The Mission of Gemini 2

As we marvel at the daily operations on the International Space Station (ISS), most do not realize that much of the technology and many of the techniques that are used routinely today on the ISS did not exist a half a century ago. The ability to keep people alive in space for long periods of time, have ships rendezvous and dock in orbit and have astronauts performing extravehicular activities (EVAs) are just some of the things that were first demonstrated as part of the often forgotten Gemini program which, just a half a century ago, was performing its last test flights in preparation for its first manned mission

A cutaway drawing of the Gemini spacecraft. Click on image to enlarge. (NASA)

The Gemini Program

The purpose of the Gemini program was to develop the technology and techniques needed to fulfill President Kennedy’s goal of landing a man on the Moon by 1970. While the six manned Mercury missions flown from May 1961 to May 1963 provided important information on how to get a single human into space, survive for periods of several hours while performing simple tasks and return safely home, the Mercury spacecraft was simply too small and its capabilities too limited to prepare us for the Moon.

NASA planners recognized this and on December 7, 1962 announced the Mercury Mk II program which was subsequently renamed Gemini on January 3, 1963. The major objectives of the program were:

– Demonstrate that humans and their equipment could survive up to two weeks in space
– Demonstrate rendezvous and docking techniques in orbit
– Demonstrate the technology and techniques needed to perform EVAs

Meeting all of these objectives was necessary if Apollo were to be successful.

Gemini was a two-man spacecraft that was roughly conical in shape with a base diameter of 3.3 meters which stood 5.8 meters tall. Built by the McDonnell Aircraft Corporation (which merged with Douglas in 1967 to become McDonnell Douglas and then with Boeing 30 years later), it consisted of two major sections: The first was the reentry module, which housed the crew in orbit and returned them to Earth, and the second was an adapter section. The adapter section, which connected the reentry module to the launch vehicle, consisted of a retrograde section which held a set of four solid retrorockets used to start the descent to Earth and an equipment section which housed in-orbit propulsion systems, life support, power systems and all other equipment not needed for the return to Earth.

Diagram showing the major components of the Gemini-Titan II. Click on image to enlarge (NASA)

With a typical launch mass of 3,700 kilograms (over twice that of the Mercury spacecraft), Gemini needed a modified Titan II ICBM called the Titan II GLV (Gemini Launch Vehicle) to get into orbit. Built by Martin Marietta (which subsequently merged with Lockheed in 1995 to form the aerospace giant, Lockheed Martin), the two-stage Titan II was the largest operational rocket available at the time and was already being modified by the USAF to serve as the basis of the Titan III family of space launch vehicles (see “50 Years Ago Today: The First Titan III Launch”).

Test Flights

Gemini 1 was the first test flight of the program launched on April 8, 1964 (see “50 Years Ago Today: The Launch of Gemini 1”). With most of the spacecraft systems yet to be qualified for spaceflight, the relatively modest goals of this first mission were to verify the performance of the new Titan II GLV, test the structural integrity of the Gemini spacecraft as well as provide training for the ground support and tracking crews. Gemini 1 met its objectives and provided three orbits’ worth of data on spacecraft performance. Since the recovery systems had yet to be qualified for flight, no recovery was attempted for this mission and the spacecraft remained attached to the spent second stage of its GLV until its orbit naturally decayed after four days. But before a crew could be flown on Gemini, flight testing of its other key systems was required.

For the unmanned Gemini 2 mission, a fully flight-qualified spacecraft, designated Spacecraft No. 2, was to be flown. For this second test flight, the primary objectives were to test the spacecraft’s heat shield and recovery systems as well as the ocean recovery procedures during an actual flight. The performance of other key spacecraft systems were also to be verified including life support, flight control and retrograde rocket systems. Among the secondary objectives, a flight test of the innovative fuel cells, which were to provide power during Gemini’s longer missions, was also scheduled.

In order to meet the main objectives, a relatively short suborbital flight profile was chosen. The steeper descent trajectory afforded by a suborbital mission would subject the spacecraft’s heat protection system to sharper heating rates and higher temperatures than would be experienced during a normal reentry. To make up for the lower total heat load from this kind of reentry, the ablative heat shield on the base of Spacecraft No. 2 was only half as thick as the standard flight article to simulate the erosion expected from a normal return from orbit.

