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ZL2VAL > SPACE 11.10.03 19:36l 103 Lines 4332 Bytes #999 (0) @ WW
BID : 7619-ZL2VAL
Subj: Brush may repair heat shields
Path: DB0FHN<DB0THA<DB0ERF<DB0MRW<DB0RGB<OK0PPL<DB0RES<ON0AR<WB0TAX<W4JAX<
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Sent: 031010/0751Z @:ZL2AB.#46.NZL.OC #:28096 [New Plymouth] FBB7.00g $:7619-ZL
From: ZL2VAL@ZL2AB.#46.NZL.OC
To : SPACE@WW
Astronauts can handle device in space for repairs
Associated Press
October 8, 2003
WASHINGTON -- A simple foam paint brush that costs only pennies at
hardware stores could be an essential tool in returning the shuttle
to orbit, NASA's administrator said Wednesday.
Space agency engineers found the brush may be just what astronauts
need to spread a patching compound on a shuttle's damaged heat
shield while the craft is in orbit.
"This thing turns out to be one of the most valuable tools we could
have invented," said Sean O'Keefe, head of NASA. "We're going to buy
it at Wal-Mart. We're not going to ask the Defense Department to
requisition it out of stock."
A clerk at a Washington-area hardware store said a 1-inch foam brush
sells for 49 cents and a 2-inch one costs 99 cents.
Designing and testing a way to repair damage in the shuttle's heat
shield is an important part of NASA's efforts to return shuttles to
space after the Feb. 1 accident that destroyed Columbia and killed
seven astronauts.
The accident was blamed on a hole in the left wing that let gases
enter the craft during reentry and sear the structure apart.
Astronauts on Columbia and engineers in Mission Control were not
aware of the extent of damage to the shuttle wing. But officials
said that, in any case, there was no equipment on the shuttle to
patch the wing even if the problem was recognized.
Officials at the Johnson Space Center said the patching compound now
under consideration could be used only for the part of the heat
shield composed of lightweight tiles.
The nose of the shuttle and the leading edge of the wings are
covered with panels of a different material, reinforced
carbon-carbon. It was a break in a carbon-carbon panel that
destroyed Columbia.
Kelly Humphries, a spokesman at the space center, said repairing the
carbon-carbon panels is more difficult and would require methods
different from the tile repair. Among the techniques under
consideration are a patch that could be internally bolted in place,
an adhesive patch, or an overwrap that would envelop a heat shield
breach.
Before returning to flight, the investigation board said NASA must
develop a way for astronauts to fix heat shield damage while the
craft is in orbit.
Such work would require a difficult spacewalk. An astronaut would
have to maneuver in weightlessness and reach gouges or holes on the
heat shield on the outside of the shuttle. The damage would require
patching with a substance that could withstand the 3,000-degree heat
of re-entry.
O'Keefe said NASA earlier studied this kind of repair and "it was
deemed . . . to be too difficult to achieve and therefore not
workable."
But after the Columbia accident, and given the mandate from the
investigation board, NASA engineers took a fresh look and found
possible solutions, he said.
To repair the heat shield, O'Keefe said engineers found a sealant
that is formed when two compounds are mixed together.
Tests showed that the combined compound expanded when heated. This
led to a plan to "underfill" a hole and then let the heat of
re-entry swell the patch and seal the hole.
Once they had a compound, the engineers had to find a way for a
spacewalking astronaut to apply the material while wearing a bulky
space suit, gloves and a bubble helmet, O'Keefe said.
Experts looked at a variety of sophisticated tools made from exotic
materials, he said. They settled on what he called "an elegant piece
of sophisticated hardware" -- a foam paint brush with a wooden handle.
==============================
73 de Alan
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