When the
space shuttle Discovery launches its seven-astronaut crew Saturday, tucked
inside its cargo bins will be two new tools for heat shield repair and a remote
control landing, though neither are expected to be needed.
NASA test
director Pete Nickolenko said Thursday that a heat
shield repair device dubbed T-RAD will be aboard Discovery as a safety
precaution should the orbiter sustain damage during launch that could be
repaired by its STS-121 astronaut crew.
The shuttle will also carry a data cable that will allow
flight controllers in Houston to land Discovery by remote
control, a first in NASA's 25
years of space shuttle flight.
"This is a first
flight," said Kyle Herring, a NASA spokesperson at the agency's Houston-based Johnson Space Center, of the cable in a recent telephone
interview. "You certainly don't expect to ever use it."
Both tools will
be packed in Discovery's middeck during its 12-day STS-121
mission - NASA's second shuttle flight since the 2003 Columbia accident - to the
International Space Station (ISS).
NASA
currently plans
to launch Discovery at 3:48:37 p.m. EDT (1948:37 GMT) on July 1.
Pink goo gun evolution
Short for
Tile Repair Ablator Dispenser, T-RAD is a 55-pound (25-kilogram) device
designed to fill cracks between a shuttle's heat-resistant tiles and door
seals, such as those found on landing gear doors, during a spacewalk repair.
NASA began
seeking such repair methods following the loss of Columbia and its astronaut crew, which
investigators attributed to heat shield damage from an errant chunk of external
tank foam. Engineers have also made several modifications to shuttle external
tanks to reduce the amount of foam insulation that can be shed during liftoff.
"We are
intent, and have expended a great deal of effort, to make sure that we can make
hardware that will increase the safety of the shuttle system," Kevin Wells,
NASA's T-RAD project manager at JSC, told SPACE.com. "We definitely want
to have a safe flight."
T-RAD is a
smaller version of the Cure
In Place Ablative Applicator (CIPAA), a
backpack-mounted system, that mixes two compounds together into a pink, goo-like material called STA-54.
"It is an
evolved version and one of the main changes is that we've reduced the size
dramatically," Wells said. "And that's because we reduced the amount of repair
material that we're flying."
T-RAD
consists of a hand vacuum-sized cylinder that runs 18 inches (45-centimeter) in
length and 10 inches (25 centimeters) in diameter that holds the two STA-54
compounds, Wells said. A 30-inch (76-centimeter) hose connects the cylinder to
its dispenser gun, which mixes the two into its final pink form, he added.
Unlike
CIPAA, which was designed to fill in gouged or dinged tiles, T-RAD is aimed at
filling small cracks between tiles and door seals, and is applied much like the
caulking agent used between bathroom tiles on Earth. A CIPAA unit did ride
aboard Discovery's STS-114
return to flight mission last July, but was not tested because NASA
officials - and the spaceflight's
astronaut crew - did not believe it was ready. The STA-54 material tended
to bubble in a weightless environment, creating voids that could compromise an
intended repair.
Wells
stressed that T-RAD is only being launched aboard Discovery in case of an
unexpected contingency, and is not expected to undergo any testing in orbit.
Also riding
in the shuttle's middeck are extra heat shield plugs
to cover any gouges in the orbiter's reinforced carbon carbon
panels along its nosecap and wing leading edges. A
sticky black NOAX
material to be smeared on RCC cracks - and which could be tested in a
potential third spacewalk during the STS-121 mission - is also on the launch
manifest along with a gray emittance wash for tile repair.
Heat-resistant
panels of carbon silicate carbide are also aboard to cover damaged tiles on the
orbiter's belly, Wells said.
Remote
landing capability
Should
Discovery's STS-121
spacewalkers be forced to make a serious heat shield repair, the chances of
which NASA officials believe to be extremely remote, flight controllers could
opt to try to save the orbiter without endangering its astronaut crew.
Herring
said that a 28-foot (8.5-meter) cable packed in the orbiter's middeck has been certified to fly in just such a situation,
which would keep an astronaut crew aboard the ISS while the orbiter returns
home on remote control.
"It's kind
of like a jumper cable that would only be used in an event where you had done a
repair, but couldn't be 100 percent certain [it] would be something that would
be flight worthy with a crew," Herring said.
The cable
would connect an avionics bay in Discovery's middeck
with the controls one level up on its flight deck, effectively allowing flight
controllers in Houston to perform landing activities
currently done by shuttle astronauts.
Those
manual activities include starting the shuttle's auxiliary power units,
deploying an air data probe, unstowing the orbiter's
landing gear and releasing its drag chute after landing, Herring said.
"The things
that would be manually controlled, this jumper cable allows them to be
controlled from mission control," Herring said.
In such a
contingency, Discovery or any future shuttle would land at White
Sands Missile Range in New Mexico, NASA said.
"We would
not target a landing site at KSC or Edwards Air Force Base [in California]," Herring said. "The prime landing
site would be at White Sands because of the wide expanse of the range."
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