[meteorite-list] Atlantis Damaged By Micrometeoroid/Space Debris

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Oct 6 13:05:33 2006
Message-ID: <200610061705.KAA22328_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/shuttle/sts116/061006nighttime/

Shuttles to resume nighttime launches; Atlantis damaged
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
October 6, 2006

[snip]

At the Kennedy Space Center, meanwhile, engineers are assessing options
for fixing a radiator panel mounted on the inside of the shuttle
Atlantis' right-side payload bay door. The panel apparently was damaged
when a piece of space debris or a micrometeoroid slammed into the
radiator, presumably during the shuttle's flight last month, blasting
.108-inch-wide hole in the upper surface and destroying the aluminum
honeycomb material below before exiting the other side.

The impact did not threaten the crew and the damage can be repaired. But
it illustrates the danger posed by micrometeoroid/orbital debris (MMOD)
and the reason why NASA considers such strikes a high risk. The odds of
a catastrophic impact-related entry failure range between 1-in-210 to
1-in-350, depending on whether the astronauts inspect the ship in orbit
prior to re-entry.

At orbital velocities, even tiny pieces of debris pose a serious threat.
An aluminum sphere just .4 inches across moving at 10 kilometers per
second, or 22,370 mph, carries the same impact energy as a bowling ball
moving at 300 mph.

A preliminary engineering analysis shows the impact in question was one
of the most significant instances of MMOD damage in shuttle history,
second only to a cargo bay door impact during shuttle mission STS-72 in
1996.

The shuttle's 60-foot-long payload bay doors each feature four radiator
panels that are exposed to space once the doors are opened in orbit. The
forward two radiator panels measure about one inch thick, feature Freon
coolant tubes positioned about 1.9 inches apart and can pivot to radiate
from both sides. The aft panels are fixed and only radiate from one
side. They measure a half inch thick and feature coolant tubes separated
by about 5 inches. The interior of the panels is made up of an aluminum
honeycomb material.

The impact on Atlantis's right-side, or starboard, radiator was found
roughly midway between two coolant lines on panel No. 4. The object
blasted a .108-inch-wide hole and presumably broke apart on impact. The
resulting spray of debris created a cone-shaped damage cavity
immediately below the face plate, destroying the honeycomb interior to
the full half-inch depth of the panel. The lower face sheet was pushed
out in two places. A .26-inch crack and a .03-inch-wide exit hole were
found.

As part of NASA's post-Columbia safety protocols, the shuttle and space
station fly in an orientation that protects the shuttle's critical wing
leading edge panels from direct, worst-case impacts in the line of
flight. In addition, the astronauts now carry out detailed inspections
of the shuttle's heat shield after reaching orbit and again before
re-entry to make sure no MMOD impacts occurred during the course of the
mission.

Areas of the shuttle that are not critical for re-entry are not
inspected and the damage to Atlantis's radiator panel No. 4 was not
discovered until post-flight servicing at the Kennedy Space Center.

A senior NASA manager said the impact damage was unlikely to prompt a
change in the shuttle's orbital orientation. He said program managers
understand the radiator panels and cockpit windows face a higher risk of
impact damage because of the shuttle's orientation. But he said the
risks associated with wing leading edge impacts are more severe.

The shuttle has two Freon coolant loops and while the loss of one would
force a crew to return to Earth at the next available U.S. landing site,
computer software is in place to immediately isolate a leak even if the
event occurred when the crew was asleep or otherwise occupied. Assuming
a leak was quickly isolated, the astronauts could implement contingency
procedures and press ahead with a near-normal mission despite the damage
to one radiator panel.

As for an impact on the shuttle's cockpit windows, engineers do not yet
know if the debris in question would have penetrated the thick
multi-pane glass. The three panes making up the six forward cockpit
windows have a combined thickness of 2.55 inches. The three panes making
up each overhead window have a combined thickness of 1.58 inches.

Some 11,000 objects 3.9 inches in diameter or greater are currently
tracked by Air Force radars and optical systems. About 100,000 objects
are believed to be present that are between .39 inches across and 3.9
inches in diameter. Most of those are not tracked and pose a threat to
spacecraft in low-Earth orbit and to communications and weather
satellites in higher orbits.
Received on Fri 06 Oct 2006 01:05:30 PM PDT