Calculating when to launch for a direct transfer.

[erkha343]

I've built a large launcher that could send an entire multi-part ship to Duna in one go, but it's so big that it's a hassle to wait in a parking orbit for the right escape angle. How can I figure out when to launch to do a direct transfer? Is it enough to launch slightly before I reach the escape angle?

Edited February 27, 2014 by erkha343

[PlonioFludrasco]

I think yes, but you must have enough TWR to do your circularization and escape burns together in an appropriate amount of time. And you won't have the opprotunity to fine-tune your orbital inclination, so you have to match it as you start the gravity turn.

[blizzy78]

You essentially need to figure out how long it takes to get to your apoapsis after liftoff. Then, lift off at the right time so that your apoapsis coincides with your escape burn point. At apoapsis, you don't burn to circularize, but burn longer to escape.

[Kasuha]

Is it enough to launch slightly before I reach the escape angle?

Generally yes but it is not exactly simple as you need to get on the right trajectory. If you can leave it up to MechJeb then it should be ok. Without that I'd recommend going to orbit first to have time to set up the maneuver.

[Kryxal]

Agreed, settling into LKO for an hour or two isn't a huge deal ... for that matter, you could hit LKO, do a burn of about half the required magnitude in the appropriate spot with NO normal component, do the normal component at apoapsis, then finish your transfer burn when you get back to periapsis maybe ... it adds a few hours, but you can spend most of the time at higher warps.