CAPE CANAVERAL, Fla. – NASA officials ordered a Discovery astronaut on Monday night to attempt an unprecedented repair job in space – plucking two slivers of errant fabric from the underbelly of the space shuttle that could cause potentially dangerous overheating during re-entry into the Earth’s atmosphere next week.
On Wednesday, astronaut Steve Robinson will make his third spacewalk of the mission, but this one will make history. Astronauts never have gone under an orbiting shuttle before and never have tried to fix a spaceship’s damaged heat tiles during flight.
If Robinson can’t grip the pieces of “gap filler” – one sticking up between the tiles about an inch and the other about half that much – then he will clamp them with mechanical forceps and snip them off with scissors or with another cutting tool.
“At the end of the day, the bottom line … (is) there is large uncertainty because nobody has a very good handle on aerodynamics at those altitudes and those speeds,” said Wayne Hale, deputy shuttle director and chairman of the National Aeronautics and Space Administration’s mission management team. “Given that large degree of uncertainty, life could be normal during entry or some bad things could happen.”
Hale said officials decided to attempt the repair to “set our minds at rest.”
“This is kind of the new shuttle program, the new NASA; if we cannot prove that it is safe, then we don’t want to go there,” he said. “This exceeded our threshold, and we needed to take action.”
Sticking up like ragged fingernails, the gap filler might make the temperature on the shuttle’s underside, which is normally about 2,000 degrees, as much as 200 degrees hotter. That’s because the two pieces might disturb the air flow surging down the shuttle’s underside as it hurtles into the outer fringes of the Earth’s atmosphere at 20 times the speed of sound.
Gap fillers are strips of material, about as thick as rigid Venetian blinds, that fill the space between the insulating tiles that protect the shuttle – and its crew – from the intense heat of re-entry.
The repair job would be a largely unrehearsed operation that includes some risk the astronaut might accidentally bump into Discovery’s fragile thermal shield and make matters worse.
“That’s something we have never done before, putting a crew member underneath the vehicle,” said Mission Control spacewalk officer Cindy Beg-ley. “They are going to have to be very careful not to damage anything while they are there.
“It’s a fairly simple task,” she said. “We just need to be sure that we are not going to hit the vehicle when we are doing that.”
Robinson will do the job alone, suspended from a mechanical arm extending from the International Space Station, where Discovery is docked.
Begley said fellow astronaut Soichi Noguchi will be nearby doing other jobs. The two men were already scheduled to make Wednesday’s spacewalk as part of Discovery’s mission.
Back on Earth, other astronauts were in the NASA training pool practicing how to do the repair procedure – and then sending their advice up to Discovery.
Gap filler protrusions have happened before, but nobody has had a chance to see one to know how far up the fabric has stuck out before re-entry.
The filler problem is different from what happened to the shuttle Columbia in 2003. Debris from its giant fuel tank came off during launch and tore an undetected hole in Columbia’s wing, causing the orbiter to burn up on re-entry. The disaster killed the seven astronauts aboard and shut down the manned space program for 21/2 years.
During last week’s launch of Discovery, another chunk of foam flew off the tank, but apparently did not strike the orbiter. The space agency quickly ordered no more shuttle launches until engineers can come up with a way to stop debris from falling off the fuel tank.
The problem with the gap filler was detected by cameras on the space station during a first-ever “on orbit” inspection of the underside of the shuttle. NASA leaders scrambled to decide whether the glitches needed fixing at all, and if so, how.
They know the problem has happened on other flights, but don’t know how far out the material extended before re-entry. Some gap fillers have apparently come loose during the bumpy ride from the launch pad to orbit more than 220 miles up.
Nor do the experts know what might happen if they simply do nothing.
“We’re not going to be able to give a definitive answer,” mission operation representative Phil Engelauf said at the Johnson Space Center in Houston.
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