C# Orbit.SynodicPeriod方法代码示例

        //Computes the time and dV of a Hohmann transfer injection burn such that at apoapsis the transfer
        //orbit passes as close as possible to the target.
        //The output burnUT will be the first transfer window found after the given UT.
        //Assumes o and target are in approximately the same plane, and orbiting in the same direction.
        //Also assumes that o is a perfectly circular orbit (though result should be OK for small eccentricity).
        public static Vector3d DeltaVAndTimeForHohmannTransfer(Orbit o, Orbit target, double UT, out double burnUT)
        {
            double synodicPeriod = o.SynodicPeriod(target);

            Vector3d burnDV = Vector3d.zero;
            burnUT = UT;
            double bestApproachDistance = Double.MaxValue;
            double minTime = UT;
            double maxTime = UT + 1.1 * synodicPeriod;
            int numDivisions = 20;

            for (int iter = 0; iter < 8; iter++)
            {
                double dt = (maxTime - minTime) / numDivisions;
                for (int i = 0; i < numDivisions; i++)
                {
                    double t = minTime + i * dt;
                    Vector3d apsisDirection = -o.SwappedRelativePositionAtUT(t);
                    double desiredApsis = target.RadiusAtTrueAnomaly(target.TrueAnomalyFromVector(apsisDirection));

                    double approachDistance;
                    Vector3d burn;
                    if (desiredApsis > o.ApR)
                    {
                        burn = DeltaVToChangeApoapsis(o, t, desiredApsis);
                        Orbit transferOrbit = o.PerturbedOrbit(t, burn);
                        approachDistance = transferOrbit.Separation(target, transferOrbit.NextApoapsisTime(t));
                    }
                    else
                    {
                        burn = DeltaVToChangePeriapsis(o, t, desiredApsis);
                        Orbit transferOrbit = o.PerturbedOrbit(t, burn);
                        approachDistance = transferOrbit.Separation(target, transferOrbit.NextPeriapsisTime(t));
                    }

                    if (approachDistance < bestApproachDistance)
                    {
                        bestApproachDistance = approachDistance;
                        burnUT = t;
                        burnDV = burn;
                    }
                }
                minTime = MuUtils.Clamp(burnUT - dt, UT, UT + synodicPeriod);
                maxTime = MuUtils.Clamp(burnUT + dt, UT, UT + synodicPeriod);
            }

            return burnDV;
        }

        //Computes the time and dV of a Hohmann transfer injection burn such that at apoapsis the transfer
        //orbit passes as close as possible to the target.
        //The output burnUT will be the first transfer window found after the given UT.
        //Assumes o and target are in approximately the same plane, and orbiting in the same direction.
        //Also assumes that o is a perfectly circular orbit (though result should be OK for small eccentricity).
        public static Vector3d DeltaVAndTimeForHohmannTransfer(Orbit o, Orbit target, double UT, out double burnUT)
        {
            //We do a binary search for the burn time that zeros out the phase angle between the
            //transferring vessel and the target at the apsis of the transfer orbit.
            double synodicPeriod = o.SynodicPeriod(target);

            double lastApsisPhaseAngle;
            Vector3d immediateBurnDV = DeltaVAndApsisPhaseAngleOfHohmannTransfer(o, target, UT, out lastApsisPhaseAngle);

            double minTime = UT;
            double maxTime = UT + 1.5 * synodicPeriod;

            //first find roughly where the zero point is
            const int numDivisions = 30;
            double dt = (maxTime - minTime) / numDivisions;
            for (int i = 1; i <= numDivisions; i++)
            {
                double t = minTime + dt * i;

                double apsisPhaseAngle;
                Vector3d dV = DeltaVAndApsisPhaseAngleOfHohmannTransfer(o, target, t, out apsisPhaseAngle);

                if ((Math.Abs(apsisPhaseAngle) < 90) && (Math.Sign(lastApsisPhaseAngle) != Math.Sign(apsisPhaseAngle)))
                {
                    minTime = t - dt;
                    maxTime = t;
                    break;
                }

                if ((i == 1) && (Math.Abs(lastApsisPhaseAngle) < 0.5) && (Math.Sign(lastApsisPhaseAngle) == Math.Sign(apsisPhaseAngle)))
                {
                    //In this case we are JUST passed the center of the transfer window, but probably we
                    //can still do the transfer just fine. Don't do a search, just return an immediate burn
                    burnUT = UT;
                    return immediateBurnDV;
                }

                lastApsisPhaseAngle = apsisPhaseAngle;

                if (i == numDivisions)
                {
                    throw new ArgumentException("OrbitalManeuverCalculator.DeltaVAndTimeForHohmannTransfer: couldn't find the transfer window!!");
                }
            }

            int minTimeApsisPhaseAngleSign = Math.Sign(lastApsisPhaseAngle);

            //then do a binary search
            while (maxTime - minTime > 0.01)
            {
                double testTime = (maxTime + minTime) / 2;

                double testApsisPhaseAngle;
                Vector3d dV = DeltaVAndApsisPhaseAngleOfHohmannTransfer(o, target, testTime, out testApsisPhaseAngle);

                if (Math.Sign(testApsisPhaseAngle) == minTimeApsisPhaseAngleSign)
                {
                    minTime = testTime;
                }
                else
                {
                    maxTime = testTime;
                }
            }

            burnUT = (minTime + maxTime) / 2;
            double finalApsisPhaseAngle;
            Vector3d burnDV = DeltaVAndApsisPhaseAngleOfHohmannTransfer(o, target, burnUT, out finalApsisPhaseAngle);

            return burnDV;
        }