Newslink: Engine for DARPA's New Military Space Plane Aces Record-Breaking Test
The company Aerojet Rocketdyne has successfully wrapped up a marathon test of the shuttle-era AR-22 engine, firing it 10 times in 10 days to test its suitability for a quick-turnaround reusable space plane.
https://www.space.com/41123-darpa-experimental-spaceplane-military-engine-test.html