SoI Hopping?

[Iforgotthis]

In the past ten seconds I've had a thought. Has been in a position in which most, if not all, of the planets in the Kerbol system have lined up in such a way that to travel between them required little if any adjustment to the spacecraft's trajectory? Is it possible? It would be cool to be able to launch a satellite and have it voyage through lots of different SoI without having to adjust its path all the time

Perhaps I just get to attached to inanimate objects that have a tendency to travel...

[Sof]

It would be very tricky to do since 3 of them lie significantly out of plane in their orbits.

However, I see nothing that would actually stop you due to the game physics.

[MarvinKitFox]

In theory, it is fully possible. You may need to wait many many many years to get the right combo of alignments.

In practice, no.

Even witht the perfect solatr system layout, and the perfect entering trajectory, the floating-point error accumulation will throw you off,eventually.

a 0.01m/s error at kerbin, translates to an error in Jool rendevous as big as Laythe's orbit.

[Iforgotthis]

In theory, it is fully possible. You may need to wait many many many years to get the right combo of alignments.

In practice, no.

Even witht the perfect solatr system layout, and the perfect entering trajectory, the floating-point error accumulation will throw you off,eventually.

a 0.01m/s error at kerbin, translates to an error in Jool rendevous as big as Laythe's orbit.

Darn. What do you think would need to be the very least amount of DeltaV necessary to visit each planet?

[Kasuha]

Without course corrections? No chance. Not even in real life, Voyagers needed course corrections as well.

With course correstions, possible but good luck with figuring out when.

With course corrections (up to tens of m/s) and if you allow multiple orbits around Sun between visits, you can do that anytime.

Maximum "inanimate" I'll give you are two visits. You can eject from Kerbin for Eve slingshot that will throw you into Moho intercept. Or Jool intercept. But I see no way to adjust that second intercept to send you any sensible way that much in advance.

Edited May 5, 2014 by Kasuha

[magnemoe]

In theory, it is fully possible. You may need to wait many many many years to get the right combo of alignments.

In practice, no.

Even witht the perfect solatr system layout, and the perfect entering trajectory, the floating-point error accumulation will throw you off,eventually.

a 0.01m/s error at kerbin, translates to an error in Jool rendevous as big as Laythe's orbit.

Yes you will need adjustments but that is very cheap, main problem is that you have to calculate the correct position and might have to wait 200 year before the alignment is right.

Moho is damed expensive anyway so I would not include it.

[R0cketC0der]

It is definitely possible, but it will be a hell of a task to figure out the right trajectory.

Here you can see the trajectory of the Rosetta spacecraft on its way to rendevous with the 67P comet: http://www.esa.int/esatv/Videos/2013/12/Rosetta_s_Journey_B-Roll/Solar_system_animation_showing_Rosetta_trajectory

It used three gravity assists of earth and one from mars. Now image having to figure out a trajectory like this, but not with a single comet as the target but with all planets in the kerbin system.

[cantab]

It's basically the same problem as the planners of Voyager faced. Someone's made a mission planning tool for this kind of stuff in KSP too, you could give it a try.

I'm actually trying a flyby grand tour at the moment but I do have a lot of delta-V on my probe so don't need to be super-efficient.

[Iforgotthis]

It's basically the same problem as the planners of Voyager faced. Someone's made a mission planning tool for this kind of stuff in KSP too, you could give it a try.

I'm actually trying a flyby grand tour at the moment but I do have a lot of delta-V on my probe so don't need to be super-efficient.

I don't suppose you know the name of that mod do you? It will definitely come in handy...

[undercoveryankee]

There's some discussion on the trajectory optimization tool thread to the effect that a full grand tour has too many constraints to globally optimize.

We might be able to break it down into a few tractable pieces, though. For instance, Duna and Dres are small and won't change your trajectory drastically. If you can find an Eve->Jool->Eeloo or Kerbin->Jool->Eeloo window that passes close to Duna and Dres, the delta-v to enter their SoIs and still get the Jool assist will be manageable.

If you want to add inner planets, you look for a Kerbin->Eve->Moho->[Eve and/or/Kerbin] that reaches the last flyby close to the time for the near outer-planets tour above.

- - - Updated - - -

I don't suppose you know the name of that mod do you? It will definitely come in handy...

http://forum.kerbalspaceprogram.com/threads/36476-WIN-KSP-Trajectory-Optimization-Tool-v0-12-1-Mission-Architect-Release!

[Alephzorg]

Maybe we should ask Kosmo-not how he did this.

[Kasuha]

Maybe we should ask Kosmo-not how he did this.

http://youtu.be/4oAgrqA9Izc

It was an Ion probe so my guess is there were many burns involved. Kerbin->Duna->Eve and Duna->Eve->Jool are exactly wrong turns in terms of gravity slingshots, you need to either have them powered or come with enough extra energy (but Duna does not have enough gravity to turn you in that case). 12 (earth) years to final slingshot is not much, though.

[Madrias]

I had one that slung me from Kerbin's SOI, past the Mun, around Minmus, and pelted me toward Jool, but that's the best I've ever had, and I did it by accident. (Too fast in a prototype SSTO with some very powerful engines behind me, and I exceeded Kerbin Escape Velocity without even trying. Then my jets flamed out. Checked the map to see what mess I'd made of my launch profile and realized that I had an SOI change from the Mun, to Minmus, to Jool. Didn't bother flying the trip, but I thought it was an amazing double-slingshot encounter.)

[undercoveryankee]

It was an Ion probe so my guess is there were many burns involved. Kerbin->Duna->Eve and Duna->Eve->Jool are exactly wrong turns in terms of gravity slingshots, you need to either have them powered or come with enough extra energy (but Duna does not have enough gravity to turn you in that case). 12 (earth) years to final slingshot is not much, though.

I've heard of Kerbin->Eve->outer planets working. Duna->Eve->Jool might be workable if the asset you're moving is already in Duna orbit. Duna->Kerbin->Eve->Jool or Duna->Kerbin->Eve->Kerbin->Jool might also be valid over a couple of orbits. But coming out from Kerbin to Duna and then turning around to go to Eve is not a useful assist.

[Kasuha]

I've heard of Kerbin->Eve->outer planets working. Duna->Eve->Jool might be workable if the asset you're moving is already in Duna orbit. Duna->Kerbin->Eve->Jool or Duna->Kerbin->Eve->Kerbin->Jool might also be valid over a couple of orbits. But coming out from Kerbin to Duna and then turning around to go to Eve is not a useful assist.

Kerbin->Eve->outer planets works only because Eve has deeper gravity well and therefore stronger Oberth effect than Kerbin. You can save a few hundreds m/s of dv if you burn to Eve and then get energy at Eve low periapsis. But after that you got to get a Kerbin slingshot again to raise your periapsis to Kerbin level for that to be useful.

Apart of that, though, the matter is that by unpowered gravity slingshot you raise or lower both your periapsis and apoapsis - at the same time and in the same direction (though by different amount). Hard stops are apoapsis at the planet's level, and periapsis at the planet's level. You can't get any further than that. If you're meeting a planet at your apoapsis, then you cannot use its gravity slingshot to lover your periapsis. And if you're meeting it at your periapsis, you cannot use it to put your apoapsis higher.

[Vector]

You can also take advantage of inclination in some cases, but not enough to go Kerbin->Eve->outer planets. Now, Kerbin->Eve->Kerbin->outer planets is doable but that's quite a different story, since you have a chance to reverse your motion relative to Kerbin, which is not possible with Kerbin->Eve->outer planets.