Optimal ascent profile for spaceplane in 1.04 ?

[Cairol]

As the title says: What's currently the optimal ascent profile for spaceplanes?

I'm not expierienced with spaceplanes. I'm building my first real SSTO right now.

What I do is this: Climbing at about 30-35° till 10k meters. Then I lower my ascent to about 10-15° until I reach my desired AP.

It works ok. But I wonder if this is efficient at all.

[GoSlash27]

My ascent profile varies with the engine type and t/w ratio. For a very low powered RAPIER, I tend to stairstep it. Once at 10k to get supersonic and once at 17k to max out the top end.

For a very low power jet, I shallow the climb around 10k to get supersonic and hang around at 16k to max out the top end.

For a high power SSTO, I usually go ludicrous speed down low and zoom climb to orbital apoapsis.

Best,

-Slashy

[Geschosskopf]

As the title says: What's currently the optimal ascent profile for spaceplanes?

There are too many variables involved with the size, mass, lift, drag, and thrust of individual designs for there to be a single optimum that works for everything. You have to do things differently for each design. The bottom line is, experiment until you find something that works for your particular plane.

That said, you can divide and SSTO's launch into 4 phases:

1. Initial subsonic flight
   
2. Supersonic flight
   
3. Rocket to Ap
   
4. Circularizing
   

The ascent profiles for phases 1 and 2 depend on jet TWR. The less you have, the flatter you have to climb. In fact, you might even have to climb slowly to 12-15km then dive back down to 10km just to break the sound barrier before starting another long, slow climb trying to build up as much speed as possible before the jets die at about 25km. But if you've got a lot of jet TWR, you can just go straight up to like 15km, then level off for really high speed. Phase 3 depends on rocket TWR in the same way. Some folks say it works best if you have enough TWR to vary your pitch so that you can keep your Ap 45-60 seconds ahead of you, but that isn't always possible. Just remember that the longer you burn the rocket here, the less fuel you'll have not only for Phase 4 but also going beyond that.