As far as I know, the Sabre heat exchanger doesn't liquefy the air as frost kills the tubing. It cools down to the boundary without going over. I believe they'v

As far as I know, the Sabre heat exchanger doesn't liquefy the air as frost kills the tubing. It cools down to the boundary without going over. I believe they've demonstrated mach 3 conditions but not mach 5, and they're on track https://www.pprune.org/military-aviation/print-619462-reaction-engines-sabre-rocket-engine-demo-core-passes-review.html https://www.pprune.org/military-aviation/print-619462-reacti...