After decades of false starts, America’s leading scramjet engine developers say scramjet-powered hypersonic flight is now within reach.

That’s partly thanks to the coming of new 3D printing technology.

Two competitors in the Defense Advanced Research Projects Agency’s (DARPA) Hypersonic Air-breathing Weapon Concept (HAWC) programme – a Raytheon-Northrop Grumman team and a Lockheed Martin-Aerojet Rocketdyne team – say they are leaning on 3D printing to bring their scramjet-powered hypersonic cruise missiles into test flights in 2020.

The companies say that their programmes are deeply indebted to the X-51A, which last flew in 2013. Built by Boeing and Pratt & Whitney Rocketdyne (now Aerojet Rocketdyne) for the US Air Force Research Laboratory and DARPA, the X-51A was the first hypersonic vehicle to be propelled over a substantial period of time by a scramjet engine that used JP-7 jet fuel.

That hydrocarbon avgas was once used by the Lockheed SR-71 Blackbird. […]

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