Unblessed Ignorance
Prevention is always easier than cure (and in a vacuum nothing "cures") - for explanations of a much more practical solution, the Sacrificial Glove, see this link
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Clad in a U.S. spacesuit, STS-114 mission specialist astronaut Soichi Noguchi - of JAXA - participates in a dry run "cure in place ablator applicator" test aboard NASA's KC-135 aircraft as part of return to flight readiness program. Credit: NASA/JSC. Click to enlarge.
Space Station Astronauts Eagerly Await STS-114 Crew's Arrival
Shuttle Discovery Stays at Launch Pad
NASA's Procedures, Culture Under Fire: Striving for Accountability
Shuttle Snapshots: Orbital Photography Safeguards Astronauts


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The Shuttle Tiles: In-Space Repairs Become an Impossible Mission
By Todd Halvorson and John Kelly
posted: 8 July 2005
5:25 p.m. ET


This story is Chapter 6 in an 11-part series by Florida Today.

Michael Brieden bore bad news. Sixteen months after the Columbia accident, Brieden stood in a conference center meeting room, a corporate amphitheater of sorts, in Ogden, Utah.

Surrounding him that day: Heavy hitters from NASA headquarters, the American aerospace industry, agency field centers, an independent oversight group and the Astronaut Office.

Brieden, then lead engineer on a project to develop wing panel repairs, was center stage. He got right to the point.

There was no chance NASA, by return to flight, could develop a way to repair the type of severe damage that doomed Columbia and its crew.

"I just laid the dirt on the table, and that boiled up a conversation really quick," said Brieden, 42. "So we had a big, energetic discussion on how come Brieden couldn't provide a good wrap in time for STS-114. And that just led me through my charts."

His PowerPoint presentation covered all the facts.

Engineers had worked overtime on a promising concept: rigid composite carbon over-wraps that could be bolted onto wing panels. They performed as protective skins that could cover holes as big as a large pizza. But the earliest delivery date was late 2005, maybe 2006. That would stall NASA's first post-Columbia flight and completion of International Space Station construction.

The estimated cost was significant: More than $100 million to design and manufacture a full set for the wing. There were operational challenge, too. Forty-four wraps -- one for each unique wing panel -- would have to be built and hauled to the station to be stowed for emergencies.

The killer was they might not even work.

The U-shaped wraps would fit over damaged panels like one taco shell over another. But they would jut up ever so slightly from the wing. Even a minuscule rise, what engineers call a "step" from the outer mold line, would generate excessive heat during re-entry.

The bolts holding a wrap in place would melt. And the wrap itself would melt or fall off, exposing the damaged panel beneath to temperatures up to 3,000 degrees. Hot gas would blowtorch through the wing. The shuttle would be ripped apart. Columbia all over again.

That day, June 9, 2004, Brieden recommended NASA put the concept on the back-burner and focus on techniques for repairing small holes or cracks.

Columbia had been downed by a 1.7-pound chunk of foam insulation that broke free from the shuttle's external tank, blasting a 6- to 10-inch hole in a wing panel. But an extensive effort to redesign the tank would preclude foam that big from shedding in the future. Even in a worst case, only small wing panel cracks -- or holes less than 4 inches in diameter -- might have to be fixed.

And other techniques would be used to handle lesser damage.

Reaction varied.

At the end of the day, NASA leaders decided to make over-wraps a long-term research project. At least for now, the agency acknowledged defeat: NASA could not fix Columbia-like damage any time soon.

"Nobody threw their badge down, and I don't think there was even a dissenting position," Brieden said.

"I think there was a realization that we had worked extremely, extremely hard on trying to give the best answer to the program that we could. And there was no doubt that we had tapped every talent we could.

"We didn't give it up without a little sorrow ourselves."

HOUSTON: Management pushes to find repair method

Shuttle Program Deputy Manager Wayne Hale tried not to worry about the roller coaster of breakthroughs and setbacks.

At the start of the shuttle program, the best engineers in the world failed to figure out a way to have astronauts repair heat shields in orbit.

"They actually gave up," Hale said. "They didn't think it could be solved. Now we think we're very close."

Even after the Columbia accident, some folks at NASA were skeptical it could be done in the short term. Technology might be better, but the shuttle and spacesuits were basically the same. All told, not much had changed.

