MAGNA — It looks like a flat, dark disk with a large steel anchor bolt through it. As unassuming as it appears, this device could be key to protecting the lives of space shuttle astronauts.
The device is a patch, designed by ATK Thiokol in Utah and built by a subcontractor, which can repair damage to the leading edge of the shuttle's wing.
In January 2003, the shuttle Columbia was damaged during liftoff when a piece of lightweight insulation foam struck that crucial section of its left wing. At the end of its 16-day mission, as Columbia was descending at high speed toward its landing runway, superheated air ate into the wing and broke apart the shuttle. Columbia's seven crew members perished.
For more than two years, while the rest of the shuttle fleet has been grounded, NASA and contractors have worked to make the flights safer. Space Shuttle Discovery is poised to thunder into orbit sometime between July 13 and July 30, in what NASA calls the "Shuttle Return to Flight," launch number 114.
As with all its flights, the spacecraft will be powered toward orbit by two gigantic boosters built in Utah by ATK Thiokol. But this time it will carry an additional Thiokol innovation, a set of the specialized wing patches.
For STS-114, patches will be demonstrated in what's called a design test objective, rather than supplied in an actual repair kit.
"We don't intend to use it outside on the orbiter" during that flight, said Mike Kahn, Thiokol vice president for Space Launch Systems. Instead, astronauts will demonstrate they can assemble the patch in the weightlessness of orbit.
The July flight will carry 12 patches, differing in their curvature to match different parts of the wing. In later flights, the shuttle will carry a tool kit of 30 to 50 of the patches, plus the equipment to install them and keep them in place.
Shortly after the Columbia tragedy, NASA began putting together a team to design a way shuttle astronauts can repair the wing's leading edge, which is made of RCC or "reinforced carbon carbon" material.
"They originally just went to the folks working on the orbiter" for team members, Kahn said during an interview in his office in Thiokol's Magna facilities. Because the company builds solid rocket boosters and did not work on the orbiter itself, its experts were not named to the team.
However, Thiokol approached NASA "and reminded them that almost all rocket motors have nozzles and the nozzles are made out of carbon," he said.
Thiokol builds nozzles able to withstand the searing, 5,600-degree heat of rocket blasts. The shuttle's wing, and any patch, must be able to stand up under heat generated by atmospheric friction during re-entry — 3,000 degrees.
"We actually have a lot of experience with carbon materials and high temperature," Kahn said. "We thought we could probably adapt some of our carbon materials that we use in nozzles to be a repair material."
Thiokol experts joined the team, and soon the company began testing "dozens and dozens of different carbon materials."
Within about six months they had found a carbon material that would do the job.
For more than a year, experts have been testing the material in NASA arc-jet facilities that re-create the fiery conditions of re-entry. The material passed the tests.
Another challenge was to determine how many of the patches, which are five or six inches across, would be needed to fix different sized holes on a shuttle wing. Also, they had to deal with the contours of the wing's leading edge, which varies from place to place.
The engineers "developed a thinner patch that can actually flex," Kahn said. That allows a patch to be used in several locations on the wing. Probably 40 or 50 different patch shapes can cover almost any part of the wing's leading edge.
An inspection system also will be tried out on the July flight. Using a camera on the end of the shuttle's boom, astronauts will check for damage to the wing or heat tiles before they return from orbit. (Replacing tiles is a different project.)
If they find a hole in a wing, they will use a patch or patches that conform to the wing's curvature.
An astronaut adjusts the patch to the shape of the wing, holds it in place, then pushes a bolt through a center hole in the patch. The bolt is like a big version of the anchor bolts used to hang pictures on a wall. Instead of steel, it's made of a special heat-resistant molybdenum alloy.
The astronaut cranks the bolt with a specialized mechanical screwdriver. Inside the wing, the bolt's two arms extend until they lock into place on the underside of the RCC material. A torque setting on the tool indicates when the patch is clamped on tight.
Astronauts were part of the development team, making sure the patch works as simply as possible. They have already shown they can operate the device on the ground wearing fat spacesuit gloves. It's also been tested in a vacuum chamber and on flights of NASA's KC-135 aircraft, which can briefly simulate weightlessness.
Now it's time to do a final check inside the shuttle while in orbit.
"We don't expect anything unusual, but we do want to do an experiment on board," Kahn said.
Everyone involved hopes the patches will never be needed. But if another incident damages a wing, they'll be ready.
E-mail: bau@desnews.com