Gemini Docks with LM Credit - © Mark Wade

Original Mercury Mark II proposal foresaw a Gemini capsule and a single-crew open cockpit lunar lander undertaking a lunar orbit rendezvous mission, launched by a Titan C-3.

In September 1961 NASA's James Chamberlin came up with a plan to use a Gemini capsule to land two men on the moon and return them safely to earth at a cost 1/20 of that of the Apollo project. The key was the use of the technique of lunar orbit rendezvous and a bare-bones, open cockpit lunar module. This would weigh 4,372 kg in the storable propellant version or 3,284 kg in the cryogenic Lox/LH2 version (calculated propellant loads 3,500 kg and 2,200 kg, respectively). The total mass to be injected into an escape trajectory toward the moon would be no more than 13,000 kg, one fifth of the 68,000 kg planned for the Nova-boosted direct-lunar landing approach favored at that time. At this mass, instead of Nova, a Saturn C-3 launch vehicle could be used. The Gemini flight schedule would have been delayed by a year in order to develop a more capable spacecraft. However by launching every 45 days instead of every 60 days Gemini would still put an American on the moon by January 1966:

The lunar module would have been launched separately by Titan II for the three Earth orbital docking missions. This moon landing project was projected to cost $ 584 million 'plus the cost of two Saturn C-3's'.

Chamberlin was actually the first member of the Space Task Group (STG) to advocate lunar orbit rendezvous (LOR) as a method for reaching the moon. Earlier efforts through 1960 and 1961 by Robert Hoboult and other engineers at Langley to interest STG in the method had been seen as the impractical musings of theorists. Chamberlin and McDonnell Aircraft did not fall in this category. They saw clearly that separating the re-entry and lunar landing functions allowed optimized spacecraft designs for each role, and solved many of the intractable engineering problems the direct-ascent advocates were struggling with.

Chamberlin made one last effort at the end of September to interest STG in including lunar Gemini as part of an "Integrated Apollo Program". This involved the same flight schedule as advocated earlier, but with the cost estimate now firmed up at $ 706 million (including the Saturn boosters!), and the lunar module mass cut to 1,800 kg. NASA brass still rejected the lunar aspects of the plan, but told STG to go ahead with negotiations with McDonnell, Martin, and Lockheed for the spacecraft and boosters. Chamberlin submitted the revised plan without lunar flights on October 27, and this was approved as the basis for project Gemini.

The actual Gemini project as flown was over a year late to the original optimistic plan. This was due to delays in development of both the Titan 2 launch vehicle and the Gemini paraglider landing system. The pivotal 14-day flight actually came in December 1965 versus January 1964 in the first Mercury Mark II proposal and August 1964 in the September 1961 plan.

It was possible to estimate when Chamberlain's Gemini moon landing would have actually occurred based on the actual delays to Gemini. It must be considered that the time necessary to develop the Saturn C-3 could not have been much less than that actually taken for the C-5 (the final December 1961 C-3B configuration differed from the C-5 only in the propellant loading in each stage and in having three F-1 engines in the first stage as opposed to five in the C-5). Therefore, with perfect hindsight, if Gemini had been selected in lieu of Apollo, the actual final program would have looked about like this:

So in the end, the first lunar landing would have been moved up by six months at best. There would have been a cost savings, but again analysis of the detailed cost breakdowns for Apollo indicate the savings would have been on the order of 'only' $ 4 billion out of the NASA $ 18 billion project share. So in retrospect it would seem that NASA's management was correct, for the Apollo missions flown were much more capable than a Gemini-based approach would have been.

Crew Size: 2. Span: 5.58 m (18.30 ft). Habitable Volume: 2.55 m3. Mass: 13,000 kg (28,000 lb).

• Gemini.  Manufacturer's Designation: McDonnell-Douglas. Class: Manned. Type: Spacecraft. Destination: Maximum Payload Orbit. Nation: USA. Agency: NASA. Manufacturer: McDonnell.

  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 maneuvering, 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 maneuvering 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 modularized 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.

  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 was 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-fertilization in the rendezvous and docking areas. But it was 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.

