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Big Gemini Mockup
Credit - McDonnell Douglas

Manufacturer's Designation: McDonnell-Douglas. Class: Manned. Type: Spacecraft. Destination: Space Station Orbit. Nation: USA. Manufacturer: McDonnell.

Big Gemini ('Big G') was proposed by McDonnell Douglas to the US Air Force and NASA in 1967 as a ballistic manned orbital logistics spacecraft to provide economical resupply of planned military and civilian space stations.

By the end of 1966 NASA's Gemini program was nearing its conclusion and the design phase of the USAF Manned Orbiting Laboratory (MOL) project was nearly finished. McDonnell-Douglas had a large manned spacecraft engineering team, built up over eight years on the Mercury, Gemini, and MOL programs that was facing dissolution. At the same time both USAF and NASA had funded space station projects. The USAF's MOL and the NASA's Apollo Applications Program Orbital Workshop (later Skylab) were to fly in 1969-1974. Both USAF and NASA were planning even larger follow-on stations - the USAF LORL and NASA MORL.

The capability of existing spacecraft (Apollo CSM, Gemini) for manned resupply missions to these stations was severely limited. In the 1970-1980 period, it appeared that at least a dozen launches would be required for logistics purposes for the Apollo Applications Program alone. MOL and the AAP workshop would require 3 to 6 flights a year, each flight delivering a crew of two or three, with 1 to 7 metric tons of cargo being sent up and up to 0.6 cubic meters of cargo being returned. Planned late 1970's stations would have crews of 6 to 24, requiring a resupply craft that could deliver up to 12 passengers and 12 metric tons of payload 6 to 14 times a year, returning up to 7 cubic meters of cargo each time. Big G could provide such a capability by 1971, using Gemini technology applied to Gemini and Apollo hardware, with minimum interference to the higher priority Apollo lunar landing program.

McDonnell Douglas conceded that the initial flights to Orbital Workshop 1 (then planned for 1970) would have to be supported by the Apollo CSM. However Big G could be available in 1971 to provide improved crew and cargo versatility for Orbital Workshop 2 and USAF MOL resupply.

Big G would consist of the following modules:

  • Launch escape tower - the LES developed for the Apollo program would be used for Big-G.

  • Big G re-entry module - This was based on the Gemini B re-entry module developed for the USAF MOL program. The Gemini B's fully integrated flight cockpit, environmental control system, and electronic system installations would be retained. However the Gemini B re-entry module conical structure would be extended to 154 inches (3.91 m) diameter (the same as the Apollo service module) to provide a large passenger compartment. This compartment could accommodate up to ten additional passengers or a mix of passengers and cargo - a capacity over twice as great as the Apollo command module at the same total re-entry vehicle mass. The standard configuration proposed for NASA had a crew of six plus substantial cargo return capability. The environmental control system for the passengers and the communication system were located under the floor of the passenger compartment. The existing hatch in the Gemini-B bulkhead would be retained to allow the pilot and co-pilot access to the passenger compartment.

  • Retrograde module - This module, tapering from 154 inches to 180 inches (4.57 m) diameter at its base, would house the solid fuel de-orbit rocket motors, separation rockets, and water and oxygen supplies.

  • Maneuvering and cargo module - This module included propulsion for orbital maneuvering, electrical power, pressurized and unpressurized volumes for cargo, a pressurized pass-through tunnel, an Apollo docking probe assembly, and a control station for controlling the docking maneuver. Unlike Gemini or Apollo, Big G would dock by its aft end with the space station (the same approach was used in the Soviet TKS resupply spacecraft). This module would vary greatly in size and mass according to the launch vehicle used. In the USAF configuration the maneuvering and cargo module was cylindrical and 180 inches in diameter, for mating to the planned Titan 3G launch vehicle. A truncated version with less than a tenth of the payload could be used with the MOL Titan 3M booster. For NASA use the module was conical, flaring to 260 inch (6.61 m) diameter for mating to the S-IVB upper stage of a Saturn INT-20 or Solid motor/S-IVB launch vehicle.

It was possible to transfer crew and cargo from Big-G to the space station without extra-vehicular activity. A pressurized tunnel led from the passenger compartment to the cargo area, and another tunnel to the docking probe.

Big G used the "packaged return capability" of the Gemini-B. This included "sealed-until-needed" oxygen supply, RCS system, and retrograde and separation motors. These features, compared to Apollo, improved crew safety by assuring the spacecraft could endure extended in-orbit quiescent storage while docked to the space station.

