Kerbin --> Eve --> Duna+Ike --> Kerbin

[Paranoid Shark]

Hi, 

I have the Duna 3 Flyby contract and I have no idea when to start my trip to Eve. I plan to fly by Eve and Ike before orbiting Duna. This is my 1st interplanetary trip, and I plan on using the Kassandra Spacecraft by @H2O. 

What angles should I have Kerbin, Eve and Duna? How long should I stay at Duna? Is there an easy way to work this out? Current date is year 3, day 70.

Thanks,

Update

Firstly let me say, many thanks to you guys. The tips you gave me helped me work out that I needed more information!

I found the KSP Trajectory Optimization Tool by @Arrowstar to be quite helpful as it has a multi-flyby plotter (had to switch to Earth time though). It has given me lots of information to digest, however I'm not sure how to turn the information that I have into an actual maneuver! The Delta V  and Departure/Arrival dates information is particularly helpful, it looks like I can get from Kerbin to Eve for 1377m/s and then do a 515m/s correction burn at Eve, giving me around 1200m/s left in the transfer stage to capture at Duna.  

Kerbin Departure Date = 
                Year 2, Day 283 06:54:04.673
                       (55925644.673 sec UT)
Eve Arrival Date = 
                Year 2, Day 334 20:28:13.330
                       (60380893.330 sec UT)
Duna Arrival Date = 
                 Year 3, Day 23 17:42:52.033
                       (65036572.033 sec UT)

Burn Information to Depart Kerbin
---------------------------------------------
Total Delta-V =                 1.377 km/s
Prograde Delta-V =              538.875 m/s
Orbit Normal Delta-V =          -1266.975 m/s
Radial Delta-V =                0.000 m/s
---------------------
Burn True Anomaly =             358.770 deg
---------------------------------------------
Burn Information to Depart Eve
---------------------------------------------
Total Delta-V =                 0.515 km/s
Prograde Delta-V =              515.340 m/s
Orbit Normal Delta-V =          -0.000 m/s
Radial Delta-V =                0.000 m/s
---------------------
Burn True Anomaly =             0.000 deg
---------------------------------------------

The problem I have now is working out when in my 750km parking orbit I need to do the Initial burn. This is the rest of the information it has given me. 

Hyperbolic Departure & Flyby Orbits

Hyperbolic Departure Orbit from Kerbin
---------------------------------------------
Semi-major Axis =               -3452.976 km
Eccentricity =                  1.391
Inclination =                   30.437 deg
Right Ascension of AN =         178.770 deg
Argument of Periapse =          180.000 deg
---------------------------------------------
Inbound Hyperbolic Flyby Orbit to Eve
---------------------------------------------
Semi-major Axis =               -4725.402 km
Eccentricity =                  2.3764
Inclination =                   28.615 deg
Right Ascension of AN =         97.408 deg
Argument of Periapse =          310.331 deg
Periapse Radius =               6503.888 km
---------------------------------------------
Outbound Hyperbolic Flyby Orbit from Eve
---------------------------------------------
Semi-major Axis =               -1984.515 km
Eccentricity =                  4.2773
Inclination =                   28.615 deg
Right Ascension of AN =         97.408 deg
Argument of Periapse =          310.331 deg
Periapse Radius =               6503.888 km
---------------------------------------------
Inbound Hyperbolic Orbit to Duna
---------------------------------------------
Hyperbolic Excess Vel. =        1.607 km/s

Sun-Centric Transfer Orbits

Phase 1 Transfer Orbit (Kerbin -> Eve)
---------------------------------------------
Semi-major Axis =             11546276.670 km
Eccentricity =                  0.18242
Inclination =                   2.426 deg
Right Ascension of AN =         27.461 deg
Argument of Periapse =          10.692 deg
Period =                     7199748.9136 sec
Departure True Anomaly =        169.308 deg
Arrival True Anomaly =          39.623 deg
---------------------------------------------
Phase 2 Transfer Orbit (Eve -> Duna)
---------------------------------------------
Semi-major Axis =             15394858.102 km
Eccentricity =                  0.36852
Inclination =                   4.649 deg
Right Ascension of AN =         54.115 deg
Argument of Periapse =          10.917 deg
Period =                    11084546.9362 sec
Departure True Anomaly =        12.788 deg
Arrival True Anomaly =          168.350 deg
---------------------------------------------

Edited February 5, 2016 by Paranoid Shark
Update

[Evanitis]

Pretty tricky plan for going on your first interplanetary trip..

