chrislo27 Posted June 4, 2012 Share Posted June 4, 2012 Can someone tell me how to calculate the semi-major axis of an orbit? P = PerogeeA = ApogeeAttempting to change the persistence file for my very explody spacestation. Reference I used Link to comment Share on other sites More sharing options...
aphazael Posted June 4, 2012 Share Posted June 4, 2012 Wouldn\'t it just be 1/2 * (P + A + 2*R), where R is the radius of the body you\'re orbiting?edit: grouping Link to comment Share on other sites More sharing options...
Candre Posted June 4, 2012 Share Posted June 4, 2012 http://kerbalspaceprogram.com/forum/index.php?topic=13471.msg205969#msg205969 Link to comment Share on other sites More sharing options...
chrislo27 Posted June 4, 2012 Author Share Posted June 4, 2012 Candre, I looked in there and I didn\'t find anything that explains it clearly to a 11 year old.Aphazael, what\'s 1/2? is it a fraction? I\'ll try your technique. Link to comment Share on other sites More sharing options...
aphazael Posted June 4, 2012 Share Posted June 4, 2012 Yes, 1/2 is one half (in other words, divide the whole thing by 2) Link to comment Share on other sites More sharing options...
chrislo27 Posted June 4, 2012 Author Share Posted June 4, 2012 Yes, 1/2 is one half (in other words, divide the whole thing by 2)So:Perogee + Apogee + (2*Radius) and then divide the whole thing in half?Kerbin = 600kmMun = 200kmMinmus = 60km (small!)EDIT: I did my calculations for a orbit of exactly 99km and the result it 699km for the SMA. To use it for the save file, it takes it in metres so Result*1000. Link to comment Share on other sites More sharing options...
aphazael Posted June 5, 2012 Share Posted June 5, 2012 Perogee + Apogee + (2*Radius) and then divide the whole thing in half?That\'s correct. At least, that is what I was attempting to convey (I derived that myself, so I can\'t guarantee its correctness, but I\'m like 98% sure it\'s right) Link to comment Share on other sites More sharing options...
chrislo27 Posted June 5, 2012 Author Share Posted June 5, 2012 That\'s correct. At least, that is what I was attempting to convey (I derived that myself, so I can\'t guarantee its correctness, but I\'m like 98% sure it\'s right)\Thanks! I tried it with the editing of my save file and then I realized my two space stations are in the same exact spot. Link to comment Share on other sites More sharing options...
Crass Posted June 12, 2012 Share Posted June 12, 2012 My basic and limited understanding is that the 'major axis' is the axis that runs thru the apoapsis and periapsis, and semi-major axis is just half that distance. So you could possibly add the elevation of your periapsis to the elevation of your apoapsis, divide that in half, and that would give you the elevation of your semi-major axis. Please by all means correct me if I am wrong. I am not a math whiz. Link to comment Share on other sites More sharing options...
aphazael Posted June 12, 2012 Share Posted June 12, 2012 My basic and limited understanding is that the 'major axis' is the axis that runs thru the apoapsis and periapsis, and semi-major axis is just half that distance.That\'s correct. However, in the game, (as far as I know), apoapsis and periapsis are measured from the surface of the body. If so, then the length of the major axis is apoapsis altitude plus periapsis altitude, plus the diameter of the planet; and then the semimajor axis would be half that. If apoapsis and periapsis are measured from the center of the body, then the formula you described is correct. Link to comment Share on other sites More sharing options...
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