The chairman of a scientific advisory group monitoring the redesign of the space shuttle's booster rockets said Friday the panel has concerns about NASA's efforts to assure continued flight safety.
H. Guyford Stever, chairman of the panel set up by the National Research Council, said he has a "broad concern, namely that the continuing program be carried out" now that the National Aeronautics and Space Administration has returned to space with two successful flights in the wake of the 1986 Challenger accident."Success breeds confidence, and that's what you want, but it can also threaten you with complacency," Stever said in an interview.
"I don't see complacency developing, but I do know they have budget problems, and how they'll solve that is difficult to say," he added.
The panel's report, delivered to NASA Wednesday, also cited two new problems with the redesigned boosters found after the Sept. 29 launch of Discovery:
-Small pieces of cork used to cover external diagnostic instruments and their electrical leads were lost during flight and one piece is believed to have damaged thermal tiles on the orbiter. Cork is also suspected of causing extensive damage to tiles on Atlantis, which was launched Dec. 2.
-Metal-to-metal seals were scratched and pitted. Stever said that removal of the seals could raise shuttle program costs. He said the scars were small and did not threaten safety.
The report also lists nine problem areas that need to be addressed before the redesign effort can be considered complete.
Among the tasks remaining are strengthening of the conical base of the booster rocket, more testing of booster segments to determine their potential to be reused safely, improving materials for bonding booster parts, developing alternative materials for O-ring seals and more test-firing at cold temperatures, the report said.
In the Challenger accident, one of the O-rings between the booster segments failed, allowing hot exhaust gases from the rocket to leak and cause the explosion that destroyed the shuttle and killed its crew of seven. Cold temperatures also contributed to the O-ring's failure.
Hercules Aerospace is involved in a NASA-funded study of rocket booster nozzles that will address design concerns; other studies are under way to examine adhesives used on the shuttle and booster.
Following the Challenger disaster, the shuttle program was put on hold while NASA and rocket maker Morton Thiokol Inc. revamped the boosters and program objectives.
Morton Thiokol examined a variety of materials for the O-ring seals, but determined Viton was the best space-age material to withstand the thermal assault of liftoff.
A cold test firing of the boosters is set at Thiokol's Brigham City, Utah, facility for sometime in January, to ensure the redesigned rockets can handle frigid temperatures. A test last December in bitter cold was hailed as a success.
NASA said it will "carefully consider all the group's recommendations."
Stever said NASA officials have told him the agency has plans to carry out some of the tasks cited in the report, including a cold-weather test scheduled next month, and is considering the others on the list.
The booster rockets worked for 24 flights before failing on the Challenger mission, Stever pointed out. Referring to the redesigned booster rockets, he said, "we don't consider it a bad design, it's just that things could be improved further."
The report also recommends several risk-reduction steps, including maintaining technically competent personnel familiar with booster design to evaluate and improve quality control, assembly and launch operations and maintaining ground-testing and in-flight performance measuring programs.
It also recommends insulating the budget for these safety activities from "competitive pressures" from other programs.
The panel of independent scientists was set up at the request of the White House-appointed Rogers commission that investigated the Challenger accident. The commission asked the panel to monitor NASA's compliance with its recommendations. The report, sent to NASA Administrator James C. Fletcher, was the panel's final one.
The report said "a number of important lessons have been learned" from NASA's redesign program.> Among them are the need for a basic understanding of all systems and the need for "a full spectrum of tests" before a system is deployed. These lessons can be applied to other NASA programs as well, the panel said.
"It is not realistic to view the mission as risk-free," the report said, but it added that confidence can be increased from performance testing of the systems before flight, monitoring of systems in flight and their inspection after flight.
Though the Challenger accident inspired NASA to establish a new set of redesign and verification standards, "it is important that these standards be continued in the flight program, and that budgetary, manpower and facilities policies be consistent with that objective," the report said.>