Tunnel 9 heater system expert passing along knowledge
Mike Metzger, a system engineer at AEDC Hypervelocity Wind Tunnel 9 in White Oak, Maryland, works on a project. Metzger recently marked his 40-year service anniversary at the White Oak facility and is among the few people familiar with the Tunnel 9 heater system. (U.S. Air Force photo by A.J. Spicer)