US Air Force performs final test on HAWC hypersonic scramjet missile

It was "an exclamation point to the most successful hypersonic airbreathing flight test program in U.S. history."
Chris Young
An artist's impression of the HAWC system.
An artist's impression of the HAWC system.

Lockheed Martin 

DARPA and the U.S. Air Force successfully carried out the final test of their scramjet-powered Hypersonic Airbreathing Weapon Concept (HAWC) missile, according to a press statement.

As Air & Space Forces Magazine points out, the U.S. Air Force recently decided to move forward with two hypersonic weapons — Lockheed Martin's AGM-183 Air-Launched Rapid Response Weapon (ARRW) and the Hypersonic Attack Cruise Missile (HACM) — while discontinuing the HAWC program.

The Air Force did, however, decide to finish scheduled HAWC tests, and DARPA's statement explains that "all primary objectives accomplished and program findings will now be used in follow-on efforts."

"The most successful hypersonic airbreathing flight test program in U.S. history"

The HAWC program used two prototype systems for its tests, a Lockheed Martin and Aerojet Rocketdyne missile and a Raytheon and Northrop Grumman system. The last test flight used the former version, which "again flew at speeds greater than Mach 5, higher than 60,000 feet, and farther than 300 nautical miles."

"This month’s flight added an exclamation point to the most successful hypersonic airbreathing flight test program in U.S. history," said Walter Price, an Air Force deputy for the HAWC program. "The things we've learned from HAWC will certainly enhance future U.S. Air Force capabilities."

DARPA hasn't released certain information, such as how much of the test was carried out traveling over speeds of Mach 5 using the scramjet system. The press statement did, however, state that the "latest flight demonstrated improved capabilities and performance."

How do airbreathing scramjet engines work?

The term hypersonic airbreathing refers to the design of scramjet engines, which take in air to mix oxygen from the atmosphere with hydrogen fuel.

Scramjet engines collect this oxygen as the aircraft or missile travels. The oxygen is then mixed with hydrogen fuel, which creates the combustion needed for hypersonic flight — Mach 5, or five times faster than the speed of sound.

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More specifically, scramjet engines feature an inlet that forces in air and compress it before it's mixed with hydrogen fuel. The hydrogen fuel ignites and is directed out of the nozzle at the back of the engine.

Though the U.S. Air Force will no longer test HAWC, DARPA plans to continue developing the technology used for the program with its More Opportunities with HAWC (MOHAWC) program. "Those missiles will expand the operating envelope of the scramjet and provide technology on-ramps for future programs of record," DARPA explained in its statement.

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