Word: halley
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...rare (once every 180 years) planetary alignment to survey the entire outer solar system. Those missions that were approved often did not receive funding for complete analysis of the return data. Others--to map the moon and check it for metal deposits, to research solar phenomena, to rendezvous with Halley's Comet--never got past appropriations subcommittees...
...even more fanciful space trips. But none of these fictional voyages was as remarkable as the mission now being planned for NASA by scientists at Pasadena's Jet Propulsion Laboratory. If all goes well, they will launch an unmanned spacecraft guided with a giant sail to rendezvous with Halley's comet when it next approaches...
Free and Inexhaustible. The fantastic voyage was proposed by a group commissioned by J.P.L. Director Bruce Murray to consider imaginative concepts for interplanetary exploration. A mission to Halley's comet, which returns every 74 to 79 years, has long been one of NASA's goals. But using conventional space-flight techniques to rendezvous and keep up with the glowing visitor-which reaches speeds of 198,000 kilometers (124,000 miles) an hour as it approaches the sun-would require enormous amounts of fuel and an impractically large and expensive rocket...
Ground controllers will then begin navigating the craft into closer and closer orbits of the sun by properly trimming the sail. Then they can put the ship-moving at a top speed of 198,000 kilometers (124,000 miles) an hour-on a course to intercept Halley's comet in March 1986. Jettisoning the sail, and "flying station" just two kilometers above the comet's head, the ship will take TV pictures and readings to determine the visitor's composition and origin. Says J.P.L.'s Murray: "We don't have a clue about comets...
Should plans for the space sailer hit a snag, earthlings could still get their first closeup view of Halley's comet in 1986. Another group at J.P.L. is working on the design of a spaceship that would be propelled by an ion engine; a small, continuous amount of thrust would be provided by the engine's ejecting ions produced when a beam of electrons (generated by electric current from solar cells) is sent through vaporized mercury. Such a low-thrust ion engine could, like the sunjammer's sail, maneuver a ship to a rendezvous with the comet...