Saturday May 20 11:28 AM ET NASA Orders Atlantis to Shut Down One Engine

By Brad Liston

CAPE CANAVERAL, Fla. (Reuters) - NASA has ordered the space shuttle Atlantis to close down one of two engines it normally uses during space flight because a shut-off valve appears to be stuck in the ``on'' position, officials said on Saturday.

Atlantis and a crew of seven blasted off from the Kennedy Space Center in Florida on Friday on a 10-day repair mission to the International Space Station.

NASA said the engine problem should not effect the mission, or the shuttle's ability to boost the faltering orbit of the fledgling space station, which has decayed in the year since astronauts last visited the unfinished, $60 billion project.

``One of the ball valves, the sort of main shut-off valves in the engine, failed to return to the fully closed position,'' lead flight director Phil Engelauf told reporters.

This came after one of several engine firings scheduled for the first phase of the mission, when Atlantis chases the station through space at about five miles per second.

The shuttle is supposed to dock with the station shortly after midnight EDT on Sunday.

Ground controllers told mission commander James Halsell and pilot Scott Horowitz not to use the left engine until it was time for a final burn, shortly before landing.

``We'll do a little planning to figure out how to do the remainder of the mission with just one engine,'' Engelauf said. He described the situation as ``relatively minor in impact.''

Because space shuttle systems were designed with many backups in mind, there was another shut-off valve that functioned normally and the engine shut down just as it was supposed to after the course correction.

Ground controllers were uncertain whether the valve actually failed or whether a faulty sensor might be at fault. The six American astronauts and one Russian cosmonaut spent their second day in space testing systems that will be used for the docking and for an upcoming space walk.

The top priority for this mission is to replace four of six solar-charged batteries aboard the station as well as some other electrical systems that are malfunctioning.

Reuters Photo Thrusters on Atlantis will be used to boost the station's orbit, which has decayed since the first two modules were joined in December 1998. A pair of space-walking astronauts will also try to fix a wobbly construction crane and repair a broken communications array.

The station, a project involving 16 partner nations, is still six months away from being fully habitable and a year away from conducting real science.

Joining Halsell and Horowitz on Atlantis is Russian cosmonaut Yuri Usachev and American astronauts Mary Ellen Weber, Jeff Williams, James Voss and Susan Helms.

http://dailynews.yahoo.com/h/nm/20000520/ts/space_shuttle_8.html

-- Martin Thompson (mthom1927@aol.com), May 20, 2000