Word: earthness
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Dates: during 1960-1969
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Some 30,000 miles from the lunar surface, Apollo will have slowed to a space-age snail's pace-2,170 m.p.h. At this point, lunar gravity will overcome the earth's diminishing pull, and the spacecraft will begin accelerating once more. Ahead, the moon will loom ever larger in the spacecraft windows. By the time Apollo curves around the western edge of the moon, its speed will have risen to 5,720 m.p.h...
Without any additional thrust, Apollo's own momentum and the weak lunar gravity would combine to carry it around the moon and fling it back toward earth in a spatial version of crack-the-whip. Indeed, if a recheck of systems and equipment convinces ground controllers and the astronauts that serious problems have developed, the crew will merely continue in this new 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...
...ideal for observation: the sun will be 6.6° above the horizon, casting the long shadows that best bring out distinctive surface features. During lunar orbit, and on both the outgoing and return legs of the mission, the astronauts will shoot television pictures of the moon and the earth and transmit them back to ground stations as Christmastime TV spectaculars...
...tenth lunar revolution, the Apollo crew will fire the SPS engine again-this time for 206 sec. -boosting their speed to 6,060 m.p.h., more than enough to break the moon's gravitational hold and start the spacecraft back toward the earth. About 57 hours later, accelerating under the pull of terrestrial gravity, the astronauts will position their craft properly and then jettison the service module. Streaking into the earth's atmosphere at an angle of 6.5° and a velocity of 24,765 m.p.h., the 11,700-lb. command module-all that will remain...
...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...