Advanced Gemini was a series of proposals that would have extended the Gemini program by the addition of various missions, including crewed low Earth orbit, circumlunar and lunar landing missions. Gemini was the second crewed spaceflight program operated by NASA, and consisted of a two-seat spacecraft capable of maneuvering in orbit, docking with uncrewed spacecraft such as Agena Target Vehicles, and allowing the crew to perform tethered extra-vehicular activities.
A range of applications were considered for Advanced Gemini missions, including military flights, space station crew and logistics delivery, and lunar flights. The Lunar proposals ranged from reusing the docking systems developed for the Agena target vehicle on more powerful upper stages such as the Centaur, which could propel the spacecraft to the Moon, to complete modifications of the Gemini to enable it to land on the Lunar surface. Its applications would have ranged from crewed lunar flybys before Apollo was ready, to providing emergency shelters or rescue for stranded Apollo crews, or even replacing the Apollo program.
Some of the Advanced Gemini proposals used "off-the-shelf" Gemini spacecraft, unmodified from the original program, while others featured modifications to allow the spacecraft to carry more crew, dock with space stations, visit the Moon, and perform other mission objectives. Other modifications considered included the addition of wings or a parasail to the spacecraft, in order to enable it to make a horizontal landing.
Background
Gemini was the second American crewed orbital spaceflight program, after Mercury. It was intended to demonstrate technologies and techniques required for the Apollo program, such as extra-vehicular activities, rendezvous and docking, maneuvering in orbit and long duration flight.
The Gemini spacecraft, which was built by McDonnell Aircraft, was derived from the earlier Mercury spacecraft, but modified to accommodate two astronauts. It was also equipped with a larger equipment module, allowing it to support longer missions, and maneuver in orbit. It was launched by the Titan II rocket flying from Launch Complex 19 at the Cape Canaveral Air Force Station. In total, twelve missions were launched, ten of which were crewed. Following two uncrewed test flights, the first crewed flight, Gemini 3, was launched on 23 March 1965. The program concluded on 15 November 1966, with the successful recovery of Gemini 12.
Many other applications were envisaged for the Gemini spacecraft at various stages before, during, and after the two years in which it was used by NASA for crewed spaceflight. Although none of these proposals ever made it into operation, many were considered seriously, and in some cases flight hardware was constructed prior to cancellation. In the case of the Manned Orbital Laboratory, a Gemini spacecraft was launched on a suborbital demonstration flight in support of the program. In some cases technology developed in the Advanced Gemini program has been reintegrated into other programs, such as components from the Titan IIIM, which was to have launched MOL, being used to upgrade other Titan rockets.
Military applications
The United States Air Force intended to use the Gemini spacecraft to transport astronauts to its proposed space stations, the Manned Orbital Development System and later the Manned Orbital Laboratory (MOL). These stations would have been launched by Titan IIIM rockets, with a Gemini spacecraft atop, eliminating the need for rendezvous and docking maneuvers. For this purpose, several modifications were made to the Gemini capsule, including the installation of a hatch in the heat shield to allow access to the space station.
In order to give its astronauts experience before these programs started, the Blue Gemini program was proposed, which would have seen USAF astronauts fly on NASA missions in order to practice various techniques required for their own missions. This would have first seen cooperative missions between NASA and the US Air Force, with two missions flying with mixed crews, followed by two missions with all-USAF crews, but performing missions for NASA. After these flights, the US Air Force would have flown a two-man Agena rendezvous and docking mission, followed by two one-man scientific or technology research missions. Other proposed missions included tests of the Astronaut Mobility Unit which was designed to assist with EVAs, inertial navigation systems, and flying a radar imaging system.
MOL Launches would have been conducted from Launch Complex 40 at the Cape Canaveral Air Force Station, and Space Launch Complex 6 at Vandenberg Air Force Base. In 1966, a test flight was launched from LC-40, using a Titan IIIC. It consisted of the Gemini B spacecraft, built from the spacecraft used for the Gemini 2 test flight, atop OPS 0855, a boilerplate MOL space station. Gemini B was released on a suborbital trajectory, and descended to Earth to test modifications made to the heat shield, and ensure that the access hatch would not affect its performance. OPS 0855 continued on to orbit. Early MOL stations would have only been staffed by a single crew, launched with the station. Later stations would have been designed to be resupplied, and support multiple crews, delivered by additional Gemini spacecraft, or derivatives.
