The Gemini Guidance Computer (sometimes Gemini Spacecraft On-Board Computer (OBC)) was a

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...

serial computer A serial computer is a computer typified by bit-serial architecture i.e., internally operating on one bit or digit for each clock cycle. Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating ma ...

designed for

Project Gemini Project Gemini () was NASA's second human spaceflight program. Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual ...

, America's second human spaceflight project. The computer, which facilitated the control of mission maneuvers, was designed by the

IBM Federal Systems Division IBM, International Business Machines (IBM), nicknamed "Big Blue", is a multinational computer technology and IT consulting corporation headquartered in Armonk, New York, United States. IBM originated from the unification of several companies tha ...

.8. J. C. Hundley and R. A. Watson, "A Digital Computer in Orbital Flight," TR 63-825-892, IBM Federal Systems Division, Owego, New York, October 1964.

Functionality

was the first with an on-board computer, as

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 ...

was controlled by computers on Earth. The Gemini Guidance Computer was responsible for the following functions:McDonnell Corporation, NASA Project Gemini Familiarization Manual, 1965, vol. 2, pp. 8.7,8.45. * ''Ascent ''– serves as a backup

guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in po ...

. The switchover is manually controlled by the astronauts * ''Orbital flight'' – provides a navigation capability to the astronauts to determine the time of retrofire and to select the landing site for safe reentry in the case of an emergency. (on extended missions ground data may become unavailable when ground data network rotates out of the

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) an ...

.) * ''Rendezvous ''– serves as primary reference by providing guidance information to the astronauts. The orbit parameters are determined by the ground tracking which are then sent to the spacecraft; the guidance computer was responsible for processing the information along with sensed spacecraft attitude. The information was presented to the astronauts in terms of spacecraft coordinates. * ''Reentry ''– feeds commands directly to the reentry control system for automatic reentry or provides the guidance information to the astronauts for manual reentry.

Specs

* The computer was architecturally similar to the

Saturn Launch Vehicle Digital Computer The Launch Vehicle Digital Computer (LVDC) was a computer that provided the autopilot for the Saturn V rocket from launch to Earth orbit insertion. Designed and manufactured by IBM's Electronics Systems Center in Owego, New York, it was one of th ...

, in particular in the instruction set; however its circuit integration was less advanced. The GGC weighed 58.98 pounds (26.75 kg) and was powered by 28V DC. During a short power outage it could be powered by the Auxiliary Computer Power Unit (ACPU) * 39-bit words memory, each composed of three 13-bit syllables *

Ferrite core In electronics, a ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability couple ...

memory of 4096 words''Computers in Spaceflight: The NASA Experience''
chapter one * Two's complement integer arithmetic * 7.143 hertz clock (140 ms per instruction); all instructions took a single cycle except for multiplication and division

References

External links

Gemini Spacecraft On-Board Computer (OBC)

{{CPU technologies Project Gemini Guidance computers IBM avionics computers Spacecraft navigation instruments

Functionality

Specs

See also

References

External links