During a Gemini flight, five IBM computers in Houston, Texas, performed 25 billion calculations every 24 hours to provide NASA flight controllers with almost instantaneous reports on the moment-by-moment progress of the mission.

The IBM Federal Systems Division's Space Guidance Center in Owego, N.Y., also designed and built a special onboard guidance computer for the Gemini astronauts that performed complex calculations to help them guide and maneuver their spacecraft.

The computer weighed approximately 59 pounds, performed more than 7,000 calculations a second, and needed no more room than a hatbox — 1.35 cubic feet — aboard the Gemini. It had an average power consumption of 94.54 watts, a 500 kc bit rate, a memory cycle time of 250 kc and an add time of 140 microseconds. The computer's memory was a random-access, nondestructive readout design with flexible instruction and data storage organization. Its nominal capacity was 4,096 39-bit words and its operational capacity was 12,288 13-bit words.

In simple terms, the computer accepted data either from gyros and similar onboard systems, from the astronauts and from ground control systems, then computed and reported navigation and control information to the two astronauts. During ascent and reentry, the IBM computer could also issue steering signals to control the flight path.

By the end of the Gemini program in 1966, IBM's guidance computer aided in the accomplishment of these space firsts:

For detailed information on the Gemini program, visit: