2 ms·

Here are some details: https://en.wikipedia.org/wiki/SABRE_(rocket_engine) https://en.wikipedia.org/wiki/SABRE_(rocket_engine) In summary, cooler air is more d

Here are some details: https://en.wikipedia.org/wiki/SABRE_(rocket_engine) https://en.wikipedia.org/wiki/SABRE_(rocket_engine) In summary, cooler air is more dense than hot air, leading to a high (desirable) compressor pressure ratio. It also allows to make the engine more lightweight due to reduced heat tolerance requirements, making it possible to reach orbit. "I'm not a rocket scientist", but to me this sounds like it would be a leap forward in the "rocket equation" department. Anyone care to comment?

baq 11y ago
the rocket equation is merciless as usual, that's why this approach is so helpful - it allows to accelerate without shedding mass, or more precisely, a fraction of mass that would be required for the same delta-v using a conventional rocket engine. in the end you have to accelerate less fuel before switching over to rocket mode. mach 5 is about 1.8 km/s, which is 20% of orbital velocity. falcon 9 reusable first stage separates at mach 6 (at a much higher altitude, though - i hear 80km and also heard mach 10 numbers). if you can do what the falcon 9 can do without the first stage... that's pretty huge.