  Full Details of the Gemini spacecraft and its subsystems could be seen at:

  Gemini Spacecraft Description

  • Gemini Technical Description - Part 1

  • Gemini Technical Description - Part 2

  • Gemini Technical Description - Part 3

  Gemini Subsystem Development Diaries

  • Gemini Environmental Control System

  • Gemini Ejection Seat

  • Gemini Fuel Cell

  • Gemini Inertial Guidance System

  • Gemini OAMS/RCS

  • Gemini Parachute

  • Gemini Paraglider

  • Gemini Radar

  • Gemini REP

  Unit Cost $: 13.000 million. Crew Size: 2. Typical orbit: 246 km circular orbit, 30.2 deg inclination. Length: 5.67 m (18.60 ft). Maximum Diameter: 3.05 m (10.00 ft). Habitable Volume: 2.55 m3. Mass: 3,851 kg (8,490 lb). RCS Impulse: 1,168 kgf-sec. Main Engine Thrust: 706 N (158 lbf). Main Engine Propellants: N2O4/MMH. Main Engine Propellants: 455 kg (1,003 lb). Main Engine Isp: 273 sec. Spacecraft delta v: 98 m/s (321 ft/sec). Electrical System: Fuel Cells. Electric System: 2.16 average kW. Electric System: 151.00 kWh. Associated Launch Vehicle: Titan 2, Titan 3C.

• LM Langley Light.  Class: Manned. Type: Lunar Lander. Destination: Moon. Nation: USA. Manufacturer: NASA Langley.

  This early open-cab single-crew Langley lunar lander design used storable propellants, resulting in an all-up mass of 4,372 kg.

  Earliest lunar orbit rendezvous schemes involved use of one or more extremely lightweight, unpressurized lunar landers to take a single astronaut to the lunar service. Others using cryogenic propellants were as low as 1,460 kg - to be compared with the 15,000 kg / 2 man design that eventually was selected. Propellant load estimated.

  Crew Size: 1. Design Life: 1 days. Length: 2.60 m (8.50 ft). Maximum Diameter: 3.50 m (11.40 ft). Mass: 4,372 kg (9,638 lb). Payload: 150 kg (330 lb). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 3,500 kg (7,700 lb). Main Engine Isp: 311 sec.

• 1961 May 7 - Titan II proposed for lunar landing program - Program: Apollo. Launch Vehicle: Titan.
  Albert C. Hall of The Martin Company proposed to Robert C. Seamans, Jr., NASA's Associate Administrator, that the Titan II be considered as a launch vehicle in the lunar landing program. Although skeptical, Seamans arranged for a more formal presentation the next day. Abe Silverstein, NASA's Director of Space Flight Programs, was sufficiently impressed to ask Director Robert R. Gilruth and STG to study the possible uses of Titan II. Silverstein shortly informed Seamans of the possibility of using the Titan II to launch a scaled-up Mercury spacecraft.

• 1961 July 31 - Improved Mercury proposed for lunar landing - Program: Apollo. Launch Vehicle: Nova, Saturn C-3.
  James A. Chamberlin and James T. Rose of STG proposed adapting the improved Mercury spacecraft to a 35,000-pound payload, including a 5,000-pound "lunar lander." This payload would be launched by a Saturn C-3 in the lunar orbit rendezvous mode. The proposal was in direct competition with the Apollo proposals that favored direct landing on the moon and involved a 150,000-pound payload launched by a Nova-class vehicle with approximately 12 million pounds of thrust.

• 1961 August 31 - Presentation to STG on rendezvous and the lunar orbit rendezvous plan - Program: Gemini.
  John C. Houbolt of Langley Research Center made a presentation to STG on rendezvous and the lunar orbit rendezvous plan. At this time James A. Chamberlin of STG requested copies of all of Houbolt's material because of the pertinence of this work to the Mercury Mark II program and other programs then under consideration.

• 1961 December 6 - Preliminary project plan for the Mercury Mark II program - Program: Gemini.
  D. Brainerd Holmes, NASA Director of Manned Space Flight, outlined the preliminary project development plan for the Mercury Mark II program in a memorandum to NASA Associate Administrator Robert C. Seamans, Jr. The primary objective of the program was to develop rendezvous techniques; important secondary objectives were long-duration flights, controlled land recovery, and astronaut training. The development of rendezvous capability, Holmes stated, was essential:
  • It offered the possibility of accomplishing a manned lunar landing earlier than by direct ascent.
  • The lunar landing maneuver would require the development of rendezvous techniques regardless of the operational mode selected for the lunar mission.
  • Rendezvous and docking would be necessary to the Apollo orbiting laboratory missions planned for the 1965-1970 period.
  The plan was approved by Seamans on December 7. The Mercury Mark II program was renamed "Gemini" on January 3, 1962.