Except one thing. Resolve.

"You have to have the laboratories; you have to do the tests," Hale said. "All that stuff costs money, and at some point people say: 'We've done enough. We're not going to spend any more money. We're just not getting there.' "

The message from the bosses: "Keep at it."

CAPE CANAVERAL: Astronauts ready to test repair options in space

Discovery commander Eileen Collins was getting anxious.

Three months before launch, senior managers were still debating what repair techniques to test on the first post-Columbia mission -- the kind of decision normally made a year or more earlier.

NASA had abandoned a method for patching wing-panel holes as large as the one that doomed Columbia because ground tests showed it probably wouldn't work. A complex "goo gun" for thermal tile repairs wasn't ready to try on the flight.

Time for crew training was running out.

"It is late," Collins said on a February trip to Kennedy Space Center.

The crew opposed testing the "goo gun," which was designed to fill dents or gouges in thermal tiles with heat-resistant material that would harden in place.

Already clad in cumbersome spacesuits, spacewalkers would have to strap on a bulky holding tank. A heat-resistant red goo would mix inside the tank, then flow through a 5-foot hose before it was squirted out of a rifle-like metal wand. Plus, the goo was difficult to apply. It didn't stick well to tiles. And it bubbled when mixed, creating voids that could weaken a repair patch.

"We are not going to fly it if it's not ready," astronaut Steve Robinson said at the time.

Managers decided to keep things simple.

Side-by-side with Robinson in the shuttle's cargo bay, Soichi Noguchi will coat damaged tiles, mounted on a sort of workbench, with a primer-like, heat-resistant material.

Dabbed on with a device like a liquid shoe polish dispenser, the "emittance wash" will increase the amount of heat that damaged tiles could reject. Robinson will be working with a caulk-gun and putty knife similar to those that can be bought at the corner hardware store. He'll fill small wing-panel cracks with repair material, then smooth the damaged area.

Inside Discovery, the two also will try a method for fixing wing holes up to 6 inches wide. They'll paint a sealant around punctured panel samples and cover the holes with composite carbon patches held in place by expanding bolts.

All of the samples will be brought back to a Houston lab and run through a simulator to see if they can withstand the intense heat of re-entry -- up to 3,000 degrees.

The goo guns won't be tested in orbit. But two will be aboard Discovery just in case.

"It's like having an ejection seat in a jet aircraft," Robinson said. "You don't plan to use it, but it is there."

HOUSTON: Hardware store provides simple tools for tile fix

James Reilly went to work in a dome-shaped vacuum chamber at Johnson Space Center, testing a new wing panel repair technique that one day might save a shuttle crew.

Wearing a full-pressure spacesuit, the veteran astronaut squeezed a bead of heat-resistant adhesive out of a 9-inch caulk gun onto a palette. Then he took a standard putty knife and worked the substance into a small crack, making the surface as smooth as possible.

Sounds simple, like repairing cracked fiberglass on a boat. And the tools are not sophisticated.

"It's pretty much the same things you would go down to Home Depot and buy and use in the house to put spackling up," Reilly said. "That's what we started with.

"We just went down to the local hardware store and bought a bunch of tools. And then we started working with them to see what we liked and what worked and what didn't work."

Doing repairs in space poses unique problems.

First, the adhesive bubbles up in a vacuum, weakening the material and making it less likely to survive the intense heat of re-entry. The repair has to fill the entire crack smoothly. The substance hardens fast and turns into a ceramic. Within a few minutes, it's too hard and stiff to work with. The repair "is a little bit of an art," he said. But it works.

Wing panel samples that Reilly repaired survived tests in a NASA re-entry simulator. Astronauts one day might actually have to use the technique. That's because tests since the accident have shown that cracks as small as one-15,000th of an inch -- about the width of four stacked pieces of paper -- could allow hot gas to tear into the orbiter on the way to the landing strip.

"Hopefully, we never have to use it," Reilly said. "But everything that we've done up to this point indicates that we can do it.

"And if I had to ride home on it, there's not much choice. Give me a ride home."


·         Florida Today Special Report: NASA's Return to Shuttle Flight

·         Fixing NASA: Complete Coverage of Space Shuttle Return to Flight

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