Ascent Profile Question

[Spaced Out]

When you are ascending out of Earth's atmosphere how far up do you turn to gain horizontal velocity with your first stage, and is that height to avoid heat, or drag?

[K^2]

The gravity turn begins almost immediately. Although, a big part of it is to get the rocket down-range early in case of an accident. All else being equal, better if debris fall into the ocean/desert than on the launch pad. But it also works out from optimization that it gives you no advantage to ascent directly up even early on. You always want at least a little bit of an angle.

In general, ascent profile can vary quite a bit between different rockets. Your main criteria are aerodynamic heating, dynamic pressure, and fuel use. On one hand, you want to be out of the atmo as quickly as possible, on another, you don't want to be moving too fast. And the sweet spot will never be exactly the same for two designs.

[Nibb31]

In reality, you don't go straight up and suddenly turn. Converting vertical speed into horizontal speed is a waste of energy. Real rockets start their gravity turn as soon as they clear the launchpad.

[kerbiloid]

And the most energetically cheap trajectory is when you are going prograde all the way.
Pure elementary physics.
You should start your gravity turn asap, experimentally adjusting the initial angle and then keeping prograde with SAS.

So, watching your exhaust trail in KSP helps to understand whether your rocket is underpowered (nose vertical, trail horizontal).
Nose and trail should be one line, otherwise something needs to be adjusted.

Edited August 18, 2017 by kerbiloid