[Question] - Solarstable orbit around Kerbin

[djnekkid]

Hi all.

I've been thinking about putting out two sattelies, one on each 'solar shift' around Kerbin. In other words on the Kerbin pro- and retrograde. Am I totally wrong, if i send up a sattelite in keosync, just that it needs to be in 270 degree orbit, and not 90 degree?

Or are that orbit just something else?

-DJ-

[iamaphazael]

No, they both need to be in eastward orbits or they won't be keostationary. You just need to position them so that when they are in their final orbits they end up where you want them.

[djnekkid]

its not keostatenary per se I want, its 'progradestationary' if you get my drift...

Hmm, or would they need to be actually just outside of kerbins SOI, but with the same semi-major axis as kerbin...

Edited September 26, 2012 by djnekkid

[Person012345]

you mean not-orbiting? You can't have it not-orbiting, unless as you say you go outside the SoI. Then you're just orbiting the sun.

[EndlessWaves]

You want them to be ahead of and trailing kerbin in it's solar orbit? i.e. Trojan points but a lot closer.

Keostationary is no good in that case as they're static with respect to the surface but the surface is rotating with respect to the orbit.

I'm not sure it's possible but you're looking at two 270° orbits that rotate at the same speed as kerbin so you're orbiting at the same speed kerbin is rotating but in the opposite direction (actually slightly less so it gradually drifts in synchronisation with Kerbin's curved path around the sun), the only difference between the satellites would be one was launched when KSC was approaching solar retrograde and one when KSC was on the opposite side of the planet.

If that's not possible because it would be over escape velocity or something then just plonk them into the same solar orbit as kerbin. Go lower/higher initially to get them ahead/behind kerbin then burn back up/down to kerbin's orbit.

If by solar shifts you mean that you want one overhead at midnight and the other overhead at high noon (with respect to a single point in the planet) then that's just two keostationary orbits launched half a kerbin rotation apart (3 hours).

[Person012345]

No, that wouldn't work, because it has to be going round it with respect to the centre of gravity, not the surface. Essentially, he needs to orbit the sun, but he can't do that within the sphere of influence of a planet because then you need to counter the gravity of the planet.

Edited September 26, 2012 by Person012345

[Person012345]

Well, I suppose he could orbit kerbin at the same rate that kerbin orbits the sun (but in retrograde) though I'm not sure that's possible whilst lso being within it's SoI

[iamaphazael]

Oh, I see what you want to do. So, what you want basically is an orbit around Kerbin that has the same period as Kerbin's orbit around the sun. (This way, your ship makes one orbit around for each orbit or kerbin around the sun, thus keeping all three in the same relative position). I just tried solving the orbital period equation for that period, and assuming that a) the data in the ksp wiki for the mass of Kerbol and Kerbin and Kerbin's orbital period is all correct, and the gravitational constant is the same in game as it is in the real world, and c) I did all my math correctly, then you would need a circular orbit at about 4,342,000,000 m around Kerbin, which is well outside of its sphere of influence. So, the best approximation you can hope for is what others here have suggested: take them into a Kerbol-centric orbit that matches Kerbin's orbit, just ahead of and behind it.

[phoenix_ca]

Indeed. Not going to happen in a patched-conics system, I'm afraid. As noted the best option would be to go into the Sun's SoI, and set-up an orbit that's the same as Kerbin's, ahead and behind it. The only way to put the satellites anywhere else would be to put it on the Kerbol-Kerbin L1, which won't happen because it's not modeled, and would require n-body math to do. In short, not gonna happen (as cool as that would be; there are very good development reasons to not add Lagrange points, as Harv explained...somewhere).

[djnekkid]

Yes... It seems like i need to go just outside kerbins SOI, and set up a solar orbit with the same semi-major axis as Kerbin.

If i build a rocket, and fire it up just as the sun goes down/up and just go streight up, I should be close to getting just behind (or ahead of) Kerbin. Let the Apoapsis be like 100.000km, and it should be good to go. Hopefully.

[Peppe]

Are Lagrangian points modeled in KSP?

http://en.wikipedia.org/wiki/Lagrangian_point#L1

[RoboRay]

Are Lagrangian points modeled in KSP?

http://en.wikipedia.org/wiki/Lagrangian_point#L1

No. That would require solving the n-body problem. KSP makes do with simpler patched-conics for 2-body solutions.

Edited September 27, 2012 by RoboRay