Happy accident... wish I knew how I did it...

[Scottiths]

So I was doing Pe kicks to get to Jool. Unfortunately Mun got in the way, but I figured "meh, it dosen't change my orbit much." (because i kinda just went right past it. Well once I exited the SOI on the up trip it turns out that I encountered Mun again coming back to Kerbin. I was like "well that kinda kills my ejection angle." Then I realized that I had just gotten an escape trajectory from kerbin for only 800 m/s Dv... I figured I would just see what planets I could get to. Turns out I can get to Duna despite my entirely wrong phase angle for only 1000 m/s Dv. Talk about happy accidents

I am going to get there with almost 8,000m/s extra Dv. Can anyone tell me any way to repeat this process in the future on purpose (and somehow maintain an appropriate phase angle)? This is the most epic gravity assist

[Richy teh space man]

I think it's more a case of luck just getting everything to line up perfectly. I don't know of any mods that do what your describing, but perhaps someone will make one in the future..

[lyndonguitar]

mechjeb can do this from kerbin orbit, burn and direct escape to duna, although you have to wait for the proper time and alignment(could take days or weeks), The same thing happened to you, only you did not plan it

[Tw1]

There's something about it in the wiki.

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Gravity_Assist

If it works as well as you describe, I might have to give it ago.

Especially, if you're less dependent on phase angles this way.

[lyndonguitar]

There's something about it in the wiki.

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Gravity_Assist

If it works as well as you describe, I might have to give it ago.

Especially, if you're less dependent on phase angles this way.

Real life probes do this all the time

[Anglave]

It only takes about 1060 m/s Dv to make an (optimal) transfer from LKO to Duna intercept. A budget of 1200 m/s Dv should give you enough to aerobrake at Duna, plus some extra for small corrections.

How are you arriving with "8000 m/s extra"?

I ask because it's possible the Munar encounter didn't do as much for you as you think?

[JeanHavoc]

Funny you mention this. Yesterday, I was gearing up to send a probe to Jool and it just so happened that as I made my ejection burn I ended up with a Munar encounter along the way. I didn't think much of it and I wasn't very worried about the effect it would have on my mission, but things got even more interesting shortly thereafter as I -also- had a Minmus encounter to top things off. I comment here because now I'm curious as to what impact, if any, both of those flybys had on my DeltaV and subsequent fuel consumption. Can such things be calculated accurately, at least within the world of KSP?

[Scottiths]

I had 8,000 because it was a planned mission to Jool, not Duna. I just went to Duna because it was there. The phase angle was waaay off for duna (I am talking months) and I still only spent about 1000 m/s. I decided to reload the game (because I quicksave on every Pe kick because of stuff like this ) and see what it would take to go to jool. I arrived at Jool having spent 3145 m/s Dv (according to Mechjeb). Keep in mind that my phase angle was off by 11 days at this point (also my I have no idea what my ejection angle was because Mun screwed it up)

I think the double gravity assist from Mun helped a lot. I just don't know how to do it reliably.

[lyndonguitar]

The problem here is that the map is hard to navigate around, we should have a free cam and not always focus on something, another problem is your projected trajectory sometimes doesn't project all of it, you can plan a gravity assist but most of the time you cannot see where it would lead, unless you use a trajectory computer like mechjeb(maneuver planner)

[Noticeably FAT]

The problem here is that the map is hard to navigate around, we should have a free cam and not always focus on something, another problem is your projected trajectory sometimes doesn't project all of it, you can plan a gravity assist but most of the time you cannot see where it would lead, unless you use a trajectory computer like mechjeb(maneuver planner)

I forget where, but you can edit a cfg. file somewhere to let KSP calculate more than 3 SOI changes.

[MRab2]

It's called a slingshot maneuver. It's done all the time in RL. By passing close to a celestial body some of its orbital velocity (I think that's the term) is transferred to you. In the case of the Mun that's a maximum of 542.5m/s of extra speed for free.

I expect Sling-shotting to feature more in the game once it's more developed - once the current planning flight paths on-the-fly is replaced.

[lyndonguitar]

I forget where, but you can edit a cfg. file somewhere to let KSP calculate more than 3 SOI changes.

That should be handy

[lyndonguitar]

I now know how to do it

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Gravity_Assist