's open-ended technology-development program has logged its first major flight test, sending an inflatable heat shield through a suborbital parabola that subjected it to 1,000F temperatures as it plunged back into the atmosphere. The flight of the third Inflatable Reentry Vehicle Experiment (IRVE-3) could help pave the way for future exploration missions to the surface of Mars by lowering the weight needed to shield robotic and eventually human explorers from the heat of entry into the planet's thin atmosphere.
Nearer term, IRVE could also shape commercial vehicles designed to return scientific samples and failed hardware from the International Space Station to Earth for analysis.
“Potential applications also include recovering launch vehicle assets,” says Neil Cheatwood of's , the IRVE-3 principal investigator. “We have actually had conversations with more than one of the vendors about looking at whether this could help there.”
The 680-lb. flight demonstration payload lifted off at 7:01 a.m. EDT July 23 from, Va., atop a three-stage Black Brant sounding rocket that carried it to an altitude of 253 nm. The payload's onboard control system flipped it over and inflated its concentric-ring structure with nitrogen into a 10-ft.-dia. aeroshell covered with a four-layer thermal blanket (see photo).
The blanket—an outer layer of ceramic-fiber Nextel, two layers of silica Pyrogel and a gas barrier to prevent burnthrough—protected the inflated structure as it reentered the atmosphere at speeds on the order of Mach 10, which generated outer temperatures of about 1,000F and mechanical loading of about 20g.
“We saw a more energetic entry than we were expecting,” Cheatwood said in a post-flight press conference. “We saw about 15 watts per centimeter squared of heating. But our thermocouples actually showed a little bit lower temperatures than we would expect in response to that.”
The testbed splashed down about 20 min. after launch off the North Carolina coast, where it was spotted from the air floating on the ocean surface. A U.S. Navy high-speed Stiletto boat was dispatched to locate and retrieve the experiment for analysis, but the equipment apparently sank before the Navy arrived. A NASA spokesman says no data were lost with the testbed, beyond a chance to inspect it for wear and tear. Cheatwood says telemetry data were solid, at least on an initial look.
So far there have been no formal expressions of interest in the technology for scientific space probes or recovery of samples and hardware from the ISS, although Cheatwood says NASA may offer it in future announcements of competitions for New Frontiers and Discovery missions. Meanwhile, the IRVE team will continue working on the ground to find better thermal-protection materials in an effort to raise its capability while lowering the payload weight.
At present there are no more flight tests planned in the nine-year-old project. If that changes, Cheatwood says one concept would involve using ISS garbage as ballast for a test of an inflatable heat shield returning from the station.
NASA was limited by the 22-in. diameter of the Black Brant nose cone, and also would like to increase the diameter of the inflated heat shield to gain more drag on reentry. At Mars, the more drag an aeroshell can provide on entry, the more surface is opened up to landings because an entry vehicle could be slowed more rapidly to the point where parachutes can be deployed in the thin atmosphere.
Beyond the data collected for future exploration and perhaps commercial operations, the test flight begins a process of developing enabling technologies before they are actually needed, an approach favored by President Barack Obama's NASA appointees over the mission-driven technology-pull approach used in the past.
“We're going to be doing many more tests just like this over the coming months and years,” says James Reuther, deputy director of NASA's Space Technology Program.