Kryxal

A ship with the delta-v readout from either KER or Mechjeb would help, and a general description of your ascent (such as initial turn of so much at some point, pointing so far at 10k, 15k, 20k...)

I still say aerobreaking at Jool is really easy, it's aeroBRAKING that's difficult...

There's a reason (well, two actually) that I saved the booster as a subassembly ... not only is it properly on the decoupler, it has a seperatron in a good place.

Also, never save while in motion on the surface during EVA ... it tends to end about the same.

Maybe turn some wheels off when you're station-keeping?

A workaround instead of actually fixing it, but maybe use Kerbal Alarm Clock?

I prefer to stay under the radius of the Mun's orbit ... you don't get all the delta-v you would going WAY out there, but you get most of it (maybe 800+ m/s), a shorter orbital period, and no chance of running into the Mun. Incidentally, to set up the burn, just next-orbit your node 6-8 hours into the future and see what happens...

I had a little mishap with a 1.25m service bay that was absolutely hilarious ... it ate Bob! I could see him clipping through and acting like the spin cycle of a washer was going!

I saw 18 once.

That depends on if there's any bias in the self-selected sample...

I'd consider making the center stack have two of the 800s ... your TWR is too high for current conditions. This would likely allow you to drop to two radial tanks (and engines) instead of four. This would also help launch stability, though you really should add some fins too.

If you like cleaning up your mess via impact, you can always attach probe cores and solar panels to the LFO boosters. A bit left over translates into FAR more delta-v once you drop the boosters, and you can plow them into Jool if you managed the whole way, or orbit back to Kerbin in solar orbit, or if you have enough thrust stop short of SoI change...

Look at the target, watch the trajectory behavior as you alter the node. Assuming you use KAC, you can approximate a lower flyby and set an alarm at a time just short of the SoI change that isn't appearing. I've had similar problems with Minmus, line's one one side of the moon, goes to not intercepting, line's on the OTHER side of the moon.

I think this is just construction and practice issues. Incidentally, if you have the correct pilot skills or probes, I'd rather hold normal than 0 or 180 if in a non-equatorial orbit due to orbital mechanics (though just having a fixed point's better than not).

I made a ship with an ion engine and a capsule, and it didn't need that long a burn to go meet something below Moho's orbit ... I think you need a better TWR. 6 hours= 21600 seconds, maybe 3000 m/s for transfer, your TWR must be under .02!

Fuel cells work well if you have an engineer ... if you don't, you end up using more fuel than you make, and should go with batteries or shut down for the night.

Do note that the small instruments (thermometer, barometer and similarly-sized stuff) are easily attached to a capsule and weigh next to nothing, but are sort of pricey. It's worth planning to bring those back with you even if you drop the other science parts.

I wouldn't be surprised if it's mostly based on time warp capability for rendezvous.

I'd probably go with a bit more delta-v to reach orbit in the "reverse" orientation, and maybe have the last stage still capable of deorbiting itself. Also use a nosecone that deorbits too.

I wouldn't say accuracy matters all THAT much on a Jool slingshot, going from a 150 degree plane change at Kerbin's orbit to 30 degrees or less at Jool's orbit is a huge savings. Also, don't forget to consider an "extra" slingshot on Laythe or Tylo.

If the payload is all that wide, I'm likely to use a multi-stack launcher, and strut the stacks together.

Actually, to enhance the Jool slingshot, consider using a Laythe slingshot ... I remember trying to do a Laythe flyby once for science and wound up solar-retrograde by accident!

I'd say get it right the first time, eyeball the orbit on the map ... place your maneuver node and make sure the orbits match as to AP, PE, placement of those two (gives you argument of) and inclination.

Actually, I don't see the CoM moving all that much ... but it's best to see what happens if you drain all the fuel out. You might want to remove the oxidizer too if you haven't already, unless you need it for stability purposes. It's also worth making sure the forward control surfaces are disabled, just to be safe.

Doing a skip reentry is also useful if you don't trust your craft to handle the heat ... multiple braking passes means less heat generated per pass.