| 'Smoking gun' found in test of shuttle
wing
KATHY SAWYER; The Washington Post
SAN ANTONIO, Texas - With a resounding thwack, a 500 mph foam bullet
Monday blew a ragged hole the size of a stop sign in a section of a space
shuttle wing, effectively shattering any remaining doubts about what
destroyed Columbia and its crew Feb. 1.
"We have found the smoking gun," said Scott Hubbard, a member of the
Columbia Accident Investigation Board, who supervised the testing. It was
the last of seven impact tests and came closest to exactly duplicating an
incident that occurred during Columbia's Jan. 16 launch, when a
suitcase-size chunk of foam insulation from the external tank broke free
and slammed into the leading edge of the left wing.
The damage was so severe Monday that the small crowd of observers
gasped in amazement. It also showed dramatically how badly engineers for
NASA and its contractors had miscalculated the vulnerabilities of the
leading edge, which they had never tested in this way.
Grabbing his stomach, Hubbard said his initial response was "in here, a
visceral reaction," and then, "Oh, my god!" Although "such a dramatic
punch-through" was completely unexpected, he said, the size of the hole is
on the order of one that investigators concluded had to exist on Feb.
1.
As the five-month investigation progressed, multiple lines of evidence
pointed with growing clarity at a single section of the wing - the eighth
of 22 panels on the leading edge - as the site of a fatal breach that
allowed superheated gases to penetrate and destroy the shuttle wing during
re-entry. The panels are made of a carbon fiber material called RCC, for
Reinforced Carbon Carbon, which is designed to withstand temperatures up
to 3,000 degrees.
Hubbard declined to comment on whether a high-powered national security
satellite could have detected a hole of this size while the shuttle was in
orbit. In what the board has called a serious mistake, NASA officials
countermanded a request by lower-level engineers to seek such images
during Columbia's flight.
One of the 16 cameras that monitored the test showed a target's-eye
view as the 1.67-pound foam rectangle, 11.5-by-20 inches, exploded into
the wing cavity like an incoming warhead. The impact drove big shards of
heat shielding into the wing, damaged a camera and left sensors hanging by
wires, Hubbard said. The hole was about 16 inches by 16 inches.
Monday's test was the culmination of the board's effort to "connect the
dots" between the Jan. 16 foam impact and the Feb. 1 tragedy by proving
that the lightweight foam - lighter than styrofoam - traveling at high
speed could have delivered enough force to blow open the required hole in
the heat shielding.
"I've now got a direct connection between foam-shedding creating a hole
that's the same order of magnitude as what must have been there when
Columbia came home," Hubbard said.
"I was surprised, I was very surprised" at the outcome, he added. "I
feel gratified that after months of work we were able to demonstrate this
connection ... but I know it was a source of tragedy, so that makes me
feel very sad."
The tests used a compressed-gas cannon with a 35-foot-long barrel to
fire foam at a million-dollar mockup of the shuttle wing. Monday's test
was only the second using actual shuttle components. The target
leading-edge panel, No. 8, was taken from the orbiter Atlantis and had
flown 27 flights - comparable to the hardware on Columbia. Panels 9 and 10
were taken from the orbiter Discovery.
Engineers for Boeing, a shuttle contractor, concluded during the
mission that such an impact would do nothing more than scuff the carbon
fiber material and that there was no threat to the safety of the vehicle
or crew.
Hubbard said the test also appeared to explain what he called "one of
the mysteries" of this investigation - the identity of an object observed
on radar floating away from the orbiting shuttle on the second day of the
doomed mission.
The mystery object could be a section of RCC shielding such as the ones
that Monday fell into the wing cavity like scattered pieces of a jigsaw
puzzle.
One piece, retrieved right after the test and displayed for reporters,
was 11 inches long and 3 to 4 inches wide.
(Published
12:01AM, July 8th, 2003)
| 
The News Tribune - Tacoma, WA
