Challenged! The Arkingthaad Nadir.

[Moar Boosters]

Like Fendleton said, different craft vary in their ascent profile depending on their ratios of airbreathing engines to rocket engines, and the lift/weight ratio as well. With enough intakes some craft can reach orbital speeds just on jet engines, so those craft don't need to angle upwards at all, you just go fast until the apoapsis starts to rise on the other side of the planet. Other planes might have underpowered rocket engines and a low amount of lift, so they have to point up at about 45 degrees just to prevent themselves falling out the sky.

The easiest path into SSTO's is probably the aeris 4a. With the Scott Manley tweaks, it's a proven design which you can use to practice ascent profiles. The next step is to build a clone using slightly different parts, and then finally progress onto bigger and better.

[helaeon]

My general SSTO profile is as follows... (I usually am flying dropships like cupcake's or jet rockets but this works pretty well with planes too)

Fly straight up to about 10km - lower if you've got a really good TWR, then pitch over to 45 degrees. At about 15km go down to 30 degrees. This is where you really want to start keeping tabs on your vertical ascent, you want to maximize the amount of time you're under air-breathing power. Now you want to keep as close to terminal velocity as you can, even exceeding it as you climb to 25km. Keep pitching down, much like a gravity turn, to keep your ascent under control because we are looking for horizontal speed. Once you start hitting your ceiling start pulling back on your throttle so your jets don't flame out if you do it right you can ease it back to almost nothing. You should still be climbing about 50-60m/s and still accelerating, even if just a little. Towards the end it will be to keep you from having your apoapsis drop from air drag. It seems to work best if you can make 40-45km before you cut your jets entirely, at which point you switch to rocket power, but resist the urge to pitch up, stay facing prograde for the burn just like your usual gravity turn. You should be going about 2km/s - 2.3km/s so your circularization burn will be tiny. At 25km you should be at 1.6-1.8km/s at least. The thing that gets you on this profile is air drag can bring your apoapsis back into the atmosphere if you don't do it right (usually 100km is safe). If you do it right you'll use very little liquid fuel and almost no oxidizer (sometimes you only need it for circularizing).

If you have something that can show you your apoapsis without checking the map and your needed air vs what you're getting (to help with the throttle part). That helps a ton.

Edited February 19, 2014 by helaeon
made some zeroes disappear