A rough road to the planets.

A rough road to the planets

The first to embark will be Magellan, setting out on April 27, 1989, to begin mapping Venus 16 months later. Galileo will depart less than six months after Magellan, bound on a six-year journey to Jupiter and its giant moons, visiting a pair of asteroids along the way. In October of 1990, Ulysses will venture forth to spend four-and-a-half years on a trek laid out to cross over both poles of the sun. Spectacular goals for a country that has not dispatched an explorer to another world in a decade.

At least that's the plan.

NASA periodically reaffirms that its goal in returning the space shuttle to flight is to do the job right, rather than "speed at any cost." Even so, the delay caused by the unexpected failure of a component during a test-firing of one of the craft's booster rockets last month (SN: 1/2/88, p.7) has focused attention on the long list of "payloads" waiting for a ride. And among the hardest pressed are the interplanetary missions, which can depart only when their destinations are in their proper orbital positions, and which therefore risk huge delays if they miss their "launch windows."

Having abandoned hope of getting the shuttle off the ground by June 2, the space agency this week tentatively announced a revised and approximate date. "The earliest possible would be mid-July," said shuttle chief Richard Truly, "but it's more likely to be in the August time frame."

At the same time, he announced that the design of the part that failed, an "outer boot ring" intended to protect the rocket nozzle from hot exhaust gases, has been replaced with a version used in a successful test-firing last summer. Still, additional testing remains.

NASA has long been aware that its timetable for bringing the shuttle back allows little margin for unexpected sources of delay, but now the itinerary is even tighter. There are four shuttle flights ahead of Magellan, for example, and even a slight postponement could set back the spacecraft's launching by more than two years, says project manager John Gerpheide of Jet Propulsion Laboratory in Pasadena, Calif. There's a possible launch window only six months after the planned one, but it occurs right around the planned Oct. 8 launch of the Galileo, and NASA is extremely reluctant to risk the strain on launch personnel and available checkout time of sending off two major planetary missions in the same month. Another chance for Magellan would come along 13 months after that, but attention then will be directed at launching the European Ulysses spacecraft, which must fly out to and around Jupiter to set up the inbound path over the sun's poles. With both possibilities essentially unavailable, says Gerpheide, Magellan must either take off next year on schedule or wait until May 25, 1991.

Galileo, meanwhile, is locked to its own calendar for an even more intricate set of reasons. Jupiter reaches a desirable position in its orbit for flights from earth about every 13 months, but safety concerns following the Challenger disaster prompted NASA to cancel the liquid-hydrogen-burning Centaur upper-stage rocket that the shuttle would have carried up to send Galileo on its way. As a result, Galileo will be using a less energetic upper-stage, which must direct the spacecraft onto an incredibly complicated trajectory that will take it through a gravitational "swing-by" of Venus followed by two of earth. Even with no other launchings in the way, a Galileo delay would slip it, too, to mid-1991.

Due for launch on June 1, 1989, is the long-awaited Hubble Space Telescope (SN: 6/23/84, p.392), which many astronomers feel may virtually revolutionize their field. To be stationed in earth-orbit, it will not need to wait for launch until other planets have lined themselves up. But sustaining the large scientific and engineering teams dedicated to this project, as well as those needed for Magellan and Galileo, is costing NASA more than $100 million a month.