US Air Force investment in Hermeus
 

And to think, all Boris Johnson got was a fancy paint-job: Hermeus Mach 5
Flug

No Trump design finally.

Are Reaction Engines Ltd's Patent lawyers putting a case together?

It is interesting that they claim to have got to Mach 5 conditions in only 9 months, using their proprietary pre-cooler (no details on that). I suppose there is more than one way to skin a cat. It also seems that they have a ramjet incorporated rather than a rocket engine, however I assume that means that they use the usual method of slowing intake air to subsonic speed (with cooling) and also some form of bypass for use at higher speeds when the ramjet could become effective.

I think we should remember that there is often quite a void between press releases and designs!

Iirc, one plausible approach to better engine performance is to use fuel to cool the compressor, something hydrogen fuel does very well. That is perhaps a less comprehensive approach than the Sabre design, but maybe less challenging technically as well.

Make a hell of a mess of the White House lawn......

ORAC|: possibly. I did see a comment on the original parabolic arc thread that suggested liquid oxygen would be used to cool the compressor. Sounds extremely iffy to me! I believe that the SABRE engine cools the air through the pre-cooler assembly and the air then arrives at the compressor. I suppose alternatives could include contact cooling directly at the first stage of the compressor and believe such compressor cooling has been used in conventional jet engine designs for subsonic increases in thrust at various stages of flight. This article (which you have probably seen) talks about the possibility of putting a pre-cooler onto an EJ-200, but I haven't heard anything more about that..