Putting astronaut crew safety first, NASA has mandated a weeks-long troubleshooting delay for a scheduled space shuttle flight.
A maddening intermittent malfunction in an external fuel tank sensor system finally forced NASA to abandon plans for its fourth space shuttle launch this year, pushing the liftoff of Space Shuttle Atlantis into next month, NASA leaders said recently.
That ended days of battling the frustrating intermittent problem, which can’t be replicated on demand so that it might be diagnosed and fixed.
All had seemed well in the smooth and flawless countdown leading to a scheduled Thursday afternoon blastoff of Atlantis from Launch Pad 39A at Kennedy Space Center (KSC).
But then, within hours of T minus zero, two low-fuel engine cutoff (ECO) warning sensors in the liquid hydrogen portion of the external fuel tank malfunctioned, and the launch was delayed to Friday. The fuel gauges are critical, because if the shuttle runs out of fuel with the engine pumps still running, an explosion might result.
Repairs probably will be done on the launch pad, without the time-consuming effort of moving Atlantis back to the Vehicle Assembly Building at KSC for the trouble- shooting and repairs.
The delay of Atlantis lifting off means NASA will have executed just three space shuttle missions to expand the International Space Station (ISS) this year, when an average of four missions yearly are needed to complete construction of the space station before the scheduled 2010 retirement of the shuttle fleet.
Only the shuttles have the size and power required to carry huge structural components into space needed to build the orbiting artificial moon.
But the delay in the launch of Atlantis won’t knock NASA off schedule in its manifest of planned shuttle launches, and the space station will be fully built before the shuttles retire, according to Bill Gerstenmaier, associate NASA administrator for space operations, speaking to reporters at a weekend briefing to detail the no-fly decision.
Gerstenmaier also pointed out that delaying the Atlantis launch from December into January “won’t impact the next mission,” called STS-123, when Space Shuttle Endeavour on Feb. 14 is to lift off to carry the Kibo Japanese laboratory into orbit for addition to the ISS.
“There’s enough margin in the system” of scheduled launches to accommodate the delay in the Atlantis STS-122 Mission, Gerstenmaier said.
LeRoy Cain, manager of launch integration and mission management team chairman, outlined the situation as NASA confronts the will-o-the-wisp sensor data glitch.
As tanking began, in the process of filling the external fuel tank, matters appeared to proceed well until “one of the sensors failed to the wet state,” Cain said. That is dangerous, because if sensor data tell the shuttle crew and ground controllers that fuel remains in the tank when in fact it is running dry, a catastrophe could ensue because the crew wouldn’t be aware that they should shut down the engines to avert a possible explosion.
Because current criteria mandate that all four ECO sensors must be working properly before a mission, that violation forced a scrub of the Atlantis mission.
The tanks were drained and the countdown to launch was discontinued.
So engineers and experts are brain-storming where the problem might be. Rather than the fuel gauge sensors themselves, suspicion centers on the wiring, connectors, junction boxes and related items, the path through which sensor data must flow to be read by the crew and ground personnel.
Just when Atlantis might fly depends on what the experts conclude, among other factors.
“We gave it a good try,” but getting the shuttle off the ground proved impossible, Launch Director Doug Lyons said.
At first, as technicians began filling the external fuel tank, all seemed well. Sensors properly indicated that the empty external fuel tank was filling up, and a test of the sensors went well, too.
But then, “two or three minutes later, [ECO] sensor 3 failed,” Lyons said, with voltages in lines suddenly rising, and indications registering that there was an open circuit somewhere.
And, since even one faulty sensor bars any launch, that was the end of attempts to get Atlantis off the ground.
As to whether NASA might drop the current requirement that all four ECO sensors operate well before launch is permitted, “we’re going to look at everything,” Cain said.
Meanwhile, NASA is left with unexpected weeks on its hands where there won’t be a space shuttle launching, or a shuttle crew working on the space station construction job.
So if life gives you lemons, make lemonade, Gerstenmaier indicated.
He said the idle time might be filled with a spacewalk by space station crew members, who might look at a problem with a solar alpha rotary joint (SARJ) that keeps a giant solar electrical generating panel correctly pointed toward the sun, for maximum electricity generating capability.
“We have a lot of options,” Cain said. Clearly, if a rollback is imperative, then “that does not support a Jan. 2 launch,” he explained. He didn’t say how late in January the liftoff might occur if a rollback is required.
Meanwhile, the Atlantis crew has broken quarantine and returned to Johnson Space Center, where they will enter training sessions.
The Atlantis crew consists of Commander Steve Frick, Pilot Alan Poindexter, mission specialists Leland Melvin, Rex Walheim, Stanley Love and European Space Agency astronauts Hans Schlegel, from Germany, and Leopold Eyharts, from France.
They will take the European laboratory Columbus to the space station for attachment to the “Harmony” connecting Node 2 module that was installed on an earlier flight.