The Orbit Attitude and Maneuvering System (OAMS) was a

reaction control system A reaction control system (RCS) is a spacecraft system that uses thrusters to provide attitude control and translation. Alternatively, reaction wheels are used for attitude control. Use of diverted engine thrust to provide stable attitude cont ...

used in

Earth orbit Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes days (1 sidereal year), during which time Eart ...

by the Project Gemini

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

. It provided both automatic and manual rotation and

translation Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

by means of 16

vernier thruster A vernier thruster is a rocket engine used on a spacecraft for fine adjustments to the attitude or velocity of a spacecraft. Depending on the design of a craft's maneuvering and stability systems, it may simply be a smaller thruster complementin ...

s using

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. T ...

propellants.

Operations

The OAMS had 16 small, fixed-position, fixed-thrust

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accorda ...

s which burned

propellants (

monomethylhydrazine Monomethylhydrazine (mono-methyl hydrazine, MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula . It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as ...

fuel using

nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

) fed under pressure from a pair of tanks located in the aft Equipment Module. Besides providing

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

, the OAMS provided for linear up, down, sideways, forward or aft

of the spacecraft. This gave the spacecraft the capability to change its orbit, required for

space rendezvous A space rendezvous () is a set of orbital maneuvers during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance (e.g. within visual contact). Rendezvous requires a precise ...

and docking with another spacecraft, the Agena Target Vehicle. The system was also used to push the spacecraft away from the spent second stage of the Titan II launch vehicle on first reaching orbit. *The eight rotational control engines were mounted off the spacecraft's center of mass around the aft section of the Equipment Module, pointed at 90 degree positions up, down, left and right. These were rated at thrust and fired in pairs, causing it to yaw, pitch, or roll to control attitude. *Six of the translational control engines were mounted on the side of the Retrorocket Module, near the spacecraft's center of mass. Four of these were rated at thrust, one each pointed up, down, left or right. The other two were pointed forward, at the three o'clock and nine o'clock positions, to provide aft thrust. These were rated at (reduced from the original spec of in July 1962). *The two thrust forward translation control engines were mounted on the inside of the aft end of the equipment adapter, at the twelve o'clock and six o'clock positions.

Project Mercury Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth orbit and return him safely, ideally before the Soviet Un ...

astronauts could only adjust yaw, pitch, or roll, but Gemini crewmen had full manual control over their flight path.

Walter Schirra Walter Marty Schirra Jr. (, March 12, 1923 – May 3, 2007) was an American naval aviator, test pilot, and NASA astronaut. In 1959, he became one of the original seven astronauts chosen for Project Mercury, which was the United States' fi ...

said that on Gemini 6 "I was amazed at my ability to maneuver. I did a fly-around inspection of

Gemini 7 Gemini 7 (officially Gemini VII) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was a 1965 crewed spaceflight in NASA's Gemini program. It was the fourth crewed Gemini flight, the twelfth crewed American spacefl ...

, literally flying rings around it, and I could move to within inches of it in perfect confidence". Because there is no turbulence in space "It was like the

Blue Angels The Blue Angels is a flight demonstration squadron of the United States Navy.

at 18,000 miles per hour, only it was easier".

Events

During

Gemini 8 Gemini 8 (officially Gemini VIII) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was the sixth crewed spaceflight in NASA's Gemini program. It was launched on March 16, 1966, and was the 14th crewed American fli ...

, on March 16, 1966, OAMS engine number 8 became stuck on, resulting in uncontrollable spinning of the spacecraft. The entire OAMS had to be shut down and the mission was terminated prematurely. This resulted in modifications to OAMS to permit engine isolation.

References

''On Shoulders of Titans: A History of Project Gemini''
Project Gemini Spacecraft attitude control {{US-spacecraft-stub