Originally, the IBM team proposed a system comprising three 7094 computers. Together they would run a mission control program and a simulation computer program. It quickly became clear, however, that this schema didn’t have the data processing prowess that would be needed for the more complex Gemini and Apollo missions.
The team drew up a five-computer system, which would come to be known as the Real-Time Computer Complex. Within this architecture, the first four computers were designated as: the Mission Operational Computer, the Dynamic Standby Computer, the Simulation Operations Computer and the Ground System Simulation Computer. The last was a standby for future software development. During the missions, these machines would perform a staggering 25 billion calculations every 24 hours, providing flight controllers with nearly instantaneous reports on the crafts’ progress.
In addition to the ground-level system, IBM developed an onboard guidance computer. Capable of storing nearly 20,000 bytes of information and performing 7,000 calculations a second, it enabled astronauts to perform their own calculations during flight for the first time. Roughly the size of two mailboxes side by side, and weighing just under 60 pounds, the machine was engineered to process data from onboard and ground control systems — as well as from the astronauts themselves — in order to deliver precise navigational and support information to the astronauts on board. This gave the pilots the power to guide and maneuver their spacecraft on their own.
This onboard guidance computer would serve as the brains behind the first ever spacecraft rendezvous, when Gemini 6 and Gemini 7 met nose to nose, 120 feet apart, 185 miles above Hawaii. It also processed the complex calculations that brought Gemini 11, on its way back to Earth, closer to the recovery carrier than any previous mission.