Explain to me like I'm 5 how to circularize an orbit

[Magmaros]

Hey all, I\'ve been messing around with Kerbal for a while now, and I can reliably get craft into eliptical orbits, but no matter which way I burn once in orbit, I can\'t get my Pe to be anywhere near what my Ap is.

HALP?

[RedDwarfIV]

You have an orbit. It has, say, an Ap of 100 km, and a Pe of 80 km.

Depending on whether you want a 100 km orbit or an 80 km orbit, you respectively burn at Apogee facing the direction your orbital path will take you [prograde] [the yellow circle on your Nav-Con], you burn at Perigee facing the way you came from [retrograde] [the yellow circle with an X through it on your Nav-Con.]

That is as simple as I can put it. In Map Mode [M key to open in-game], you will be shown your orbit, and it will tell you how high Ap and Pe are.

[RedDwarfIV]

Here\'s a visual representation.

[Magmaros]

thanks muchly and if I want to swing it back out into an elliptical later on I just do the reverse?

[RedDwarfIV]

thanks muchly and if I want to swing it back out into an elliptical later on I just do the reverse?

Now you get it! That\'s exactly right. Although really, thrusting in either direction will make it eliptical.

Ap and Pe are the most efficient points to burn at for changing your orbit.

[Magmaros]

Oh, one other question, I was looking up how to get a geo sync orbit and I saw that there was an ideal orbital height and speed, I get how to set up the height now, but how do I go about changing the speed of my orbit without changing the height of it?

[RedDwarfIV]

The way an orbit works is by moving fast, so as you fall towards a planet, you just miss it. So the faster you are, the more you miss it, and the higher your orbit.

Basically, a certain orbital height, say 100Km, might require you to be going 2400 m/s. A 200Km orbit might require 3600 m/s. The two are proportional. As one rises, the other must too.

My advice is to ignore the speed, and focus on getting a circular orbit at the altitude required for geosync.

[Magmaros]

Alrighty, so if I can get up to where it should be for Geo Sync and circularize it, it should be at about the right speed for Geo Sync on its own?

[Anachronda]

One thing I\'m wondering if everyone else experiences (i.e., is it the game or my weaksauce PC) is that the more circular the orbit gets the more the Ap and Pe markers dance about. I currently have a ship in an orbit with about 100m difference between Ap and Pe and the markers and they dance around very rapidly over about 45 degrees of the orbit.

Here\'s a sequence of screenshots I made by just punching F1F1F1F1 really quickly:

Is this normal?

[deadshot462]

That\'s a normal side effect. I\'m not sure what SQUAD plans to do about it but I figure it\'s not game breaking so low priority to 'optimize.'

To make it go really crazy, use the 'precise' RCS mode to narrow down that 100m difference down to a few meters, lol

[Anachronda]

To make it go really crazy, use the 'precise' RCS mode to narrow down that 100m difference down to a few meters, lol

\'Cept it\'s kinda hard to get a reading on it with it jumping around so much.

[Nibb31]

Alrighty, so if I can get up to where it should be for Geo Sync and circularize it, it should be at about the right speed for Geo Sync on its own?

Yes, when you are on a circular orbit, speed is a function of altitude. If you change your speed, you will change the orbit.