I blundered across this recently. It sounds like it might actually work. If so, getting into orbit will be a lot easier/cheaper. It's supposed to require only 1/5 the mass of fuel to make it into orbit as a normal liquid fuel rocket. That would give it a GURPS Spaceships delta/v of .75 per module. That's even better than a NTR at TL 9. This seems to have been around for a while, has anyone stated it out for GURPS Spaceships? I'd go with the same cost and thrust as a HEDM rocket, but with a delta/v of .75 and liquid hydrogen/oxygen as fuel. It's supposed to only need hydrogen for fuel while in atmosphere, I'm not sure how you'd represent that.
https://en.wikipedia.org/wiki/Skylon_(spacecraft)
The only thing from what I've read about this that I don't get is why they can't seem to get enough funding, also why on earth is NASA still working on a new spacecraft while this is on the horizon? BTW if my numbers are off I'd be happy to be corrected.