Triple Gravity Assist

[Cooly568]

Gravity assist around mun, minmus, then kerbin to launch into solar orbit. nuff said.

[NetBlitzer]

So would that mean we get into orbit around Minmus, transfer to the Mun, and then pass by that and Kerbin? Or would we do the other way around?

Either way, this would require a lot of planning and timing.

[Bluejayek]

I think he means go from an LKO, then do a flyby gravity assist by the Mun, and without any power applied gravity assist off minimus, and then back to kerbin, and finally out to kerbol. That would have to be one precise original orbit...

[Cooly568]

I think he means go from an LKO, then do a flyby gravity assist by the Mun, and without any power applied gravity assist off minimus, and then back to kerbin, and finally out to kerbol. That would have to be one precise original orbit...

Yup. Thats the challenge.

[Jarnis]

I think he means go from an LKO, then do a flyby gravity assist by the Mun, and without any power applied gravity assist off minimus, and then back to kerbin, and finally out to kerbol. That would have to be one precise original orbit...

Not certain this can be done.

The velocity you will have after passing Mun, no matter the trajectory, will be FAR too fast for Minimus to slingshot you back towards Kerbin. Minimus gravity well is just too small to do what you suggest.

Well, I guess in theory you could have a trajectory from Kerbin towards Minimus that just barely enters Mun SOI and then just barely makes it to Minimus but even then... if the return path should actually re-enter... not sure if possible. Any "real" slingshot past Mun (add any meaningful amount of speed) would put you far past of what Minimus could then bend back towards Kerbin.

Kerbin -> Mun slingshot towards Minimus -> Slingshot out of Kerbin influence to interplanetary trajectory would be doable. Somewhat complicated to time but doable.

Edited August 22, 2012 by Jarnis

[PakledHostage]

I agree with Jarnis. Kerbin -> Mun slingshot towards Minimus -> Slingshot out of Kerbin influence to interplanetary trajectory is doable.

It is also possible to fly a gravitationally assisted trajectory past the Mun to Minmus and back to Kerbin with very little expenditure of fuel. See the Mun/Minmus Gravity Slingshot Challenge for details.

It is not possible to slingshot off Kerbin when starting from an orbit within Kerbin's SOI. Orbital slingshot manoeuvres work because they transfer momentum from the planet to the spacecraft. Kerbin is at rest relative to objects in orbit about it, and therefore Kerbin has no momentum to transfer.

[Giggleplex777]

Pretty easy, actually did it by accident trying to land on Minus

[Giggleplex777]

It doesn't say that you can't use rockets for retro burn.

[erkle64]

It is not possible to slingshot off Kerbin when starting from an orbit within Kerbin's SOI. Orbital slingshot manoeuvres work because they transfer momentum from the planet to the spacecraft. Kerbin is at rest relative to objects in orbit about it, and therefore Kerbin has no momentum to transfer.

I'm not sure if it works in KSP, but the Oberth Maneuver around Kerbin would still be useful to maximize the delta-v of an interplanetary burn.

How about LKO -> Mun -> Minmus -> Kerbol -> Kerbin -> Deep Space?

Edited August 22, 2012 by erkle64

[Markus Reese]

interesting challenge about a slingshot from kerbin to mun->minmus->kerbin and escape? As it stands, a regular mun slingshot does allow enough velocity for a solar escape.

[maltesh]

I'm not sure if it works in KSP, but the Oberth Maneuver around Kerbin would still be useful to maximize the delta-v of an interplanetary burn.

How about LKO -> Mun -> Minmus -> Kerbol -> Kerbin -> Deep Space?

The Oberth Effect definitely works in Kerbal Space Program. If the Oberth Effect didn't work, the game would not be calculating kinetic energy or momentum correctly, and that would mean most of the orbital equations wouldn't work, either. It would have been impossible to write accurate orbital calculators without painstaking experimentation or access to the source code.

From LKO, it requires less than 100 m/s extra delta-V to Escape Kerbin than to intercept the Mun, and less than 20 m/s extra delta-V to escape than to intercept Minmus. With the game's current instrumentation, when aiming for a specific target in interplanetary space, you're much better off burning direct from LKO; Unless you're really willing to wrangle with orbital equations and launch windows, its pretty easy to wind up with a Munar/Minmal slingshot that's a less efficient path to your interplanetary destination.

[architeuthis]

Fun challenge idea, but to interject, the Oberth effect isn't the same thing as a gravity assist. The Oberth effect just comes from the conservation of mechanical energy (trading propellant potential energy for rocket kinetic energy), whereas the gravity assist is a way to increase your velocity in a paticular inertial refrence frame (usually the one with respect to the sun or Kerbol ibn this case), by exchaning angular momentum by another body. In this case for instance you could use the Oberth effect to good use burning close in to Kerbol, but you can not use Kerbol for gravity assists (as Kerbol is at rest with respect to the entire solar system). I think it would be neat to see someone use a gravity assist at a moon somewhere to slow down and brake into orbit sans aerobraking.

[tavert]

You're not interjecting when the conversation started and ended 8 months ago.

Mind the old threads, eh?

[architeuthis]

You're not interjecting when the conversation started and ended 8 months ago.

Mind the old threads, eh?

Ah, just noticed that. Chalk one up for another case of unintentional thread necromancy.