As another alternative (obviously not favored by McDonnell Douglas) the Big G re-entry capsule could be used with an Apollo Service Module and the Apollo Applications Program Multi-Mission Module (a palletized cargo carrier mounted, like the Lunar Module, behind the SM, with which Big G would have to dock and extract from the spent booster).

Total mass of the Big G would depend on the launch vehicle. The Titan 3M version would total 15,600 kg, delivering 9 crew and 2,500 kg of supplies to MOL in a 480 km, 50 degree inclination orbit. The NASA INT-20 version weighed 47,300 kg and could deliver 9 crew and 27,300 kg of payload to the same orbit. The Titan 3G configuration would have an orbital insertion mass of 59,000 kg in a 28.5 degree, 150 x 220 km orbit.

McDonnell's sales pitch was summarized as follows:

  • NASA needed an economical logistics vehicle for the Apollo Applications Program
  • USAF was interested in a similar logistics vehicle for MOL
  • Both NASA and USAF had studies in work for advanced logistics systems for the late 1970's (ILRV - this would eventually become the space shuttle), but nothing existed for the early to late 1970's flights
  • A modified Apollo or Big G were the only logical contenders for the role
  • Big G was preferable to a modified Apollo because:

    • Big G would not interfere with the high-priority lunar program
    • Big G could more economically accomplish projected AAP logistics requirements by utilizing existing developed equipment
    • Big G could be developed on a cost-sharing basis by NASA and USAF together, reducing costs to both Agencies and providing equipment commonality
    • Big G would utilize an experienced, available, and successful industrial team

Big G was not to be. Even at the time the concept was originated both NASA and USAF manned space projects were being cut back. Within 18 months, MOL would be cancelled, and AAP would be limited to using only spacecraft and boosters surplus to the moon landing program. Soon thereafter the shuttle became the only funded space project for the 1970's, and all space station work was abandoned. The Gemini spacecraft - and the American push to rapidly exploit the cosmos - were dead.

Crew Size: 9. Length: 11.50 m (37.70 ft). Maximum Diameter: 4.27 m (14.00 ft). Habitable Volume: 18.70 m3. Mass: 15,590 kg (34,370 lb). Payload: 2,500 kg (5,500 lb).

  • Big Gemini RVOther Designations: Reentry Vehicle. Part of: Big Gemini. Class: Manned. Type: Spacecraft Module. Purpose: Crew and cargo return.

    Crew Size: 9. Length: 5.18 m (16.99 ft). Basic Diameter: 4.27 m (14.00 ft). Maximum Diameter: 4.27 m (14.00 ft). Habitable Volume: 18.70 m3. Mass: 5,227 kg (11,523 lb). L/D Hypersonic: 0.30.

  • Big Gemini AMOther Designations: Adapter Module. Part of: Big Gemini. Class: Manned. Type: Spacecraft Module. Purpose: Earth orbit maneuver and retrofire.

    Length: 1.60 m (5.20 ft). Basic Diameter: 4.27 m (14.00 ft). Maximum Diameter: 6.61 m (21.68 ft). Mass: 4,450 kg (9,810 lb). RCS Coarse No x Thrust: 16 x 440 N. RCS Propellants: N2O4/MMH. RCS Isp: 273 sec. Main Engine Propellants: N2O4/UDMH. Spacecraft delta v: 350 m/s (1,140 ft/sec). Electrical System: Fuel Cells.

  • Big Gemini CMOther Designations: Cargo Module. Part of: Big Gemini. Class: Manned. Type: Spacecraft Module. Purpose: Space station resupply.

    Length: 3.40 m (11.10 ft). Basic Diameter: 4.27 m (14.00 ft). Maximum Diameter: 6.61 m (21.68 ft). Mass: 5,910 kg (13,020 lb). Payload: 2,500 kg (5,500 lb).