Diagram showing the instrument pallets carried in the place of astronauts on the Gemini 2 mission. Click on image to enlarge. (NASA)

Since no crew was carried on this flight, the astronauts’ seats were instead occupied by a pair of instrumented pallets. In addition to a variety of sensors to measure environmental parameters, a set of film cameras were also carried. Two of these cameras were used to record the readings from the instrument panels in the cockpit during the flight. A third camera was pointed out the left-hand window of the spacecraft providing a view of what an astronaut would see during launch and recovery.

Preparing Gemini 2

After the very successful Gemini 1 mission, program officials were confident that they could launch Gemini 2 towards the end of August 1964 followed by a manned flight coming by mid-November with as much as four weeks of slack in the schedule. Unfortunately, delays in the final assembly and testing of Spacecraft No. 2 coupled with an unprecedented string of bad weather scuttled this optimistic schedule.

The Gemini 2 launch vehicle, Titan GLV-2, arrived at Cape Kennedy on July 10, 1964 and was subsequently erected on its pad at Launch Complex 19. The launch crews expected to have GLV-2 ready by mid-August for Spacecraft No. 2 whose delivery was well behind schedule as engineers at McDonnell’s St. Louis, Missouri assembly facility struggled to resolve a host of technical problems with this complex craft. But as ground crews at the Cape were preparing for final ground testing of GLV-2 on August 17, LC-19 was struck by lightning at about 11:30 PM EDT as a severe thunderstorm passed over the Cape. Inspections of the ground facilities at LC-19 showed no signs of damage but there were concerns about the state of GLV-2. Officials even briefly considered the possibility of swapping out GLV-2 with GLV-3 but this did not prove to be necessary. Subsequent testing did reveal some failed electronics on GLV-2 that needed replacement but there were no signs of the rocket taking a direct hit from the lightning.

A mosaic of early NIMBUS weather satellite images showing Hurricane Cleo after it had passed Florida on August 27, 1964. This and the threat of two subsequent hurricanes played a role in delaying preparations for the Gemini 2 mission. (NOAA)

Mother Nature continued to wreak havoc with NASA’s schedule as a string hurricanes threatened Cape Kennedy. Hurricane Cleo hit the Cape on August 27, 1964 so quickly that the ground crews only had time to remove the second stage of GLV-2 and get it into the hanger leaving the first stage to weather the storm on the pad. Hurricane Dora brushed by the Cape just twelve days later adding to the delays as did the threat of Hurricane Ethel which kept the Titan grounded until September 14. Preparations for other NASA launches were also delayed by this string of bad weather including the second Apollo orbital test flight, A-102 (see “50 Years Ago Today: The Second Apollo Orbital Test Flight”).

After the series of bad weather delays, work restarted to prepare GLV-2 for launch. But by the time Spacecraft No. 2 arrived at Cape Kennedy on September 21, the launch of Gemini 2 had slipped to mid-November with the Gemini 3 mission coming no earlier than the end of January 1965. But as technical issues continued to cause more schedule problems, the Soviet Union beat the first two-man Gemini mission into orbit by launching a three-man crew on Voskhod 1. Launched on October 12, 1964, the one-day Voskhod 1 mission had an Apollo-size crew in orbit years ahead of the US maintaining the Soviet’s apparent lead in the Space Race as a result (see “50 Years Ago Today: The Mission of Voskhod 1”)

With the launch of Voskhod 1 on October 12, 1964, the Soviet Union had beaten the first two man Gemini mission by launching an Apollo-size crew years ahead of the US.

Getting Gemini 2 Off the Ground

Gemini 2 was finally ready for launch on December 9, 1964. But as the countdown reached zero at 11:41 AM EST, the engines roared to life and then shutdown just one second later. Ground crews noted that a loss of pressure in the primary hydraulic system of the launch vehicle had prompted the automated response from the Titan’s guidance system. Unable to immediately resolve the problem, the launch was officially scrubbed 15 minutes later. An investigation into the malfunction revealed that an aluminum housing had failed under unexpectedly high pressure in the hydraulic lines. These housings, which were thinned to save weight on the GLV, were replaced with the more robust ones still used on the ICBM version of the Titan II which had never experienced this problem.

