andygonzm Posted September 12, 2012 Share Posted September 12, 2012 If you know the periapsis and the apoapsis, is there any formula to know:-The orbital period?-the velocity at the periapsis and at the apoapsis?(sorry for my bad english) Link to comment Share on other sites More sharing options...
Serratus Posted September 12, 2012 Share Posted September 12, 2012 Both are dependent on grav force of the body underneath You. 100Km orbit over Kerbin will require higher speed than over Mun for ex. The second thing is the same - depends on the body You orbit. Look in Wikipedia for formulas. That's where I learned all my stuff. But TBH I never came across what You're looking for. To be more honest, I wouldn't know it even if I was to stare at it for a day. Link to comment Share on other sites More sharing options...
maltesh Posted September 12, 2012 Share Posted September 12, 2012 (edited) If you know the radius (rb) of the body you're orbiting, and your orbit is elliptical, you can get your orbit's semimajor axis from your periapsis altiude and apoapsis altitude. Your semimajor axis (a) is half the linear distance between those two points.rb is the radius of the body, and hap and hpe are the apoapsis and periapsis altitudes, respectively.With the semimajor axis, and the standard gravitational parameter(μ) of the body currently being orbited, you can find the orbital period (T).With the semimajor axis, the standard gravitational parameter of the body being orbited you can find the specific orbital energy (õ) of your orbit.And with the specific orbital energy of your orbit, you can find the speed (vs) that your spacecraft will have at any altitude (hs) your orbit takes it to.Some interesting things to note, here. Any two orbits around a body that have the same semi-major axis will have the same period, regardless of eccentricity. Any two orbits around a body that have the same semi-major axis will have the same speed at any altitude that they share. Edited September 12, 2012 by maltesh Link to comment Share on other sites More sharing options...
Serratus Posted September 12, 2012 Share Posted September 12, 2012 See? Told You I wouldn't know even if I was looking straight at it. Link to comment Share on other sites More sharing options...
andygonzm Posted September 12, 2012 Author Share Posted September 12, 2012 thank you, maltesh. With that formulas and kerbin´s information (in the ksp wiki) i will be able to intercept mun, minmus and other planets (in .17) without mechjeb (I havent done it yet ) Link to comment Share on other sites More sharing options...
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