69 lines
2.6 KiB
Plaintext
69 lines
2.6 KiB
Plaintext
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function hohmannDeltaV {
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parameter r1 is 1, r2 is 1, mu is 1.
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local vCirc to sqrt(mu / r1).
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local vHohmann to sqrt(mu * (2 / r1 - 2 / (r1 + r2))).
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return vHohmann - vCirc.
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}
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function angleBetween {
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parameter posA to V(1, 1, 0), posB to V(1, 1, 0).
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local angle to arcTan2(posB:y, posB:x) - arcTan2(posA:y, posA:x).
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if angle < 0 set angle to angle + 2 * constant:pi.
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return angle.
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}
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function hohmannTransfer {
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// parameter targetPeriapsis is 60000.
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parameter tgtBody is Mun.
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// get the approximate required deltav for a transfer
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local r1 to ship:orbit:semimajoraxis.
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local r2 to tgtBody:orbit:semimajoraxis.
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local vTransfer to hohmannDeltaV(r1, r2, kerbin:mu).
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// compute the transfer time
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local transferSMA to (r1 + r2) / 2.
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local transferPeriod to 2 * constant:pi * sqrt(transferSMA^3 / kerbin:mu).
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local transitTime to transferPeriod / 2.
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// get lead angle (how far ahead the tgtBody must be)
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local tgtAV to 2 * constant:pi / tgtBody:orbit:period.
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local leadAngle to tgtAV * transitTime.
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local transferAngle to constant:pi - leadAngle.
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// find the next time the phase angle condition is satisfied
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local shipAV to 2 * constant:pi / ship:orbit:period.
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local relativeAV to tgtAV - shipAV.
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// get the phase angle to the target
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local bodyToShip to (ship:position - body:position):normalized.
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local obtNorm to vCrs(bodyToShip, ship:velocity:orbit:normalized):normalized.
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local bodyToTgt to vXcl(obtNorm, (tgtBody:position - body:position):normalized):normalized.
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local signVec to vCrs(obtNorm, bodyToShip):normalized.
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local phaseSign to vDot(bodyToTgt, signVec).
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local currentPhaseAngle to vAng(ship:position - body:position, tgtBody:position - body:position) * (constant:pi / 180).
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if phaseSign < 0 set currentPhaseAngle to -1 * currentPhaseAngle + 2 * constant:pi.
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// get the time to start the maneuver
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local phaseError is transferAngle - currentPhaseAngle.
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if phaseError < 0 set phaseError to phaseError + 2 * constant:pi.
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local waitTime to phaseError / relativeAV.
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if waitTime < 0 set waitTime to waitTime + ship:orbit:period.
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set nd to node(time:seconds + waitTime, 0, 0, vTransfer).
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add nd.
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// print "Transfer DeltaV (m/s) : " + round(vTransfer, 2).
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// print "Transit Time (s) : " + round(transitTime*57.3, 0).
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// print "Lead Angle (deg) : " + round(transferAngle*57.3, 2).
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// print "Relative AV (deg/s) : " + relativeAV*57.3.
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// print "Phase Angle (deg) : " + round(currentPhaseAngle*57.3, 2).
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// print "Phase Error (deg) : " + round(phaseError*57.3, 2).
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// print "Wait Time (s) : " + round(waitTime, 0).
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}
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hohmannTransfer(Mun). |