Circular Orbits and their Oddities

[[ Jeremy ]]

As I was playing around, I somehow managed to get a circular orbit so precise (1m difference) that things start to turn "weird".

What's weirder is when you enter on-rails warp, our good friend floating point imprecision miscalculates the Ap and Pe and makes it less circular.

[p331083]

Kerbals have not perfected Calculus yet.

[boomerdog2000]

Yeah, if your orbits get too precise it also starts taking into account the difference from your ships control point I believe. It's either that or center of mass. So if you start rotating things get even worse.

[SofusRud]

If you think about it it makes sense, if every point on the orbit is the same then the apoapsis and periapsis must be simultaneously everywhere on the orbit and opposite each other, so its no surprise it goes all squiggly

[boomerdog2000]

Only if you had an absolutely perfect circular orbit. Since we are human and can't do that they shouldn't be jumping around some much. On the other hand it was made by humans who aren't perfect so it's allowed to be finicky.

[frizzank]

It should take the average ap and pe taken over the last few frames and not just the real-time data. Also when your orbit is really close to circular it should just say that its circular at a number rounded to the nearest meter and drop the Ap and Pe designations. The same way when you pick a target for orbit intercept using the nodes when you get really close to it there is no longer 2 points of intersection just one.

[phunk]

The problem is it's giving the Ap and Pe of the control part on your ship, not the CoM of the ship as a whole. So every little vibration or sas movement is tweaking the orbit a bit from that point of view, even if the ship as a whole isn't accelerating.

[RSwordsman]

I've had vibrations of the nodes like that before even getting to 1m precision. I don't worry about any eccentricity where the difference is less than 1km, because even if it wiggles like that, you know it's circular enough to start a transfer burn from anywhere without undue loss of efficiency.

[Kasuha]

That happens regularly with even less circular orbits if your ship or station is wiggly enough. Or in interplanetary space. The fact that the menu to add a maneuver is jumping all around the place is very annoying.