Endeavour thruster problem + small y2k problem

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Note camera problem at end of article.

Sunday, February 13, 2000

Thruster problem could cut mapping a little short By MARCIA DUNN -- The Associated Press

CAPE CANAVERAL, Fla. -- Space shuttle Endeavour's astronauts pelted Earth with more radar signals Sunday as NASA struggled to understand a thruster problem that could cut their mapping of the world a little short.

A valve on the end of the 197-foot radar antenna mast jutting out of Endeavour's cargo bay was not providing nearly enough thrust, despite a constant flow of nitrogen gas. Engineers suspected a tiny leak somewhere in the gas line.

To compensate, Endeavour's pilots had to fire the shuttle thrusters more than usual to keep the mast -- the longest rigid structure ever flown in space -- in the right position.

This did not interfere with the crew's radar scanning or the quality of data being collected for the most precise and complete 3-D map ever produced of the Earth. More than 14 million square miles of terrain had been charted as of Sunday morning, roughly equivalent to an area four times larger than the Unites States.

The added thruster firings meant more fuel was used than anticipated, and flight controllers said mapping might have to be halted eight hours early next Sunday.

NASA stressed the eight-hour loss was a best guess and the estimate would become more precise later in the week.

Mission Control asked the astronauts to turn the valve on and off in an effort to pinpoint any leaks. Engineers also were looking for ways the astronauts might conserve fuel, in hopes of regaining those eight hours.

Scientists already have lost a full day of mapping and are loath to lose even another hour.

Last month, NASA surprised scientists by reducing the number of mapping days from 10 to nine. Shuttle managers wanted to leave enough time at the end of the mission for the astronauts to go out and crank in the mast if it jammed.

The decision resulted in a 10 percent loss of data. Nonetheless, scientists still expected to map more than 70 percent of the Earth's terrain, as far north as Hudson Bay and as far south as Cape Horn.

Michael Kobrick, a scientist working at Mission Control, said without any thruster firings, the shuttle and the mast constantly would try to roll right-side up in orbit.

Engineers installed the cold-gas valve on the end of the mast to help preserve shuttle fuel. The force that's supposed to be exerted by nitrogen flowing through this valve is just one-third of an ounce.

"That's about the weight of a penny in the palm of your hand," Kobrick said. "It's hard to believe that that can make any difference, but I think Archimedes said, 'Give me a lever long enough and a place to stand, I can move the world.' Well, given a long enough lever, like 200 feet, a third of an ounce can move the orbiter around."

The astronauts, meanwhile, encountered one other problem Sunday, this one involving Y2K.

Pilot Dominic Gorie reported that the time set for a Hasselblad camera was for the correct date -- in the year 1900. "And when you try to go up to 2000, it jumps back to 1900," he said.

Mission Control's response: "Huh?" Flight controllers later advised Gorie not to worry about it.


-- Martin Thompson (mthom1927@aol.com), February 13, 2000

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