Air Force Basic Research Key to Successful Supersonic Bomb Release

  • Published
  • By Molly Lachance (Anadarko/CIBER)
  • Air Force Office of Scientific Research
ARLINGTON, Va. --  An Air Force Office of Scientific Research (AFOSR)-funded program was crucial to the successful supersonic test release of an MK-82 Joint Direct Attack Munition (JDAM) from a weapons bay at Mach 2, or two times the speed of sound.

It was the first successful test release of any air delivered munition at this speed.

Researchers from the Air Force Research Laboratory (AFRL) and The Boeing Company conducted the test on a rocket sled at the 10-mile Holloman High Speed Test Track in New Mexico. They did so for a program called High Frequency Excitation Active Flow Control for Supersonic Weapon Release, or HIFEX.

Solving the supersonic weapon dispense problem involved stabilizing the air flow within the weapons bay as well as initiating a proper nose-up release trajectory. If these two conditions could not be met, the supersonic weapon release would be unsteady and therefore, unpredictable.

The HIFEX researchers needed a way to stabilize the weapon during release at such high speeds. They found an answer in a supersonic micro-jet actuator array, developed during an AFOSR program that sought a solution to a different problem.

In 1999, AFOSR awarded funding to researchers at the Florida A&M University and Florida State University (FAMU-FSU) College of Engineering--one of only a few research institutions supported through the congressionally funded, Historically Black College and University (HBCU) program. The research, initiated by Dr. Anjaneyulu Krothapalli and subsequently led by Dr. Farrukh Alvi, explored the use of supersonic micro-jets for flow control in applications associated with Short Takeoff and Vertical Landing (STOVL) aircraft.

In their flow control approach, the team arranged supersonic micro-jets, or nozzles, around a STOVL jet flow to minimize disruption at takeoff and landing.

To complement the expertise provided by Dr. Alvi's team, Dr. Anuradha Annaswamy of the Massachusetts Institute of Technology joined the effort and helped develop the control scheme used to dictate how and when the micro-jets would fire.

As Dr. Alvi's team was perfecting the results of its supersonic micro-jet research, the Defense Advanced Research Projects Agency (DARPA) began the HIFEX program, which emphasized more advanced flow control approaches.

Not long after the program began, DARPA requested that the FAMU-FSU team, in collaboration with Dr. William Bower of The Boeing Company, apply their micro-jet research to help achieve safe weapon dispense at supersonic flight speeds.

The supersonic micro-jet actuator array developed for STOVL applications proved to be a workable solution. The team found that when placed upstream of the weapons bay, the micro-jets reduced the unsteady pressures inside the bay and modified the flow outside the bay to ensure that the JDAM test vehicle flew out of the rocket sled on a proper nose up trajectory.

As a part of the new program, Dr. Alvi's team tested a 2 percent scale weapons bay model using a supersonic wind tunnel built for the program. They later conducted extensive testing of a 10 percent scale model at Boeing's Polysonic Wind Tunnel.

HIFEX transitioned from DARPA to AFRL as the project matured to a full-scale rocket sled demonstration. The researchers will conduct additional full-scale JDAM tests at Holloman Air Force Base in the near future.

"This work is a great example of the broad applicability of basic research and technology transition from the university setting to more applied efforts," said Dr. John Schmisseur, AFSOR program manager. "It also shows the strength of the research capabilities at FAMU-FSU, which in this case led the efforts of a team with members from a leading national research university."