what's the best way to reach Jool?

[omelaw]

1. Jool aerobrake

2. Laythe areobrake

3. Tyro graivity assist

P.S can I run away with fuel cells and solar panels or will I need a RTG?

[Gaarst]

It depends. Do you want to flyby Jool, orbit it or crash into it? In any cases, seriously consider gravity assists, they are extremely simple in the Jool system, very satisfying to do and a lot more efficient than anything else (aerobraking usually requires you to haul a large heatshield to Jool). If you're going to dive in Jool/Laythe anyway, then just aim straight for the atmosphere (but be careful with heat on atmospheric entry).

Solar panels are fine if you don't intend to use lots of electricity. As long as you don't try to run a science lab 24/7, drill, refine or have hundreds of reaction wheels on your craft, a pair of Gigantors should be more than enough for anything. RTGs are not powerful, but lighter than big panels, so if you only send a small probe, it's the best choice. Finally, fuel cells are what you need if you intend to power some big things, usually the best when paired with a refinery because you actually create the fuel they use.

[WanderingKid]

Under most circumstances, a Tylo/Laythe Grav Assist (depends on which one is easier to hit) + Jool Aerobrake if needed after is my preferred entry method.  Particularly with the new overheating, it gives you more room for error during the aerobrake and you don't have to go as deep. 

You can get away with a decent solar panels if you're not doing anything intensive, like orbital/ground research MPLs or mining.  Probes will be fine with a pair of 1x6's, just put them in hibernation during warp (advanced tweakables).  If you're mining, you'll want Fuel Cells for sanity purposes, but you can get away with a monstrous solar array if you wanted to. If you're doing research, just bring a good sized solar array and do it in orbit so you don't have to worry about a large battery array for overnight processing.

[A_name]

You might want to skip the Jool aerobrake. I'm not entirely sure if that’s still the case, but it used to be that even grazing Jool’s atmo at interplanetary speeds would mean instant death. Plus, Tylo and Laythe have enough gravity to let you capture without the need to even touch Jool. I’m sure there are fancy ways to set up your gravity assists, but honestly what I do is, once I have a Jool encounter, I set up a mid-course correction burn (at around Duna’s orbit) and just fiddle around with the maneuver node until I get a Tylo or Laythe encounter that will capture me. It’s fairly easy to do from far away since it takes only small burns to move around your Jool trajectory all over the system until you find a point that gives you the encounter. Just remember the rule of thumb tat passing in front = slowing down and passing behind = speeding up, and the closer your Pe is the larger the effect. You’ll end up with a highly eccentric orbit that will pass through most of the moons’ orbits, so once you’re captured its easy to set up a second assist to further lower yourself around Jool. Set up a maneuver at your Jool Ap (without pulling on the levers, but just as a place marker) and use the next orbit button to find your next encounter and adjust your Pe accordingly to get the orbit you want.

As for electricity, despite the distance to the sun, the regular size deployable panels are enough to keep you going (unless you’re going to be mining or using ion engines or something very energy expensive like that). You can slap on a small fuel cell for emergencies, but honestly you won’t need it.

[Lunar Sea]

Capture burn at 200,001m altitude 

[Tyko]

I'd suggest a rocket or a spaceplane

[Aegolius13]

Tylo or Laythe gravity assist,  in multiple passes if need be.  Aerocapture on Jool is possible with a heat shield, buthe unless you want low Jool orbit you'll have to spend some fuel getting your perhapsis back up.  

Laythe aerobraking works to finish a capture or landing around Laythe, but can get hot.   A gravity assist first will make it easier. 

 

Also,  solar panels will workvif your power needs are low,  but bring at least a few 1x6s.  Fuel cells will work,  but I've never liked them.   I tend to go radioactive. 

Edited February 1, 2017 by Aegolius13
Wow, my phone corrected "Tylo" to "Typo." Sweet irony.

[Superfluous J]

Laythe gravity assist. It's closer to Jool so easier to get an encounter by just tweaking radial and prograde on your mid-course correction. Though Tylo's not that hard to nail from over a year away.

I've not aerobraked at Jool since before 1.0 and doubt I ever will again.

[FancyMouse]

3 hours ago, A_name said:

I'm not entirely sure if that’s still the case, but it used to be that even grazing Jool’s atmo at interplanetary speeds would mean instant death.

I believe it was only 1.0 era thing. Now it's reasonable to do 180k and even lower if you're prepared for it. I've rarely done Jool aerocapture because it requires extra ship design work, and I'm still waiting for the bug of "ship under acceleration below 1Mm, can't go back KSC" to be fixed. At least it was still there in early versions of 1.2, haven't got a chance to test this in 1.2.2, though...

27 minutes ago, Aegolius13 said:

buthe unless you want low Jool orbit you'll have to spend some fuel getting your perhapsis back up.  

nope you could still do gravity assist to raise periapsis - that's the fun part playing in Jool system.

[Reusables]

Proper Laythe aerocapture through the high atmosphere provides both powerful gravity assist and enough aerobraking. Laythe is quite a bit closer to jool than Tylo, which makes deceleration more effective. Moreover, thanks to its faster speed gravity assist could give more deceleration on Laythe than that on Tylo.

So, I think Laythe powered aerocapture will be efficient enough capture for short-term missions on Jool.

Edited February 1, 2017 by Reusables
More specification.

[Birdco_Space]

4 hours ago, 5thHorseman said:

Laythe gravity assist. It's closer to Jool so easier to get an encounter by just tweaking radial and prograde on your mid-course correction. Though Tylo's not that hard to nail from over a year away.

I've not aerobraked at Jool since before 1.0 and doubt I ever will again.

I second this.  Laythe encounters are generally easy to arrange when coming in from interplanetary, and it has the mass and orbital velocity to easily capture the vessel in Jool Orbit.