Astronauts Make 100th Spacewalk

Wednesday, February 14th 2001, 12:00 am

By: News On 6

SPACE CENTER, Houston (AP) â€” Two astronauts floated outside space shuttle Atlantis on Wednesday, making the 100th spacewalk in U.S. history as they worked on the international space station.

Thomas Jones and Robert Curbeam Jr. continued the string begun in 1965 by Edward H. White II. White's spacewalk on the Gemini 4 mission lasted just 21 minutes.

Jones and Curbeam were to put the finishing touches on the international space station's newly installed science laboratory, Destiny, and perform some final chores during their spacewalk â€” the third and last of their mission.

The bulk of their mission's objective â€” to mount and install the $1.4 billion Destiny on space station Alpha â€” was done on their previous spacewalks.

During Wednesday's scheduled five-hour excursion â€” which began about a half-hour ahead of schedule â€” Jones and Curbeam were to check cable connections between Destiny and a docking port that was attached to the lab during the second spacewalk. Also on their work list was attaching a spare communications antenna to Alpha.

They also planned to take photographs of latches which never fully locked into place on the base of the huge solar panels installed in December. Flight controllers will use the photographs to determine how they might fix the latches during a future mission.

If time permits, Jones and Curbeam will also practice for disaster.

They plan to practice emergency techniques that could be used in the future to assist an incapacitated spacewalker. Each astronaut will take a turn playing a limp crewman while the other pulls him back into the shuttle.

At the end of the spacewalk, the hatches between Atlantis and Alpha were to open so the five shuttle astronauts and three space station crewmembers could continue transferring water and other supplies between the two spacecraft.

On Tuesday, Alpha reached two milestones: Its attitude in orbit was controlled by solar-powered gyroscopes instead of small thruster rockets â€” and the station was controlled by Americans rather than Russians.

On Mission Control's cue, computers inside Destiny sent commands to four gyroscopes that were delivered by shuttle astronauts last fall. The gyroscopes, in turn, took over the steering of the space station from fuel-guzzling Russian thrusters.

The computers â€” and the gyroscope motors â€” were powered by electricity from the giant solar wings installed in December. The gyroscopes help the space station save rocket thruster fuel, which is costly and burdensome to deliver.

When the gyroscopes were in control, so was NASA's Mission Control in Houston. Until that moment, flight controllers in Russia had always been in charge.

Mission directors were trying to solve one problem in setting up Destiny: Its carbon dioxide-removal system was not working because of a bad pump.

The eight astronauts and cosmonauts in orbit had to rely instead on the air purifiers aboard Atlantis and the Russian segments of the space station.

Even with the glitch, flight controllers said they were pleased with how smoothly the mission and station operations have gone. The shuttle undocks Friday and is scheduled to land back to Earth on Sunday.

``This has been an amazingly complex mission when you look at all the new systems being activated,'' space station flight director Andy Algate said.

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