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[Peewee]

Unless you intend to lithobrake, it would be wiser to aerobrake through Duna's atmosphere instead, as it doesn't really have enough gravity to do the trick from that angle. If it were coming toward you, it might be able to slow you down slightly, but at that angle, anything you do will either increase your (duna-based) orbital speed, or redirect you almost directly away from the planet.

[sluissa]

Yeah, slingshotting is pretty simple, in theory. If you want to speed up, you want to be moving in roughly the same direction as the body you're slingshotting with. The gain you get being pulled in by its gravity will be greater than what you lose trying to leave it. Especially if you enter the sphere of influence from a significantly different angle than the slingshot body's orbit.

The same goes for slowing down. You want to exit the slingshot body's sphere of influence going in roughly the opposite direction of its orbit. In that case it's gravity pulling on you as you leave will be greater than the gain you get from its gravity pulling you in.

As said, the velocity you gain or lose depends heavily upon how massive the object you're slingshotting with is. Don't expect much from a tiny little moon. Even the Mun can usually only give you 300-400 m/s of acceleration per pass, and that's under ideal circumstance. Your angle is not really ideal and your speed is way too different from Duna's to be changed efficiently by gravity alone. I'd agree to try for an aerobrake manuever in Duna's atmosphere. That seems like your best bet, but even then, you're going to have to dip pretty deep in there and endure a decent number of G's since your relative velocity with duna, (at least a good 2000 m/s or more, depending on the exact angle.) and the thin atmosphere of Duna could make it easy to just shoot right through if you don't go deep enough to slow down enough.

[Nao]

... The gain you get being pulled in by its gravity will be greater than what you lose trying to leave it. Especially if you enter the sphere of influence from a significantly different angle than the slingshot body's orbit.

The same goes for slowing down. You want to exit the slingshot body's sphere of influence going in roughly the opposite direction of its orbit. In that case it's gravity pulling on you as you leave will be greater than the gain you get from its gravity pulling you in.

As said, the velocity you gain or lose depends heavily upon how massive the object you're slingshotting with is. Don't expect much from a tiny little moon. Even the Mun can usually only give you 300-400 m/s of acceleration per pass, and that's under ideal circumstance.

I find most of points in your post are untrue.
Since Im bad at explaining things I would like to point you out to this link: http://en.wikipedia.org/wiki/Gravity_assist.

In short energy gained through gravity slingshot comes not from net gravitational pull, witch stays roughly the same (hence we can have stable elliptical orbits) but from second body speed in a given reference frame. For example of when slingshotting a planet going around the sun, both craft and planet exchange orbital energy (speed) in solar reference frame. In an ideal 180deg turn (with zero spacecraft weight) spacecraft gains double of planets orbital velocity.
Also smaller planets/moons does not give less speed due to smaller mass but usually due to orbit constraints. The smaller the object's mass the lower the pass altitude, witch is constrained by object's surface radius.

Hope this helps somehow, maybe ill edit to be more clear when I'm back at home.

Also @ LoSboccacc   areobrake is your best option i think, from personal experience dunes atmosphere effects on spacecraft are similar to kerbals at 1/2 altitude so a pass below 17.000 meters would slow the craft enough for immediate landing. 20.000 to 25.000 should give you elliptical orbit around Duna.

[Rose]

All I know about gravity slingshots is that I accidentally used one to escape the Kolar system.

[LoSboccacc]

there are two effect at work here:

one is the deflection that a planet does on your trajectory: you're exchanging eccentricity for apoapsis. this happens both if you gain or if you lose energy (speed)

one is the gain or loss of energy (speed) that happens as you are accellerated toward the planet. this changes your speed as you exit the planet soi, and you gain or lose depending on the entry/exit position relative to your direction. this is independent to your change in eccentricity (you can lose apoapsis height but gain speed - raise pe)

[peskyninja]

Hey fellas, has anyone sucessfully created an airplane capable of going into orbit?

[LoSboccacc]

you should post a definition, there are planes that went to minmus and back but using non aerial engines

[10ebbor10]

Also keep in mind that KSP isn't a perfect simulation. If you fly towards a big object, your speed increases, but when you fly away, it doesn't decrease by the same amount, because you're travelling faster, and therefore leaving the gravity field of the planet faster, causing the game to register less gravitationall slowdown.

[ank]

Hey fellas, has anyone sucessfully created an airplane capable of going into orbit?

Yes multiple times.
A few pages back I have posted a plane that can reach any planet. also pictures.

[forsaken1111]

Also keep in mind that KSP isn't a perfect simulation. If you fly towards a big object, your speed increases, but when you fly away, it doesn't decrease by the same amount, because you're travelling faster, and therefore leaving the gravity field of the planet faster, causing the game to register less gravitationall slowdown.

