Encyclopedia Astronautica
Gemini - Double Transtage

Translunar Gemini with Double Transtage - LEO Configuration
Credit: © Mark Wade
American manned lunar orbiter. Study 1965. In June 1965 astronaut Pete Conrad conspired with the Martin and McDonnell corporations to advocate an early circumlunar flight using Gemini.

Discretely called 'Gemini - Large Earth Orbit', the plan would use a Titan 3C-launched Transtage to boost the Gemini to translunar speed.

A declassified memorandum from the Director, Gemini Systems Engineering, documents a June 24, 1965 meeting at Manned Spaceflight Center between the contractors' corporate heads and highest NASA management. At this meeting the companies provided a detailed proposal to launch a refurbished, modified Gemini around the moon by April 1967 for $ 350 million. The Gemini would have 521 kg of mass deleted, half of it by removing the solid fuel retrograde rockets used to initiate re-entry (the liquid fuel Orbital Maneuvering System would be reengineered to increase its reliability). The Titan 2-launched Gemini would rendezvous and dock with a Titan 3C-launched 'Double Transtage'. The Double Transtage consisted of an unmodified first Transtage that would place itself and a second Transtage into low earth orbit. The first Transtage retained the navigation and maneuvering systems necessary to move the assembly to the rendezvous orbit with Gemini. The second Transtage would be stripped of unnecessary equipment (the orbital maneuvering system) but was equipped with an Agena-type docking collar.

After docking with the Double Transtage, the first Transtage would be cast off and the second Transtage would propel the Gemini into a circumlunar trajectory. The flights themselves, assuming go-ahead was given in September 1965, would follow immediately after the last Gemini flight. In December 1966 a Titan 3C would drive a 2450 kg circumlunar Gemini capsule to 11 m/s re-entry velocity to verify the heat shield design. This would be followed by a February 1967 manned qualification flight in earth orbit. A manned Gemini would dock with a Double Transtage and be propelled into a high orbit and re-entry speed. In April the sequence would be repeated, this time the Gemini being sent by Transtage into a loop around the moon.

The author of the memo thought that Gemini extension efforts would be better directed towards proving space station assembly techniques and procedures using Gemini and Agena. He also thought the schedule and cost estimates to be over-optimistic. The reaction of top NASA management was more categorical. Pete Conrad managed to stir Congressional interest, but NASA administrator James Webb informed them that any extra funds Congress cared to appropriate for such a project would be better spent accelerating the Apollo program. After further internal struggles, Conrad finally got NASA approval for the Agena on his Gemini 11 flight to boost him into a record 1,570 km orbit. This high flight was the only remnant of lunar Gemini.


Crew Size: 2. Habitable Volume: 2.55 m3. Spacecraft delta v: 3,600 m/s (11,800 ft/sec). Electric System: 150.00 kWh. Electric System: 2.20 average kW.

Gross mass: 15,200 kg (33,500 lb).
Unfuelled mass: 4,600 kg (10,100 lb).
Height: 11.70 m (38.30 ft).
Thrust: 71.17 kN (15,999 lbf).
Specific impulse: 311 s.

More... - Chronology...

Associated Countries
See also
  • Gemini The Gusmobile could have conquered space - faster, better cheaper. An endless number of Gemini derivatives would have performed tasks in earth orbit, and flown around and landed on the moon. Could the US have won the moon and space station races at a fraction of the expense? Browse through the many might-have-been Geminis! More...
  • Manned Circumlunar Boosting a manned spacecraft on a loop around the moon, without entering lunar orbit, allows a trip to be made near the moon with a total low earth orbit mass of as little as 20 tonnes. This was attractive during the space race as a manned mission that could be accomplished early with limited booster power. Gemini, Apollo, and Soyuz were all supposed to have made circumlunar flights. Only Soyuz reached the circumlunar flight-test stage under the L1 program. Any L1 manned missions were cancelled after the Americans reached lunar orbit with Apollo 8. The idea was resurrected in 2005 when a $100 million commercial flight around the moon was proposed, again using Soyuz. More...

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
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • McDonnell American manufacturer of spacecraft. McDonnell, St Louis, USA. More...

Associated Propellants
  • N2O4/UDMH Nitrogen tetroxide became the storable liquid propellant of choice from the late 1950's. Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. More...

  • Hall, Edwin H, "Memorandum to Deputy Director, Gemini Program, "Circumlunar Missions"", June 29, 1965.

Gemini - Double Transtage Chronology

1965 June 24 - .
  • Proposal to launch Gemini around the moon - . Nation: USA. Spacecraft: Gemini - Double Transtage. Gemini contractors proposed to launch a refurbished, modified Gemini around the moon by April 1967 for $ 350 million. The Titan 2-launched Gemini would rendezvous and dock with a Titan 3C-launched 'Double Transtage', which would propel the Gemini into a circumlunar trajectory. McDonnell-Douglas and Martin Marrietta's proposal was suppressed by NASA as a threat to the Apollo program.

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