Help with geostationary orbit

[Chris]

Ok so I have a satellite at pretty much the exact apo and periaps of a geostationary orbit, however, my velocity with respect to the surface is not 0m/s or close to so how can i get the surface velocity to 0m/s even though I have the correct apo and periaps? Any advice? Cheers!

[Jupiter3927]

Did you account for the radius of the planet in your math?

[Chris]

Ap/Pe are both 2,863.33km

[Chris]

Originally posted by Jupiter3927:

Did you account for the radius of the planet in your math?

No I didn't to be honest, it's strange, the surface velocity increases, then decreases after I pass Periaps, however it never goes to 0m/s and I can't to save my life, maintain 0m/s.

[Jupiter3927]

KSP measures your altitude from the surface of the planet instead of from the center so you need to add the planetary radius to your altitude for numbers that don't throw your math off.
You should get your target altitude in meters since your 2,863.33km target allows for a 10 meter variance.
10 meters isn't much but every meter counts.

It is possible to go perfectly geostationary but you need to set your engines down to 0.5% thrust for the accuracy to do it.

[Chris]

I see, I have exactly both Ap/Pe at 2,863.33, what altitude exactly should I aim for if I decrease the thrust limiter? Also, does the orbital plane affect the surface velocity? Do I need a perfectly 0 degree orbit around the equater as well or does that not matter if I'm like .3 degrees off?

[Chris]

Ahh that may be why I have like 15m/s surface velocity, I think I have a .3 degree inclination, so I need an exact 0 degree inclination from the equater and 2,863.33km Ap/Pe to get 0m/s surface velocity?

[Jupiter3927]

Your inclination will throw your surface velocity off.
Since you're at Kerbin, you can target the Mun for the perfect equitorial orbit.

Just doing the math, you would need a period of 5 hours, 59 minutes, 9.4 seconds or 21549.4 seconds.
The standard gravitational parameter of Kerbin is 3.5316*10^12
And the equitorial radius is 600,000 meters.
Radius is equal to ((Gm*T^2)/(4*pi^2))^(1/3) or ((3.5316*10^12*21549.4^2)/(4*pi^2))^(1/3).
It comes out to 3,463,331.4 meters.
Subtracting the equitorial radius gives 2,863,331.4 meters so aim for this one.

You can get your orbital period by taking the time between your Ap and Pe and doubling it.
If you get it to 21,549 seconds, you're close enough.
Geosynchronous orbits are a lot easier to get to because they don't care about inclination and only want your Ap and Pe to average out to geostationary orbit instead of being right on it.
Ike is geosynchronous around Duna.

[Chris]

Cheers mate! I've just applied the math and managed to get the surface velocity to 0.2m/s, that will do fine for me since I adjusted the inclination. I'll save that math and use that as a reference for future geostationary missions! Thanks buddy!

[Chris]

Yeah I think it's only Kerbin, Eve and Jool right? I only need the Kerbin one because I'm playing hard mode with extra surface stations turned off.

[Jupiter3927]

All of the tidally locked bodies (The Mun, Ike, Jool's moons) and Moho have geosynchronous orbits outside the SOI.

You only really need geostationary orbits if a contract calls for it or you want your relays to look pretty.

[Chris]

Oh I got you! Yeah cheers buddy! Much appreciated.