Did some research with new 1.0 stock airodynamics.. Basically figuring out standard SSTO parameters.
In space:
Wet:
First, I'm figuring out what 1 SABRE engine can do. It seems to be able to get at least 17 tonnes of spacecraft into orbit.
I tried heavier, but a dilemma surfaces:
Too big wings means the SABRE cannot push the SSTO past mach 1 presumably because of air resistance. Try to fly higher and the angle of attack increases. It seems to also massively increase trust towards mach 3+ (~250% or so more than at mach 1), so you have to get your SSTO flying fast. So definetely small wings, but not too small, as your wing loading, thus Angle of Attack will be too high, resulting in drag you need to overcome.
So I suspect 1 engine can push ~20 tonnes into orbit in an optimized SSTO. Thus calculate 1 engine per 20 tonnes of SSTO, and about 6-7 lift rating. It also used about 7 tonnes of fuel.
I suspect the intake cooling thing to be very important, so you probably want to include that in the design.
The flight path needs to be carefully controlled, because if you stay too long in atmo, you are likely to overheat and burn up. If you get into space too soon, you will not have enough speed.
Nevertheless, it seems possible to build extremely poweful and useful SSTO's taking your cargo where you need it!
