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Heliosynchronous orbit AFTER interplentry transfer?


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It is rather easy to get into Sun-Synchronous Orbit in kerbin but how about you want to some satellites in that polar orbit in duna, dres, eve or even laythe?

 

The plane change will need a huge amount of delta V which I am trying to avoid. Is there any ways to do that? Thanks!

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2 hours ago, Carrot said:

It is rather easy to get into Sun-Synchronous Orbit in kerbin but how about you want to some satellites in that polar orbit in duna, dres, eve or even laythe?

 

The plane change will need a huge amount of delta V which I am trying to avoid. Is there any ways to do that? Thanks!

From the KSP Wiki - In the real world, there exists a sun-synchronous orbit. It's important to note that, although the name implies it, the orbit is not synchronous around the Sun. Instead, it describes an orbit around Earth which itself rotates, such that it appears the orbiting object is motionless relative to the Sun. Since it requires objects to have uneven gravitational fields, it is impossible to simulate in KSP.

However, there are a few threads with some detail, this one is one of the better ones, explanation wise:

 

Regarding getting into a polar orbit around a planet that you are transiting to from Kerbin, as long as you make your burns way out from the planet you can do it for almost no Delta-v, so when you arrive in system you are already on the right orbit.

EDIT - Just read the after transfer bit.  If you are already in system then the best way of doing it is to burn to a highly elliptical orbit, then make your plane change at the furthest point away from the body.  This will minimise the Dv requirement.

Hope that helps!

SM

Edited by Speeding Mullet
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4 hours ago, Speeding Mullet said:

From the KSP Wiki - In the real world, there exists a sun-synchronous orbit. It's important to note that, although the name implies it, the orbit is not synchronous around the Sun. Instead, it describes an orbit around Earth which itself rotates, such that it appears the orbiting object is motionless relative to the Sun. Since it requires objects to have uneven gravitational fields, it is impossible to simulate in KSP.

However, there are a few threads with some detail, this one is one of the better ones, explanation wise:

 

Regarding getting into a polar orbit around a planet that you are transiting to from Kerbin, as long as you make your burns way out from the planet you can do it for almost no Delta-v, so when you arrive in system you are already on the right orbit.

EDIT - Just read the after transfer bit.  If you are already in system then the best way of doing it is to burn to a highly elliptical orbit, then make your plane change at the furthest point away from the body.  This will minimise the Dv requirement.

Hope that helps!

SM

Can I say it is almost no way to burn into a polar orbit on the day/night-line on the other planet directly?

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Correct; you can enter an orbit such as you describe, but as the planet revolves around the sun, the day/night line (called the terminator in astronomy) will rotate around the planet as well, for one full rotation per year.  Simulating an orbit that changes to keep itself always over the terminator that would require your polar orbit also to have a variable longitude of ascending node with the rate of variation equal to 360° per local year.  However, KSP doesn't simulate orbital variation.  The value of the LAN is treated as constant unless one of two things happens:  either you execute a burn to change it, or you intercept another celestial body's sphere of influence (in which case the orbit technically remains constant; it is simply recalculated with respect to the new primary celestial).

You may get results if you try it in Principia, which is an N-body gravity simulation mod.  I would assume until proven otherwise that there is a way to simulate your orbit there, but I must confess to admit that I don't know how to set one up.

Edited by Zhetaan
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Coming from interplanetary space, you can tweak your encounter so that you pass over the a pole of your target planet.  This way you can capture directly into a polar orbit.

 

You can do this just when you enter the target's SOI. Play with the normal/antimnormal and radial-in/out burns to see how your flyby is changing.

Edited by Chaos_Klaus
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I think (though am not sure) that sun-synchronous orbits are impossible even with Principia, since Principia's main thing is N-body gravitation, and precession is caused by non-uniform gravitational fields (mostly: planets bulging at their equators).

You can do N-body gravitation with point masses without modeling precession and non-uniform gravitational fields, and I suspect you can do non-uniform gravitational fields (and thus precession) without N-body gravitation.

As to how to cheaply get into a polar orbit: the best way is to set up your transfer (or set up a small correction burn while still far from the destination) to pass over the poles. If it's too late for that, usually your go-to methods for large inclination changes are either to use gravity assists from moons, or to use a bi-elliptic transfer (raise your apoapsis to near the edge of the SOI, adjust your inclination there, bring it back down at periapsis).

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2 hours ago, Starman4308 said:

I think (though am not sure) that sun-synchronous orbits are impossible even with Principia, since Principia's main thing is N-body gravitation, and precession is caused by non-uniform gravitational fields (mostly: planets bulging at their equators).

skiming at the principia thread I found this:

Quote

This initial configuration also includes J2 for the Sun, the planets, the Moon, and Vesta, so the resulting effects are felt (precession of Earth orbits, the possibility of heliosynchronous orbits, etc.).

Notice that i know almost nothing about the mod. I'm just quoting the author.

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On 5/5/2017 at 2:57 AM, Chaos_Klaus said:

Coming from interplanetary space, you can tweak your encounter so that you pass over the a pole of your target planet.  This way you can capture directly into a polar orbit.

 

You can do this just when you enter the target's SOI. Play with the normal/antimnormal and radial-in/out burns to see how your flyby is changing.

IF I can place the ap at the AN/DN, it will cost the least fuel to change the inclination. Am I correct? Does ksp allow it though?


 

 
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Edited by Carrot
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2 minutes ago, Carrot said:

Thanks all for the answers! Just a last question IF I can place the ap at the AN/DN, it will cost the least fuel to change the inclination. Am I correct? Does ksp allow it though?

Yes or no, but definitely maybe.

Burning perpendicular to your velocity (normal/anti-normal/radial in/radial out) will be more efficient when you velocity is lower (ap) and a burn to reduce relative inclination is more efficient when the orbits are closer (an/dn). But the question is: how much it will cost to make  both situations coincide?

In particular it don't make much of a difference if inclination and/or eccentricity  are low.

 

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@Spricigo is definitely right.  I had a situation of trying to bring a refuelling tanker to my station around Minmus.  As soon as I had my encounter the patched trajectory had me not only at a bad inclination but also entering orbit in the wrong direction.  All of this I fixed by tweaking the normal/antinormal and the radial handles of the maneuver node.  And you can experiment with this as well, move the whole node closer and then farther away and making the adjustment while watching the Delta V gauge.  You will observe that corrections at a greater distance are more dramatic with far less Delta V than up close.

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