“Science Friction” - Beating the Heat of Atmospheric Entry
NASA’s Office of the Chief Technologist (OCT) is taking head-on the blistering heat loads encountered during atmospheric entry of spacecraft in a novel way. Visualize using high-strength, temperature thwarting, and flexible materials to create a heat-resistant, inflatable decelerator!
That’s the idea behind OCT’s Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project. Now being prepared for a demonstration flight under the HIAD initiative is the Inflatable Reentry Vehicle Experiment Three, or in NASA lingo, IRVE-3. IRVE work is one endeavor within OCT’s Game Changing Development program.
This technology would be ideal for use on a number of proposed NASA missions, from Mars, to Venus, or even Titan, a moon of Saturn. Nearer to home, quite literally, HIAD-inspired know-how can be applied to returning payloads heading for Earth that are dispatched from the International Space Station.
“If a planet has an atmosphere…we can use it,” says F. McNeil (Neil) Cheatwood, Principal Investigator for the IRVE program at NASA’s Langley Research Center in Hampton, Virginia.
The objective of the upcoming suborbital test flight of IRVE is to show that a spacecraft hot footing its way back to Earth can use an inflatable heat shield—or aeroshell—to slow and protect itself as it enters the atmosphere at hypersonic speeds.
Likewise, an inflatable heat shield would not be constrained by the fairing diameter of a launch vehicle, translating into a larger, more capable payload that can be flown.
Now being readied for its high altitude shot above Earth, IRVE-3 will be launched from NASA’s Wallops Flight Facility near Chincoteague Island, Va.
IRVE is to be vacuum-packed into the payload shroud of a powerful three-stage Black Brant 11 sounding rocket. At high-altitude, IRVE will be inflated by nitrogen to take on its mushroom shape; a ready-for-re-entry-contour made of layers of silicone-coated industrial fabric.
IRVE’s shape is controlled by the inflation of beams—polyurethane bladders covered with a polyester braid—much like a bicycle tube and tire. Several minutes after liftoff, IRVE will start its heat-defying plunge toward Earth making use of an outer heat shield material made of thermal resilient Nextel™ ceramic fiber.
“We have tested IRVE’s thermal protection system in a number of facilities,” Cheatwood explains. “We’ve demonstrated on the ground that IRVE 3 can handle a lot more than it is going to be seeing for real…the heat rate coupled with the pressure force and other factors.”
Basically, IRVE-III’s imminent journey will make use of the Earth’s atmosphere as a wind tunnel in the sky.
Taking the Heat Pulse
Earlier testing of the IRVE involved a successful suborbital flight in August 2009.
“We demonstrated that IRVE was stable when we inflated it to shape,” Cheatwood recalls. “It behaved like a rigid blunt body of the same shape…and we made it through the heat pulse.”
This time, IRVE 3 is a slightly different system, crafted to push the technological boundaries and further validate that an inflatable spacecraft heat shield is feasible.
Gazing into the future, Cheatwood is buoyant on where the IRVE test flights can lead.
For one, far more precise landings on Mars of robotic craft are feasible. He adds that the technology is envisioned to be scalable for piloted expeditions to Mars.
Adopting inflatable heat shields could lead to landing more mass on the red planet at higher surface elevations. The larger the diameter of a protective aeroshell, the bigger the payload can be.
Then there is the prospect of returning mass back to Earth from the International Space Station.
“The nice thing is that you can scale this within reason. We’ve got a couple of knobs to turn,” Cheatwood adds. “But for now, flying is really what you’ve got to do before you have full-confidence in this technology. And that’s what we’re doing.”