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NASA Sets Shuttle Launch Date for July 26

21 July 2005

Scientists, engineers still working to solve launch-stopping sensor problem

Washington -- NASA announced July 20 it would begin a countdown three days later for the July 26 launch of the space shuttle Discovery (STS-114) on its return-to-flight mission, the first shuttle flight in the more than two years since the Columbia accident.

Space agency engineers are concluding a troubleshooting plan to track down a problem in the fuel-sensor system that caused shuttle managers to suspend a launch attempt during countdown July 13. 

A dozen teams, with hundreds of engineers across the country, have been working through a troubleshooting plan to find the source of the intermittent sensor problem. In a July 20 briefing, NASA managers explained that the teams are still working through the final steps of the effort to resolve the problem as they head toward the July 26 launch. They are conducting tests to look at the possibility of electromagnetic interference as a factor in the malfunction of the sensor-system circuit.

They will also be swapping circuits for two of the sensors in an attempt to isolate the system in which the problem is occurring.  As the countdown begins July 23, the NASA team will also be keeping a close watch on the behavior of this sensor-system circuit as the tank is filled with super-cooled propellants.

The sensors protect an orbiter's main engines by triggering them to shut down safely if fuel runs low unexpectedly.

The sensor circuit failed a routine prelaunch check during the countdown July 13, delaying Discovery’s first launch attempt.

“AMAZING TEAM” WORKING ON PROBLEM, NASA SAYS

In a July 18 briefing, shuttle Deputy Program Manager Wayne Hale said NASA has had a lot of help in its search for the sensor problem.

“The original designer of the point sensor box in the 1970s has come out of retirement and is on our team,” he said.

Offers of help have also come from the Jet Propulsion Laboratory in Pasadena, California, experts from the commercial launch vehicle industry, and the Japanese Aerospace Exploration Agency, which had its own problems with low-level sensors on its H2 rocket.

“We’ve got an amazing team that’s come together to volunteer to work on this problem,” Hale said.

The launch window – the time period within which Discovery must launch to accomplish its mission – is determined by the position in orbit of the International Space Station, Discovery’s destination, and the need to launch the shuttle during daylight hours so multiple cameras can record the liftoff for safety reasons.

Including the first launch attempt on July 26, there are at least four opportunities for Discovery to launch during the current window, which extends until July 31. NASA managers are also looking at the possibility of additional launch opportunities in the first week of August.

Discovery is scheduled for a 12-day flight to deliver equipment and supplies to the International Space Station.

The latest information on the space shuttle's return to flight is available on NASA’s Web site.

(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)