September 14, 2012
Alien Soil Could Be Used For Future Heat Shields
Lee Rannals for redOrbit.com — Your Universe Online
If all goes well in the next test, alien soil could be a key ingredient to a new generation of heat shield being developed.Scientists are about to start an important test next week to see if whether a heat shield made up of soil from the moon, Mars or an asteroid would be able to protect a spacecraft from Earth's atmosphere.
NASA is looking into the possibility of creating a heat shield with alien soil so that future spacecraft could leave Earth without carrying a heavy heat shield, but instead it would create one on another world and ride it home safely.
Being able to shave off the extra pounds opens up new possibilities ranging from using smaller rockets to carrying more supplies on an exploration mission.
Michael Hogue, a researcher at NASA's Kennedy Space Center in Florida, came up with the idea during a brainstorming session last year, the space agency said. They were discussing how to use extraterrestrial soil, which is known as regolith.
"Others were talking about how regolith can be used to make bricks or landing pads and I said, 'Well, if it's good for that, why can't it be used to make atmospheric entry heat shields?' " Hogue said in a press release.
Engineers have been trying out various mixtures and techniques to find out whether the idea has any potential, and so far tests have been very successful.
"I expected some to fail," Hogue said in the release. "There is an optimum range of density you need to hit for each material where it's light enough to have low enough thermal conductivity, but also structurally strong enough to survive the forces of atmospheric entry. All of our formulations that we tested with a cutting torch at least passed that."
The bricks created by the team, which are made up of a different combination of materials, will be facing their toughest test so far next week. Engineers will be placing them inside the arc jet facility at NASA's Ames Research Center to send a scorching plasma stream across them. This will test out the durability of the bricks in conditions similar to those a spacecraft faces in reentry.
Although the new concept is promising, NASA said that it is far from becoming operational at this point. It is currently a one out of nine on the technology readiness scale.
The team will have to take the concept through a series of evaluations, adaptations, inventions and tests, including a sample disc being placed on the bottom of a cargo spacecraft returning from the International Space Station.
Hogue said his attitude towards the project has gone from being a skeptic, to a hopeful enthusiast.
NASA said that in order to make the heat shield in space, a robotic device or automated system would have to be developed. The spacecraft would have to mix the regolith with a rubbery substance in a mold or heat a large disc of regolith until the soil elements fuse together.
Another advantage of using regolith as a heat shield is that with the low gravity found on places like an asteroid or a moon, it would be easier to lift the spacecraft off the ground regardless of the extra weight.
"You can make it massive and if it heats up and ablates off, all the better because the ablated mass takes heat with it." Hogue said in the release. "After about five minutes you jettison the shield over water and you're done."