interesting development
http://aviationweek.com/space/reaction-begins-building-us-hypersonic-engine-test-site
"A high-temperature airflow test site designed to evaluate a key technology
in the Reaction Engines’ hypersonic air-breathing combined cycle Sabre
rocket engine is under assembly at Front Range Airport near Watkins,
Colorado.
Construction of the facility follows the award earlier this year of a U.S.
(DARPA) contract to test the engine’s pre-cooler heat exchanger, or HTX.
The test work, which is due to start in 2018, will focus on running the HTX
at airflow temperatures in excess of 1,800 deg F (1,000 deg C),
representing inlet conditions at Mach 5......."
