Gemini Lunar SRS Credit - McDonnell Douglas Media Gallery

This version of Gemini would allow a direct manned lunar landing mission to be undertaken in a single Saturn V flight, although it was only proposed as an Apollo rescue vehicle. The unmanned spacecraft would make a landing near a stranded Apollo lunar module.

An extended Gemini reentry capsule had a passenger compartment for up to three rescued astronauts. The basic LSRS design used three modified Apollo 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. The first Service Module completed the translunar injection maneuver 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.

In the wake of the Apollo fire, NASA reexamined many safety aspects of the Apollo project. The Apollo mission profile was inherently risky, and the likelihood of a crew being stranded in lunar orbit or on the lunar surface was relatively high. McDonnell returned to a concept first studied in 1962 - the use of Gemini as a Lunar Rescue Vehicle. Use of the Gemini B capsule, then in construction for use with the US Air Force's Manned Orbiting Laboratory, with various combinations of Apollo lunar module stations, would provide a rescue vehicle that could pick up Apollo astronauts stranded in lunar orbit or on the lunar surface. Three variant rescue schemes were studied:

• Gemini Lunar Orbit Rescue Vehicle
• Gemini Lunar Surface Survival Shelter
• Gemini Lunar Surface Rescue Spacecraft

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

	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

McDonnell concluded that an unmanned Gemini 'Universal Lunar Rescue Vehicle' could be developed that would perform all three tasks. The Gemini capsule would be extended to allow up to three rescued Apollo crew members to be returned. Such a craft could rescue the entire Apollo crew at any point along the Apollo mission profile. Some sketches appear to show a two-man Gemini crew in addition to three crew couches in the Gemini capsule extension. The unspoken point was that the Saturn V was in fact large enough to land men on the moon using the direct-ascent method. Use of lunar orbit rendezvous was only necessary because of NASA's adherence to the 6 metric ton, three-crew Apollo command module design. The 2 metric ton Gemini capsule, even in a form stretched to accommodate three to five crew, could accomplish a direct landing on the moon using Apollo components.

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.

Crew Size: 3. Length: 12.56 m (41.20 ft). Maximum Diameter: 6.24 m (20.47 ft). Span: 15.04 m (49.34 ft). Habitable Volume: 5.00 m3. Mass: 46,000 kg (101,000 lb). Main Engine Thrust: 88.060 kN (19,797 lbf). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 36,400 kg (80,200 lb). Main Engine Isp: 311 sec. Spacecraft delta v: 5,600 m/s (18,300 ft/sec). Associated Launch Vehicle: Saturn V.

• Gemini Lunar RM.  Other Designations: Reentry Module. Part of: Gemini Lunar Surface Survival Shelter. Class: Manned. Type: Spacecraft Module.

  Calculated mass based on mission requirements, drawing of spacecraft.

  Crew Size: 2. Length: 3.35 m (10.99 ft). Basic Diameter: 2.32 m (7.61 ft). Maximum Diameter: 2.32 m (7.61 ft). Habitable Volume: 2.55 m3. Mass: 2,386 kg (5,260 lb). Structure Mass: 573 kg (1,263 lb). Heat Shield Mass: 221 kg (487 lb). Reaction Control System: 121 kg (266 lb). Recovery Equipment: 124 kg (273 lb). Navigation Equipment: 118 kg (260 lb). Electrical Equipment: 146 kg (321 lb). Communications Systems: 194 kg (427 lb). Crew Seats and Provisions: 413 kg (910 lb). Crew mass: 144 kg (317 lb). Miscellaneous Contingency: 123 kg (271 lb). Environmental Control System: 150 kg (330 lb).

• Gemini LSRS AM.  Other Designations: Ascent Module. Part of: Gemini Lunar Surface Rescue Spacecraft. Class: Manned. Type: Spacecraft Module.

  Calculated mass based on mission requirements, drawing of spacecraft, dimensions of propellant tanks.

  Length: 3.40 m (11.10 ft). Basic Diameter: 5.90 m (19.30 ft). Mass: 15,000 kg (33,000 lb). RCS Coarse No x Thrust: 16 x 440 N. Main Engine Thrust: 44.030 kN (9,898 lbf). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 12,500 kg (27,500 lb). Main Engine Isp: 311 sec. Spacecraft delta v: 1,000 m/s (3,200 ft/sec).

• Gemini LSRS LM.  Other Designations: Landing Module. Part of: Gemini Lunar Surface Rescue Spacecraft. Class: Manned. Type: Spacecraft Module.

  Calculated mass based on mission requirements, drawing of spacecraft, dimensions of propellant tanks.

  Length: 1.80 m (5.90 ft). Basic Diameter: 4.21 m (13.81 ft). Maximum Diameter: 15.00 m (49.00 ft). Mass: 20,000 kg (44,000 lb). Main Engine Thrust: 88.060 kN (19,797 lbf). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 16,700 kg (36,800 lb). Main Engine Isp: 311 sec. Spacecraft delta v: 2,400 m/s (7,800 ft/sec).

• Gemini LSRS LOIM.  Other Designations: Lunar Orbit Insertion Module. Part of: Gemini Lunar Surface Rescue Spacecraft. Class: Manned. Type: Spacecraft Module.

  Calculated mass based on mission requirements, drawing of spacecraft, dimensions of propellant tanks.

  Length: 3.45 m (11.31 ft). Basic Diameter: 4.21 m (13.81 ft). Mass: 8,000 kg (17,600 lb). Main Engine Thrust: 62.270 kN (13,999 lbf). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 7,200 kg (15,800 lb). Main Engine Isp: 311 sec. Spacecraft delta v: 3,200 m/s (10,400 ft/sec).

• 1966 May 11 - Plans for Apollo space rescue discontinued - Program: Apollo.

  MSC Deputy Director George M. Low recommended to Maxime A. Faget, MSC, that, in light of Air Force and Aerospace Corp. studies on space rescue, MSC plans for a general study on space rescue be discontinued and a formal request be made to OMSF to cancel the request for proposals, which had not yet been released. As an alternative, Low suggested that MSC should cooperate with the Air Force to maximize gains from the USAF task on space rescue requirements.

• Gemini-Derived Lunar Rescue Vehicles, Briefing, McDonnell Douglas, ca. 1966. Thanks to Mike Macowski for discovering and providing this material.

• Ertel , Ivan D; Morse , Mary Louise; et al, The Apollo Spacecraft Chronology Vol I - IV NASA SP-4009, NASA, 1966-1974. Accessed at: http://www.hq.nasa.gov/office/pao/History/SP-4009/cover.htm.