AFRL research key to successful supersonic bomb release Published June 3, 2008 By Molly Lachance Air Force Office of Scientific Research ARLINGTON, Va. -- Air Force Research Laboratory-funded research of active flow control capabilities ultimately played a crucial part of the first-ever supersonic test release of an air-delivered munition. The successful event--which demonstrated the safe release of an MK-82 Joint Direct Attack Munition (JDAM) test vehicle from a weapons bay at Mach 2, or twice the speed of sound--occurred at the 10-mile-long Holloman High-Speed Test Track, Holloman Air Force Base, N.M. The research team completed the effort as part of AFRL's High-Frequency Excitation Active Flow Control for Supersonic Weapon Release program, otherwise known as HIFEX. In seeking a reliable way to stabilize the weapon on the rocket sled throughout the high-speed release, the researchers turned to a supersonic microjet actuator array developed for an earlier AFRL program. The microjet technology was a direct result of the lab's 1999 funding of researchers at two different Florida universities--Florida A&M University and Florida State University (FAMU-FSU) College of Engineering. The academic research explored the use of supersonic microjets for flow control in applications associated with short takeoff and vertical landing (STOVL) aircraft. The Florida-based team's specific flow control approach involved the arrangement of supersonic microjets, or nozzles, around a STOVL jet flow to minimize disruption at takeoff and landing. A team from the Massachusetts Institute of Technology joined the effort and subsequently helped to develop the control scheme governing how and when the microjets would fire. Not long after this AFRL-sponsored endeavor began, the Defense Advanced Research Projects Agency--as the initiator of the HIFEX program--requested that the FAMU-FSU team collaborate with Boeing to apply the microjet research towards the HIFEX goal of achieving safe weapons dispense at supersonic flight speeds. The supersonic microjet actuator array originally developed for STOVL applications proved a workable solution for high-speed munitions release as well. Specifically, the research team found that placing the microjets upstream of the weapons bay reduced unsteady pressures inside the bay and modified airflow outside the bay, ensuring that the JDAM test vehicle flew out of the rocket sled on a proper nose-up trajectory. The HIFEX program transitioned from DARPA to AFRL as the effort matured to a full-scale rocket sled demonstration. Researchers will conduct additional full-scale JDAM tests at Holloman AFB as further developments occur.