Jool capture with incredibly low TWR

[jarmund]

Alright, so my Jool5 is getting ready to depart from kerbin. It consists of 3 landers and a mothership/tug with 4 LV-Ns and a stupid amount of liquid fuel. My DeltaV is literally off the charts: NaN m/s. I have enough fuel for around 5 hours of continuous burn.

This, ofcourse, comes at the expense of TWR, which is 0.05 at the moment.

I'm raising my kerbin AP little by little, trying to keep it approximately in line with the desired escape. However, I will not have this option once I get to jool - My question then is: What's the best approach for ensuring a jool capture in a timely manner? I wouldn't want to aerobrake at Laythe, as my contraption probably won't survive the forces. My number one priority is ensuring I don't simply scoot through the joolian system, so where should I aim my PE? Tylo? Jool?

Edited November 7, 2015 by jarmund

[Empiro]

I'd go for a reverse gravity assist. If you correct your inclination before you arrive, it's very easy to get an encounter with any of the 3 inner moons.

[Superfluous J]

Nail your Jool encounter way out. Preferably while still in Kerbin's SOI but at the midpoint or AN/DN should be fine. Burn to pass Jool on the right (so you're going the same direction as the moons) and get your trajectory passing right through Laythe or Tylo's SOI. Laythe's good because it's close and Jool's gravity gradient's more pronounced, and Tylo's good because it has more weight to throw (you) around.

Do that burn, and if you're lucky you'll actually get an encounter with that moon, and for a couple decimeters per second you can tweak the encounter (I suggest using a maneuver node to tweak, so you only have to burn once) to enter the moon's SOI from behind, and exit from the side putting you into a Jool orbit. If you're not lucky, no biggie. Just (again, use a maneuver node. Measure twice, burn once as they say) do a burn that is a combination of radial and -grade for - again - a few decimeters per second and you'll get an encounter in no time. Then tweak it as above.

If it's too squirrely (it's hard to do a perfect 2-decimeter burn with a massive hulk of a ship) just go forward about halfway to Jool, and the burn will take more dV and therefore be a bit easier to fudge.

[Snark]

What Horseman said. Reverse gravity assist FTW, plus of course get a good transfer window so that your velocity on Jool arrival is manageable.

[cantab]

If you have a ton of delta-V then who gives a flying fig about Oberth. Capture into a wide orbit round Jool, then go as desired from there.

[jarmund]

Sounds like a reverse gravity assist via Tylo is my best bet for my ship not to just fly through. It'll result in a retrograde orbit, but fixing that afterwards shouldn't be a problem with the amount of dV i have. Cheers for your inputs.

[Superfluous J]

Sounds like a reverse gravity assist via Tylo is my best bet for my ship not to just fly through. It'll result in a retrograde orbit, but fixing that afterwards shouldn't be a problem with the amount of dV i have. Cheers for your inputs.

It doesn't have to put you retrograde. Keep playing with those maneuver nodes. Or, check your resultant orbit, it may not be retrograde at all.

[KerikBalm]

I second that... there is no reason that a gravity assist from one of the moons has to put you in a retrograde orbit of Jool. Laythe or Tylo are your best bets.

I prefer laythe because

a) thats where my exploration stuff is focusing on and where I plan on putting most of my assets in the Jool system

after enough gravity assists, you can also start aerobraking to get a more circular and regular orbit.

[jarmund]

after enough gravity assists, you can also start aerobraking to get a more circular and regular orbit.

Aerobraking with this behemoth of a ship on this potato of a computer will result in something catching fire - Not sure if my ship or my laptop will first.