Help with Aerobraking

[neoblacksmith]

So, I am currently doing several manned missions to Duna, and I have FINALLY begun to understand how to manipulate my encounters to be as clean as possible.

But I want to start saving fuel and understand aerobraking better...

Do you have to be going a certain speed for it to work? Any explanation would be appreciated.

[TheDarkStar]

When you go through an atmosphere, you are constantly slowed down be the air. The lower you are, the more there is stopping you because the atmosphere is denser. Even if it doesn't look like at first, you are being slowed down by air when you are in an atmosphere. You lose about 2000 m/s of delta-v to drag when you launch in Kerbin's atmosphere.

That said, when you want to aerobrake to lower delta-v costs, you want to have your periapsis be somewhere in the lower atmosphere.

Duna: 12-15km, quicksave and reload to find out exactly or aim high

Laythe: Either 20-26km or 18-22km, depending on whether you intercepted it from a prograde or a retrograde orbit, and also if it's straight from Kerbol's SoI or from a Jool orbit.

Eve: Usually 57-75km, depending on your relative speed.

Kerbin: I'm not quite sure, since I usually just land, but somewhere around 30km should work.

[neoblacksmith]

When you go through an atmosphere, you are constantly slowed down be the air. The lower you are, the more there is stopping you because the atmosphere is denser. Even if it doesn't look like at first, you are being slowed down by air when you are in an atmosphere. You lose about 2000 m/s of delta-v to drag when you launch in Kerbin's atmosphere.

Awesome, that's the way I understood it so far. So it shouldn't matter how fast I'm going, as long as I keep the apogee high enough?

[Skorpychan]

When you go through an atmosphere, you are constantly slowed down be the air. The lower you are, the more there is stopping you because the atmosphere is denser. Even if it doesn't look like at first, you are being slowed down by air when you are in an atmosphere. You lose about 2000 m/s of delta-v to drag when you launch in Kerbin's atmosphere.

That said, when you want to aerobrake to lower delta-v costs, you want to have your periapsis be somewhere in the lower atmosphere.

Duna: 12-15km, quicksave and reload to find out exactly or aim high

Laythe: Either 20-26km or 18-22km, depending on whether you intercepted it from a prograde or a retrograde orbit, and also if it's straight from Kerbol's SoI or from a Jool orbit.

Eve: Usually 57-75km, depending on your relative speed.

Kerbin: I'm not quite sure, since I usually just land, but somewhere around 30km should work.

For Kerbin, <40KM will mean you're going to hit the ground. Atmosphere stops at ~70km, and you need to be going <50KM to get any significant drag.

I've done a LOT of experimenting with my Mun landers. They seldom have much fuel left after escaping the Mun.

[Taki117]

http://alterbaron.github.io/ksp_aerocalc/ will help with determining altitude needed.

[neoblacksmith]

http://alterbaron.github.io/ksp_aerocalc/ will help with determining altitude needed.

Thanks alot!!!

[Vanamonde]

Your speed determines the altitude required to accomplish sufficient braking; the faster you're going, the deeper you'll need to venture. Note that in the real world, over-doing things would result in the ship burning up or breaking apart, but since atmo affects in KSP are incomplete, this is less of a consideration.