Last month, the Defense Advanced Research Projects Agency (DARPA) took a hypersonic missile prototype built by Raytheon Missiles & Defense and Northrop Grumman and completed a successful free-flight test.

This test involved a Hypersonic Air-breathing Weapon Concept (HAWC) missile. The HAWC’s engine got it to as fast as five times the speed of sound, about 3,853 miles per hour. It was a monumental moment for hypersonics, which are expected to be the new frontier for advanced weaponry. 

But now, Reuters reports the Pentagon is saying hypersonics are too expensive. It requests defense contractors cut the ultimate cost of such weapons as a unit can cost tens of millions.