‘85 Study Saw No Peril in Rocket Seal Erosion : Analysis Did Not Find Threat to ‘Flight Safety’ or Any Reason to Suspend Scheduled Missions

A detailed study of erosion and charring detected in solid rocket booster seals after space shuttle launchings last year concluded that the problem was not a threat to “flight safety” and could be corrected without suspending scheduled missions, a ranking National Aeronautics and Space Administration official said Sunday.

Michael B. Mann, director of the shuttle program’s research analysis branch, said that a series of measures to strengthen seals between sections of space shuttle solid rocket boosters was “implemented immediately” after postflight inspections showed evidence of leakage.

Corrections Implemented

“There was a review of the charring, and at that time the recommendation was that . . . it was not a flight safety issue,” Mann said in an interview. “There were some actions taken at the time to alleviate the problem. There were some decisions made to improve the integrity of the seals. They were implemented immediately.”

A plume of flame spurting from the side of the space shuttle Challenger’s right-hand booster rocket has emerged as a leading suspect in the search for what caused the catastrophic Jan. 28 explosion that destroyed the $1.2-billion spacecraft and its seven-member crew. Four days after the tragedy, the space agency released pictures showing a plume erupting from the side of the rocket casing 13 seconds before Challenger blew apart in a fireball.

NASA sources said it was believed that 6,000-degree emissions spewed from a seam between segments of the multi-sectional rocket, heating the adjoining fuel tank--loaded with liquid hydrogen and liquid oxygen--to the point of rupture and explosion.

However, in a related development Sunday, other space agency sources said investigators were studying photographs that possibly indicate problems in the spacecraft’s 154-foot fuel tank even before flames erupted from the right solid booster.

The sources said voluminous photographic coverage of the accident included frames in which smoke or vapor appeared to cling to the wall of the tank before there was visible evidence of a booster rupture.

A failure in the tank before or simultaneous with the failure of the booster would force investigators to look for a common cause. There already has been speculation that unusually cold weather in central Florida on the eve of the launching played a role in the accident, perhaps causing a non-flammable sealant inside the casing at the seams to come loose.

No ‘Catastrophic Concern’

Mann said he could not recall how many times after previous flights evidence of leakage and charring had been detected within the system of seals designed to prevent escape of hot propellant from seams between the rockets’ 11 sections.

But Mann said that engineers he interviewed did not view the pattern as a “catastrophic concern.”

He said: “It wasn’t the kind of thing where every launch we watched with bated breath, praying that it wouldn’t be a problem.”

Mann’s characterization of the level of concern conflicted dramatically with the impression created by a July 23 memorandum written to him by a subordinate. The memorandum was among NASA documents obtained by the New York Times from what the newspaper identified as a “solid-fuel rocket analyst.” Portions of the documents were quoted in a report published Sunday.

Damaging Memorandum

The most damaging of the documents appeared to be a memorandum to Mann by Richard C. Cook, who worked for Mann in the shuttle program’s research analysis branch. Its function is to determine budget requirements for the program.

The memorandum, as quoted, said that “there is little question . . . that flight safety has been and is still being compromised by potential failure of the seals, and it is acknowledged that failure during launch would certainly be catastrophic.”

Cook was also quoted as having written that the charring of seals constituted “a potentially major problem affecting both flight safety and program costs.”

Mann said that Cook did not have the scientific wherewithal to draw such drastic conclusions and might not have understood what he had been told by engineers about the problem.

He said that Cook had come to NASA as a speech writer on July 4--three weeks before the memorandum was written--and “at the time didn’t even know what an SRB (solid rocket booster) looked like.”

“He had no technical understanding of the SRB, and no technical training,” Mann said.

According to Mann, Cook was being trained to be a budget analyst for the solid rocket program and as an introductory assignment had been asked to determine what budget impact could be expected because of the seal problem.

He said that Cook subsequently had been criticized for writing reports “based on emotion rather than hard evidence” and only recently left the space agency to work elsewhere.

“He no longer works for NASA as of right now,” Mann said. “To quote him, he was at a point in his career where he did not want to work the hours that he worked and have the pressure put on him. He said he was going to a job at Treasury, where he could work 40 hours a week and not have the pressure.”

Extensive efforts to find Cook on Sunday were not successful.

In responding to the published report, the presidential commission investigating the Challenger accident asked the space agency Sunday to produce all information dealing with problems relating to seals on the shuttle’s booster rockets.

White House spokesman Mark Weinberg said the commission’s chairman, former Secretary of State William P. Rogers, had asked NASA for “all internal documents and reports of investigations dealing with problems relating to seals on the booster rockets.”

