Interplanetary transfer from Kerbin orbit with Mechjeb

[Tupin]

Alright, so this is a problem I've had for a very long time. I can't transfer to other planets while I'm in Kerbin's SOI. I know it's possible and I know how to time a launch for rendezvous, but I just want to know how to transfer to them from say, a 100km equatorial Kerbin orbit. Any help?

[Leatherneck]

OK, from the thread title I'm assuming you want to know how to use MechJeb to do this. Very simple.

1. You have a ship with sufficient delta-V for the job in a 100km Kerbin orbit and it's a day or so before the launch window.

2. Select the destination planet as your target.

3. Open MJ's Maneuver Planner and page through the various maneuvers until you see "Transfer to Another Planet". This works with the planet you have as your target.

4. Hit the "Create Node and Execute" button.

5. MJ will create the ejection node, warp until it's time to do it, do the burn, and so you're on your way.

6. Wait until you're a day or 2 out of Kerbin's SOI and then take a good look at your trajectory. If the target planet is in an inclined orbit, probably you don't have an encounter, maybe not even closest approach markers.

7. Make sure the destination is still set as your target.

8. Open the Maneuver Planner again and select "Fine Tune Closest Approach to Target"

9. Enter the periapsis you want when you get there. NOTE: When you actually get there, you won't have this periapsis but you'll be in the ballpark.

10. Hit the "Create Node and Execute" button again. Voila.

11. Warp until you're about 7/8 of the way to the target, then repeat the "Fine Tune Closest Approach" again.

12. When you enter the target's SOI, NOW you can finally set your periapsis exactly where you want it.

13. Get captured into orbit.

EDIT: ^ Best answer.

Edited November 5, 2013 by Leatherneck

[TelluriumCrystal]

Unless you have an intuitive understanding for these things, it is hard to figure it out just by messing around with maneuver nodes. Thus, I present to you this handy calculator: http://ksp.olex.biz

With it's power insight, you will finally be able to figure out when and where to time your burns to make perfect interplanetary intercepts! Not to mention you'll be making the trips as short as possible, so your kerbals won't be subjected to 4+ year long flight times.

Edited November 5, 2013 by Thrfoot

[Geschosskopf]

OK, from the thread title I'm assuming you want to know how to use MechJeb to do this. Very simple.

1. You have a ship with sufficient delta-V for the job in a 100km Kerbin orbit and it's a day or so before the launch window.

2. Select the destination planet as your target.

3. Open MJ's Maneuver Planner and page through the various maneuvers until you see "Transfer to Another Planet". This works with the planet you have as your target.

4. Hit the "Create Node and Execute" button.

5. MJ will create the ejection node, warp until it's time to do it, do the burn, and so you're on your way.

6. Wait until you're a day or 2 out of Kerbin's SOI and then take a good look at your trajectory. If the target planet is in an inclined orbit, probably you don't have an encounter, maybe not even closest approach markers.

7. Make sure the destination is still set as your target.

8. Open the Maneuver Planner again and select "Fine Tune Closest Approach to Target"

9. Enter the periapsis you want when you get there. NOTE: When you actually get there, you won't have this periapsis but you'll be in the ballpark.

10. Hit the "Create Node and Execute" button again. Voila.

11. Warp until you're about 7/8 of the way to the target, then repeat the "Fine Tune Closest Approach" again.

12. When you enter the target's SOI, NOW you can finally set your periapsis exactly where you want it.

13. Get captured into orbit.

[Tinyboss]

I hope five months is not too much of a necro, but I have a related question: what's the best way to time a launch so that step 5, waiting for the ejection node, doesn't take too long? I went to Eve last night, and every time I'd launch, the ejection node was about a year into the future. Worse, when I took the advice in MJ's manual about recalculating far-future nodes, by cancelling and re-creating it 20 days in advance, it said I'd need to wait another year-plus for the next ejection window!

I tried waiting for the phase angle to be -54.whatever, and that didn't help, but maybe I just barely overshot and had to wait a full cycle? Is there any function of MJ that will ensure a launch during the transfer window?

[Guest]

The only reason you would want to hit a transfer window exactly is for the fuel savings. When transfering to Eve, those fuel savings really aren't that big. You can leave Kerbin SOI at any time and then plan a regular Hohman transfer after matching planes with Eve. It's a little easier to see the position and timing of your node this way.

Other than that, Kerbal Alarm Clock will help you handle planetary transfer windows by pausing the game and throwing up a reminder window at whatever time you designate.

[wilt57]

I hope five months is not too much of a necro, but I have a related question: what's the best way to time a launch so that step 5, waiting for the ejection node, doesn't take too long? I went to Eve last night, and every time I'd launch, the ejection node was about a year into the future. Worse, when I took the advice in MJ's manual about recalculating far-future nodes, by cancelling and re-creating it 20 days in advance, it said I'd need to wait another year-plus for the next ejection window!

I tried waiting for the phase angle to be -54.whatever, and that didn't help, but maybe I just barely overshot and had to wait a full cycle? Is there any function of MJ that will ensure a launch during the transfer window?

Most likely you just overshot it by a bit. I'm pretty sure MJ's new warp helper has a phase angle mode now, but I haven't used it yet so I cannot comment on its accuracy. Otherwise Otis has a good suggestion. I mainly use Kerbal Alarm Clock. I cannot remember exactly right now because I haven't done any interplanetary stuff in a while, but there are two modes to calculate transfer times. I think MJ uses one mode for inward travel and the other for outward. I wish I could log on right now and check to help out more, but I can't.