From left, John Hile, an Arnold Engineering Development Complex (AEDC) test engineer, explains how an arc heater works to Sen. Bill Hagerty of Tennessee during a visit by the senator to the headquarters of AEDC, Arnold Air Force Base, Tenn., Aug. 23, 2021. Arc heaters allow for the testing of thermal protection systems in simulated environments representative of hypersonic flight. (U.S. Air Force photo by Jill Pickett)