Gemini Lunar SRS - Exploded view of the Gemini Lunar Surface Rescue Spacecraft. From top to bottom: the Gemini reentry module; the lunar ascent stage; the lunar descent stage; the lunar orbit insertion stage. Credit: McDonnell Douglas. 23,395 bytes. 183 x 465 pixels.

Right up to the end of the Gemini program, the Gemini spacecraft was considered by its contractor and certain factions within NASA as an alternate means of reaching the moon. The Gemini re-entry capsule, smaller and lighter than that of Apollo, would allow direct launch of a mission to the moon using a single rocket. Alternatively, rendezvous and docking of components launched by two small rockets (Titan 3C's or Saturn IB's) would eliminate the need for development of the Saturn V.

There were several proposals for lunar Gemini, right up to the very end of the program:

• Circumlunar flights by Gemini, boosted by Centaur, as part of the original Mercury programme plan (August 1961)

• Lunar landing by Gemini, boosted by a Saturn C-3, in competition with Apollo, as part of the revised original Gemini programme plan (September 1961)

• Use of Gemini, launched atop a Saturn V, as a Lunar Logistics and Rescue Vehicle (September 1962)

• Circumlunar Gemini, launched by Saturn IB, to replace cancelled Apollo circumlunar flights (March 1964)

• Circumlunar Gemini, propelled by Titan 3C-launched double Transtage (June 1965)

• In the wake of the Apollo fire, use of Gemini B, launched atop a Saturn V, as a Universal Lunar Rescue Vehicle (April 1967)

At its birth Gemini was known as the Mercury Mark II programme. NASA was already committed to the three-man Apollo spacecraft and considered Gemini an interim spacecraft to test rendezvous, docking, and EVA techniques before Apollo was available. But NASA's James Chamberlin and McDonnell Aircraft considered Gemini as a viable competitor to Apollo for the circumlunar and lunar landing missions. Such proposals might be welcomed by the current 'cheaper, better, faster' NASA. But in 1961, as a direct challenge to the Apollo project and Lyndon Johnson's dream of a Southern High Technology Crescent, they were anathema.

The original August 14, 1961 Mercury Mark II program plan went like this:

The Centaur would be launched atop a Titan II booster. The lunar Gemini spacecraft would have weighed 3,170 kg, an extra 270 kg over the basic rendezvous Gemini. The difference consisted of a backup inertial navigator and additional heat shielding for re-entry at 11 km/sec instead of 8 km/sec. This program was estimated to put an American around the moon for only $ 60 million more than the basic $ 356 million program. An even more aggressive alternative, a nine-flight program, was promised to cost only $ 8.5 million more than the basic program and fly around the moon in May 1964! This first attempt to fly Gemini to the moon was quickly suppressed, and a revision of the plan was issued only a week later, with all mention of lunar flights deleted.

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Gemini-Centaur - Gemini Docked to Centaur for Circumlunar Flight Credit: © Mark Wade. 2,766 bytes. 567 x 143 pixels.

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September 1961 - Gemini Lunar Landing

But the idea seemed too good to just drop and a month later Chamberlin came up with an even more ambitious plan. He proposed to not just fly around the moon, but to land on it, 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 favoured at that time. At this mass, instead of Nova, a Saturn C-3 launch vehicle could be used. The 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:

Date	Flight	Description
Titan 2 Launches
Mar 1964	Gemini 1	Unmanned orbital
May 1964	Gemini 2	Manned orbital
Jun 1964	Gemini 3	7-day manned orbital
Aug 1964	Gemini 4	14-day manned orbital
Sep 1964	Gemini 5	Agena docking
Nov 1964	Gemini 6	Agena docking
Dec 1964	Gemini 7	Agena docking
Feb 1965	Gemini 8	Centaur docking, boost to high Earth orbit
Mar 1965	Gemini 9	Centaur docking, boost to high Earth orbit
May 1965	Gemini 10	LM docking
Jun 1965	Gemini 11	LM docking
Jul 1965	Gemini 12	LM docking
Sep 1965	Gemini 13	Centaur docking, boost to Lunar flyby
Oct 1965	Gemini 14	Centaur docking, boost to Lunar flyby
Saturn C-3 Launches
Nov 1965	Gemini 15	Manned Lunar orbital
Jan 1966	Gemini 16	Manned Lunar landing

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Langley 4,372 kg LM - Langley 4,372 kg lunar lander Credit: © Mark Wade. 993 bytes. 162 x 120 pixels.

