Feature Interview with Principal Investigator Dr. Neil Cheatwood.
IRVE-3 Data Download
The future of inflatable heat shields got a solid boost in July, when the Inflatable Reentry Vehicle Experiment-3 (IRVE-3) was hurled spaceward on July 23, 2012, riding atop a sounding rocket launched from NASA’s Wallops Flight Facility on Wallops Island, Va.
Inflatable aeroshell technology could find use within the International Space Station program, as well as improve the capability of placing large payloads onto the distant landscapes of Mars or any outer space destinations with an atmosphere.
High into the sky over the Atlantic Ocean, the three-stage Black Brant XI sounding rocket took roughly six minutes to climb 280 miles (450 km) above the Earth. IRVE-3 separated from its booster stage, fully pressurized itself, and then plunged back through the atmosphere. The experimental craft splashed down in the Atlantic Ocean about 20 minutes after liftoff.
“The experiment went perfectly. We couldn’t have asked for better,” says Dr. F. McNeil (Neil) Cheatwood, Principal Investigator for the IRVE program at NASA’s Langley Research Center in Hampton, Va.
IRVE-3’s flight was the third attempt in a series of tests to gather critical data to further NASA’s development of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This research is actively underway, supported through NASA's Space Technology Program.
Cheatwood observes that data gleaned from the instrumented IRVE-3 suborbital trip was outstanding. “When we do tests on the ground, while they are very important, we can’t simulate all the parameters together. IRVE-3 delivered extraordinary data which should allow us to characterize the overall system performance and calibrate our engineering tools.”
IRVE-3 is essentially a stack of high-tech inner tubes (or doughnuts) that are covered by layers of heat resilient Nextel™ ceramic fabric and pyrogel insulation. An on-board system pumped the inner tubes full of nitrogen, stretching the woven blanket over them to create a heat shield, also known as an aeroshell. That heat shield protected a payload that consisted of four segments including the vehicle’s inflation system, steering mechanisms, telemetry equipment and camera gear.
While outside the Earth’s atmosphere, IRVE-3 was fully pressurized in some three minutes, Cheatwood explains. “The inflation system worked great, just liked we had planned. Our leak rate was lower than we designed for, so we remained inflated far beyond our official end of experiment. As a result, we were able to conduct additional bonus maneuvers,” he adds, with the IRVE-3 aeroshell expanding to a mushroom shape nearly 10 feet (3 meters) in diameter.
Nose-diving through the atmosphere, IRVE-3 hit hypersonic speeds up to roughly 6,000 mph (2.7 km/s)! A center of gravity offset mechanism worked as planned, shifting the payload of the craft which caused the aeroshell to generate a lift vector.
The inflated structure entered Earth’s atmosphere at Mach 10— ten times the speed of sound. Temperatures experienced by IRVE-3 reached as high as 1,000 degrees Fahrenheit (roughly 540 Celsius) with the craft encountering forces of 20 G’s.
“We actually were able to track the vehicle all the way through the full mission,” Cheatwood says, from atmospheric interface, into the heat and pressure pulses, and through transonic into subsonic flight. IRVE-3’s attitude control system was rock solid throughout the flight, “a first step in demonstrating controllability in HIAD,” he notes.
In fact, Cheatwood points out, the craft’s attitude control system worked so flawlessly that enough onboard fuel remained to conduct “bonus maneuvers.”
HEART of the Matter
“We got our full set of data,” Cheatwood says. “You couldn’t ask for cleaner data.”
As for the future, Cheatwood says a follow-on flight is being considered, flying a larger IRVE on a similar suborbital trajectory. Supported by IRVE data, NASA is also investigating HIAD technology to deliver large payloads to higher elevations on Mars–areas heretofore unexplored by landed probes and where there’s evidence of recent water activity on the Red Planet.
The IRVE flight tests are also leading NASA to move forward on a High-Energy Atmospheric Reentry Test (HEART) concept. That initiative could make possible returning several metric tons back to Earth from the International Space Station, making use of an aeroshell of some 26 feet to 32 feet (7.9 meters to 9.8 meters) in diameter.
“The IRVE-3 flight really went beautifully,” Cheatwood concludes. “We are gathering invaluable data from these cost-effective flight tests.”