Image: Atlantis
Win Mcnamee  /  Getty Images
The space shuttle Atlantis sits on its launch pad at NASA's Kennedy Space Center on Thursday. NASA has decided to go ahead with a launch attempt on Friday, after weighing concerns about the shuttle's electrical system.
updated 9/7/2006 8:06:11 PM ET 2006-09-08T00:06:11

Caught in a scheduling squeeze, NASA decided to try to launch the space shuttle Atlantis on Friday without replacing a troublesome electrical component.

Friday had been the last launch day available before the U.S. space agency ran into a potential scheduling conflict with the Russian space agency. But NASA managers now believe they can try Saturday, if needed, and they were finalizing negotiations with the Russians.

There was a 30 percent chance bad weather would interfere at the 11:40 a.m. ET Friday launch time.

On Thursday, NASA decided not to change out an electricity-generating fuel cell whose coolant pump had given erratic readings, causing a scrub a day earlier. Replacing the 250-pound (113-kilogram) pump could have delayed any launch attempt by several weeks and might have been riskier than leaving it in place, said Steve Poulos, shuttle orbiter projects manager.

The most likely cause of the erratic reading was thinning wires on a motor that hadn’t been used in seven years, Poulos said.

“Pulling out a 250-pound piece of hardware and getting it in and out ... and at the end of the day not having a problem — well, there’s just risk associated with that,” Poulos said. “It became a very easy recommendation for me ... to say ’We’re good to go fly.”’

Not a unanimous decision
The decision to try a launch on Friday wasn’t unanimous. Officials in NASA’s safety office felt the fuel cell should be changed out not because of a safety issue, but because they were concerned about whether the mission could be carried out successfully. The fuel cell’s manufacturer, UTC Power, wanting NASA to use a pristine unit, also recommended against flying until it was swapped out, said Wayne Hale, space shuttle program manager.

A spokesman for UTC Power couldn’t be reached after business hours.

“I feel very confident that we’re not racing, that we have in fact taken a very slow, methodical thorough and safety-approach in this whole matter,” Hale said.

A question of timing
After this weekend, the next daylight launch opportunity is not until the end of October. NASA's current rules say Atlantis must lift off in daylight so that its big external fuel tank can be photographed for any signs of broken-off foam of the sort that destroyed Columbia three and a half years ago.

Slideshow: Month in space: Future frontiers

If Atlantis does not get off the ground on Friday, NASA officials had two options they were reluctant to exercise that would permit a launch attempt before the end of October: Try on Saturday, or relax the daylight-launch rule.

NASA managers originally believed the 11-day construction mission would have to be shortened if Atlantis were launched on Saturday. NASA had made an agreement with the Russians to undock from the space station by Sept. 17 because Russia is launching a three-person Soyuz capsule to the space station on Sept. 18.

But NASA was negotiating with the Russians about possibly undocking Sept. 18 if the U.S. space agency decides to launch the space shuttle on Saturday, said Mike Suffredini, space station program manager.

Relaxing the daylight rule would open up launch chances in late September and early October.

Ambitious schedule ahead
Atlantis’ astronauts are to restart construction on the half-built international space station for the first time since the Columbia disaster. NASA has delayed the shuttle's launch for more than a week already, due to a lightning strike and a tropical storm, so the agency wants to take advantage of any safe opportunity to get the mission started.

NASA is already facing an ambitious launch schedule to complete assembly of the space station by 2010, when the shuttle fleet is due for retirement. Many of the major components yet to be attached to the station, including laboratory modules built by Japan and the European Space Agency, were designed to be flown into orbit on the space shuttle.

This report was supplemented by information from

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