Aerospace Sciences

Successful flight experiments provide new hypersonic insights

The Thermophysics Technical Committee promotes the study and application of mechanisms involved in thermal energy transfer and storage in gases, liquids and solids.

In July, DARPA and the U.S. Air Force completed the second successful test flight with a Hypersonic Air-breathing Weapon Concept, HAWC. This variant, which was flown successfully for the first time in 2021, consists of a missile by Raytheon Technologies and a Northrop Grumman scramjet. During the flight, the first stage boosted the missile to the expected scramjet ignition envelope. The scramjet engine ignited and propelled the missile to speeds greater than Mach 5. It traveled over 300 nautical miles (555 kilometers) and reached altitudes higher than 60,000 feet, according to DARPA’s press release. The test met the primary objectives of vehicle integration and release sequence, safe separation from the launch aircraft, booster ignition and boost, booster separation and engine ignition, and cruise. HAWC was designed to use a widely available hydrocarbon fuel, and since it uses air for combustion, it does not have to carry the added weight of an onboard oxidizer. These key attributes allow for a safe, efficient and tactically sized, long-range hypersonic weapon. The second HAWC design was flown for the first time in April. This Lockheed Martin-built missile was accelerated to speeds over Mach 5 by the Aerojet Rocketdyne scramjet and traveled a similar distance and altitude as the Raytheon variant. 

At an AIAA Aviation forum special session in June, scientists at NASA’s Ames Research Center in California and NASA’s Langley Research Center in Virginia presented the results of their airborne observations of the Hayabusa2 sample capsule’s reentry. For the dominant atomic line transitions measured, NASA simulations agreed very well with the flight data over most of the trajectory. This agreement is unprecedented for observation campaigns and was attributed to the improved measurement quality and enhanced coupled multiphysics modeling. Launched in 2014 by the Japan Aerospace Exploration Agency, or JAXA, Hayabusa2 deployed an impactor that created a small crater in the near-Earth asteroid Ryugu and collected samples for return to Earth. NASA, in collaboration with JAXA and the Australian Space Agency, led an airborne observation campaign with two Gulfstream III aircraft, each equipped with a suite of optical instruments, to image the atmospheric passage of the Sample Return Capsule, which entered Earth’s atmosphere at 11.6 kilometers per second in December 2020. NASA researchers used data gathered in the observation campaign to simulate these measurements and verify their computational tools. The lessons learned will inform the modeling of reentry environments, thus improving designs of future atmospheric entry systems.

In January, the University of Kentucky presented the first set of flight data from the Kentucky Re-entry and Universal Payload System capsules. The experiment marked several firsts, including the first time a U.S. university flew a vehicle that traveled at hypersonic speeds, the first time a university-built entry capsule transited a planetary atmosphere, and the first entry mission featuring a 3D-printed heat shield. Students at the University of Kentucky developed the three low-cost KRUPS space capsules to collect flight data during reentry. The capsules’ heat shields were equipped with thermocouples to measure surface temperatures, which were transmitted during entry in December 2021 after release from the International Space Station. One of the capsules’ heat shields was fabricated from LI-2200 tiles, the same material that comprised the space shuttle orbiter heat shields, fabricated at NASA Ames. The heat shield for the other capsule was a novel 3D-printed design developed by researchers at NASA Ames, Oak Ridge National Lab in Tennessee and NASA’s Johnson Space Center in Texas. The temperature measurements recorded over a nine-minute span will help scientists build better thermal protection systems and improve the reliability of current design tools. The next flight campaign will test new instruments and new TPS materials, and aim to collect shock-layer data during hypersonic entry.  

Successful flight experiments provide new hypersonic insights