Hippaforalkus

I have been experimenting with SSTO spaceplanes for quite some time, and I have built a number of highly successful ones. There are two basic types: Pure rocket SSTO's, and hybrid jet/rocket SSTO's. In both cases, Mechjeb helps a lot. I assume that you're trying to build a hybrid jet/rocket spaceplane. I have built such a spaceplane with a jet TWR of only 2.40, and a rocket TWR of only 1.07, and it flies like a dream. In theory, I could probably go lower and still get to orbit. Your spaceplane has extra TWR, which is always a good position to be in. Jet engines are like SRB's, except they have controllable thrust and wickedly awesome specific impulse. The specific impulse is so amazingly high, in almost all cases, you need not worry about 'wasting' fuel with an inefficient ascent trajectory in the low atmosphere. Recommended ascent trajectory: To 8 Km - 10-20 degree ascent (If you are really hardcore and need to save jet fuel for some reason, fly it like a rocket at 70-80 degree ascent) To 12 Km - Level out ascent slowly, to ~5 degree ascent. Make absolutely sure your green velocity indicator is near the horizon, but just slightly ascending. To 20 Km - Maintain ~5 degree ascent and build crazy velocity. To 25 Km - Begin shutting down your outermost jet engines to prevent asymmetric flameout. VERY carefully begin climbing again. Use the Mechjeb ascent guidance to slowly raise the nose of your aircraft. Do not fly manually. If you pitch up too violently, your aircraft will spin and likely fly apart. Try and go for 10-15 degree ascent. To 35 Km - Your velocity should be nearing 2 Km/sec. If it is not, you needed to build more velocity from 12-25 Km. Your TWR will drop as you shut off engines; as soon as it drops below 1, fire your rockets. As you exit the (flyable) atmosphere, pitch up to 45 degrees. In order to go this high on turbojets alone, use a stack bicoupler on the front of every engine assembly, with two ram air intakes per engine. If you can put more on elsewhere, even better. I generally aim for an apoapsis around 180 Km. If all goes well, your rocket burn to establish apoapsis will last only a few seconds. Another short burn ( <400 Delta-V) as you reach Apoapsis will circularize your orbit, leaving you with thousands of additional delta-V for your exo-orbital mission. I have not tried putting LV-N Atomic Rocket Motors on an SSTO spaceplane in lieu of ordinary liquid-fuel rockets, but they also have specific impulse analogous to that of jet engines. If you have a large enough spaceplane with a high enough rocket-fire altitude, the amount of fuel you require in order to do things goes WAY down, and the heaviest component of the plane would be the LV-N's. Another word of advice - use a liquid fuel rocket with thrust-vectoring. Toroidal Aerospike Rockets are really only useful for pure rocket SSTO's, which need good specific impulse on the runway as well as during ascent.