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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 optimised 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.

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Langley 1,460 kg LM - Langley 1,460 kg lunar lander Credit: © Mark Wade. 1,779 bytes. 159 x 193 pixels.

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Date	Flight	Description
Apr 1964	Gemini 1	Unmanned booster orbital test; boilerplate spacecraft.
Jan 1965	Gemini 2	Unmanned suborbital test of spacecraft
Mar 1965	Gemini 3	Manned orbital
Jun 1965	Gemini 4	4-day manned orbital
Aug 1965	Gemini 5	8-day manned orbital
Dec 1965	Gemini 7	14-day manned orbital
Dec 1965	Gemini 6	Rendezvous with Gemini 7 (Agena target failed to orbit)
Mar 1966	Gemini 8	Agena docking
Jun 1966	Gemini 9	Agena docking
Jul 1966	Gemini 10	Agena docking
Sep 1966	Gemini 11	Agena docking
Nov 1966	Gemini 12	Agena docking

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Gemini Docks with LM - Gemini rendezvous above lunar surface with open cockpit Lunar Module after first lunar landing in 1966 Credit: © Mark Wade. 36,780 bytes. 373 x 288 pixels.

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It is possible to estimate when Chamberlin'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:

Date	Flight	Description
Titan 2 Launches
Apr 1964	Gemini 1	Unmanned booster orbital test; boilerplate spacecraft.
Jan 1965	Gemini 2	Unmanned suborbital test of spacecraft
Mar 1965	Gemini 3	Manned orbital
Jun 1965	Gemini 4	4-day manned orbital
Aug 1965	Gemini 5	8-day manned orbital
Dec 1965	Gemini 7	14-day manned orbital
Dec 1965	Gemini 6	Rendezvous with Gemini 7 (Agena target failed to orbit)
Mar 1966	Gemini 8	Agena docking
Jun 1966	Gemini 9	Agena docking
Aug 1966	Gemini 10	Centaur docking, boost to high Earth orbit
Oct 1966	Gemini 11	Centaur docking, boost to high Earth orbit
Nov 1966	Gemini 12	LM docking
Jan 1967	Gemini 13	LM docking
Feb 1967	Gemini 14	LM docking
Mar 1967	Gemini 15	Centaur docking, boost to Lunar flyby
Apr 1967	Gemini 16	Centaur docking, boost to Lunar flyby
Saturn C-3 Launches
Aug 1967	Gemini 17	Unmanned test of Saturn C-3
Feb 1968	Gemini 18	Unmanned Lunar orbital test
Oct 1968	Gemini 19	Manned Lunar orbital
Dec 1968	Gemini 20	Manned Lunar landing

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Gemini-Agena - Gemini docked to Agena Credit: © Mark Wade. 3,073 bytes. 460 x 140 pixels.

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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.

This was not the end of lunar Gemini. At least three times in the next four years such plans were again actively discussed.

September 1962 - Gemini Lunar Logistics and Rescue Vehicle

In the summer and fall of 1962 NASA headquarters asked Space Technology Laboratories and McDonnell to study use of Gemini as a 'lunar logistics and rescue vehicle'. The eight week study looked at using Gemini to land two men directly onto the lunar surface and identified the design changes required to accomplish this. An estimate was made of the cost of purchasing extra Gemini spacecraft for this purpose. But at that point in time Gemini was in deep financial and schedule problems, and the matter was not pursued further.

In the spring of 1964, with manned Apollo flights using the Saturn I having been cancelled, use of a Saturn I to launch a Gemini around the moon was studied. This could either be flown in the long gap between the end of Gemini and the start of Apollo/Saturn IB flights, or as a contingency to beat the Russians around the moon if Apollo suffered severe delays. But Von Braun and others were not interested in Congress getting wind of anything that could undermine support for Apollo. On June 8 NASA headquarters issued instructions that "any circumlunar mission studies related to the use of Gemini will be confined to in-house study efforts" and prohibiting issuance of contracts to McDonnell to pursue the matter.

