An interesting milestone:

Mojave, CA, November 20, 2014 – XCOR Aerospace today announced it has completed the latest test series for the liquid hydrogen engine it is developing for United Launch Alliance (ULA). This is an important milestone in the long-running LH2 (liquid oxygen and liquid hydrogen) program. It is also a step toward running the engine in a fully closed cycle mode.

In its most recent milestone, XCOR successfully performed hot fire testing of the XR-5H25 engine’s regeneratively cooled thrust chamber,with both liquid oxygen and liquid hydrogen propellants supplied inpump-fed mode, using XCOR’s proprietary piston pump technology.

“This test marks the first time liquid hydrogen and liquid oxygen have been supplied to a rocket engine with a piston pump,” says XCOR Chief Executive Officer Jeff Greason. “It is also the first time an American LH2 engine of this size has successfully fired liquid hydrogen and liquid oxygen together in pump-fed mode. We are happy to be making solid progress on the engines. This will also bring us to a new phase in our plans for orbital flight.

“ULA has an ongoing effort to develop rocket engines for our next generation upper stage, and we are thrilled to see that progress continuing with XCOR,” added ULA Vice President George Sowers.

Upcoming test series will fully integrate the nozzle with the engine and piston pumps. Fully closed cycle testing will follow soon afterwards and will complete the sub-scale demonstration engine program.

The XR-5H25 engines are being developed under contract to ULA as potential successors to the Delta and Atlas series upper stage engines currently used. These engines will also help power orbital launches.

I suspect they’ll find it useful for their own launchers as well.