Space: The Moon in Their Grasp

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During the first three orbits of Gemini 6, Command Pilot Schirra made a number of ground-computed corrective maneuvers. To change his elliptical orbit into a circle that reached up closer to Gemini 7, he made several "posigrade" burns—bursts from his forward-thrusting rockets. At two hours and 18 minutes after launch, for instance, Schirra made a posigrade burn when Gemini 6 reached its second apogee over the Indian Ocean. That thrust helped the change from ellipse to circle by increasing the perigee from 100 to 140 miles above the earth; following the laws of orbital mechanics, though, it also reduced Gemini 6's closing speed on Gemini 7, now only 500 miles ahead. Later, he moved his flight path sideward and edged into the same orbital plane as Gemini 7 by yawing his spacecraft 90°, then firing a brief but finely timed thrust toward the south at right angles to his direction of motion.

Right Answers, Right Time. Despite such complexities, the scheduled maneuvers were perfectly calculated by one of the unsung heroes of the mission: an IBM 7094 Mode II computer, one of five located deep in the bowels of NASA's Mission Control Center near Houston. Primped and primed and ready to go for more than a year, the electronic memory housed in the grey, blue-trimmed cabinets had been taught all the incredible complications of orbital calculations, had learned the long, involved equations worked out by teams of crack mathematicians.

As information about Gemini 6 and Gemini 7 was fed back from NASA's worldwide tracking stations, the computer was ready to deliver, in microseconds, answers that its human tutors would take too long to supply. Its orders constantly changed Gemini 6's flight plan, pumped out new burn times, duration of burn, power of burn, direction of thrust. It was the computer, for example, that noticed the apogee was half a mile low and called for a tiny "tweak" burn at the second perigee. "During the rendezvous," says NASA Flight Director Chris Kraft proudly, "it gave us the right answers at the right time."

Over the Atlantic, during the third orbit of Gemini 6, the radar transmitter in the spacecraft's nose locked onto a transponder on Gemini 7. The transponder returned signals that were translated into position data by a computer aboard Gemini 6, now only 235 miles behind. At about the same time, the two capsules established voice contact. "We are reading you loud and clear," called Borman. "Good, Frank. See you soon," replied Schirra confidently. "We will be up there shortly."

Blue Lights. After Gemini 6 was jockeyed into a nearly circular orbit 170 miles above the earth and only 17 miles below Gemini 7's flight path, Copilot Stafford caught his first glimpse of 7's blue acquisition lights pulsing in the blackness above the South Atlantic. "Spotted Gemini 7 at 12 o'clock high," he reported.

Astronauts Borman and Lovell, who had been flying most of their mission in underwear, were now in their space suits. If the two spacecraft inadvertently bumped, their skins might rupture and the astronauts would need protection against decompression of the cabin. Meanwhile, Schirra made another posigrade burn to lift his ship into a higher orbit that would lead to its meeting with Gemini 7.