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Gemini/Transtage-LEO - Translunar Gemini with Double Transtage - LEO Configuration Credit: © Mark Wade. 4,989 bytes. 635 x 251 pixels.

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June 1965 - Gemini / Double Transtage

Still the matter would not die. A year later, astronaut Pete Conrad conspired with 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 Manoeuvring 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 manoeuvring systems necessary to move the assembly to the rendezvous orbit with Gemini. The second Transtage would be stripped of unnecessary equipment (the orbital manoeuvring 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.

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Gemini/Transtage-TLI - Translunar Gemini with Transtage - Translunar Configuration Credit: © Mark Wade. 3,548 bytes. 437 x 223 pixels.

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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.

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• Gemini Lunar Orbit Rescue Vehicle - This version could rescue an Apollo CSM crew stranded in lunar orbit. The Gemini would be launched unmanned on a translunar trajectory by a Saturn V. Following lunar orbit insertion it would automatically rendezvous with the disabled Apollo. The three Apollo crew members would transfer by spacewalk to the passenger compartment of the stretched Gemini re-entry module. It would then boost itself and the rescued crew to a transearth trajectory.

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  Gemini LORV - Gemini Lunar Orbit Rescue Vehicle, studied for rescue of an Apollo crew stranded in lunar orbit. Gemini would be launched by Saturn V. Following lunar orbit insertion it would rendezvous with the disabled Apollo. The three Apollo crew members would transfer by spacewalk to a compartment in the stretched Gemini capsule. It would then boost itself on a transearth trajectory. This was rejected in favor of the more flexible Gemini Lunar Surface Rescue Vehicle. Credit: McDonnell Douglas. 20,861 bytes. 407 x 286 pixels.

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• Gemini Lunar Surface Survival Shelter - Prior to an Apollo moon landing attempt, the shelter would be landed, unmanned, near the landing site of the Apollo Lunar Module. In the event the LM ascent stage would not light to take the crew back to the Apollo CSM in lunar orbit, the two astronauts could go to the shelter and await a rescue mission. The astronaut in the CSM would return alone in the Apollo spacecraft.

• Gemini Lunar Surface Rescue Spacecraft - The unmanned Gemini spacecraft would be piloted by remote control to a landing near a stranded Apollo lunar module. An extended Gemini re-entry capsule had a passenger compartment for the two rescued astronauts. The basic LSRS design used three Lunar Module descent stages for lunar orbit insertion, lunar landing, and lunar ascent.

  An alternate configuration used two Apollo Service Modules and a repackaged LM descent stage. In the alternate configuration the first Service Module completed the translunar injection manoeuvre begun by the S-IVB stage; the second SM accomplished lunar orbit insertion and then functioned as a 'lunar crasher' stage, bringing the Gemini to just above the lunar surface. The Gemini and the third transearth-lunar landing stage would then hover to a landing near the stranded lunar module. The same final stage then boosted the Gemini capsule into a transearth trajectory.

McDonnell summarised the advantages of the various schemes, as contrasted with use of Apollo hardware for the same task, in the following matrix:

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Gemini Lunar SSS - Drawing of the Gemini Lunar Surface Survival Shelter. The shelter would be landed, unmanned, near the landing site of a stranded Apollo Lunar Module. In the event the LM ascent stage would not light to take the crew back to the Apollo CSM in lunar orbit, the two astronauts could go to the shelter and await a rescue mission. The astronaut in the CSM would return alone in the Apollo spacecraft. Credit: McDonnell Douglas. 28,505 bytes. 522 x 395 pixels.

