Capturing an Errant Satellite

By J.D. Reed

Challenger's astronauts complete a historic repair mission

Trailing streaks of vaporized gas, with the dawn light glinting on its white thermal coating, space shuttle Challenger swooped over the sun-baked mountains of California's Mojave Desert late last week for a perfect, centerline landing. Indeed, the touchdown was what shuttle pilots approvingly call a wow WONG (weight on wheels, weight on nose gear). As the 98-ton orbiter rolled to a stop on the seven-mile-long, hard-baked desert runway at Edwards Air Force Base, mission control radioed a heartfelt "Welcome back!"

The finale of the shuttle's eleventh and most ambitious mission was supposed to have taken place at the Kennedy Space Center in Florida, site of the launch. But just as Shuttle Commander Bob Crippen and his crew prepared to descend from orbit and end their seven-day, more-than-2 million-mile flight, storm clouds began gathering near Cape Canaveral, complicating Challenger's descent. The California touchdown will force NASA to transport Challenger back across the U.S. to Florida and will add hundreds of thousands of dollars to the cost of the mission. The trip across the continent will delay Shuttle Mission 12, scheduled for June 19, by a week or more.

But those problems were largely forgotten as Challenger 's five-man crew stepped down the ramp from their cabin into the 42DEG desert morning. The focus was still on their historic achievements. Shuttle Mission 41-C had written a new and vital chapter in the use of the space vehicle and confirmed the ability of astronauts and sophisticated machinery to work in on-site weightlessness.

The voyage may have ended in triumph, but its early stages were marred by uncertainties: a critical hardware failure; a dangerously wobbling satellite; minute-by-minute calculations of depleted fuel; and a pulse-pounding race against dying batteries that threatened to set back the space program's future.

NASA'S carefully detailed script for the mission was showy but simple. Its highlight was to be a free-floating walk in space to retrieve the ailing Solar Maximum Mission satellite (Solar Max). Sent aloft to monitor the sun's activity, Max broke down three years ago, after only ten months in orbit. Challenger's mission last week was to stop the rotation of Max, use the spacecraft's 50-ft. remote-controlled arm to lift the satellite into the ship's cargo bay, and set it back in orbit after repairs were made.

The celestial service call, if successful, would mean a saving of $185 million over the cost of replacing Max. It would be a technical and psychological boost for NASA'S program of future maintenance on other orbiting machinery and a giant step toward fulfilling one of President Reagan's commitments: to construct a permanent U.S. space station by the early 1990s.

The curtain for the 106 1/2 -orbit flight went up with a glitch-free liftoff. For the first tune, Challenger hurtled directly into orbit instead of making the conventional three-part ascent. The lineal climb was designed to save the craft's maneuvering rocket fuel for the tricky rendezvous with Max.

On their second day in space, Challenger's crew deployed an eleven-ton, school bus-size cylinder that contained 57 experiments contributed by nearly 200 scientists in nine countries. That device, called a long-duration exposure faculty, will remain in space until it is hauled in by a shuttle vehicle next February. It will gather data on how such materials as shrimp eggs, tomato seeds and plastics fare in space. It will also take samples of interstellar gas to learn more about the evolution of the universe. Inside the spacecraft another, more active scientific venture was also going on. In a test devised by a Tennessee college student, more than 3,000 honeybees were sent aloft in a special container to determine the effects of weightlessness on the construction of hives.

Day 3 was more dramatic. Mission Commander Crippen, 46, a three-flight shuttle veteran, gently juggled Challenger to within 200 ft. of Solar Max. George ("Pinky") Nelson, 33, an astronomer and high school athlete who was once offered a contract by the Minnesota Twins, then donned the $ 10 million manned maneuvering unit (MMU), the Buck Rogers-style jet backpack tested on last February's mission, to retrieve the crippled Max. His untethered ride seemed agonizingly slow. It took him 10 min. to traverse the 200 ft. from the open cargo bay across the reach of black vacuum. The short journey was historic: an unleashed spaceman going to work in orbit.

The script called for Nelson to float to within arm's reach of Max's 7-ft.-long, windmill-Uke solar array panels and fire the minijets on his MMU to match Max's spin of one revolution every 6 min. Using a trunnion-pin attachment device (TPAD), a hollow canister-shaped mechanism strapped like a huge belly button to the chest of his suit, Nelson would gently bump the 5,000-lb. satellite's protruding trunnion pin (installed for just such a rescue). Three rubber-coated, spring-loaded jaws in Nelson's TPAD were supposed to snap like a mousetrap, firmly locking Max's trunnion into place.

The device refused to work. "O.K., the jaws didn't fire that time," Nelson radioed after his first attempt. Twice more, with increasing force, he banged against Max without results (TPAD has no manual trigger for an astronaut to operate). Nelson's efforts turned the gentle wobble of Solar Max, whose inoperable attitude controls had been shut down as a precaution by its ground controllers, into a precarious, crazy cartwheel. Radioed a frustrated Crippen: "Is there any way that you think you can do it with your hands?"

Nelson grabbed one of the solar array panels, but the movement made Max tumble even faster and more erratically. With the MMU's nitrogen propellant half exhausted and Challenger down to a fifth of its own reserves of forward-thruster fuel--close to the bare minimum needed to rescue an astronaut in free flight--Crippen ordered Nelson to return. Inside Challenger 's cockpit, Mission Specialist Terry Hart, 37, tried three times to snake the remote-controlled mechanical arm past the panels to snatch the satellite, but it remained tantalizingly out of reach. Said Crippen: "We came close that time, but no cigar."

