A New Setback for the Shuttle

By Frederic Golden

Design flaw in Challenger's engines forces another launch delay

Ever since last November, the new space shuttle Challenger has been perched proudly on its Florida pad, pointing skyward like an anxious eagle. Last week NASA officials gloomily conceded that their $1 billion bird may have to sit in its nest a while longer. The latest delay involves the most serious problem yet encountered with the troubled Challenger: a basic defect in design that requires overhauling all three of the main engines. Unless the flaw can be quickly corrected, the problem could create a horrendous backup of civilian and military satellites waiting to be carried aloft and add millions of dollars to the cost of the shuttle program.

Ironically, the defect stems, at least in part, from NASA'S own supercaution. To improve performance, Challenger's engines were built to operate at 9% greater thrust than those of the first orbiter, Columbia, when the throttle is fully opened. Realizing that this extra power would vibrate the spacecraft more violently, NASA engineers at the Marshall Space Flight Center made a design change. They ordered reinforcement of the metal piping that carries hot, gaseous hydrogen fuel into the small chamber where the engines are first fired up and begin revving to their full 480,000 lbs. of thrust.

The modification took the form of a sleeve that was brazed, or soldered, around the pipes. Presumably, the added metal would have protected the fuel lines from chafing against other parts inside the crowded engine. After the brazing, however, the pipes became so rigid that they developed hairline cracks during test firings, allowing the highly combustible fuel to escape. Such leaks during a flight could cause a calamitous flash fire.

In testimony before a congressional subcommittee on science and technology last week, Air Force Lieut. General James A. Abrahamson, NASA'S associate administrator and boss of the shuttle program, said that discovery of the defect was a tribute to the space agency's quest for safety. He might have added that it was also because of an odd bit of luck. In late January, only days before Challenger's originally scheduled liftoff, NASA inspectors discovered that hydrogen was leaking from the No. 1 engine.

The seepage was traced to a 3/4-in.-long crack in the engine's manifold, where hydrogen and oxygen come together under extremely high temperatures and pressures. That crack was the result of an inadequately hardened weld ordered up to repair some damage sustained during manufacture. But when the No. 1 engine was removed, its replacement also showed signs of leakage. This time oxygen was pouring out of a heat exchanger, a situation that might have triggered an explosion and fire.

Alarmed NASA technicians then investigated Challenger's other engines. On Feb. 25 they found a hydrogen leak in the No. 2 engine. A day or so later, the same kind of leak turned up in the No. 3 engine. Faced with this mounting crisis on the eve of a launch, Abrahamson rushed out to the pad, clambered up the launch tower and personally inspected the inner plumbing of the engines. It became clear that NASA's original fix had only exacerbated the problem: instead of preventing chafing during the vibrations at full power, the brazing and extra sleeves had made the fuel lines so stiff that they cracked during test firings.

Neither NASA nor Rocketdyne, the Rockwell International subsidiary that makes the shuttle engines, could yet explain how these hairline cracks had escaped notice during inspections in the manufacture, testing and installation of the engines. Said one NASA engineer: "After that sleeve was brazed on, somebody should have studied the metallurgy, stresses and embrittlement, fatigue and all that. But apparently they didn't." Now only one course seems possible: all three boosters are being removed and repaired.

The work involves the surgically precise removal and replacement of the 10-in.-long reinforced sections, using computerized welding rather than brazing to make the tubing more pliable. But Challenger's engines will probably not be permitted to run at full power until the problem is more thoroughly understood. The extra kick, however, will not be needed until 1985, when shuttles begin taking off with purely military cargoes from Vandenberg Air Force Base in California.

Because this launch site is farther north than Cape Canaveral, spacecraft get less of a boost from the earth's rotation (whose velocity is highest at the equator) and thus need more power on liftoff.

If the fixes can be made quickly at the Kennedy Space Center, Challenger may be able to take off on its maiden voyage by late March or early April, two months behind schedule. The delays have already cost more than $3 million. And the tab could climb still higher. At week's end technicians found that a lashing rainstorm had left deposits of fine grit, possibly beach sand or salt crystals, inside the payload bay. This could mean an expensive, time-consuming cleanup.

Challenger's cargo is a revolutionary new satellite called TDRS (for tracking and data-relay satellite). It will open up communications with spacecraft beyond the range of ground stations. Additional delays would play havoc with NASA's timetable, postponing the placing in orbit of as many as 30 other satellites. Rescheduling would also stall the launch of Spacelab, Western Europe's contribution to the shuttle program, now listed for a September flight on Challenger. Says one irreverent NASA official: "Abrahamson is praying, 'Engines, heal thyself.' ''

-- By Frederic Golden.

Reported by Jerry Hannifin/ Washington

With reporting by Jerry Hannifin This file is automatically generated by a robot program, so viewer discretion is required.