NASA LaRC Flight Projects Directorate
THOR - Terrestrial HIAD Orbital Reentry
Inflatable spacecraft technology is one step closer to reality with the Terrestrial HIAD – Hypersonic Inflatable Aerodynamic Decelerator - Orbital Reentry, or THOR, flight test. THOR will test the heat shield capabilities of a second generation HIAD inflatable structure and flexible thermal protection system in an entry flight environment similar to that found on Mars. When inflated the THOR aeroshell looks like a 12-foot diameter child's stacking ring toy composed of giant braided, reinforced, high-tech fabric hoops lashed together – then covered by a thermal blanket made up of layers of heat resistant materials.
The project, which is led by NASA's Langley Research Center in Hampton, Virginia, for the Space Technology Mission Directorate, will use existing hardware and launch as a secondary payload on a cargo resupply flight to the International Space Station. The demonstration flight is targeted for September 2016 on an Antares rocket from Wallops Flight Facility on the Eastern Shore of Virginia. This flight will allow the project to test the structural and thermal performance capability against mission relevant flight loads.
THOR will be released from the Antares launch vehicle after second stage burnout and orbital injection and will perform a deorbit burn. The HIAD will coast for several minutes and then, two to three minutes before reentry, the aeroshell will inflate. It will pump up to a size of 3.7 meters – a little more than 12 feet - with an internal pressure of 15 PSI in preparation for entry. It will plunge through the high heat of the atmosphere into the Atlantic Ocean, with cameras recording video and sensors recording temperatures, heat flux and pressures. Some of the flight data will be sent to researchers on the ground as it is being recorded. The rest will be stored in a data recorder that will be ejected prior to water impact. A GPS transmitter will guide aircraft to the floating module for data recovery.
Many members of the THOR team worked on the successful 2012 Inflatable Reentry Vehicle Experiment (IRVE-3), which was part of the HIAD project. IRVE-3 was a 10-foot diameter aeroshell launched by sounding rocket. It entered Earth's atmosphere at 10 times the speed of sound and easily survived temperatures of 250 degrees Celsius - 480 degrees Fahrenheit - and forces of 20 G's. THOR will reenter Earth's atmosphere three times faster than IRVE-3 and as a result will experience three times more heating that is expected to penetrate past the surface into the structure. Temperatures are expected to reach 400 degrees Celsius or 750 degrees Fahrenheit.
A Hypersonic Inflatable Aerodynamic Decelerator could allow NASA to send more cargo - even people - to Mars, because it weighs less and can expand from being packed inside a rocket to accommodate larger payloads that can land at higher altitudes.