At Goddard Space Flight Center in Maryland, ground controllers worked furiously to stabilize Solar Max. For 36 hrs. their labors seemed to be fruitless. The problem: the errant satellite's solar-energy panels were in long periods of shadow, and its batteries were dying. Scientists shut down nearly all of its systems to conserve dwindling energy. Finally, with only 5 min. to go before Max's batteries went dead, the satellite's computer responded to a new set of ground instructions that pointed the panels toward the sun. Frank Cepollina, Solar Max repair chief, said later of the good fortune, "Maybe we had a little divine intervention up there."

The stabilization worked so well that Max stood virtually still in its orbit. But this posed another dilemma: Challenger did not have enough fuel to maneuver around Max if the grappling fitting was on the far side of the satellite. Goddard Center scientists coaxed Max into a slow spin of one revolution every 12 min.; Crippen and Pilot Dick Scobee, 44, flying head down, closed to within 30 ft. of the infirm satellite.

For an anxious 6 min., Challenger was out of radio and televison contact. While ground control waited tensely, Hart snagged Max on the first attempt by crooking the Canadian-built mechanical arm at its "elbow," slipping a sleeve over Max's grapple fixture (see diagram) and securing the coupling with three crossed-wire loops. As Challenger burst into radio contact again over the Indian Ocean, Crippen announced, "O.K., we've got it!" While Hart secured Max on a platform in the cargo bay, weary NASA controllers in Houston, Florida and Maryland broke into cheers. Said one technician: "Can you believe it? We're back with the he script." To which NASA Capsule Communicator Jerry Ross added, "Outstanding!"

President Reagan telephoned his congratulations.

To Hart, the President said, "Terry, you made one long reach for man this morning."

And he joked to Veteran Crippen, "Bob, I understand that the satellite you have on board would cost $200 million at today's prices. If you can't fix it up there, would you mind bringing it back?"

That planned-for contingency proved unnecessary. On Day 6 of the journey, after being awakened by the Rocky theme, Nelson and James ("Ox") van Hoften, 39, a former fighter pilot, set to work on Max. Van Hoften replaced Max's 500-lb., 4-ft.-square attitude-control module.

Working through several sunrises and sunsets, his boots set in a footplate on the remote-controlled arm, Van Hoften employed a special $100,000 power wrench to loosen bolts. Then the astronauts cut through the polyester fiber insulation, removing 28 tiny screws in order to replace Max's main electronic box. "I lost two screws," Nelson radioed. "One went over the tail."

Nelson's main chore was to repair the interior of the main electronic box. He also installed a vent baffle in a Solar Max machine that measures solar flare emissions. All the work was done in half the planned time, delighting NASA observers. Van Hoften even found time to whiz playfully around in the cargo bay with his MMU. Mission Control finally radioed, "It's time for Jim-Boy and Pinky to come in and wash their hands for dinner."

Challenger's crew had dubbed themselves the "Ace Satellite Repair Co." and even sported T shirts carrying that logo during a TV interview in Challenger's cabin. After the satellite was tested from the ground, Crippen and his colleagues released the revitalized Max, which will stay in orbit until about 1991. The satellite, however, could not be carried to a higher elevation, which would have added another year to its life. The shuttle had too little fuel for the maneuver.

Hart, operating the remote-control arm, gently released Max early Thursday. After receiving confirmation that the satellite's systems were working, Challenger backed cautiously away. It had to avoid hitting the satellite with its maneuvering jets, which could jiggle Max out of its orbit. In the process of their historic mission, the Challenger crew helped set a record: the shuttle's five astronauts, along with six cosmonauts in Soyuz Tll and Soviet space station Salyut 7, achieved a high mark of eleven men hi orbit at one time. (Eight circled the earth last February, five of them on Challenger's tenth flight, three in Salyut 7.)

The eight-day Soviet flight, which ended last week with a perfect parachute landing of the capsule 1,500 miles southeast of Moscow, carried the first cosmonaut from India, Rakesh Sharma, 35.* He performed weightless yoga as a possible solution to the vexing problem of space sickness.

For U.S. astronauts, a number of problems remained unsolved. One nagging question: Why did the critical TPAD fail despite rigorous ground and space tests? At week's end the evidence was inconclusive, but experts speculated that a less-than- 1/2-in. pin used to secure Max's insulating blanket might be the villain. Early simulations did not include the pin, which was set hi place an inch away from the trunnion. It may have prevented a solid triggering position for Nelson's TPAD.

Still another problem: Why did NASA not try to capture Max initially with the remote-controlled arm? Some observers speculated that it was simply less dramatic than a spacewalk hookup. Not so, insisted NASA officials. At Max's original rotation speed of one revolution every 6 min., they said, an arm attempt was unfeasible: the satellite was rotating far too fast. An astronaut needed to stop the spin with his minijets to effect the arm's ultimate catch. With nothing to lose after Nelson's failed attempt, the decision was made to try the 50-ft. grabbing device.

Despite its glitches and problems, there was little doubt that Mission 11 was a striking success. Said ground control to the crew: "Just call it a super mission." NASA is already lining up additional repair orders. Landsat 4, the $250 million earth-resources system sent into space two years ago, has developed power-generating problems. NASA says it is also ready to handle the retrieval and repairs of the two $75 million communications satellites, which strayed from the Mission 10 launching in February, if their owners ask for it. Says Solar Max Repair Chief Cepollina: "The era of the throwaway satellite is over."

--ByJ.D. Reed. Reported by Jerry Hannifin and David S. Jackson/Houston

* Washington and Peking last week reached a tentative agreement to send China's first spaceman aloft on a future U.S. shuttle mission. There have been meetings between NASA and Peking officials to put the plan into effect. The program will probably be announced next month on President Reagan's trip to China.

With reporting by Jerry Hannifin and David S. Jackson/Houston