High or low periapsis more efficent?

[HollowKing]

If you are trying to insert yourself into orbit of a celestial body is it better to have a low or high periapsis for delta vis?

For example if I insert myself into Moho orbit with a periapsis of 1 million kilometers is it more efficent then inserting myself into orbit at 100 thousand kilometers?

[GeneralVeers]

If you're planning to return home, the escape burn to get back to Kerbin will be a lot more efficient with a low periapsis.

So for most missions, yes. You'll probably want to get low.

[Jupiter3927]

Lower is generally better to save on fuel.
you can keep your orbit eccentric to save on return fuel too.

[HollowKing]

Thanks guys

[ray.mcdonough]

I agree.

How about if you are trying to increase your AP by burning prograde at your PA? Does lower still conserve fuel?

[HollowKing]

Originally posted by ray.mcdonough:

I agree.

How about if you are trying to increase your AP by burning prograde at your PA? Does lower still conserve fuel?

I believe apoapsis is always best to burn at except when inserting youself into orbit

[ray.mcdonough]

So long as your are not skimming the top of an atmosphere, and loosing Delta-V?

[ray.mcdonough]

Originally posted by cyberwaffle:

Originally posted by ray.mcdonough:

I agree.

How about if you are trying to increase your AP by burning prograde at your PA? Does lower still conserve fuel?

I believe apoapsis is always best to burn at except when inserting youself into orbit

I concur

[ray.mcdonough]

Originally posted by cyberwaffle:

Originally posted by ray.mcdonough:

I agree.

How about if you are trying to increase your AP by burning prograde at your PA? Does lower still conserve fuel?

I believe apoapsis is always best to burn at except when inserting youself into orbit

But, I was talking about raising Apoapsis at Periapsis. I was asking if a lower PA would help if you were buring prograde to raise your orbit.

[King_BR0K]

burns are most efficent when done at lowest possable pa, for insertion or ejection

[ray.mcdonough]

Originally posted by AKing1:

burns are most efficent when done at lowest possable pa, for insertion or ejection

Right. As long as no aerobraking is going on.

[King_BR0K]

yep

[MAD]

Originally posted by cyberwaffle:

If you are trying to insert yourself into orbit of a celestial body is it better to have a low or high periapsis for delta-V

Aerobraking (if atmospher is available) is the most efficient way to slow down and be captured.

Otherwise - If you just want an orbit, any old orbit,
stick your Pe just above the atmosphere and your Ap just below the SOI radius.
While on the edge of the SOI use your radial and anti-radial tabs to adjust your Pe
When you get to Pe burn to retrograd so your trajectory just forms an ellipse.
That is the most efficient way, its called a Marginal Capture.



If you want a circular orbit there will be an optimal radius given by the difference in your current hyperbolic velocity and the circular velocity for a given radius. This usually involves a bit of Math to calculate but in KSP it is easy enough to find with a little experimention.
After you have just entered a bodies SOI adjust your trajectory to try variouse Pe altitudes and place hypothetical nodes to circularize. Dunas minamum for example is 560km altitude.

[MAD]

Originally posted by ray.mcdonough:

So long as your are not skimming the top of an atmosphere, and loosing Delta-V?

You don't loose Delta-V, you loose velocity.
And in the case of trying to be captured that is a good thing.