Why the space shuttle can withstand reentry temperatures up to 2,300 degrees.
- By Damond Benningfield
- Air & Space magazine, May 2006
(Page 2 of 2)
Until recently, damaged tiles could be repaired only after the shuttle returned to Earth. That is about to change. Although the 2003 Columbia accident was caused by debris shed from a reinforced carbon-carbon panel on the wing’s leading edge, the accident investigating board recommended, among other things, that NASA give the astronauts the capacity to perform “on orbit” repairs to the shuttle’s exterior, including its tiles. The agency has developed two solutions.
The first is called an emittance wash—a material that looks like shoe polish and consists of silicon carbide fibers mixed with the glue that bonds the tiles to the orbiter. Ground tests indicate that the material can increase the amount of heat that a damaged tile radiates by about 70 to 160 degrees. An astronaut on a spacewalk would dab the wash on a damaged tile with a tool that looks like a shoe polish applicator.
Last summer, astronauts on the STS-114 mission tested the system on a tile during a spacewalk. “The crew was able to use the tool without incident or concern,” says Steve Poulos, NASA’s former manager of the shuttle’s thermal systems.
Engineers are completing ground tests of how the wash would perform with different types of tile damage. “It’s not a panacea,” Poulos says, but the wash can make a marginal tile safer.
For bigger dings, astronauts may bolt on a 12- by 25-inch plate of carbon-silicon carbide composite. The plates are just .03 inch thick but are expected to provide the same thermal protections the original tiles did.
Currently, NASA plans to include both the plates and the emittance wash on the next shuttle mission: a Discovery flight, now scheduled for May. Says Poulos: “I’m very optimistic that by the end of this year, we’ll have our repair capabilities done.”