what's the typical depth to aerobrake around jool?

[Cirocco]

I'm planning to do my first ever jool mission soon by sending a mothership with a crapton of probes and sattelites to the joolian system, so I was wondering: if I aerobrake on jool istelf, what depth should I (roughly) aim for if I want to have my apoapsis end up somewhere in the region of laythe's orbit?

thanks in advance guys.

[Brainlord Mesomorph]

also want to know this....

[Panzerbeard]

There's no one right answer, honestly, it depends on a number of parameters. Your best bet would be to use this:

http://alterbaron.github.io/ksp_aerocalc/

Obviously, you'll need to be in Jool's SOI already to know your exact orbital velocity, so the calculator isn't ideal for planning ahead, but it is (mostly) accurate from my experience. Just be aware that if you have a lot of lifting surfaces like wings the calculator will be less reliable.

Also I don't think this will work with FAR or NEAR.

[SRV Ron]

An early version using a player's design gave me an intercept after aerobraking. The window is critical. Too high and you will fly out of the system. Too low and you will crash on the surface.

After the maneuver.

[Cirocco]

An early version using a player's design gave me an intercept after aerobraking. The window is critical. Too high and you will fly out of the system. Too low and you will crash on the surface.

http://i.imgur.com/J4ihOIi.jpg

After the maneuver.

http://i.imgur.com/BQ69bjR.jpg

that seems like roughly the orbit I'd be aiming for (I probably would prefer a slightly lower one, but this is close enough). What height was your periapsis when aerobraking?

[capi3101]

I'll tell you this much - you don't want to go in very much at all; Jool's aerobraking envelope is thin. Jool's atmo starts around 150,000 meters. I sent a probe carrier to aerobrake at 140,000 meters once; it went in. Reverted and set to 148,000 - it didn't aerobrake enough.

Yeah, Ashflare's given you the link to the aerobrake calculator; that's your best bet.

[Cirocco]

I'll tell you this much - you don't want to go in very much at all; Jool's aerobraking envelope is thin. Jool's atmo starts around 150,000 meters. I sent a probe carrier to aerobrake at 140,000 meters once; it went in. Reverted and set to 148,000 - it didn't aerobrake enough.

Yeah, Ashflare's given you the link to the aerobrake calculator; that's your best bet.

I'll have a look at the calculator, but even "between 140 000 and 148 000" is already a big help, otherwise I probably would have spent a ton of time trying to aerobrake at lower altitudes.

[DuoDex]

Highly suggest the Trajectories mod. Simplifies aerobraking an insane amount by drawing aerobraking calculations in-game.

[Slam_Jones]

For the types of craft I send to Jool (and the speed at which they approach) I usually have to dip pretty far into the atmosphere. I can't remember off the top of my head what my ships usually hit, but I'm 90% it's lower than 140,000. It may not work for you, but with my ships I think I usually hit 90,000 - 120,000. Last time I flew to Jool and aerobraked (aerobroke?) it put me in an orbit just passed Laythe, allowing my orbit to increase and encompass all the moons and I pass/get grav assist from them.

I figured this out using trial and error (quicksave/quickload) and suggest you do something similar.

Good luck!

[RexKramer]

Well, I normally shoot for about 120km when approaching directly from Kerbin.

My most recent approach from Kerbin, I was shooting for Laythe. I had a target of about 117km, ended up with 116.87km PE and went with that. Worked out pretty good, my AP ended up being halfway between Laythe and Vall's orbits.

If your orbit more closely matches Jool's when you hit Jool's SOI, you'll need a higher aerobraking PE.

[Oafman]

I usually find myself aiming for 118km, when I've consulted the calculator. I still check it each time, every interplanetary trajectory is slightly different.

[wasmic]

You can also do it a slightly less risky way and ditch the aerobraking entirely, and use the gravity of the moons of Jool to sling you into a stable orbit. It takes quite a bit of planning, but pulling it off is much less risky. I once got inserted into Jool orbit using only ~400 m/S of delta-V, by exploiting the gravity of Tylo and Vall.