The MOL program was cancelled on 10 June 1969, in favor of uncrewed reconnaissance satellites. Some systems developed for the program were later used on uncrewed missions, while the space suits which were under development were transferred to NASA. The Titan IIIM rocket which was to launch MOL never flew, but some of the upgrades that were built into it were later used to upgrade other Titan rockets — the stretched first and second stages became the Titan 34, which was used as the core of some later Titan IIIB flights, and on the Titan 34D. The seven-segment solid rocket boosters were later introduced on the Titan IV-A.
Gemini Ferry Several Gemini Ferry spacecraft were proposed to provide transportation of crews and cargo to NASA and USAF space stations in low Earth orbit. NASA contracted McDonnell to conduct a study into what modifications would be needed to allow the Gemini spacecraft to support this. Three spacecraft were envisioned; a spacecraft to transport crew to the stations, a spacecraft with a cargo module for both crew and cargo delivery, and a dedicated uncrewed spacecraft to resupply the station every three or four months.
The studies looked at minimizing required modifications to the Gemini spacecraft. Three docking methods were considered. The first was use of the existing docking system used on Gemini-Agena missions. This would have allowed the mission to be accomplished with little modification to the Gemini spacecraft needed, however crew transfer could only have been accomplished by means of an extra-vehicular activity (EVA). Changes that would have been required included strengthening the nose, installing two solid rockets to be used for a separation burn, adding the necessary equipment to perform the transfer EVA, and providing provisions for flight to and from the station. The number of retro-rockets would have been increased from four to six. A second method would have seen the spacecraft dock in the same way, but after docking, the spacecraft would be swung round and attached to the side of the space station. A tunnel would then have been placed over the Gemini's hatches, allowing the crew to transfer to the station without performing an EVA. Some modifications to the hatches would have been required. The final proposed docking method was to use a port mounted on the rear of the equipment module, which would have allowed the crew to transfer directly between the spacecraft and space station, through the docking port.
A modified version of the spacecraft was proposed, which would have included a cargo module attached to the back of a modified equipment module. The spacecraft would have approached the station, and docked backwards using a port on the rear of the cargo module. If one of the forward docking configurations had been used for the Gemini itself, the docking would have been controlled remotely from the station, with the Gemini then separating from the cargo module and flying around the station to dock normally on a different port. The rear-docking Gemini would have simply remained attached to the cargo module, with the crew boarding the station through it. Its docking would have been controlled by its own crew, from a station at the back of the cargo module.
Two Gemini-derived spacecraft were considered for uncrewed resupply flights. The first of these would have involved a Gemini spacecraft, with all systems for crewed flight, re-entry and landing removed. The spacecraft would have docked using a port at the front of the spacecraft. Cargo would have been transferred through the nose of the spacecraft, where the re-entry attitude control system was located on the crewed spacecraft. The spacecraft was equipped with a liquid propellant engine to perform rendezvous, and to reboost the space station. The other proposal was for a new spacecraft to be built for uncrewed missions, but re-using as many Gemini systems as possible. It would have had a higher cargo capacity than the stripped-down version of the Gemini spacecraft.
Crew-only or cargo-only supply missions would have been launched aboard a Titan II, and the Saturn I or Saturn IB would have been used for the combined crew and cargo spacecraft. Because of the increased power of the Saturn I, the Gemini spacecraft's ejection seats would not have been able to propel the crew far enough in the event of an explosion, so a launch escape tower was proposed, based on the one used on the Mercury spacecraft. The Titan IIIM was also considered to launch the heavier spacecraft.
Big Gemini
Big Gemini, or Big G, grew out of a 1963 proposal called Gemini Transport, to develop an enlarged Gemini spacecraft with docking capability, which would take advantage of the increased capacity offered by the Saturn IB and Titan IIIM rockets. It was designed to transport between nine and twelve astronauts into space, and to be able to dock with space stations, in support of Apollo Applications and MOL missions. It would have been launched by a Heavy lift launch vehicle; either a Titan IIIG or Saturn INT-20, the former being intended for use on US Air Force missions and the latter being intended for NASA missions. The Titan IIIM was also considered, which would have launched a smaller version of the spacecraft due to its lower capacity, to resupply MOL space stations later in the program. NASA also proposed several Saturn IB derivatives with solid first stages as alternatives to the INT-20, offering similar payload capacity.
The shape and mass of the spacecraft would have varied depending on the rocket that was to launch it. The Saturn-launched version had a short, conical cargo module, and a total mass of whereas the Titan IIIG-launched version featured a longer, cylindrical module, with a total mass of . The Titan IIIM version would have been much shorter and lighter, with a mass of , as that rocket had less payload capacity than the Titan IIIG or Saturn. The IIIG variant would have carried twelve crew, while the others had a maximum capacity of nine. Use of the NASA variant with the Apollo Service Module was also considered.