Word: orbiters
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Once the ship is in orbit, the astronauts and ground controllers will check out all the systems on board, making certain that they are operating properly and that the duplicate and backup systems are in working order. On their second revolution around the earth, if no problems have arisen, the Apollo crew will reignite the S-4B rocket engine over the Pacific near Hawaii. In a 5-min. 11-sec. burning period, the S-4B will accelerate to an "escape" velocity of 24,200 m.p.h., pushing Apollo out of earth orbit and off toward the moon...
...dummy lunar module (LM) carried in its nose. The astronauts will then simulate docking with the LM-an operation that will be particularly important on the lunar-landing mission next year, when an Apollo spacecraft will dock nose-to-nose with a real LM before taking it into orbit around the moon. Finally, after the astronauts have jockeyed their craft some 8,000 ft. away, the S-4B will dump its remaining fuel into space. That action will generate just enough thrust to shove the S-4B out of the way and into orbit around the sun. Alone in space...
...course and travel back to earth. But if everything seems all right, Apollo's powerful SPS (service propulsion system) engine will be fired for 246 sec. to slow the spacecraft and allow it to be pulled by the moon into a 70-by 196-mile elliptical lunar orbit. Two revolutions later, a brief 10-sec. burn will change the path to a 70-mi.-high circular orbit. Traveling at 3,640 m.p.h., Apollo will circle the moon once every two hours. For 45 nerve-racking minutes during every revolution-when it is behind the moon and blocked from radio...
During their lunar orbiting, the astronauts will take turns shooting still, motion and stereo pictures in color and black-and-white. They will study craters and ridges to see how easily they can be recognized as landmarks. They will plot their position for navigational fixes that will be useful for lunar-landing crews on later missions. On the seventh revolution, they will be able to survey a prime LM landing site at a time when illumination is ideal for observation: the sun will be 6.6° above the horizon, casting the long shadows that best bring out distinctive surface features...
...matter how carefully it is planned and executed, however, the December flight of Apollo 8 will involve some chilling perils. Besides anticipating the kinds of problems that could occur in a simple near-earth orbital flight, lunar-mission planners must plan realistically for troubles that would be magnified by sheer distance from earth. Should life-support or power systems begin to fail on earth-orbital flights, astronauts are usually within half an hour to three hours of recovery on land or water; a relatively small thrust from a retrorocket can lower their orbit into the atmosphere, where friction provides...