MrBark Posted March 2, 2012 Share Posted March 2, 2012 SIAP: Trans-Kerbin InjectionWould 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. Link to comment Share on other sites More sharing options...
Kosmo-not Posted March 2, 2012 Share Posted March 2, 2012 By Kerbal, do you mean Kerbin? Link to comment Share on other sites More sharing options...
MrBark Posted March 2, 2012 Author Share Posted March 2, 2012 By Kerbal, do you mean Kerbin?Dang it! I knew a quick reply was based on something stupid I posted. Thanks for the heads-up. Link to comment Share on other sites More sharing options...
AlexanderB Posted March 2, 2012 Share Posted March 2, 2012 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 Link to comment Share on other sites More sharing options...
Kosmo-not Posted March 2, 2012 Share Posted March 2, 2012 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. Link to comment Share on other sites More sharing options...
MrBark Posted March 2, 2012 Author Share Posted March 2, 2012 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. Link to comment Share on other sites More sharing options...
AlexanderB Posted March 2, 2012 Share Posted March 2, 2012 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 Link to comment Share on other sites More sharing options...
Iskierka Posted March 2, 2012 Share Posted March 2, 2012 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. Link to comment Share on other sites More sharing options...
MrBark Posted March 3, 2012 Author Share Posted March 3, 2012 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. Link to comment Share on other sites More sharing options...
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