Big Gemini Chronology
  • 1969 August 21 - McDonnell Douglas Corporation, under contract to MSC, submitted an eight-volume final report on a "Big G" study. -
    Three features of the McDonnell Douglas 'Big G' study, performed under contract to MSC, are shown here. For additional information on the proposed system, see the 21 August 1969 entry. Graphics supplied by McDonnell Douglas. The study was performed to generate a preliminary definition of a logistic spacecraft derived from Gemini that would be used to resupply an orbiting space station. Land-landing at a preselected site and refurbishment and reuse were design requirements. Two baseline spacecraft were defined: a nine-man minimum modification version of the Gemini B called Min-Mod Big G and a 12-man advanced concept, having the same exterior geometry but with new, state-of-the-art subsystems, called Advanced Big G. Three launch vehicles-Saturn IB, Titan IIIM, and S-IC/S- IVB-were investigated for use with the spacecraft. The Saturn IB was discarded late in the study. The spacecraft consisted of a crew module designed by extending the Gemini B exterior cone to a 419-cm-diameter heat shield and a cargo propulsion module. Recovery of the crew module would be effected by means of a gliding parachute (parawing). The parametric analyses and point design of the parawing were accomplished by Northrop- Ventura Company under a subcontract, and the contents of their final report were incorporated into the document. The landing attenuation of the spacecraft would be accomplished by a skid landing gear extended from the bottom of the crew module, allowing the crew to land in an upright position. The propulsion functions of transfer, rendezvous, attitude control, and retrograde would be performed by a single liquid-propellant system, and launch escape would be provided by a large Apollo-type escape tower. In addition to the design analyses, operational support analyses and a program development plan were prepared. The summary report acknowledged the cooperation of NASA Centers and companies that provided technical assistance during the study. Principal contributors were MSC, MSFC, KSC, AC Electronics Division of General Motors Corporation, Bell Aerosystems Company, Collins Radio Company, IBM's Federal Systems Division, Kollsman Instrument Corporation, Amecom Division of Litton Systems, Inc., The Marquardt Corporation, Denver Division of Martin Marietta Corporation, Government Electronics Division of Motorola Corporation, Rocketdyne Division of North American Rockwell Corporation, Space Craft, Inc., Science and Technology Division of TRW Systems Group, and Hamilton Standard System Center of United Aircraft Corporation.


Bibliography:

  • Big G, Briefing, McDonnell Douglas, 20 December 1967.
  • Advanced Gemini Spacecraft, Briefing, McDonnell Douglas, ca. 1967.
  • Marks, C D and Quest, R G, AAS Science and Technology Series, Vol. 21, "Low Cost Orbital Transportation: How Big A Step!", 1969.


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Big Gemini
Credit- NASA

Big Gemini Configs
Compared are the Big Gemini configurations planned for use with the Titan 3G for the Air Force (180 inch diameter base) and for use with Saturn launch vehicles for NASA (260 inch diameter base). A shorter version of the Titan 3G version could be used with the Titan 3M....
Credit- McDonnell Douglas
Compared are the Big Gemini configurations planned for use with the Titan 3G for the Air Force (180 inch diameter base) and for use with Saturn launch vehicles for NASA (260 inch diameter base). A shorter version of the Titan 3G version could be used with the Titan 3M.

Big Gemini Landing
Big Gemini would land on dry lake beds or airstrips on skids, as were used on the X-15 and were planned for the X-20 and basic Gemini. A parasail would allow the pilot to manoeuvre to a pinpoint landing....
Credit- McDonnell Douglas
Big Gemini would land on dry lake beds or airstrips on skids, as were used on the X-15 and were planned for the X-20 and basic Gemini. A parasail would allow the pilot to manoeuvre to a pinpoint landing.

Big Gemini Cutaway
Dimensioned cutaway view of Big Gemini as proposed for NASA. This view shows: The location of the aft control station for docking. The ejection seats provided for all crew members. The locations of the parasail 'recovery system'. The underfloor location of the passenger environmental control system....
Credit- McDonnell Douglas
Dimensioned cutaway view of Big Gemini as proposed for NASA. This view shows: The location of the aft control station for docking. The ejection seats provided for all crew members. The locations of the parasail 'recovery system'. The underfloor location of the passenger environmental control system.

Big Gemini Model
Cutaway model of the Big Gemini re-entry module. This version would accommodate two crew and six passengers; versions for NASA with ejections seats would accommodate two crew and four passengers plus return cargo....
Credit- McDonnell Douglas
Cutaway model of the Big Gemini re-entry module. This version would accommodate two crew and six passengers; versions for NASA with ejections seats would accommodate two crew and four passengers plus return cargo.

