Failure of Mars Probe Blamed on Fuel Leak : Space: A federal panel investigating the ill-fated mission also cites sloppy workmanship and criticizes JPL management of the project.

A federal panel investigating the disappearance of NASA’s Mars Observer space probe concluded Wednesday that the spacecraft leaked enough fuel--barely two tablespoonfuls--to cause an explosion, knocking the first U.S. mission to Mars in 17 years out of contact with Earth.

The panel of NASA-appointed experts, which has conducted an exhaustive review of the project since the spacecraft vanished Aug. 21, also cited evidence of sloppy workmanship and criticized management at the Jet Propulsion Laboratory, which had overall responsibility for the interplanetary probe, as “inappropriate.”

The Mars Observer, the first U.S. interplanetary probe to fail in flight since 1967, was designed to provide the most detailed look yet at the planet, serving as a pathfinder for an international armada of probes to be launched toward Mars in coming decades.

Officials at the National Aeronautics and Space Administration and at JPL, who concurred with the board findings Wednesday, earlier had blamed the failure of the $980-million mission on a broken transistor in a small but crucial on-board clock. Another group, called the Mission Success Review Team at Martin-Marietta Corp., which built the missing probe and two other satellites that failed last year, attributed the Observer’s demise to an attitude: overconfidence on the part of the engineers who built the probe.

No one knows for certain exacply what happened to Observer. No sign of the probe has been detected since last August. Mission controllers plan one last attempt to contact the missing spacecraft next month, but they do not expect the probe to reply.

“The board, in fact, found no smoking gun,” said Timothy Coffey, research director of the Naval Research Laboratory, who led the panel.

“There was no telemetry from the spacecraft, no hard evidence to investigate. Therefore, it was impossible to provide conclusive evidence,” Coffey said. “The most probable scenario was a massive rupture of the pressurization system.”

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The Observer’s 450-million-mile voyage had proceeded uneventfully until three days before its scheduled rendezvous with Mars. To avoid damaging its communications gear, ground controllers at JPL turned off the spacecraft’s communications system while its propulsion system was pressurized. Contact was never restored.

After evaluating 60 different failure scenarios, the panel concluded that the most likely cause was a rupture of the probe’s titanium fuel lines, triggered by a slow leak of nitrogen tetroxide and monomethyl hydrazine during the spacecraft’s silent 11-month journey through space.

When the tanks were pressurized Aug. 21, the dribble of volatile chemicals could have ignited inside the fuel line, generating pressure of up to 10,000 pounds per square inch and a temperature as high as 2,000 degrees Centigrade in a few millionths of a second. At such a temperature, Coffey said, the fuel line would have the strength of butter.

At best, the ruptured fuel line would act like a jet to send the spacecraft tumbling out of control. At worst, the probe could have exploded.

“In all likelihood, there is still a Mars Observer up there,” Coffey said, but it is a craft that is “essentially dead. The spacecraft would not know which direction it was pointing or in what direction it is rotating.”

While the panel settled on the possible fuel leak as the most likely mechanical cause of the probe’s disappearance, it said there were broader design and management problems as well.

“JPL was not as familiar with the spacecraft as it should have been,” Coffey said. He cited “systemic weaknesses” that “remain a concern for future programs.”

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When the Mars Observer was conceived more than a decade ago, agency planners designed it as a low-cost, production-line spacecraft--the first in a series of inexpensive “generic” planetary probes that would capitalize on existing technology, just like the series of low-cost Discovery probes that the agency is developing today under similar budget constraints. The design also utilized equipment developed to operate safely in the shelter of low Earth orbit, but it was subjected to the more extreme conditions of interplanetary space.

As funding dwindled and subsequent planetary missions were canceled in the 1980s, however, agency managers were unable to keep their technical expectations within the boundaries of a fixed-cost contract. They changed the instrument packages the probe was to carry. They did not work closely enough with the engineers constructing the probe, the panel said, and lost sight of the changes that transformed the Observer into a custom-built spacecraft.

JPL officials acknowledged the problem. “The (JPL) management approach certainly made the job more difficult,” said JPL Director Edward Stone. JPL Deputy Director Larry N. Dumas characterized the problem as “creeping requirements” and “management Band-Aids.”

“The pressure of the number of changes and demands for systems integration was much greater than expected,” Dumas said.

Troubled Spacecraft A federal panel Wednesday announced the findings of its inquiry into the Aug. 21 disappearance of the $980 million Mars Observer spacecraft. Exactly what happened to the space probe is not known, but the independent panel found these problems: Mechanical flaw: A leak of volatile hydrazine fuel may have caused an explosion when the spacecraft’s tanks were pressurized. Design flaw: NASA engineers used technology that had been developed for operation in near-Earth orbit but was unsuitable for the more extreme conditions of interplanetary space. Management flaw: Project managers at the Jet Propulsion Laboratory did not exercise sufficient control continuing changes in the spacecraft’s design and its scientific instruments. Source: NASA