Brighter Future for Nasa?

By MICHAEL D. LEMONICK

Under the pressure of a growing backlog of unlaunched domestic satellites and increased competition from foreign space agencies, NASA finally received two pieces of good news last week. President Reagan announced Friday that he is ordering construction of a fourth orbiter to replace the shuttle Challenger, which carried seven astronauts to their death on Jan. 28. The new orbiter should be completed by 1991, its estimated $2.8 billion price to be paid in part out of money the space agency will save during the present launch hiatus. With a reduced launch schedule, the President said, the shuttle fleet will no longer carry commercial payloads, giving private industry a strong incentive to develop its own launchers.

Earlier in the week, addressing a problem that must be solved before any shuttle can fly, NASA tentatively selected a $500 million redesign for the shuttle's solid-fuel booster, the rocket responsible for the disaster. "We have taken every step to understand what failed on the Challenger and to incorporate a design that won't allow that to happen again," said John Thomas, who headed the modification effort at NASA's Marshall Space Flight Center. Formal adoption, which might take months, will hinge on exhaustive tests by both the agency and booster contractor Morton Thiokol.

January's disaster was the result of 38 degrees temperatures, which weakened an O ring, one of a pair of synthetic-rubber washers that keep hot gases from squirting through tiny gaps in the joint between sections of the solid-fuel rocket. When the O ring failed, escaping gas cut into the shuttle's liquid-fuel booster like a blowtorch and triggered a massive explosion. The modified design, said Thomas, will make a repeat catastrophe virtually impossible.

The most important changes are a new material for the O rings (probably a nitrosilicon rubber), which NASA expects to pass tests down to 31 degrees, and a small heater installed at each joint, just in case. Another is a "capture latch," a metal lip containing an added O ring, which would force escaping gas to turn an extra corner and lose momentum. The maximum distance that joints can pull apart under the stress of launch will be reduced from the current one thirty-thousandth of an inch to one-fifth that figure. A "vulcanized, rubbery substance" will replace the putty that now fills the gap as a sealant.

The proposal has the advantage of using booster sections that already exist, and the primary alterations will be made only at the joints. So testing could begin at Morton Thiokol's Brigham City, Utah, plant later this month. But starting from scratch is still under consideration. Says Thomas: "The solid-rocket industry is to provide, by the end of October, a clean-sheet design (of solid boosters), which means that they are not constrained to existing hardware." Rebuilding the existing boosters, however, now seems the most likely solution, especially since it has the best chance of meeting NASA's current takeoff target of early 1988. This prospect, coupled with the go-ahead for a fourth shuttle, indicates that the wounded space agency is moving forward again.

With reporting by Jerry Hannifin/Washington