THOR

THOR (launch configuration) [NASA]

THOR (heatshield deployed) [NASA]

THOR (Terrestrial HIAD – Hypersonic Inflatable Aerodynamic Decelerator - Orbital Reentry) is a mission to 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.

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 Cygnus 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 use the existing IRVE-3 Built-To-Print centerbody, containing a duplicate of the IRVE-3 inflation system, CG offset system, avionics, and attitude control system (ACS). These systems will be somewhat modified to accommodate a 3.7 m diameter inflatable aeroshell fabricated using second-generation HIAD structural and TPS materials. The improved structure can handle higher temperatures than the previous designs while maintaining structural performance. Initial load tests indicate that it will be able to handle deceleration loads with adequate margin while inflated to approximately 105KPa (15psi). The improved TPS has been shown in ground testing to be capable of handling cold wall heat flux profiles peaking at 65W/cm², with longer test durations than the THOR reentry. The THOR aeroshell will be fabricated with a 70° half-cone angle, instead of the 60deg angle used on the previous flights, to demonstrate the stability and drag differences between the two geometries and somewhat offset the increased inflation volume of the larger diameter vehicle. The larger aeroshell diameter requires an additional structural toroid, as well as a slight increase in the minor diameter of each toroid.

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 a Black Brant-11 sounding rocket. It entered Earth's atmosphere at 10 times the speed of sound and easily survived temperatures of 250°C 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°C.

THOR will be released from the Antares-230 launch vehicle, where it is sidemounted on the second stage, after second stage burnout and orbital injection and will perform a deorbit burn before having completed a full orbit. The HIAD will coast for several minutes, discard the shell with the retro motors and then, two to three minutes before reentry, the aeroshell will inflate. It will pump up to a size of 3.7 meters 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.

THOR was cancelled.