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Aviation History
1990
1990 - 1824.PDF
NEWS ANALYSIS ELEPHANT, WHITE KNIGHT Ten years from now, barring further accidents, NASA's Space Shuttle should gain recog nition as representing a step for ward in spaceflight. Today, opinion is mixed. Launch frustrations vie for headlines with mission successes and the 1986 Challenger tragedy still looms in the background. That the Shuttle is the most complex and capable manned spacecraft yet built is, at once, its weakness and its strength. Post- Challenger safety strictures effec tively rule out a trouble-free launch, yet once in space Shuttle performs well. Even setbacks can be turned to advantage, illustrating the Shut tle's unique ability to "go back and get it right". That ability extends to putting right mistakes relating to expendable boosters which, in the aftermath of the Challenger accident, have largely usurped Shuttle's satellite- launching role. fflfflffimmi "Shuttle's unique ability is to go back and get it right." wmmmmmmm -woe The 1992 mission to reboost the stranded Intelsat VI-F3 communications satellite, for which NASA will charge the international telecommunica tions organisation $90 million, maintains a record of rescue mis sions which have burnished Shuttle's tarnished image. In 1984 Challenger retrieved, repaired and reboosted the sci ence satellite Solar Max, launched in 1980. Later that year Discovery retrieved and returned to Earth two commercial communications satellites, Palapa B-2 and Westar 6, stranded in orbit when their boost motors failed for deploy ment from Challenger in Feb ruary 1984. In 1985 Discovery retrieved, repaired and reboosted the mili tary communications satellite Leasat 3 after its boost motor failed to fire following deploy ment earlier that year from the same Orbiter. Earlier this year, Columbia re trieved and returned to Earth NASA's long-duration exposure facility (LDEF) after an un expectedly long exposure to space caused by the post-Chal lenger Shuttle grounding. LDEF was deployed on the Solar Max repair mission in 1984. The LDEF retrieval and the successful deployment of NASA's Hubble Space Telescope in April enhanced Shuttle's image, al though neither required as tronauts to venture into space. Shuttle prepares for its greatest test— The Intelsat rescue mission, ten tatively scheduled for February 1992, will require extra-vehicu lar activity (EVA) and may be combined with the first in-orbit refurbishment of Hubble, brought forward from 1993 be cause of problems with the space telescope. "The rescue offers us an opportunity for expanding our experience base in the planning, training and performance of EVA . . . helping preparations for the Freedom space station," says former Shuttle astronaut Bob Crippen, now director of the programme. iembling space station Freedom. The last Shuttle EVA was per formed in November 1985, to rehearse construction techniques necessary to assemble a space station. A spacewalk is planned for the Gamma Ray Observatory deployment mission in Novem ber, to test "space cart" transport ers designed for Freedom. The Intelsat rescue mission promises to be eventful, as Or biter Endeavour (the Challenger replacement) is currently sched uled to deploy a Geostar commuications satellite and re trieve the Eureca free-flier on the same flight. Ironically, Intelsat IV-F3 is stranded in low Earth orbit by the malfunction of the Titan booster that has superseded Shuttle as the launch vehicle for large satellites. Intelsat VI is now safely separated from its Titan upper stage, but is minus its boost motor. Endeavour will therefore carry into orbit a lOt solid-rocket motor which two astronauts will attach to the stranded satellite. The rescue mission may be cancelled, however. Although Intelsat VI's altitude has been increased to minimise the risks, the satellite may be too badly damaged after its two-year stay in low Earth orbit for the mission to go ahead. To assess the damage caused by exposure to space, the November Shuttle mission to deploy the Ulysses solar polar orbiter will carry sections of Intelsat VI solar array into orbit. Although Crippen is to have an opportunity ' to once again demonstrate the versatility of the Space Shuttle", NASA apparently had to be persuaded to take on the mission. The space agency's concerns may include the mounting pressure on its Shuttle flight schedule caused by re peated launch delays. An over-ambitious flight schedule was identified as one of the factors contributing to the Challenger explosion and it is ironic that the safety measures introduced to prevent further ac cidents cause launch delays which make it impossible for NASA to adhere to its flight schedule. • 26 FLIGHT INTERNATIONAL 27 June-3 July 1990
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