Hours later, NASA issued a terse statement indicating that it would comply with Rogers’ request. The space agency has been under increasing criticism for its unwillingness to discuss what it knows about the Challenger tragedy with the press.

The full statement said: “NASA today began assembling all internal documents and reports pertaining to the investigation of seals on the shuttle solid rocket boosters for presentation to the Presidential Commission on the Space Shuttle Challenger accident at its Monday meeting.

“Dr. William Graham, acting administrator of NASA, has assured the commission of full cooperation from all NASA employees. Following the commission’s open meeting Tuesday, a NASA spokesman will be available to answer questions from the press. Details will be announced Monday.”

Mann said that after he received Cook’s memorandum he went to the engineers the subordinate had interviewed and asked them if the memo had accurately captured their concerns about leaks in booster seals.

“I talked to the engineers after I got the memo and I didn’t get any feeling there was a catastrophic concern,” he said. “And I certainly didn’t get any recommendation that we shut down the program or do anything like that.”

Mann said he was told the manufacturer of the solid rockets, Morton Thiokol, was at NASA’s request conducting an extensive study of the problem.

Mann said he later saw a copy of the Morton Thiokol analysis, which he said ran for 50 pages and contained extensive detail about the erosion problem.

“They recommended a program that would be implemented and phased in over time and several years,” he said. “And they recommended some changes in procedures.”

The report did not characterize the problem as a flight safety issue, Mann said.

The booster rockets contain 11 sections. They are joined together at the factory, forming four larger sections. Those four are put together at the Kennedy Space Center. According to sources in the shuttle program, the task of mating the segments of the solid rocket booster after they have arrived in Florida is one of the most delicate tasks in preparing for launching.

The segments are joined by dozens of structural pins around the circumference of the huge rocket, and then the seam is sealed by rubber-like rings, called “O rings,” which are in turn covered by a non-flammable putty.

For burning propellant to escape from a joint between two segments, it would have to penetrate not only the non-flammable putty sealant, but both a primary and backup “O ring,” before reaching the structure of the rocket casing.

From the outset of the shuttle program, the mating of the segments with the “O ring” assembly has been one of the most difficult tasks in preparing a vehicle for flight, and it has not been uncommon for rocket segments to be “de-stacked” when pressure checks disclosed leaks after assembly.

An engineer at NASA’s Marshall Space Flight Center in Huntsville, Ala., recalled on Sunday an incident when assembled segments had to be taken apart when a few bristles from a soft brush used to clean the “O rings” had come loose on the rubbery material, causing it to leak.

“Every time they light off a booster,” he said, “the ‘O rings’ are my biggest concern, because they must be assembled absolutely right.”

The same booster engineer, who commented on condition that he not be identified, said he was aware of one instance in which the “O rings” were found to have seriously eroded during flight.

Another internal memorandum quoted in the New York Times report stated that there had been 12 instances where a primary “O ring” had shown signs of erosion.

At the first presidential commission meeting Thursday, Judson A. Lovingood, deputy director of shuttle projects at NASA’s Marshall Space Flight Center, conceded that seal damage had been found after an unspecified number of past missions.

“We have seen some evidence of what we call blow-out of those seals, some erosion of those seals, the primary seal. We’ve never seen any erosion of the secondary seal,” he testified. “But we have seen evidence of soot between the two seals.”

Mann said that the Morton Thiokol analysis, which he believed was issued in August, called for alterations in the method for seating the “O rings” into the joint casings. It was discovered, he said, that the previous methods sometimes put pressure on the putty that could “blow a hole” through it, undermining the first line of defense against leakage.

He said also that, as a result of the analysis, design modifications to prevent leakage at the seals were made in a new generation of solid booster rockets to be implemented when shuttle launchings begin at Vandenburg Air Force Base, Calif.

Mann said he reviewed a copy of the Morton Thiokol report, which was addressed to L. Michael Weeks, NASA deputy associate administrator for technical matters. Weeks’ secretary said he was at work Sunday but would not grant interviews.

A Morton Thiokol spokesman also refused to comment on the study.

Meanwhile, divers battled murky waters and debris from 30 years of missile tests as they searched the ocean floor off Cape Canaveral for an auxiliary booster rocket that was to have launched a satellite from the Challenger’s cargo bay.

At the same time, other salvage crews searched for the craft’s main solid rocket boosters, which could help determine what precisely triggered the explosion. Searchers, led by “pingers” attached to the rocket casings, were believed to have gained a fix on the rockets’ locations on the sea floor. NASA spokesmen refused to elaborate.

Staff Writers Maura Dolan in Washington, Scott Kraft in Chicago and Kim Murphy at the Kennedy Space Center, Fla., contributed to this report.