You'll need the Launch Window Planner. You just enter the start and destination planets, your orbit, the date, and click calculate. It will give a colorful chart - click on a deep-blue spot (that means the least required dV), and it gives you the ideal time to depart, as well as the ejection angle to aim for. In case that angle is just a strange number for you, it's explained here what it means.

The next step is tricky. You can orbit Eve and do the same process above to find a window for Duna. But going for that orbit will probably take some dV (even if you can use Gilly's gravity to slow down a bit). It would be better to use Eve's gravity to get you to Duna during a flyby, but than the red planet should also be on the right spot. I don't really know how to find a planetary alignment for all three.

But anyhow, I'd read up on gravity assisting too - even knowing the very basics and using the moons on the way (Mun, Gilly even Ike on the way home) will let you save fuel on the trip. And if you are lucky (or do math that's beyond me), Eve will just fling you straight to Duna.

Edited February 5, 2016 by Evanitis

[Snark]

My personal favorite launch window planner is http://ksp.olex.biz .  It doesn't have the fancy colorful chart, but it's extremely easy to use, and has a really nice graphical display of the angles involved.  Just put in the start and destination planets and the height of your parking orbit at the origin.

For a launch to Eve from Kerbin, you'll have a burn of a bit over 1000 m/s (depending on height of parking orbit), when Eve is about 54 degrees behind Kerbin in its orbit.

As for getting from Eve to Duna + Ike:  That sort of multi-planet "bank shot" is tricky to figure out, as @Evanitis points out.  There are various strategies, depending on what you're trying to optimize for.  Here's a suggestion that's a reasonable compromise between trying to save dV on the one hand, and not being too hard to figure out on the other.

1. Set up an efficient trip from Kerbin to Eve, using the transfer window planner of your choice.
2. Upon arrival at Eve, have a low Pe (but out of atmosphere!)
3. Use Eve to get a gravity assist to raise your Ap.  Basically, you want your trajectory past Eve to be going behind it in its orbit around the Sun.
4. You want to raise your solar Ap up to Duna's orbit.  I'm guessing an Eve gravity assist alone won't be enough to do that, but you can do an Oberth maneuver to help nudge it along.  Set up a maneuver node at your Eve Pe to burn prograde by enough to raise your Ap up to Duna's.  Note:  You're not trying to get a Duna encounter, just raise your Ap up so that it touches Duna's orbit.
5. Once you're past Eve and on your way, set up a maneuver node at your Ap so that you will get a Duna encounter.  This is where there's a certain amount of luck involved, in terms of how many orbits it will take to get a Duna encounter.  You may have to wait an orbit or two.  But with a modest dV burn there, you should be able to get an encounter within a couple of orbits at most.

 

[Warzouz]

And why note get to Duna first , stay in orbit and do a Ike FB too ? Wait for a proper Eve window and try to get a dirty Kerbin encounter with gravtiy asist at Eve.

Duna is quite cheap, to it's possible to wait there for a bargain while doing a Ike encounter.

[SpaceNomad]

On 5.2.2016 at 5:49 AM, Snark said:

My personal favorite launch window planner is http://ksp.olex.biz .  It doesn't have the fancy colorful chart, but it's extremely easy to use, and has a really nice graphical display of the angles involved.

The combination of Kerbal Alarm Clock and Transfer Window Planner also has a great visualization of ejection angles since the newest KAC version v3.5.0.0 (see this post for a demonstration).