"Parking" ships on Jool's orbit - in orbits that cross Jool's moons. Is it safe?

[juanml82]

Ok, so my first flotilla of ships to reach Jool is finally there/getting there. And here's the issue. Typically, I just do science, kethane survey, take selfies, whatever once I reach another planet's orbit, then I just leave the ships in orbit until I have a return to Kerbin window and, in the meantime, do other things with other ships in other places.

But Jool's system, being large and having several moons has another challenge. After capture, some of my ships end up in orbits that cross the inner moons orbits. One of them, for instance, will enter Vall's SOI (at almost 0° inclination, so that's not affected) and will just receive a small gravity assist that will increase the orbit altitude just a bit... this time. So, I wonder, what happens when a ship enters another body SOI when it's not on focus (ie, I'm playing with a ship on Eve's orbit or whatever). Does the game run the same calculations anyway? Meaning that I need to make sure none of my ships on Joolian orbit cross a moon's orbit, or that all of them are in an orbital resonance with the moons in their way (is that even possible)?

Basically, I'm trying to keep my ships in orbit for some 100 game days while expending the least amount of fuel possible. What's the best way to achieve it?

[Pulstar]

First of all no it is not safe, vessels that are not in focus may get flung out of Jool's SoI by a pesky moon while you're doing other stuff. I wouldn't worry about Vall doing it though, Laythe in particular but also Tylo are quite fond of doing it as their SoI's are very big so it is easy to get an encounter. Vall's SoI is rather small, so the risk of an encounter is small, and if you get one Vall's weak gravity won't change your craft's orbit much.

Personally I park all my stuff around Laythe, usually I do a direct aerocapture at Laythe itself rather than diving into Jool's atmo. Saves a lot of delta-v, doesn't take a lot to escape Laythe's SoI, makes orbital rendezvous fairly easy.

The other option would be to do an aerocapture around Jool, but you'll end up with a periapsis very close to Jool and unless your apoapsis is also low odds are the vessel will also be on Laythe's SoI's spacecraft sweeping path. Best place to park it from a Jool aerocapture would be between Vall's and Laythe's orbits, takes a bit of delta-v to do it though as you'll need to raise periapsis to a decent altitude beyond Laythe's reach.

Really depends where and what you want to do around Jool though.

[Tex]

I'd think the safest and most efficient method would be to enter orbit around one of the moons themselves. Choose the one nearest you (the one easiest to reach) and get into orbit there. It doesn't even have to be a very circular orbit either, but the SOI of the "parking moon" will ensure that you're not picked off by any other SOIs.

[Kasuha]

So, I wonder, what happens when a ship enters another body SOI when it's not on focus (ie, I'm playing with a ship on Eve's orbit or whatever). Does the game run the same calculations anyway?

It will get the gravity kick and may be sent in a direction you wouldn't like. If you want to park your ships safely, make sure they don't have a chance to cross the SOI of any of the moons. Options include changing your inclination or Pe/Ap so it does not come anywhere near either moon trajectory, or parking it inside SOI of one of moons (e.g. Tylo).

[pauix]

Never park somewhere that crosses a satellite's SOI. I did that once and my space probe that was supposed to be orbiting Duna almost crashed into Kerbol.

[PDCWolf]

OR you can adjust the orbit's period so as to never come in contact with a moon or at least not in a thousand years. If done correctly could save more dV than the other methods, you'll have to look at which one of the solutions is better for your situation.

[Skorpychan]

Never park somewhere that crosses a satellite's SOI.

This. My Duna mission had terrible trouble with Ike for a while, and things slamming into it at high timewarp.

[juanml82]

I've feared that. Now to see what's the cheaper way to make it to a stable orbit. Multiship missions to Jool are complicated

[cantab]

The one you really want to avoid is an orbit that doesn't cross those of the moons, but is close enough to come into their SOIs. You get no warning of the encounters until they happen, and then they tend to lead to collisions since the ship is moving slowly relative to the moon.

[biohazard15]

There is two places that is relatively safe:

1) Low Joolian orbit - set a base here, if you wish to explore inner moons (Laythe, Vall, Tylo)

2) Orbit between Tylo and Bop (but not too close to Tylo!) - good for exploring outer moons, also good for return burns (again, set a base here - you may do science from inner base, then transfer to outer base, refuel here and fly back home)

Never set your orbit between inner moons - this almost always results in collisions with them.

[Spaceisbeautifulul]

Jool is... not safe. When you leave ships in orbit around it they will always get an encounter sooner or later. There's just so many moons with tons of gravity. If you want to put it in a parking orbit, put it above the system (beyond pol) and that should be safe.

Also, something I've found is that when your using time warp in Jool, without any warning, your craft will just fly out of SOI, presumably from the moons...

Dun dun dunnnnnn

*ahem*

[Jouni]

There is a lot of room for safe orbits between the inner moons. The safe zone between Laythe and Vall is almost 10000 km wide, while the width of the safe zone between Vall and Tylo is about 12000 km.

[moonboy13]

I too have had ships disappear while orbiting Jool, maybe the Kraken on Pol is only sleeping..

[Blue]

Technically it would be theoretically possible to make an orbit that matches the moons' orbital phase resonance but this is impractical due to the inaccuracy of orbit changing without directly editing the save to make it perfect.