Northrop's HACM shows scramjet details

The U.S. Air Force awarded Raytheon Technologies a contract for the Hypersonic Attack Cruise Missile, or HACM, in September 2022 and described it as an air-launched, scramjet-powered hypersonic weapon built to hold high-value targets at risk from standoff range. Northrop Grumman is supplying the scramjet propulsion system for the weapon, according to company materials and DARPA statements on predecessor flight tests. A social-media thread this week revived interest in the program by circulating technical details about how HACM fits into the Pentagon’s broader air-breathing hypersonic effort. The core public facts are narrower than some online claims: the Air Force has confirmed the weapon uses a scramjet, and DARPA has published HAWC test results showing Northrop Grumman hardware in sustained hypersonic flight, but exact HACM performance figures remain undisclosed. (af.mil) ### How is HACM supposed to fly after launch? DARPA has described the HAWC concept as an air-launched hypersonic cruise missile that is first boosted into the right flight regime and then transitions to scramjet-powered cruise. In the 2021 HAWC test, DARPA said a Raytheon-built vehicle used a Northrop Grumman scramjet engine after release from an aircraft, with the engine compressing incoming air, mixing it with hydrocarbon fuel and igniting that airflow mixture in flight. (af.mil) The Air Force used similar language for HACM in its 2022 contract announcement, calling it “scramjet-powered” and air-launched. Northrop Grumman says scramjets can deliver speeds above Mach 5 while allowing a smaller missile form factor than some traditional designs, because the engine breathes atmospheric oxygen instead of carrying oxidizer for the full cruise phase. (darpa.mil) ### What do the public HAWC tests actually prove? DARPA said in 2022 that a third HAWC flight used a Northrop Grumman scramjet engine to propel the vehicle at speeds greater than Mach 5 for more than 300 nautical miles and above 60,000 feet. Andrew “Tippy” Knoedler, the HAWC program manager in DARPA’s Tactical Technology Office, said that test explored more of the vehicle’s flight and scramjet operating envelopes. (af.mil) A separate 2021 DARPA release said an earlier HAWC free-flight test also exceeded Mach 5 with a Northrop Grumman scramjet after air launch. Public U.S. government releases do not confirm the higher peak-speed figures that circulate online, and the available official record is limited to “greater than Mach 5” and other broad envelope details. ### Where does Northrop Grumman fit inside HACM? (darpa.mil) Northrop Grumman says its team was selected to develop the Air Force’s HACM in conjunction with SCIFiRE, the U.S.-Australia Southern Cross Integrated Flight Research Experiment. Company materials describe HACM as a “first-of-its-kind weapon” and identify Northrop’s role as providing the scramjet propulsion system while Raytheon serves as prime contractor on the Air Force award. (darpa.mil) In January 2024, Northrop Grumman said its Hypersonics Capability Center in Elkton, Maryland, would support HACM development and production and was designed for large-scale manufacturing of air-breathing propulsion, including ramjet and scramjet systems. That manufacturing push is one of the clearer public signs that the Pentagon’s air-breathing hypersonic work is moving beyond one-off demonstrations. (northropgrumman.com) ### Is HACM just HAWC under a new name? DARPA says HAWC was a joint DARPA-Air Force effort to demonstrate critical technologies for an affordable air-launched hypersonic cruise missile. DARPA’s newer MOHAWC program is intended to continue that work by expanding the scramjet operating envelope and creating technology on-ramps for future programs of record. (news.northropgrumman.com) The Air Force’s program of record is HACM. Public material links HACM to HAWC and SCIFiRE, but the government has not published a full set of operational specifications, target sets or final fielding timelines. DARPA’s MOHAWC page and the Air Force’s HACM program notices are the clearest official markers to watch for the next disclosed milestone. (darpa.mil 1) (darpa.mil 2)