Skylon Aerospace Plane & Sabre Rocket Engine

[davester65]

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.

[Anthony]

Originally Posted by davester65

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.

That article is, um, wildly optimistic. There's no question that a dual-mode airbreathing/rocket engine would be useful for launch purposes if it can be made to work, but we're not even close to making it work. Even ignoring dual-mode, achieving the targeted atmospheric performance (Mach 5.4 on jets) is improbable by 2019.

[davester65]

Yeah, I suppose I need to remember to take stuff in Wikipedia with a healthy dose of salt. I actually designed something like the Skylon using GURPS Spaceships and with a delta/v of .75 per tank I got a delta/v of over 15 mps with 13 slots of fuel. Which is high considering the article says the Skylon won't get higher than the ISS. If I reduce the delta/v to .30 I get a more realistic 6.24 mps. Still twice as good as regular rockets, but less than NTR's or HEDM. Still, we can always hope.

[Anthony]

Originally Posted by davester65

Yeah, I suppose I need to remember to take stuff in Wikipedia with a healthy dose of salt.

Well, Wikipedia is accurately reporting on what the Skylon people want to achieve. It's just that they probably won't -- the history of spaceflight is littered with the debris of clever plans.

Jets have an extremely high nominal Isp when used in atmosphere at moderate velocities, for the simple reason that they're getting the vast majority of their reaction mass from the atmosphere instead of from the fuel (LOx/hydrocarbon is 75-80% oxygen by weight, LOx/LHd is 89%). This advantage drops off as air speed increases, but it's still very substantial.

However, they haven't even taken the first step of building some experimental planes and having them blow up when they try to fly them (c.f. the HTV-2 Falcon and the X-43). It's realistic for them to achieve that step by 2019, but it's a long way from there to production (I can't think of a space launch system that didn't blow up a few times in development and testing).

[Flyndaran]

The best rockets are always nice bombs.