General Delta V cost question about Vall landing

[llamatoes]

I am attempting my first manned landing in the Joolian system, and have picked Vall.

I have, depending on how much I burn, I either a direct Vall, Laythe or Jool encounter. Would it cost less to Brake directly around Vall, Aerobrake round Laythe and performing a transfer or simply aerobraking Jool and performing a transfer?

[Tw1]

Is this a question about capture, rather than landing?

I had a probe in these situation, and read somewhere that aerobreaking at Laythe, then doing a holman to your target saves a fair bit of delta V, as you're not climbing out of Jool's gravity well.

However, aerobreaking at Jool is safer, as it's more gradual.

I wouldn't pass the opportunity to save fuel if you're good to aerobrake.

I say choose based on what your craft can take.

(As long as Laythe is on the right side Jool to give you a Prograde orbit after aerobraking.)

An option you could consider is aerobraking at Jool, but only enough to put your vessel in an orbit where the Apoapsis meets the orbit of Vall. Then you wait till intercept is near, and tweek your orbit.

This is fine if you're able to wait.

However, I have not yet tested this, only read about it.

So I'll be interested to hear how it goes.

Edited April 27, 2013 by Tw1

[saik0]

I am attempting my first manned landing in the Joolian system, and have picked Vall.

I have, depending on how much I burn, I either a direct Vall, Laythe or Jool encounter. Would it cost less to Brake directly around Vall, Aerobrake round Laythe and performing a transfer or simply aerobraking Jool and performing a transfer?

Aerobraking into a Vall intercept from Laythe would be difficult. My vote goes to aerocapturing into Jool orbit with Ap near Vall's orbit altitude, then waiting for an encounter.

[llamatoes]

I can get a vall encounter, that is my destination.

[Tw1]

I'd suspect that breaking at Vall would be most expensive, but I've got no figures to back this up.

It could be a burn from low Jool orbit would cost more. Also depends on the trajectory of your Jool encounter.

If everything was in alignment, there would be less relative velocity between yourself and Vall, than yourself and Jool.

Perhaps another way would be to aerobrake at Laythe, but into a slightly elliptical Jool orbit rather than Laythe capture.

Then you'd just raise the apoapsis at the right point to intercept Vall.

Slower, but more efficient.

Edited April 27, 2013 by Tw1

[Giggleplex777]

If you use multiple Vall slingshots to put your final orbit somewhat similar to Vall's, orbital insertion should only cost bout 400 m/s.

[bsalis]

Braking directly around Vall... I think you can rule that out. It's either Jool or Laythe.

I could type quite a bit about the benefits and drawbacks of either. If you asked what my preference is I would say do a direct aerobrake into Laythe, then transfer to Vall. If you do want to do this efficiently then you need to...

a) Set your plane alignment precisely for Jool, since plane changes in Laythe orbit are a pain, because the most efficient way do this is to initially set your Ap high, but SOI of Laythe is so damn small.

Know how to get an intercept for Laythe as soon as you enter the Jool SOI.

c) Direct aerobrake into Laythe orbit has very fine tolerances. So be prepared for a *lot* of quickloading, or a lot of passes, or just use the MechJeb re-entry simulator info.

[SunJumper]

If you use multiple Vall slingshots to put your final orbit somewhat similar to Vall's, orbital insertion should only cost bout 400 m/s.

Yes, that may be so, but your craft should be engineered to not rely on so many gravity assists...

[tomf]

I calculated the other day that the best way was to aerobrake with jool to get an orbit that is just captured, burn at ap just inside the soi to raise your pe to val orbit before burning to be captured y val. Basically a bi-elliptic transfer. It 's not a quick option though.