With the issue with Titan’s hydraulic system resolved with the delivery of replacement parts on January 6, 1965, everything was ready for a second launch attempt on January 19. Along with the usual list of issues that cropped up and were resolved during the countdown, the fuel cells on Gemini 2 continued to present problems. While these were older model P2B units whose design was updated in early 1964, they were still expected to provide a useful test of the reactant delivery system during the brief suborbital flight. With the stack of a half dozen fuel cells continuing to have problems with their plumbing during the countdown and with their testing considered only a secondary objective of the flight, it was decided to deactivate them and fly Gemini 2 on battery power alone.

The launch of Gemini 2 from LC-19 at Cape Kennedy on January 19, 1965. (NASA)

Finally at 9:03:59 AM EST, the 3,122-kilogram Gemini 2 lifted off from LC-19 and headed downrange over the Atlantic Ocean. Although the flight was being controlled from the Cape, the mission was also being monitored as an exercise from the new Mission Control Center (MCC) in Houston, Texas which was scheduled to control all missions starting with Gemini 4. Unfortunately, a power failure right at liftoff threw the MCC into darkness because all the extra TV lighting had caused an overload. While the personnel at MCC were forced to listen to mission coverage via their connection with the Cape, GLV-2 operated as planned placing Gemini 2 into a perfect suborbital trajectory with an apogee of 171.1 kilometers.

After separating from the launch vehicle, Gemini 2 used its own engines to move away from the rocket with a 4.6 meter-per-second delta-v and then performed a preplanned sequence of maneuvers. At 6 minutes and 54 seconds after launch with Gemini 2 flying tail first, the equipment section was jettisoned and its four solid retrograde motors were fired one at a time. The now expended retrograde section was then jettisoned and reentry began with the radio blackout starting at 9 minutes 5 seconds into the flight. Gemini 2 was then placed into a roll of 15°-per-second to cancel out the reentry module’s lift for a ballistic reentry. After 150 seconds, Gemini 2 stopped its roll and assumed a maximum-lift attitude for the rest of the descent.

A view out of a window during the reentry of Gemini 2. This view (shown in the video below) was the first time a reentry was filmed from on board a returning spacecraft. (NASA)

Gemini 2 easily survived its reentry and automatically began to deploy its parachutes at an altitude of 3,200 meters above the Atlantic. The spacecraft finally splashed down 3,422 kilometers downrange after a flight of 18 minutes and 16 seconds about 63 kilometers from its planned landing point. About 90 minutes after splashdown, Gemini 2 was recovered by the US Navy support aircraft carrier USS Lake Champlain. Initial inspections on board the recovery ship indicated that the reentry module had survived its mission with a minimal amount of damage.

The recovery of the Gemini 2 reentry module by the USS Lake Champlain after its splashdown in the Atlantic Ocean. (NASA)

A more detailed examination of the hardware back at the Cape along with a review of all the transmitted and recorded telemetry had shown that Gemini 2 had met all of its objectives. All spacecraft temperatures during reentry were at or below those predicted. The heat shield had passed its test and was now qualified to fly more stressing maximum-lift reentries during subsequent missions. Gemini was now ready for its first three-orbit manned test flight.

Having survived its flight in such good shape, the 2,130-kilogram reentry module from Gemini 2 was subsequently refurbished at the McDonnell plant in St. Louis and flown again on a suborbital test flight for the USAF MOL (Manned Orbiting Laboratory) program (see “The USAF Manned Orbiting Laboratory Test Flight“). Launched on a Titan IIIC atop of a simulated MOL workshop on November 3, 1966, it tested a new heat shield design that included a hatch that allowed the astronauts to gain access to the MOL beneath them after reaching orbit without the need to perform an EVA. The reentry module survived this 33-minute test flight and is now on display at the Air Force Space & Missile Museum at the Cape Canaveral Air Force Station.

A view of the Gemini 2 reentry module on display at the Air Force Space & Missile Museum after it was reflown by the USAF in 1966 as part of a MOL test flight with a hatch in its heat shield.

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General References

David Baker, The History of Manned Space Flight, Crown Publishers, 1981

Barton C. Hacker and James M. Grimwood, On the Shoulders of Titans: A History of Project Gemini, SP-4203, NASA History Division, 1977

David J. Shayler, Gemini: Steps to the Moon, Springer-Praxis, 2001