Five years after NASA's shuttle Columbia disintegrated during reentry and killed seven astronauts, the agency looks to test new safety features even beyond the upcoming launch of the Atlantis orbiter.
Columbia was lost in 2003 after a piece of foam insulation fell off the external fuel tank and struck the shuttle's wing during launch. That allowed hot gas to seep into the wing as the shuttle later reentered the atmosphere, with catastrophic results. NASA spent the next two and a half years and $1.4 billion preparing its remaining space shuttles for a return to flight.
"Unfortunately, none of us will ever really know how much damage occurred on Columbia," said Steve Poulous, NASA's orbiter project manager. "But we believe that if damage were to occur today, we have the capabilities and tools to deal with it."
One such tool acts as a caulking gun that can fill cracks between the shuttle's heat tiles and door seals. Called a Tile Repair Ablator Dispensor, T-RAD mixes two compounds together to form a pink, goo-like material.
Shuttle Atlantis will carry T-RAD as a safety precaution when it launches Feb. 7, but astronauts on the following STS-123 mission — slated to lift off no earlier than March 11 — will test the device on some spare damaged tiles.
Poulos noted some arguments about whether the T-RAD material will "come out in a foam-like fashion" in the vacuum of space, as opposed to its usual consistency of "toothpaste or peanut butter." NASA ran a series of tests under vacuum conditions on Earth, without seeing a change in the pink goo.
"My personal expectation is that it's going to perform in orbit exactly as we've seen on the ground," Poulos said.
Finding spots that need repair is another matter. Each shuttle now performs a "Rendezvous Pitch Maneuver" upon approach to the International Space Station by flipping 360 degrees, allowing the station crew to photograph virtually the entire vehicle.
The next part of shuttle inspection involves the Orbiter Boom Sensor System (OBSS), a 50-foot pole with cameras and laser sensors that deploys after the shuttle docks with the space station. The shuttle's robotic arm grabs one end of the pole and scans along the edges of the wing and the nose cap — not unlike waving a wand over an airport passenger.
"It takes about six hours to do," said Stan Love, STS-122 mission specialist, in a NASA interview. "It's a long day. We'll rotate four of our crew members through it, so just about everybody gets a shot."
Continuous practice since Columbia has allowed both astronauts and NASA analysts on the ground to move more smoothly through the choreography of safety inspections.
"As people become familiar with tools and the data we're getting, what took 36 hours on the first flight now takes anywhere from 12 to 24 hours," Poulos said.
NASA also continues to redesign the shuttle's external tank in order to prevent possible damage in the first place.
Air bubbles inside the foam insulation can build up pressure under some circumstances and cause foam pieces to pop off, according to John Chapman, NASA's external tank project manager. The aerodynamic pressure of a shuttle launch may also reach into small cracks to detach loose pieces of foam.
Solutions involve spraying foam on so that air bubbles don't form, or removing unnecessary foam blocks. Electric heaters now warm the attachment points between the shuttle and external tank to keep them ice-free, replacing the large foam blocks such as the one that fell off and doomed Columbia.
A new external tank modification will similarly remove excess foam from the ice frost ramps that protect the brackets between the vessel's external plumbing lines and orange exterior, although Atlantis and the following shuttle mission will use the older version of the tank. That upgrade, which will replace the brackets with new versions built from titanium, is expected to debut during the planned April launch of the shuttle Discovery, NASA engineers have said.
"We're not in a rest-on-our-laurels position," said Chapman. "We look at data from each and every flight, and incorporate that into tank design and production."