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Hello ! Nice tool ! It would also be really cool if the trajectory could be drawn when clicking a point.

Yes, I think that it would be possible to input Kerbal universe in it. But, being a realistic simulator (for real world use) it implements multiple point gravity, so for KSP use, we would have to write a plugin with a gravity model based on sphere of influence. I am still investigating it to see how useful it would be...

Hello, I have just discovered GMAT, and open source simulator made by the NASA. I wonder if it could be of any use as a KSP tool ? (I am still investigating it) http://gmat.gsfc.nasa.gov/

Well, if before your flyby with the Mun you were orbiting around Kerbin, and after, without thrusting, you have left Kerbin sphere of influence, then it is likely to have been a slingshot. Unless you were very close to escape velocity, and when you left the system was toward the sun, lowering just enough the escape velocity so you escaped Kerbin. (Though, I don\'t know if this is likely)

Not really. Or not in one go at least : during a slingshot with the Mun, your trajectory your mechanical energy with the Mun, and trajectory with will stay the same. But once you would have escaped its SOI, you would have lost energy compared to Kerbin (slowed down compared to it). But it could have slowed down you enough compared to Kerbin so that you periapsis is now in the planet. Hence the free return flight back home after a Mun flyby (you won\'t even need to lower you periapsis to land). As far as I understood, in real life, slinghsots are mostly used to alter energy to reach a third body (slingshoting around Jupiter to reach Pluto, or even reach the solar system escape velocity). They also are used ot get enough energy to change the plan in which the probe is orbiting (slingshot with jupiter to to able to have the probe flying above the pole of the sun). Though, in that case, I am not sure that the slingshot (change in energy) is really the main effect. It might just be that a slight change in the plan of the orbit around the sun is amplified when flying close to a planet...

Well, to the 'none of this is modelled in KSP', actually, yes it is : It is a direct consenquence of the fact that you ship is being attracted by a moving object (the Mun) which has a limited sphere of influence (compared to Kerbin). So with movement and gravity, no need to add anything else in the model to have that effect. So actually, everytime a ship enters the infuence zone of Mun and leaves it, its mecanical energie compared to Kerbin would have been altered. The question, is how to make the most of (but I reckon : how would we define 'the most') What isn\'t modelled though, is the Mun\'s change of velocity after after the slinghsot. But the mass of the craft is so small compared to the Mun, that it can be omitted. This is partly true. I have done calculations with the vectors (it wasn\'t that difficult, but it is the kind of exercise that I haven\'t done since 15 years...). Actually, if the speed of you craft compared to the Mun (Vcm) is quicker than the speed of the Mun to Kerbin (Vmk), then after the slingshot, you would could have added or substracted twice the speed of the Mun to Kerbin to your original speed of to craft to Kerbin (Vck). - If you were moving in the same direction then, you would have slowed down (see second animation in first post). - If you were moving opposit to the movement of the Mun, then, you would have accelerated. If speed of the Mun to Kerbin was higher than the speed of your craft to the Mun, then the max change of speed would have been twice the speed of your craft to the Mun. You would get the optimal change of speed if you were moving exactly on the same axis as the Mun, and would leave on the same axis, but in the opposit direction : (Taken from the article http://en.wikipedia.org/wiki/Slingshot_effect ) So, if I sum up the words above : Lets have : Vck : the initial speed of your craft to Kerbin V final : the speed of you craft to Kerbin after the slingshot Vcm : the inital speed of your kraft to the Mun Vmk : the speed of the Mun to Kerbin Then : If Vcm > Vmk and you originally move in the same direction as the Mun, then V final = Vck - 2*Vmk If Vcm > Vmk and you originally move int the opposit direction of the Mun, then V final = Vck + 2*Vmk If Vcm < Vmk and you originally move in the same direction as the Mun, then V final = Vck - 2*Vcm If Vcm < Vmk and you originally move int the opposit direction of the Mun, then V final = Vck + 2*Vcm But this is theoritical, and it doesn\'t really tells how to use it... Edit : Check out the deepspace manual at this page. It is originally written for orbiter, but contains interresting technics related to slinghsots.

I knew someone would reply that... : I meant, those 2 graphics don\'t appear on any english pages in the wiki. Or at least I don\'t know where to find them. True 'optimizing' is very vague and depends on your purpose. Well, what I meant was increasing as much as possible the rocket\'s energie in the original system (kerbin)

Hello, I wonder if we have any tool or good rule of thumb to optimize the slingshot effect we could get from the Mun... Or estimate how much energie we got / will get from it. (take from the french version in wikipedia. I am not sure where to find those in the english version) http://fr.wikipedia.org/wiki/Assistance_gravitationnelle Edit : One of the use for example, is the free return to Kerbin after visiting the Mun : http://kerbalspaceprogram.com/forum/index.php?topic=6058.0 Some others would be to launch further into space (then, predicting the course would be even more complicated...)

Hmm. I see the principle : at periapsis, it would behave as if we are orbiting, but a much greater speed than the attraction would allow. So we need to compensate g with thrust. That would be very expensive indeed. I suspect that the 'solution' I tried were more efficient in terms of fuel, but worked in growing the apoapsis roughly in the direction I wanted. I can\'t try again though : I am away from my Kerbal able computer for a month or so...

Hello ! That tools looks very useful (but might require some time to master...). A suggestion though : would it be possible to have thousands separators for an easier reading of large figures ?

I had tried that close to the Mun. It mainly grew the apoapsis instead of turning it (And I ended orbiting the sun...). I feel that vertical or perpendicular to the trajectory is the key (unless making the orbit circular is more efficient... )

Hmm, it might more efficient in terms of fuel if done close to periapsis... The idea of 'vertical' is good though. I have done some tests : - when close to periapsis (but not right there) and firing perpendicular to the trajectory I could push the apoapsis opposit of me if thrusting toward the inside (inward ?) of the orbit (brown side of the ball in front) - I could have the apoapsis come closer to me when thrusting toward the outside. I don\'t really know how efficient it is in terms of fuel... and what the optimum would be (toward the planet, perpendicular of the orbit, toward the center of the orbit ? How far from periapsis...)

Hello ! Do you know if is possible to rotate the apoapsis of an orbit with an high eccentricity (That is, apopsis is at 90° from earth and move it a few degrees East or West) ? (I mean, apart from making it circular, and firing when opposite of the place that I want to turn into apoapsis)