Isn't that how you pick up speed on gravity slingshots?

[10ebbor10]

Also keep in mind that KSP isn't a perfect simulation. If you fly towards a big object, your speed increases, but when you fly away, it doesn't decrease by the same amount, because you're travelling faster, and therefore leaving the gravity field of the planet faster, causing the game to register less gravitationall slowdown.

Isn't that how you pick up speed on gravity slingshots?

Yup, don't know how you can use it to slow down.

[sluissa]

... The gain you get being pulled in by its gravity will be greater than what you lose trying to leave it. Especially if you enter the sphere of influence from a significantly different angle than the slingshot body's orbit.

The same goes for slowing down. You want to exit the slingshot body's sphere of influence going in roughly the opposite direction of its orbit. In that case it's gravity pulling on you as you leave will be greater than the gain you get from its gravity pulling you in.

As said, the velocity you gain or lose depends heavily upon how massive the object you're slingshotting with is. Don't expect much from a tiny little moon. Even the Mun can usually only give you 300-400 m/s of acceleration per pass, and that's under ideal circumstance.

I find most of points in your post are untrue.
Since Im bad at explaining things I would like to point you out to this link: http://en.wikipedia.org/wiki/Gravity_assist.

In short energy gained through gravity slingshot comes not from net gravitational pull, witch stays roughly the same (hence we can have stable elliptical orbits) but from second body speed in a given reference frame. For example of when slingshotting a planet going around the sun, both craft and planet exchange orbital energy (speed) in solar reference frame. In an ideal 180deg turn (with zero spacecraft weight) spacecraft gains double of planets orbital velocity.
Also smaller planets/moons does not give less speed due to smaller mass but usually due to orbit constraints. The smaller the object's mass the lower the pass altitude, witch is constrained by object's surface radius.

Hope this helps somehow, maybe ill edit to be more clear when I'm back at home.

Also @ LoSboccacc   areobrake is your best option i think, from personal experience dunes atmosphere effects on spacecraft are similar to kerbals at 1/2 altitude so a pass below 17.000 meters would slow the craft enough for immediate landing. 20.000 to 25.000 should give you elliptical orbit around Duna.

I might have explained it poorly, but with regards to the effects it's not untrue.

[ank]

@NAO
After reading up on the subject I can completely concur:
Maximum Delta-V -+ from slingshot are twice the planet/moons velocity!
Amazing... this might actually enable us to get back from Eve.

[Peewee]

Eh, some of you don't seem to get it, so here's a few diagrams to help

Imagine a Hohmann transfer to Duna. The circle around Duna represents its sphere of influence.

Left: Hohmann transfer
Right: Entering Duna's SoI

When the craft enters Duna's SoI, you transfer to a different reference frame.

Left: Kerbol reference frame
Center: Vector math, Woo!
Right: Duna reference frame

The Duna-centric orbit is obviously hyperbolic, so let's draw an approximation of that, assuming you don't interact with the local moon...


Since the craft isn't changing its orbital energy relative to Duna, it will be going the same speed when it leaves Duna's SoI.
Upon leaving Duna's SoI, you have to change reference frames back to Kerbol.
(note: Duna will have moved slightly around Kerbol, but it's not significant over the course of this craft's interaction)

Left: Duna reference frame
Center: More vector math, yay!
Right: Kerbol reference frame

You'll notice that the exit velocity is significantly larger than the entry velocity.
(note: IRL, the net energy the same, because Duna would have lost the same energy being pulled toward the craft as the craft gained by being pulled toward Duna.)
That means your Kerbol orbit has more energy, so your orbit has been raised.

If you exit Duna's orbit going a different direction, your Kerbol-centric orbit will end up different.

Any questions?

[Nao]

Also keep in mind that KSP isn't a perfect simulation. If you fly towards a big object, your speed increases, but when you fly away, it doesn't decrease by the same amount, because you're travelling faster, and therefore leaving the gravity field of the planet faster, causing the game to register less gravitationall slowdown.

This effect in KSP is only true because of rounding when counting very big numbers at finite intervals (the space kraken), it will not be noticeable at all during normal flights.

I would like to point out that when you are in planets plane of reference while performing slingshot you are doing an orbital (usually parabolic) pass there is no net gain or loss of speed. The fact that you gained energy (flying faster) is only in sun's frame of reference. Gravitational slingshot does not use gravitation of a planet as a way to add energy only as a means of changing vectors, the energy added is in a sun frame of reference (energy added for craft is subtracted from planets orbital energy) and suns gravitation stays roughly the same since distance from it almost constant during this maneuver.

@sluissa I just wanted to clarify how the actual slingshot works, you were right about it's effects. Sorry for bad wording it. I think Peewee will do a better work at it when he finishes. =3