67 lines
2.2 KiB
Plaintext
67 lines
2.2 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 apoapsis is ORBIT:APOAPSIS.
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parameter periapsis is ORBIT:PERIAPSIS.
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return (apoapsis + periapsis + 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 semi_major_axis is semi_major_axis().
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return 2 * CONSTANT:PI * SQRT(semi_major_axis^3 / BODY:MU).
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}
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function orbital_period_from_ap_pe {
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parameter apoapsis, periapsis.
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return 2 * CONSTANT:PI * SQRT(semi_major_axis(apoapsis, periapsis)^3 / BODY:MU).
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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 semi_major_axis is semi_major_axis().
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return SQRT(BODY:MU * ((2 / (altitude+BODY:RADIUS)) - (1 / semi_major_axis))). // 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, apoapsis, periapsis.
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return orbital_velocity(altitude, semi_major_axis(apoapsis, periapsis)).
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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 apoapsis is ORBIT:APOAPSIS.
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parameter periapsis is ORBIT:PERIAPSIS.
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return (apoapsis - periapsis) / (apoapsis + periapsis).
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}
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