OT nasa death glider, part 2

OK, how did this happen? did they miss this in the pre-launch
inspection, or did the violence of the launch somehow work this stuff
out? don't they do simulations on parts like this to ensure they are
properly secured? if it's no yes and yes to the above, then was it a
supplier problem or an installation problem?

over 300% beyond spec? two incidents, and both near a critical system?
surgery with a hacksaw? i just can't believe this.

G


Astronaut Might Need to Take a Walk to Repair Shuttle
By John Johnson Jr., Times Staff Writer


HOUSTON -- While most of the surface damage on the Space Shuttle
Discovery has been deemed safe, concern over two protruding pieces of a
heat-resistant fabric on the underside of the craft is causing NASA to
consider a first-ever space walk to make a major shuttle repair,
officials said Sunday.

Paul Hill, the lead flight director for the 114th shuttle mission, said
an engineering team of aero-heating specialists are expected to have a
recommendation Monday on whether an astronaut will be sent out with a
hacksaw to trim off the fabric, known as a "gap filler."

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"We have viewed the options from pulling the gap fillers out to
trimming the gap fillers to putting (them) back down into the gap,"
Hill said.

Thousands of gap fillers -- made of a flexible, ceramic-coated material
about as thick as a credit card -- are placed between the
heat-resistant tiles covering the shuttle.

Two of them near Discovery's main landing gear door are sticking out as
much 1.1 inches, well beyond the quarter-inch allowed by engineers.

The concern is that even a small protrusion could disrupt air flow
under the extreme conditions of re-entry, increasing the heating just
behind the protrusions by almost 600 degrees. That could be hot enough
to threaten the integrity of tiles protecting the spacecraft.

Protruding gap fillers have been observed on previous flights but
always after the shuttle had landed. This time, dozens of new sensors
and cameras installed after the destruction of the Space Shuttle
Columbia on re-entry two years ago have allowed engineers to see damage
while the shuttle is in orbit.

If the National Aeronautics and Space Administration managers decide to
fix the problem, an astronaut would have to be carried on either
Discovery's or the International Space Station's robotic arm to the
underside of the shuttle, where the damage is.

The repair itself should not be difficult. Because the gap fillers are
bonded to the vehicle with glue, they could be pulled out.

The problem is that no space walk procedure is completely safe. This
one was not practiced during the years the crew trained for the
mission, although Discover does carry "EVA scissors," a special
hacksaw-like device provided for just such a situation.

Engineers and aerodynamicists are working overtime to come up with a
recommendation. "They're pressing decades of study into two days," said
deputy shuttle program manager, N. Wayne Hale Jr.

He said engineers were keeping in mind the famous remark by former
astronaut John Young: "There's not anything that happens to the shuttle
that you can't make worse by trying."

The protruding gap fillers are in a particularly sensitive area near
Discovery's front landing gear door. Temperatures can reach 2,300
degrees Fahrenheit as the craft uses the Earth's atmosphere to brake
from 17,500 mph to a safe landing speed.

The silica tiles that cover most of the aircraft are not designed to
accept the worst heating, which is why the nose and leading edges of
the wings are covered with expensive reinforced carbon panels.

The engineers could well decide to leave the craft as is. "My immediate
reaction is, we can live with this," Hale said.

But if the engineers are unable to assure him that there would be no
dangerous excess heating, the management team might decide to err on
the side of caution and fix the problem. "Why should I lose sleep over
gap fillers?" Hale said.

There is one historical precedent for the gap filler problem on
Discovery. That was the STS 73 mission in 1995, when a gap filler in
the same general area bulged out about 1.4 inches.

"There was some noticeable additional heating, but nothing that
ultimately became a concern," said Steve Poulos, manager of the orbiter
project office.

The flight of Discovery has been dogged by a series of problems,
beginning the day of launch, when a large piece of foam fell off the
external fuel tank. Even though it missed hitting Discovery, NASA
quickly grounded the shuttle fleet pending a resolution of the problem.

In the succeeding days, one problem after another, from tile damage to
blemishes on the reinforced carbon panels, have raised concerns. Each
one, until now, was ultimately found to be no threat to the vehicle.

The new sensors and imagers on Discovery have "put the orbiter thermal
protection system under a microscope," Hale said.

While space agency managers on the ground debated what to do about the
gap fillers, Sunday was the lightest day of work so far for the crew.

The seven-person crew had enough spare time to make the rounds of the
morning television talk shows, where they defended the space program,
but also voiced concerns about NASA's engineering decisions.

Some of the astronauts said that they were disappointed and surprised
to learn that a three-foot piece of foam, weighing about one pound, had
broken away from the fuel tank during liftoff.

Crew member Andrew Thomas said the engineering decisions that approved
the liftoff must be questioned.

"The area where the foam came up is an area that was not examined, or
decisions were made not to look at it and not to test the foam there,"
Thomas, 53, said on NBC's "Meet the Press."

"I think we do need to address why that decision (was) made," said
Thomas, who holds a doctorate in mechanical engineering and has been a
part of three previous missions to space. "Was there some technical
reason why they made that decision -- or was it subject to cost
pressures and schedule pressures?"

The commander of Discovery, Eileen Collins, said she was aware before
launch that NASA officials had decided not to retrofit the surface area
from which the foam broke loose.

Both Collins and NASA Administrator Michael Griffin said the decision
not to retrofit the area was based on X-ray and other noninvasive
testing that found nothing suspicious.

Los Angeles Times staff writer David Willman contributed to this
report.

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