67 lines
2 KiB
Plaintext
67 lines
2 KiB
Plaintext
@LAZYGLOBAL OFF.
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function semi_major_axis {
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//
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// Semi-major axis
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// Based on:
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// https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes
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// http://www.orbiterwiki.org/wiki/Front_Cover_Equations
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//
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parameter ap is APOAPSIS.
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parameter pe is PERIAPSIS.
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return (ap + pe + 2*BODY:radius) / 2. // Add 2x body radius because KSP measures apoapsis/periapsis from the surface
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}
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function orbital_period {
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//
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// The orbital period.
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// Note that for all ellipses with a given semi-major axis, the orbital period is the same, disregarding their eccentricity.
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// Based on:
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// https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes#Astronomy
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// http://www.orbiterwiki.org/wiki/Front_Cover_Equations
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//
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parameter sme is semi_major_axis().
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return 2 * CONSTANT:PI * sqrt(sme^3 / BODY:mu).
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}
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function orbital_period_from_ap_pe {
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parameter ap, pe.
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return orbital_period(semi_major_axis(ap, pe)).
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}
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function orbital_velocity {
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//
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// The required velocity to maintain orbit at provided altitude.
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// Based on:
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// https://en.wikipedia.org/wiki/Orbital_speed#Precise_orbital_speed
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// http://www.orbiterwiki.org/wiki/Front_Cover_Equations
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// https://en.wikipedia.org/wiki/Vis-viva_equation
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parameter altitude.
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parameter sma is semi_major_axis().
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return sqrt(BODY:mu * ((2 / (altitude+BODY:radius)) - (1 / sma))). // add body radius because KSP measures altitude from the surface
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}
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function orbital_velocity_from_ap_pe {
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parameter altitude, ap, pe.
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return orbital_velocity(altitude, semi_major_axis(ap, pe)).
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}
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function orbital_eccentricity {
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//
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// The orbital eccentricity, i.e. the ratio by which the orbit deviates from a perfect circle, where e=0 is circular.
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// Based on:
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// https://en.wikipedia.org/wiki/Orbital_eccentricity#Calculation
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// http://www.orbiterwiki.org/wiki/Front_Cover_Equations
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parameter ap is APOAPSIS.
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parameter pe is PERIAPSIS.
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return (ap - pe) / (ap + pe).
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}
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