in the course of which the problems of rendezvous, docking, and learning how to do work in a spacesuit in zero-G were tackled and solved. It is said that not much of this was fed back to Apollo, since the two projects had completely different sets of contractors and there was little cross-fertilisation in the rendezvous and docking areas. But it is undeniable that important issues in regard to working in zero-G were discovered and solved and both flight and ground crews gained experience that would make the Apollo flights successful.

Gemini was to have continued to fly into the 1970's as the return capsule of the USAF Manned Orbiting Laboratory program. However with the MOL's cancellation in 1969 work at McDonnell came to an end and the last models of the finest spacecraft ever built were scrapped.


Unit Price $ : 13.00 million. Craft.Crew Size: 2. Total Length: 5.7 m. Maximum Diameter: 3.0 m. Total Habitable Volume: 2.55 m3. Total Mass: 3,851 kg. Total Propellants: 455 kg. Total RCS Impulse: 119,103.00 kgf-sec. Primary Engine Thrust: 72 kgf. Main Engine Propellants: N2O4/MMH. Main Engine Isp: 273 sec. Total spacecraft delta v: 323 m/s. Electric system: 2.16 total average kW. Electric System: 151.00 total kWh. Electrical System: Fuel Cells.

Gemini Chronology


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Last update 12 March 2001.
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© Mark Wade, 2001 .