Leaving and returning to Kerbin SOI

[JenBurdoo]

I'm in career mode, and thinking of pulling into Kerbol orbit, doing some science, and returning. Am I right in thinking this would be about 6500 delta-v? (4500 into LKO, 1000 to escape Kerbin, 1000 to return to Kerbin)?

Also, how much more would it take to get to within 1 million KM of Kerbol for "low-altitude" science?

I am assuming I might be able to have grav-assists.

What can I expect if I do this? What would the mission profile look like? Am I going to fall behind Kerbin once in Kerbol's SOI and either have to wait for it to come round again or spend more D-v returning? And what would be preferable, going towards Kerbol or away?

Edited February 7, 2014 by JenBurdoo

[Vanamonde]

In career mode, you can just pop out of Kerbin's SOI and then burn a little to get back in and get quite a lot of science because it is considered "space high above the sun." Sorry I don't have the figures handy for it, but a ship which can reach the moons can probably do it. Getting close to the sun is quite a lot harder, though.

[DeMatt]

Just popping out of Kerbin SOI should take ~1000 m/s dV to leave, but swinging around to return will take significantly less, because you don't actually care about dropping back into orbit, and just need to aim for Kerbin. Unless you plan to stay outside Kerbin SOI for a prolonged period of time, I'd recommend a trajectory out-system, that's almost tangential with the border of the SOI when it crosses. Do your science, pull back into Kerbin SOI, then finish deorbiting from there. Shouldn't take more than two weeks game time.

Low Kerbol orbit is a very different kettle of fish. You might be able to reach the zone (from Kerbin orbit) with 3 km/s dV, but if you actually want to drop into a "low Kerbol orbit" rather than just speed through, you'll be spending upwards of 8 km/s dV.

[Taki117]

The best way to go about getting into Low Kerbl Orbit is to do something called a

. BAsically you raise your Apoapsis super high, then when you get there burn just a little to lower your periapsis, and then you're good.

[Kryxal]

I would think it would be enough to JUST escape Kerbin's SOI, you could then get back in with maybe a few dozen m/s burn ... and if you manage it straight from LKO, and aim your burn to be at Kerbin and a bit retrograde, I would think you could deorbit right off. It's probably best to quicksave just before you leave the SOI, though.

[Streetwind]

Yes, this works reliably. Just make sure you fly ahead of the Kerbin system for the easiest time returning. Then all you need to do after exiting Kerbin's SoI is to perform your science and then brake hard (burn retrograde). Kerbin will simply catch up with you again and collect you along the way (you will see a Kerbin intercept show up after you burned enough).

Edited February 5, 2014 by Streetwind

[blizzy78]

Just make sure you fly ahead of the Kerbin system for the easiest time returning.

Shouldn't this be as easy as leaving retrograde? Brake to leave Kerbin's SoI, do science, then go Kerbin prograde again to encounter its SoI? There might be a little difference in dV requirements, but I don't think it is harder to pull off. Haven't tried it, though

[JenBurdoo]

Thanks for the tips, folks, it worked like a charm. Got close to 500 sci for an 8-day flight with Bob Kerman.

I'm curious about using a bi-elliptic transfer to get into "low" Kerbol orbit -- wouldn't that take, like, forever? Couldn't you do it more easily by using a few gravity assists?