The space agency said the fuel gauge problem is most likely an electrical grounding problem, and the only way to thoroughly check the system is to fuel Discovery and have all its equipment running.
“We believe the best way to go through this is to do a countdown,” said shuttle program manager Bill Parsons on Wednesday, reported the Associated Press. “If the sensors (gauges) work exactly like we think they will, then we’ll launch on that day. If anything goes not per the plan that we’ve laid our in front of us, then we’ll have a scrub and we’ll have to talk about it.”
If all goes well during the final preparations for launch, the countdown clock will start ticking Saturday afternoon. Liftoff is scheduled for 10:39 a.m. Tuesday.
NASA may also proceed with the launch if the fuel gauge problem reoccurs but is considered well understood.
That would mean NASA relies on three out of four hydrogen fuel gauges at the bottom of Discovery’s external tank. The fuel gauges are intended to keep a shuttle’s main engines from shutting down too early or too late after liftoff — both potentially disastrous situations, according to the AP.
Only two of the four are needed to ensure safety, but ever since the 1986 Challenger explosion during liftoff, NASA has required all four gauges to be working.
“Right now, we think we have eliminated all the common causes that we believe could do this and we’ve done everything we possibly could on the vehicle,” Parsons told reporters.
Discovery’s countdown was halted just two hours before it was set to lift off the afternoon of July 13 when the fuel gauge malfunctioned.
NASA is planning to send Discovery on a 12-day mission to the International Space Station. The current launch window closes Aug. 4, and the next window opens in September, according to Newsday.
Discovery’s flight will be the first since a chunk of foam punched a hole in Columbia’s left wing, causing the shuttle to break apart during re-entry on Feb. 1, 2003, killing all seven astronauts on board.