How do I use nuclear or ion engines for interplanetary purposes?

[SpaceToad]

Hey all,

So.... I want to use ion engines and nuclear engines to send a craft to Duna. Now, burn times are larger than my orbital period, so I was thinking why not do multiple burns. But then it hit me that my phase angle would change over time as I perform these burns... Any ideas?

[Superfluous J]

Time it so the final burn happens at the time you'd normally just do your one burn. It also helps to re-place the maneuver node each time, or at least on the final burn so you know you're doing it correctly.

Also, interplanetary burn windows are generally pretty wide, several days usually. Once your orbit will get big enough to care about the time it takes, you're at the point where you should just do the whole burn because you're only "saving" a couple dozen dV before ejection anyway.

[The_Rocketeer]

Time it so the final burn happens at the time you'd normally just do your one burn. It also helps to re-place the maneuver node each time, or at least on the final burn so you know you're doing it correctly.

Also, interplanetary burn windows are generally pretty wide, several days usually. Once your orbit will get big enough to care about the time it takes, you're at the point where you should just do the whole burn because you're only "saving" a couple dozen dV before ejection anyway.

Yeh, if you can get into a highly eccentric orbit ahead of time, say to Minmus altitude on an 'almost right' angle for your transfer burn, you can make your transfer burn during your last pass by Kerbin. As 5thHorseman says, you don't need to bullseye the centre of the window to get a near-perfect-efficiency transfer, and being a couple of degrees off course costs practically nothing to correct as long as you sort it at the Kerbin end.

[Kryxal]

I prefer to stay under the radius of the Mun's orbit ... you don't get all the delta-v you would going WAY out there, but you get most of it (maybe 800+ m/s), a shorter orbital period, and no chance of running into the Mun. Incidentally, to set up the burn, just next-orbit your node 6-8 hours into the future and see what happens...

[Red Iron Crown]

I wrote a little tutorial on splitting up burns to make the times more manageable while still hitting the transfer window at the right time and angle. It includes some precomputed burns as well as a spreadsheet for calculating your own. Take a look here: http://forum.kerbalspaceprogram.com/threads/109670

[xtoro]

When you enter Duna's SOI, make a maneuver node at the periapsis. Pull retro until you have the desired orbit. Now next to your NavBall you have dV, burn time and time to node. Take the burn time, divide it by half, and start your burn when the time to node matches half the burn time. Of course you want to be burning towards the blue maneuver node...

If it's a very very long burn and your orbit is getting wonky, you can steer a little towards radial or anti-radial to make adjustments as you burn.

[thedanieldude]

The KSP Trajectory Optimization Tool Mission Planner has a tool that lets you plan burns. Here's a link if you want it, http://forum.kerbalspaceprogram.com/threads/36476-WIN-MAC-KSP-Trajectory-Optimization-Tool-v1-5-0-Optimizations!

[cantab]

If you're using ions you probably have lots of delta-V and can afford to use higher parking orbits, that's how I handle things.