July 24, 2012
A spacecraft re-entering Earth’s atmosphere encounters temperatures as high as 1850 degrees Fahrenheit as it plummets downward at speeds approaching 7600 miles per hour. All this energy makes a robust shield to absorb the heat absolutely necessary to protect astronauts and equipment inside. But throughout NASA’s history, these heat shields—typically constructed out of rigid materials—have posed a safety issue, with brittle ceramic tiles responsible for the 2003 Columbia disaster.
Yesterday, NASA conducted a test of a novel approach to this problem: an inflatable fabric heat shield. Early yesterday morning, a rocket carrying a prototype launched 288 miles upward from NASA’s Wallops Flight Facility on Virginia’s Eastern Shore. After the experimental vehicle—known as the Inflatable Reentry Vehicle Experiment (IRVE-3)—was ejected from the rocket, the shield inflated according to plan and safely descended back to Earth over the course of about 20 minutes, landing in the Atlantic East of Cape Hatteras, North Carolina.
“Everything went like clockwork. The IRVE-3 performed just as it was supposed to,” said Neil Cheatwood, the principal investigator on the project. “It entered Earth’s atmosphere at Mach 10, ten times the speed of sound, and successfully survived the heat and forces of the journey.”
After three years in development, NASA’s research team created the innovative design, which is able to stand up to the stresses of space flight using lighter and more flexible materials. At launch, the shield is made up of a cone of uninflated rings of kevlar-woven fabric, all surrounded by a thermal blanket. During flight, the 680-pound heat shield separates from the launch rocket, and an inflation system pumps nitrogen into the unit until it forms a mushroom shape, with the upper cylinder roughly 10 feet in diameter.
“We like it when it looks simple,” said Carrie Rhoades, flight systems engineer. “It actually took quite a bit of work to get to where we are now. We have to do all kinds of different testing—in wind tunnels, high temperature facilities and laboratories.”
A previous experiment, IRVE-2, also successfully survived re-entry in August 2009, but with a much lighter payload and at much slower speeds. IRVE-3 experienced about 10 times as much heat, similar to what a heat shield would be expected to endure on an actual mission.
During the experimental flight, engineers closely monitored data from onboard cameras and thermometers to track whether the shield sufficiently protected from the craft from the immense amounts of heat generated. As they cheered the success, a high-speed U.S. Navy boat was dispatched to the splashdown area to retrieve the craft, so NASA personnel can study it for future missions.
NASA is conducting the tests to show that such inflatable designs could be used in the future to protect space capsules during planetary entry or descent and help return cargo to Earth from the International Space Station.” It’s great to see the initial results indicate we had a successful test of the hypersonic inflatable aerodynamic decelerator,” said James Reuther, deputy director of NASA’s Space Technology Program. “This demonstration flight goes a long way toward showing the value of these technologies to serve as atmospheric entry heat shields for future space.”
NASA plans to test increasingly-larger inflatable heat shields with other types of heat-resistant fabrics before eventually putting them to work on an actual mission. Next up is the High Energy Atmospheric Re-entry Test (HEART)—a concept design includes a larger heat shield, nearly 30 feet in diameter.
Using inflatable designs could allow for heat shields of significantly reduced sizes and weights—and consequently, spacecraft that can accommodate larger amounts of scientific equipment and life-sustaining supplies. NASA scientists predict the technology could be useful on future missions to anywhere with an atmosphere, including Mars, Venus, or even Titan, Saturn’s largest moon.
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