The night before Challenger's launch, space agency officials were concerned that subfreezing temperatures might cause a seal to crack open in one of the shuttle's solid-fuel booster rockets, a NASA official yesterday told the newly appointed presidential commission investigating the shuttle disaster.
He said officials feared the cold might have robbed special large rubber "O-rings" of their ability to maintain a seal between the stacked cylindrical segments of which a booster is made. Without a pressure-tight seal, the rocket's hot exhaust gases could seep out the rupture.
After consulting experts from Morton Thiokol Corp., which makes the boosters, it was decided the temperatures were not a problem and Thiokol "recommended to launch," said Judson A. Lovingood, deputy manager of shuttle projects at the Marshall Space Flight Center in Huntsville, Ala., which is responsible for the boosters.
NASA films of Challenger's last flight show a "plume" that appears to be white-hot flame escaping from a rupture in the casing of its right-hand, or starboard, solid-fuel booster. A leading theory holds that the plume caused the explosion, about 15 seconds later, by blow-torching the nearby tank of liquid hydrogen.
Yesterday's meeting of the commission, chaired by William P. Rogers, who was secretary of state in the Nixon administration, was the first for the panel appointed on Monday by President Reagan. The commission has 120 days to find the cause of Challenger's explosion and to recommend corrective action to prevent recurrences.
The testimony emerged from an all-day session in which officials of the National Aeronautics and Space Administration tried to present a broad overview of the shuttle program and commission members kept zeroing in on cold temperatures at the launch pad as a possible cause of the disaster. NASA officials repeatedly discounted the idea.
Aside from effects on rubber seals, cold weather can have other adverse effects on rockets. Experts in solid fuel technology, for example, have said that if the fuel gets too cold, it can form cracks that will allow combustion to reach the inner walls of the casing.
Space agency officials said that just before the launch the manufacturer of the shuttle, Rockwell International Corp., had expressed concern about ice on Challenger and on the launch tower but NASA determined it was not a problem.
The concern was that chunks of dislodged ice might knock loose some of the shuttle's heat-shielding tiles needed during reentry.
Except for ice, Arnold D. Aldrich, NASA's manager of the shuttle program at the Johnson Space Center in Houston, told the commission, "we had no concern expressed for the temperatures then, nor do I at this time."
According to the fuel's manufacturer, Morton Thiokol, it is designed to withstand temperatures down to 40 degrees Fahrenheit. The night before the Jan. 28 launch, air temperatures were in the 20s.
This, however, was not a problem, according to Lovingood, who told the panel that it was estimated that the solid fuel never dropped below 55 degrees.
He said that while there are no thermometers in the fuel, its temperature could be calculated from the booster's thermal properties and the surrounding air temperature.
As if to emphasize the panel's eagerness to win public confidence and to proceed quickly, yesterday's hearing was held in public at the National Academy of Sciences headquarters here just one day after the newly appointed members met one another for the first time.
Rogers said the panel's subsequent meetings will be closed to the public but that he plans eventually to hold other open sessions. The panel has yet to hire a full staff.
Rogers conducted the hearing while flanked by Neil Armstrong, the first human on the moon, and Sally Ride, the first American woman in space.
Both are members, along with Charles (Chuck) Yeager, the former test pilot, who did not attend the opening session; Richard P. Feynman, a Nobel laureate in physics, and Robert B. Hotz, former editor of Aviation Week and Space Technology magazine.
Yesterday, President Reagan named Joseph F. Sutter, a principal in the development of the Boeing 747 jumbo jet, to the commission. Sutter, an executive vice president of the Boeing Commercial Airline Co., becomes the 13th member of the panel.
Commission members, hoping to reconstruct events that occurred in the days before Challenger's liftoff, asked NASA for minutes or other records of their meetings and decisions. Space agency officials said they had no such records.
Several times commission members asked for specific information about Challenger and NASA officials were unable to supply the answers.
None of the seven top officials present, for example, could tell the panel how many times Challenger's main engines or its recyclable booster segments had been used before.
The officials did take issue with statements last Sunday by acting NASA administrator William R. Graham, who said the Challenger crew could have tried to abort its flight, detaching from the rest of the launch vehicle and gliding to safety if it had known of the rupture soon enough.
All the officials emphasized that such a tactic has never been seriously considered in contingency plans because of the likelihood the shuttle would collide with the detached apparatus.
"It is thought to be unsurvivable," Aldrich said of the maneuver.
Meanwhile, Sen. Edwin Jacob (Jake) Garn (R-Utah) announced yesterday that the thousands of dollars that Americans have donated as a tribute to the seven Challenger astronauts will go to a special fund to help build a new spacecraft.
"I can think of no finer tribute to the men and women who went down with Challenger," Garn told a news conference.