Is it possible to achieve a geostationary orbit in KSP?

[Two of Three]

Is it possible to achieve a geostationary orbit in KSP? If so, how?

Edited February 4, 2015 by Two of Three

[wibou]

Yes.

A perfect circular orbit of 2 868.75 km would be stationary compared to the ground.

But (just like in real life) it is very hard, if not impossible, to achieve _perfect_ geostationary orbit (due to imprecision in the physic engine) and as such you will have to correct the orbit slightly every now and then.

[Tank Buddy]

Google is a wonderful resource: http://wiki.kerbalspaceprogram.com/wiki/Synchronous_orbit

[Leszek]

Yes.

A perfect circular orbit of 2 868.75 km would be stationary compared to the ground.

But (just like in real life) it is very hard, if not impossible, to achieve _perfect_ geostationary orbit (due to imprecision in the physic engine) and as such you will have to correct the orbit slightly every now and then.

I normally use Mech Jeb or KER to set my orbit. I set my AP at 2868.7 KM and burn until my orbital period is 6 hours. I can get to well under a 5th of a second accuracy. It takes on the order of 250 days to notice any drift with that, and only if you have other geo sats to compare it too.

[LethalDose]

Is it possible to achieve a geostationary orbit in KSP? If so, how?

Technically, no, since Earth isn't in the game. Geostationary orbits are, by definition, around the Earth.

But enough smart***ery. Stationary orbits are totally possible around most planets, including Kerbin. Most moons have SoI's that are too small for stationary orbits, though.

The "how" is to get into an orbit with orbital period is equivalent to the parent body's sidereal day. Previous posts have done an excellent job describing the how in more detail. If you want to understand it, though, it's gonna take 'teh maths.'

Oh, and for it to be perfectly stationary, it has to have a perfectly equatorial, circular orbit. Orbital eccentricity will cause E-W libration, and orbital inclination will cause N-S libration.

Edited January 31, 2015 by LethalDose

[Jimbimbibble]

A couple of versions ago the devs changed the length of a Kerbal day. It used to be a siderial day was 6hrs. Now a "normal" day is 6 hours and the siderial day is a little bit less.

[LethalDose]

A couple of versions ago the devs changed the length of a Kerbal day. It used to be a siderial day was 6hrs. Now a "normal" day is 6 hours and the siderial day is a little bit less.

I'm pretty sure it was 0.24 where this change was discussed by the devs. The problem is, it doesn't appear to have happened. I've set orbital periods to what the sidereal day was supposed to be, but the satellite sped up in orbit, advancing ~ 30 deg longitude over several game months. This has been confirmed by other players, and the Kerbin's sidereal rotation appears to remain 6 hrs. The wiki entry still lists the sidereal day as 6 hrs.

Basically, it looks like the devs screwed up: they announced the change, even though its not in the game.

I also had a question about synchonous orbits around Tylo and Laythe in a rep comment (Thanks! I appreciate it!). According to the wiki, neither is possible, since the orbital altitude for synchronous orbits lie outside the moons' spheres of influence. Laythe's circular synchonous orbit altitude is ~4.7 Mm, but it's SoI only extends to 3.7 Mm. Tylo's circular synchronous orbit is > 14 Mm, but it's SoI extends < 11 Mm.

Except for Minmus and, shockingly, Gilly, all the moons in the game are tidally locked to their parent. Tidally locked bodies have very slow rotation, requiring much higher orbital altitudes for synchronous orbits. The wiki actually states synchronous orbits are possible around Minmus and Gilly, though I've never tried either.

Again, everything above is supported using the Wiki. I haven't confirmed the data with my own calculations, but I've found the wiki to be extremely accurate.

[Mars Mullo]

Yes you can .. read all above...

[Devric]

http://wiki.kerbalspaceprogram.com/wiki/Synchronous_orbit

[EtherDragon]

Let's ask the question a different way, with some scientific definitions and see if you can't answer your own question!

"Is it possible to achieve a geostationary orbit in KSP?"

What is a geostationary orbit? It's an orbit where the orbital period is equal to the length of the day. So let's re-ask the question:

"Is it possible to achieve an orbit where the orbital period is the same as a single day?"

Well, to have a given orbital period, you need to have a specific semi-major axis. Ask again:

"Is it possible to achieve an orbit where the semi-major axis results in an orbital period of one day?"

Now for one other fact - the semi-major axis of a circular orbit is equal to the radius:

"Is it possible to achieve a circular orbit where the radius results in an orbital period of one day?"

As Two of Three pointed out, yes! A circular orbit with a radius of 2,868.75 km results in an orbital period that is equal to one day.

[viktor19]

Is it possible to achieve a geostationary orbit in KSP? If so, how?

As everyone mentioned, orbit of 2,868,750m should do the trick. However, RCS or Ion is recommended for setting the exact orbit.

[EdFred]

As everyone mentioned, orbit of 2,868,750m should do the trick. However, RCS or Ion is recommended for setting the exact orbit.

Or getting close, and then going into the sfs file, and editing it.

[Two of Three]

OK, Thanks for the help!