Behind Mission Control

I COMMEND BRIDGET Mintz Testa for her excellent article “Mission Control” (Spring 2003). You might like to know that there was also a second real-time computer facility during the Apollo program, in addition to Mission Control’s Real Time Computer Complex (RTCC). The Real Time Auxiliary Computing Complex (RTACC), located in the other wing of Building 30, was staffed by NASA and TRW engineers, and it performed computations for trajectory, mass properties, solar radiation, extravehicular-activity heat load, and numerous other matters. Some were confirmations of calculations by the RTCC; others were things it couldn’t do. We worked with punch cards and printer output. The printout was placed under a TV camera, and flight controllers could dial Channel 35 to see the image. The RTACC had the flexibility to make changes during a flight, unlike the RTCC, whose software was frozen long before a mission, and during the flight of Apollo 11 we attempted to determine the orbit of a surprise unmanned Russian lunar probe, to avoid collision with it. There was a contingency plan to fly the RTACC staff and a group of flight controllers to the Goddard Space Flight Center if a hurricane threatened Mission Control, and this was not just a remote possibility. During Hurricane Carla, in 1961, the area where the Mission Control Center was later built was underwater. The RTACC was disbanded after Apollo 12 , with increased confidence in the space program and an awareness that some of its obscure capabilities, like using the lunar module to bring the command module back to earth in an emergency, would never be needed.