Tinkering with Solar Max

By Frederic Golden

Challenger's astronauts will attempt the first satellite repair

Every eleven years the sun's outer layers erupt in a blaze of turbulent magnetic storms, characterized by an increase in sunspots and fiery explosions known as solar flares. In February 1980, on the eve of one such outburst, NASA launched an instrument-packed scientific satellite called the Solar Maximum Mission. Nicknamed Solar Max, the spacecraft was to photograph and monitor the sun's activity, which even at a distance of 93 million miles can disrupt global communications and power transmissions, influence weather and endanger space voyagers.

After ten months in orbit, however, Solar Max blew three critical fuses. The failure impaired its ability to keep properly turned toward the sun, left it wobbling like a top, and triggered breakdowns in its battery of instruments. The $325 million Solar Max program seemed moribund.

Now, in a six-day flight that should demonstrate anew the space shuttle's versatility, the orbiter Challenger will attempt to revivify Solar Max. If these celestial dramatics succeed, they will represent the space age's first retrieval and repair of an earth satellite. Challenger is scheduled to begin its historic fix-it flight from Florida's Kennedy Space Center on Friday, April 6, at 8:59 a.m. E.S.T On this eleventh shuttle journey, Navy Captain Bob Crippen, 46, a veteran of two earlier missions, and his four-man, all-rookie crew will be breaking other new ground.

For the first time, the delta-winged spacecraft will climb directly into orbit with only one intermediate firing by its orbital maneuvering engines. A steeper ascent, made possible by improvements in engine thrust, will save fuel, which may be needed for the rendezvous maneuvers with Solar Max. Once it is 245 miles high, the shuttle will use its remote-controlled mechanical arm for another first: the deployment of a 30-ft.-long cylindrical package, called the long-duration exposure facility (LDEF), which contains 57 separate scientific experiments contributed by nearly 200 scientists in nine countries. LDEF will be left in orbit 10 1/2 months to collect cosmic materials, test solar cells and measure the effects of space on a variety of materials, including 12 million tomato seeds, which will be distributed next year to biology students. Other passengers on the flight: 3,300 honeybees, which are being sent aloft because one collegian wants to see if the insects build the same honeycomb structures in zero-g that they do in normal gravity.

If all goes well, Solar Max's capture will be attempted on the third day of flight, when Challenger closes to within 300 ft. of the errant satellite. Mission Specialist George Nelson, 33, who has a doctorate in astronomy, will buckle himself into a manned maneuvering unit (MMU), the jet-powered Buck Rogers contraption that enabled astronauts to make the historic, untethered space walk on Challenger's February flight. Mission Specialist James van Hoften, 39, a onetime hot-tub salesman with a Ph.D. in hydraulic engineering, will act as an emergency backup.

The spectacular walk to the satellite should take about ten minutes. The most breathtaking moment will occur when Nelson threads his way past Solar Max's 7-ft.-long solar panels, which are slicing through space like slow-motion helicopter blades (the satellite rotates once every 6 min.). If Nelson can dodge this orbital buzz saw without incident, he will try to halt Solar Max's spin.

In anticipation of just such a rescue, Solar Max's creators equipped the satellite with a pin, or trunnion, near its midriff. It forms a perfect mate with a gadget to be carried by Nelson that looks like a fat belly button. NASA calls that protrusion TPAD (for trunnion pin attachment device). Nelson will attach the TPAD to the pin and then fire some of the MMU'S thrusters to brake Solar Max's rotation.

At that point, Challenger will edge to within 30 ft. of the satellite. Then the shuttle's 50-ft.-long, remote-controlled mechanical arm, operated from inside the cockpit by Electrical Engineer Terry Hart, 37, will lock onto a grappling device on Solar Max. (Challenger's fifth astronaut is Dick Scobee, 44, a onetime airplane mechanic who will be Crippen's copilot.) With helpful nudges from Nelson and Van Hoften, Solar Max will be eased into a special cradle in the cargo bay for the repair. The astronauts' task in the bay will be to remove a defective attitude-control module, a 500-lb., orange-crate-size package that contains the whirling gyroscope-like wheels and other electronic gear for maintaining Solar Max's position in space. The entire job, from grappling the satellite to installing the new module, should take six hours.

Once controllers at the Goddard Space Flight Center in suburban Washington are convinced that Max is functioning, it will be lifted out of the cargo area with the mechanical arm and set afloat in space. (If the tinkering fails, the astronauts will strip Solar Max of its cumbersome solar panels, lay it on its side in the cargo bay and carry it back down to the ground for an overhaul.) By then, Challenger will have climbed to an altitude of 270 miles. The higher orbit will reduce the effect of atmospheric braking and extend the satellite's lifetime until at least 1989, or possibly even into the early 1990s, when the sun again erupts. For the next eight hours, the shuttle will hover near by while ground controllers make a final check on Solar Max's performance in orbit.

The orbital repair completed, Challenger's crew will return to Florida on Thursday, April 12. If the complex mission works as planned, Challenger will have shown the world that costly satellites need no longer be allowed to die wastefully in space. --By Frederic Golden. Reported by Jerry Hannifin/Washington and Geoffrey Leavenworth/Houston

With reporting by Jerry Hannifin/Washington, Geoffrey Leavenworth/Houston