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Trans Kerbin Injection


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SIAP: Trans-Kerbin Injection

Would love a better flyer to try this out. I\'m trying to pin down the bare minimum apoasis figure.

Scenerio: Munar orbit (or suborbit if just launched from surface), heading of 270-degrees west.

Steps: Wait for Kerbin to set. Fire up engines. Get apoasis to be 5M(?) on mun\'s orbit directly behind it (opposite it\'s direction around Kerbin).

What happens: As the Mun goes around Kerbin, you fall out of it\'s sphere of influence. End up in a eccentric Kerbin orbit with periapsis around 200K-300K. Still far enough out to immediately fire engines retrograde and bring periapsis into the atmosphere.

Question: What\'s the minimum value for the munar apoasis to break orbit this way? This seems very fuel efficient to me, but more eyes on it would be appreciated. I\'m still a rookie earning his wings.

Sorry if this particular TKI has been posted before. I searched but didn\'t see anything.

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Height doesn\'t really matter, the escape velocity is all you need (about 600 m/s, if I recall correctly.)

But there is a lot to be found, so I\'ll continue experimenting with it. So far, I had a lucky Munar takeoff that put me in a 'fall like a brick' orbit back, no other burns required to land on the surface, no giant 800+ km orbit. still trying to replicate :)

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What I usually do is start with an equatorial orbit around the moon heading 270. Once I\'m over the crater in the screenshot I attached, I make my TKI burn (I forget my final velocity as I haven\'t flown many Mun missions recently. Somewhere 800-900). It ends up with an orbit that either intersects the planet, or somewhat close.

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Height doesn\'t really matter, the escape velocity is all you need (about 600 m/s, if I recall correctly.)

But there is a lot to be found, so I\'ll continue experimenting with it. So far, I had a lucky Munar takeoff that put me in a 'fall like a brick' orbit back, no other burns required to land on the surface, no giant 800+ km orbit. still trying to replicate :)

Cool. I know this game\'s depiction of gravity and sphere\'s of influence isn\'t real-life, as there is no gradual change between the two sphere\'s of influence in the game, so I wasn\'t sure if that made altitude more relevant somehow. That\'s not to say I was smart enough to know the escape velocity before you said it. I wasn\'t. Thanks! :)

Sidebar: I\'m also interested, in-game reality, of keeping G-Forces down to real-life survivable levels. Fall like a brick may work, but what G\'s are there? My friend flew a successful mission, but experienced 50+ G\'s! I gave him a hard time and said it was hardly a success, just to give him the hard time.

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What I usually do is start with an equatorial orbit around the moon heading 270. Once I\'m over the crater in the screenshot I attached, I make my TKI burn (I forget my final velocity as I haven\'t flown many Mun missions recently. Somewhere 800-900). It ends up with an orbit that either intersects the planet, or somewhat close.

ah :) i\'ll look into it..

btw, I said 600, might just as well be 800 or 900 :) time to copy this flying technique :)

Sidebar: I\'m also interested, in-game reality, of keeping G-Forces down to real-life survivable levels. Fall like a brick may work, but what G\'s are there? My friend flew a successful mission, but experienced 50+ G\'s! I gave him a hard time and said it was hardly a success, just to give him the hard time.

totally true, keeping the 'gee's down is more realistic, most of my missions don\'t go over 3 or 4, but comming in at 2500m/s and parachuting down at once is probably not a really good idea in reality :)

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Final velocity doesn\'t decide whether you\'ll change to Kerbin\'s SoI, your apoapsis does, as OP thought. Minimum altitude is (IIRC) 2400-odd km. 2500 should get you out neatly, though you\'ll have significant velocity to burn off, so your 5000-km exit might actually be more efficient.

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Final velocity doesn\'t decide whether you\'ll change to Kerbin\'s SoI, your apoapsis does, as OP thought. Minimum altitude is (IIRC) 2400-odd km. 2500 should get you out neatly, though you\'ll have significant velocity to burn off, so your 5000-km exit might actually be more efficient.

Just tried 2.5. It works, but you\'re right. The orbit I ended up in wasn\'t as efficient. Not solid on the math, but I\'m pretty sure the fuel I used to raise my apoasis up from 2.5 to 5 was definitely less than the fuel I used to change the orbit that 2.5 put me into.

Now I\'m curious what the most efficient apoasis would be, but those math skills left me long ago, if I ever had them. :D

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