UK company Reaction Engines has tested its innovative precooler at airflow temperature conditions equivalent to Mach 5, or five times the speed of sound. This achievement marks a significant milestone in its ESA-supported development of the air-breathing SABRE engine, paving the way for a revolution in space access and hypersonic flight.
Source:
https://phys.org/news/2019-10-air-breathing-precooler-record-breaking-mach.html