A 5,000-pound, GPS-guided GBU-72–an envisioned follow-on to the Raytheon Technologies’ [RTX] GBU-28 “bunker buster”–had its first release on July 23 and another successful firing from a U.S. Air Force 96th Test Wing F-15E flying at 35,000 feet over the Eglin AFB, Fla., range on Oct. 7, Air Force Materiel Command (AFMC) said on Oct. 13.

The GBU-72, fitted with a BLU-138 warhead and a Boeing [BA] Joint Direct Attack Munition (JDAM) tail kit, is a new start munitions procurement in fiscal 2022. The service has requested $36 million for 125 GBU-72s in fiscal 2022 and may build 500 such munitions. The BLU-138/GBU-72 is the result of a 2014 Hard Target Munitions (HTM) Analysis of Alternatives (AoA) and has been in development by the Air Force since 2017.

Tracy Woodard, chief of the Direct Attack Division of AFMC’s Armament Directorate, wrote in an Oct. 14 email that “depending on fiscal authorization (new start) and pricing received from competition, the Air Force plans to buy between 80 and 125 [GBU-72s] in FY22.”

Albuquerque-based Applied Research Associates, Inc. (ARA) was the prime contractor for the BLU-138 test warhead, and Pittsbugh-based Superior Forge and Steel, and Cincinnati-based Faxon Machining were subcontractors, per Woodard. The Air Force is expected to issue a solicitation in the coming months for the BLU-138/GBU-72 production versions.

The Air Force has used the GBU-28 dating back to Operation Desert Storm in 1991. Capable of carriage on the Northrop Grumman [NOC] B-2 stealth bomber and the Boeing [BA] F-15E, the service used the munition during the Kosovo air war in 1999 and more recently during the conflicts in Afghanistan and Iraq.

The BLU-138/GBU-72 “Advanced 5,000lb Penetrator (A5K) has optimized performance against the HTM AoA priority target set of tunnels and bunkers,” per the Air Force fiscal 2022 budget request. “With enhanced survivability, increased lethality, smart fuzing and utilization of fielded JDAM navigation tailkits, the GBU-72 significantly improved performance reducing the number of weapons required to achieve a kill at lower AUR [all-up-round] cost.”

The test goals for the GBU-72/BLU-138 since the first test on July 23 “were to show the weapon could safely release from the aircraft and validate a modified 2,000-pound joint-direct-attack-munition tail kit’s ability to control and navigate a 5,000-pound weapon,” AFMC said. “The test series, deemed a success by the Armament Directorate’s Direct Attack Division, consisted of three flights. Those flights and drops were made much more complex since this was the first GBU-72 release.”

The Air Force has said that it designed the GBU-72 by using modeling and simulation for the performance parameters of survivability, lethality, accuracy and penetration and that “the government determined the optimum A5K design to manufacture production representative prototypes to include warheads, fuzes and modified JDAM kits.”

In the Oct. 13 AFMC statement, James Culliton, the GBU-72 program manager, said that such modeling and simulation is expected in designing all future direct attack weapons.

GBU-72 “lethality is expected to be substantially higher compared to similar legacy weapons like the GBU-28,” per AFMC.

The munition is to undergo further JDAM integration flight testing and developmental and operational testing next year, AFMC said.