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An inflatable heat shield was successfully tested, demonstrating for the first time that light, flexible devices could be used to protect a spacecraft as it enters the atmosphere at hypersonic speeds. The outside of the shield is made of several layers of 3M’s Nextel heat-resistant fabric woven from thin strands of ceramic. This covers several layers of DuPont’s Kapton heat resistant film and several layers of Kevlar, all of which surrounds an inner pouch of silicon-coated Kevlar that gives the shield its balloon-like shape. NASA sent a prototype of the new shield, called the Inflatable Re-entry Vehicle Experiment, to an altitude of 131 miles (211 km) on a small rocket from agency’s Wallops Flight Facility on Wallops Island, Va. It was the first successful test of an inflatable heat shield. Other spacecraft use solid heat shields that either drop away as the spacecraft near the surface, as happened with the Mars rovers, or gradually erode in the atmosphere. But these solid shields are heavy, and their weight limits the mass of the spacecraft they are designed to protect, since both must launch on the same rocket. Their physical size is also limiting, since the shields must be small enough to fit inside a launch rocket. “It’s like if you’re swinging a ping-pong paddle through the air edge-on, and then you turn it sideways,” says principal investigator Neil Cheatwood of Langley Research Center. “That is spreading your energy across more area. The whole item, whether it’s a ping-pong paddle or an inflatable, is all exposed to the air.” The team hopes to subject the shield to higher temperatures during the next flight test – at a higher altitude – in early 2012. |