How to hit Duna?

[lucidLemon]

Using olex's orbital calculator and a protractor mod, I've managed to line everything up (multiple times) but it seems that Duna's eccentricity is completely throwing off the calculations. When I look at the map, it seems like the intercept could work for when Duna is at the lowest point in it's orbit, but not for any other point. Am I using the calculator incorrectly, and if I'm not, then how do I account for Duna's eccentricity?

[adammada]

just fix your orbit en route. Thrust up or down looking at course.

[olex]

As posted in the calculator thread, here's how you perform the corrections to account for a late or early intercept due to target eccentricity:

What you need to do if you don't get a straight intercept, is warp until mid-transfer, and then first burn to adjust your transfer inclination to meet with the target orbit, and then possibly do a couple burns to offset the phase angle error introduced by eccentricity. To do that, you need to judge whether you are "too early" or "too late" at the transfer point (a quicksave and warping to rendezvous point is a good way to determine that). If you are early, burn between RAD+ and retrograde to shorten your orbit while still keeping it near the target, and if you're late, burn between RAD- and prograde - with those corrections, if the inclination is correct, you'll definitely get a rendezvous (as long as you have enough fuel for the correction burns).

[lucidLemon]

I think I understated the severity of how off course my trajectory is, it's not even close, despite phase and ejection angle and ejection velocity being matched almost perfectly.

It's only sending me around halfway the distance between Duna and Kerbin, but it definitely looks like it would intercept if Duna were at the lower altitude section of it's orbit.

EDIT:

You ninja'd me olex, I hadn't really been able to access most of the forums due to lag. I'll try this out.

Edited September 22, 2012 by lucidLemon

[adammada]

dont look at speed, just burn until your orbit will meet dune orbit.

[lucidLemon]

I think I must be doing something horribly wrong, because the delta-V that I would have to spend on corrections seems absolutely enormous.

The values in parenthesis are the values given to me by the calculator. The picture below was with a phase angle .01 less than the target phase angle (44.36), an ejection angle +/-1 away from the target ejection angle (150.91),10 m/s above the target ejection velocity (3289.2), and altitude 200-500 m above the intended altitude (100 km)

All that other junk is the sad total misses that followed trying to raise the apoapsis to match duna's orbit

EDIT:

Aha! I was going at the ejection angle actually about 60 degrees before the ejection angle I needed

Edited September 22, 2012 by lucidLemon

[djnekkid]

I managed to get a sattelite in duna orbit just a couple of hours ago. Trying to transfer the fuelefficient way in the mentioned calculator. But i were about 2mill km behind. Circulizing the orbit made me hit the planet SoI after about half an orbit. Now I can use the roundevouz module in MechJab to let me be 14,5mill km away from the planet, and it should be easier to hit the next time

Edited September 22, 2012 by djnekkid
typo

[Znath]

A lot of quicksaving and loading for me.

Intercepting an orbit isn't bad as long as you're not too low or too high.

There's apparently mods that will show what you need to do for a good orbital interception, but I don't have those right now.

My method of getting out of Kerbin's orbit is doing an approach to Mun and trying for a gravity assist then thrusting as I begin to leave it. If that's not enough to escape, I let the craft fall back down to Kerbin and thrust off again until I can achieve an escape. After that I wait until the lowest part of the orbit to thrust again forcing the peak into Duna's orbit.

After you get that far, it's just a matter of intercepting it and making sure your orbits are lined up.

My biggest problem now is getting back!

I can land on Duna with almost 1 full tank of fuel... unfortunately this is barely enough for me to get to intercepting the Kerbin orbit. My next design has 2 more 1/2 tanks and 2 more large solid boosters on the base. I haven't tested it yet, but hopefully it won't explode, and hopefully those two changes will be enough. I don't know if the single nuclear thruster has the power to leave Duna with the extra weight though..

[The Destroyer]

Hmm, i never used any exact calculations. i just looked at map, then at the page at www.ksp.olex.com and when they look similar, i burn untill it says encounter. also, go to settings.cfg and change maxpatchconics (somthing like that) to 5 (normal=2) because if you dont, it wont show that you have an encounter untill you escape kerbin.

[lucidLemon]

After I fixed what i was doing wrong before, I did the corrections as olex specified, and I landed on Duna!

I got that feeling that I had on my first moon landing, I love this game.