Ksp RSS how can I make complicated gravity assists ?

[berkekrkn]

So now I can make the simple gravity assist. For example I could make a gravity assist from Venus to go to Mars. But now I want to go to Saturn.

I searched a mission called Cassini and that spacecraft gone to Saturn with Earth-->Venus-->Venus--->Earth--->Jupiter. Without gravity assist I need 7700 m/s ejection deltaV. it is really a lot.

With launch window I could make the simple assists but now it becomes really complicated.

I've found a program Ksp Trajectory optimization tool: 

 

That calculates my path good. 

On the delta v section it says total delta V: 32.332 m/s. 

This costs more than a direct burn. Is this correct ? if so what should I do to lower that ? 

 

To sum up: How can I calculate these type of complicated burns ? And can you guys offer me a program that calculates these type of manuevers very well. The results from ksp TOT not covincing I think.

[Red Iron Crown]

Something is wrong with that calculated maneuver, an ejection burn should never have that much normal dV or a retrograde component.

You could try Flyby Finder for RSS, it's a good bit simpler than KSPTOT for finding good times to do a slingshot. Check it out here:

 

[berkekrkn]

2 hours ago, Red Iron Crown said:

Something is wrong with that calculated maneuver, an ejection burn should never have that much normal dV or a retrograde component.

You could try Flyby Finder for RSS, it's a good bit simpler than KSPTOT for finding good times to do a slingshot. Check it out here:

 

Thanks for the answer I also tried that program but as result it is showing nothing. 

 

 

On ksp tot what is wrong with the planning ? I selected multi flyby manuever sequencer, I put launch window time same as the ksp time. I am not sure what to put in latest departure time but I've put 10 years after the ksp time. 

 

I've entered Earth--->Venus---->Earth---->Earth for Jupiter like Galileo spaceraft did. I left the orbit info blank cuz I didn't launch the spacecraft yet.

 

And that's all I can. And they seem to be correct. Is something wrong here. Or can you quickly plan same route for yourself and compare your result with mine ?

 

Btw. the flightpath is correct. I've double-checked it with the galileo's flightpath and they were same except the delta V requirement.

Edited July 12, 2016 by berkekrkn

[Red Iron Crown]

Sorry, I don't have much experience with KSPTOT. Maybe ask in the thread for the mod? I know @Arrowstar is very helpful.

[Epox75]

This kind of trajectory is very complex, I can tell you are trying to redo the Cassini mission. The Cassini spacecraft did a very long deep-space maneuver before the 2nd Venus flyby. When you install RSS, you install also Kopernicus which follows the real calendar, so a good day to launch would be the 15th of October 1997. If you want to see the real date in KSP you can install RSS date formatter. 

Anyway as I was saying, Cassini and many other spacecrafts did correction maneuvers before the gravity assists and KSPTOT multi fly-by finder doesn't calculate this. 

So my suggestion is to take a mission timeline (Wikipedia has a very nice page: https://en.wikipedia.org/wiki/Timeline_of_Cassini–Huygens) and follow it step by step.  Also http://dmuller.net/ has a lot of useful information about all the past and present missions. 

If you look for Gravity Assist Trajectories to the Outer Planets on Google you will find a lot of PDF documents reporting list of possible launch widows for multi-flyby missions. And http://trajbrowser.arc.nasa.gov/traj_browser.php is a useful trajectory browser by NASA.

 

 

 

 

[PLAD]

Earth-Venus-Venus-Earth-Jupiter, or E-V-E-E-J involve a double flyby (also called a "direct-return" flyby) where you go by the same planet twice in a row. My Flyby Finder can't handle those and last time I checked TOT can't do it either, although he has been adding a lot of features to it so you should check. In addition (as noted by @Epox75 above) Cassini (and Galileo) made deep space maneuvers that are also tricky to plan. 

However it is possible to slowly find ballistic paths with double flybys using my LambertRSS spreadsheet and Flyby Finder together. I search for E-V-E paths, then for E-J paths (or E-J-Saturn), and try and find ones where both A) the Earth arrival from Venus and the Earth departure to Jupiter a separated by exactly two Earth years, and B) then Vinf in and Vinf out from Earth are nearly the same. Then I use Lambert to make sure the turning angle at Earth allows a flyby that is above the atmosphere. I've found two EVEEJ paths so far (obviously I was trying to simulate Galileo). Here's the best one:

Leave Earth day 2530.3 with an ejection dV of 3772m/s from a 200x200km orbit. This is game Year 7 day 340 and Dec 4, 1957.

Flyby Venus day 2703 (=Y8 d148) altitude 4930km.

Flyby Earth day 3028 (=Y9 d108) altitude 6095km.

Flyby Earth day 3757.7 (=Y11 d107) altitude 1804km.

Reach Jupiter day 5185 (=Y15 d75).

You can then flyby Jupiter at 171,000km and arrive at Saturn at day 11160 (=Y31 d210) but that is a ridiculously long flight.

If you do this flight you'll notice that the Earth-Jupiter leg is not a good Hohmann, that is where a DSM between the Earth encounters would help.

.

[Epox75]

Hi again! I think I have info on your specific "problem"  It's the SMA (Semi Major Axis) option. 800 is quite well under the Earth's Surface. A value of 6800/6900 should be fine