Shuttle to Carry Tools for Repair and Remote-Control Landing

Shuttle to Carry Tools for Repair and Remote-Control Landing
NASA engineers have developed the Tile Repair Ablator Dispenser (T-RAD) to fly aboard Discovery's STS-121 mission as safety precaution.
(Image: © NASA/JSC.)

When thespace shuttle Discovery launches its seven-astronaut crew Saturday, tuckedinside its cargo bins will be two new tools for heat shield repair and a remotecontrol landing, though neither are expected to be needed.

NASA testdirector Pete Nickolenko said Thursday that a heatshield repair device dubbed T-RAD will be aboard Discovery as a safetyprecaution should the orbiter sustain damage during launch that could berepaired by its STS-121 astronaut crew.

The shuttle will also carry a data cable that will allowflight controllers in Houston to land Discovery by remotecontrol, a first in NASA's 25years of space shuttle flight.

"This is a firstflight," said Kyle Herring, a NASA spokesperson at the agency's Houston-based Johnson Space Center, of the cable in a recent telephoneinterview. "You certainly don't expect to ever use it."

Both tools willbe packed in Discovery's middeck during its 12-day STS-121mission - NASA's second shuttle flight since the 2003 Columbia accident - to theInternational Space Station (ISS).

NASAcurrently plansto launch Discovery at 3:48:37 p.m. EDT (1948:37 GMT) on July 1.

Pink goo gun evolution

Short forTile Repair Ablator Dispenser, T-RAD is a 55-pound (25-kilogram) devicedesigned to fill cracks between a shuttle's heat-resistant tiles and doorseals, such as those found on landing gear doors, during a spacewalk repair.

NASA beganseeking such repair methods following the loss of Columbia and its astronaut crew, whichinvestigators attributed to heat shield damage from an errant chunk of externaltank foam. Engineers have also made several modifications to shuttle externaltanks to reduce the amount of foam insulation that can be shed during liftoff.

"We areintent, and have expended a great deal of effort, to make sure that we can makehardware that will increase the safety of the shuttle system," Kevin Wells,NASA's T-RAD project manager at JSC, told SPACE.com. "We definitely wantto have a safe flight."

T-RAD is asmaller version of the CureIn Place Ablative Applicator (CIPAA), abackpack-mounted system, that mixes two compounds together into a pink, goo-like material called STA-54.

"It is anevolved version and one of the main changes is that we've reduced the sizedramatically," Wells said. "And that's because we reduced the amount of repairmaterial that we're flying."

T-RADconsists of a hand vacuum-sized cylinder that runs 18 inches (45-centimeter) inlength and 10 inches (25 centimeters) in diameter that holds the two STA-54compounds, Wells said. A 30-inch (76-centimeter) hose connects the cylinder toits dispenser gun, which mixes the two into its final pink form, he added.

UnlikeCIPAA, which was designed to fill in gouged or dinged tiles, T-RAD is aimed atfilling small cracks between tiles and door seals, and is applied much like thecaulking agent used between bathroom tiles on Earth. A CIPAA unit did rideaboard Discovery's STS-114return to flight mission last July, but was not tested because NASAofficials - and the spaceflight'sastronaut crew - did not believe it was ready. The STA-54 material tendedto bubble in a weightless environment, creating voids that could compromise anintended repair.

Wellsstressed that T-RAD is only being launched aboard Discovery in case of anunexpected contingency, and is not expected to undergo any testing in orbit.

Also ridingin the shuttle's middeck are extra heat shield plugsto cover any gouges in the orbiter's reinforced carbon carbonpanels along its nosecap and wing leading edges. Asticky black NOAXmaterial to be smeared on RCC cracks - and which could be tested in apotential third spacewalk during the STS-121 mission - is also on the launchmanifest along with a gray emittance wash for tile repair.

Heat-resistantpanels of carbon silicate carbide are also aboard to cover damaged tiles on theorbiter's belly, Wells said.

Remotelanding capability

ShouldDiscovery's STS-121spacewalkers be forced to make a serious heat shield repair, the chances ofwhich NASA officials believe to be extremely remote, flight controllers couldopt to try to save the orbiter without endangering its astronaut crew.

Herringsaid 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 returnshome on remote control.

"It's kindof like a jumper cable that would only be used in an event where you had done arepair, but couldn't be 100 percent certain [it] would be something that wouldbe flight worthy with a crew," Herring said.

The cablewould connect an avionics bay in Discovery's middeckwith the controls one level up on its flight deck, effectively allowing flightcontrollers in Houston to perform landing activitiescurrently done by shuttle astronauts.

Thosemanual activities include starting the shuttle's auxiliary power units,deploying an air data probe, unstowing the orbiter'slanding gear and releasing its drag chute after landing, Herring said.

"The thingsthat would be manually controlled, this jumper cable allows them to becontrolled from mission control," Herring said.

In such acontingency, Discovery or any future shuttle would land at WhiteSands Missile Range in New Mexico, NASA said.

"We wouldnot target a landing site at KSC or Edwards Air Force Base [in California]," Herring said. "The prime landingsite would be at White Sands because of the wide expanse of the range."

  • Gallery: Shuttle's First Flight
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