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	Lunar Orbit Rescue		Lunar Surface Survival Shelter		Lunar Surface Rescue
	Gemini	Apollo	Gemini	Apollo	Gemini	Apollo
Vehicle Description	Modified Gemini & repackaged LM Ascent Stage	Apollo CSM	Modified Gemini & Modified LM Descent Stage	Modified SM & Modified LM	Modified Gemini, repackaged LM Ascent Stage & Modified LM Descent Stages	Apollo CSM & LM
Mission	Unmanned to lunar orbit, three man direct return	Unmanned to lunar orbit, three man direct return	Unmanned to lunar surface, 28 day quiescent storage, 28 day 2-man operation	Unmanned to lunar surface, 30 day manned operation	Unmanned to lunar orbit, 30 day unmanned quiescent stay, 2 man direct return	Unmanned to lunar orbit, LM to lunar surface, LM to lunar orbit, 2 man return
Advantages	Uses developed equipment	No new development Can be accomplished with current acquisitions	Extension of lunar orbit vehicle	Similar to planned post-Apollo exploration shelter	Extension of lunar orbit/shelter vehicle No rendezvous required Direct return	No new development Same as existing mission
Disadvantages	New spacecraft development	Possibility of same failure mode	New spacecraft development	Requires modifications to existing hardware	New spacecraft development	Rendezvous required May be difficult to automate transpose docking
Recommendations	Do not develop-rescue capability too limited. Greatest emergency potential at lunar surface		Do not develop - need for shelter and total number of Saturn launches reduced by providing an on-station backup return capability		Modify to a 'Universal' Rescue Vehicle by improving capability to cover three-man cases

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Gemini Lunar SRS - Gemini Lunar Surface Rescue Spacecraft. This spacecraft would be piloted by two crew to a landing near a stranded Apollo lunar module. The extended Gemini reentry capsule had a passenger compartment for the two rescued astronauts. The LSRS used three Lunar Module descent stages for lunar orbit insertion, lunar landing, and lunar ascent. Credit: McDonnell Douglas. 51,464 bytes. 538 x 408 pixels.

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This last attempt to resuscitate Lunar Gemini failed as well. At that point in the Apollo program cut-backs already had begun. No funds would be forthcoming to build additional launch vehicles and spacecraft beyond those already purchased. There was definitely no money to provide a rescue capability, using either Apollo or Gemini hardware.

Not considered at the time, but truly having the potential for a reduced-cost, reduced-risk program would have been a purely Titan-based, USAF-managed project. By using earth-orbit rendezvous and Titan 2 and Titan 3C as the launch vehicles, a program can be constructed that would have landed an American on the moon much earlier than Apollo. With a 2,500 kg open-cockpit LM the moon landing could be accomplished using only two Titan 3 launches: one a Titan 3E, putting a Centaur upper stage into low earth orbit; the other a Titan 3D, putting a Lunar Gemini-LM combination into low earth orbit, which would dock with the Centaur and then proceed to the moon. Such a program, taking into account the actual Gemini and Titan 3C development schedules, would have looked something like this:

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Gemini Lunar SRS - Alternate configuration for a Gemini Lunar Surface Rescue Vehicle. In place of 3 LM descent stages , this version uses 2 Apollo Service Modules and a repackaged LM descent stage. The first SM completes the translunar injection begun by the S-IVB stage. The second SM brakes into lunar orbit and then acts as a 'lunar crasher' stage, burning out just above the lunar surface. The third stage hovers to a landing near a stranded lunar module, and later boosts the Gemini capsule intotransearth trajectory. Credit: McDonnell Douglas. 26,593 bytes. 546 x 315 pixels.

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Gemini ULRV Mission - Mission Summary for Gemini Universal Lunar Rescue Vehicle. Credit: Mark Wade. 9,018 bytes. 715 x 559 pixels.

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• Baker, David, The History of Manned Space Flight,Crown Books, 1982.
• Hacker, Barton C. and Grimwood, James M.On the Shoulders of Titans - A History of Project Gemini, NASA, 1977.
• Hall, Edwin H., Memorandum to Deputy Director, Gemini Program, "Circumlunar Missions", June 29, 1965.
• McDonnell Douglas Briefing Materials, Universal Lunar Rescue Vehicle, April 1967.
• Many thanks to Tom Gangale for his thoughts and references on this subject, to Scott Lowther for discovering and providing the June 1965 memorandum, and to Mike Mackowski for uncovering details of the 1967 Gemini Universal Lunar Rescue Vehicle.

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Gemini-Centaur-LM - Gemini for lunar landing with Centaur and Langley open cockpit Lunar Module Credit: © Mark Wade. 2,613 bytes. 632 x 143 pixels.

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