Even the Aussies were pretty far advanced in Hypersonics back in the day. I’ve been following some of the stuff you’re talking about. Surprisingly none of the stuff in the 90’s dealing with Hypersonics was classified. I read many open source white papers. Those white papers helped me greatly in my efforts on some of the later technologies I worked on. I’m sure it helped the Chinese get to where they are today too.
Open source defense.