Big Gemini /Titan 3M
Minimum Air Force version of Big Gemini, launched by a Titan 3M for advanced Manned Orbiting Laboratory (MOL) resupply. This version had a minimal cargo module capability. Total mass was 15,600 kg, and it could deliver 9 crew and 2,500 kg of supplies to a 480 km, 50 degree inclination orbit....
Credit- McDonnell Douglas
Minimum Air Force version of Big Gemini, launched by a Titan 3M for advanced Manned Orbiting Laboratory (MOL) resupply. This version had a minimal cargo module capability. Total mass was 15,600 kg, and it could deliver 9 crew and 2,500 kg of supplies to a 480 km, 50 degree inclination orbit.

Big Gemini / LORL
Big Gemini docked to one version of the planned Air Force Large Orbiting Research Laboratory (LORL), planned late 1970's follow-on to the Manned Orbiting Lab (MOL)....
Credit- McDonnell Douglas
Big Gemini docked to one version of the planned Air Force Large Orbiting Research Laboratory (LORL), planned late 1970's follow-on to the Manned Orbiting Lab (MOL).

Big Gemini Evolution
Chart showing how the Big Gemini could be derived from existing hardware. Use of the basic re-entry module with a range of propulsion and cargo modules was possible. A further evolutionary development would lead to the 'Advance Logistic Spacecraft' of the late 1970's (eventually the Space Shuttle)....
Credit- McDonnell Douglas
Chart showing how the Big Gemini could be derived from existing hardware. Use of the basic re-entry module with a range of propulsion and cargo modules was possible. A further evolutionary development would lead to the 'Advance Logistic Spacecraft' of the late 1970's (eventually the Space Shuttle).

Big Gemini / SIVB
Big Gemini as launched by a Saturn derived launch vehicle composed of five solid motors with an S-IVB upper stage. This version weighed 47,300 kg and could deliver 9 crew and 27,300 kg of payload to a 480 km, 50 degree inclination orbit. The sketch shows the flight phases of the capsule, including the parasail landing....
Credit- McDonnell Douglas
Big Gemini as launched by a Saturn derived launch vehicle composed of five solid motors with an S-IVB upper stage. This version weighed 47,300 kg and could deliver 9 crew and 27,300 kg of payload to a 480 km, 50 degree inclination orbit. The sketch shows the flight phases of the capsule, including the parasail landing.

Big Gemini / OWS
Use of Big Gemini as a more cost-effective manned logistics vehicle for use with the Apollo Applications Orbital Workshop (eventually Skylab)....
Credit- McDonnell Douglas
Use of Big Gemini as a more cost-effective manned logistics vehicle for use with the Apollo Applications Orbital Workshop (eventually Skylab).

Big Gemini NASA
Comparison of potential NASA configurations for Big Gemini. The preferred, top configuration uses all new hardware. The middle ALSS configuration uses a logistics module developed for the Apollo Orbital Workshop program. The bottom configuration uses the Big Gemini re-entry capsule with an Apollo Service Module and Apollo Applications Multi-Mission Module....
Credit- McDonnell Douglas
Comparison of potential NASA configurations for Big Gemini. The preferred, top configuration uses all new hardware. The middle ALSS configuration uses a logistics module developed for the Apollo Orbital Workshop program. The bottom configuration uses the Big Gemini re-entry capsule with an Apollo Service Module and Apollo Applications Multi-Mission Module.

Big Gemini NASA
Larger version of comparison of potential NASA configurations for Big Gemini. The preferred, top configuration uses all new hardware. The middle ALSS configuration uses a logistics module developed for the Apollo Orbital Workshop program. The bottom configuration uses the Big Gemini re-entry capsule with an Apollo Service Module and Apollo Applications Multi-Mission M...
Credit- McDonnell Douglas
Larger version of comparison of potential NASA configurations for Big Gemini. The preferred, top configuration uses all new hardware. The middle ALSS configuration uses a logistics module developed for the Apollo Orbital Workshop program. The bottom configuration uses the Big Gemini re-entry capsule with an Apollo Service Module and Apollo Applications Multi-Mission Module.

Big Gemini Briefing
Cover page of Big Gemini briefing to NASA, Dec 20 1967. Big Gemini is shown returning its crew of ten to a runway landing beneath its Rogallo wing paraglider....
Credit- McDonnell Douglas
Cover page of Big Gemini briefing to NASA, Dec 20 1967. Big Gemini is shown returning its crew of ten to a runway landing beneath its Rogallo wing paraglider.