MechJebModuleAscentClassicAutopilot.cs

using System;
using JetBrains.Annotations;
using KSP.Localization;
using UnityEngine;

namespace MuMech
{
    [UsedImplicitly]
    public class MechJebModuleAscentClassicAutopilot : MechJebModuleAscentBaseAutopilot
    {
        public MechJebModuleAscentClassicAutopilot(MechJebCore core) : base(core) { }

        private double _actualTurnStart;

        protected override void OnModuleEnabled()
        {
            base.OnModuleEnabled();
            _mode = AscentMode.VERTICAL_ASCENT;
        }

        protected override void OnModuleDisabled()
        {
            base.OnModuleDisabled();
            AscentSettings.Enabled = false;
        }

        public double VerticalAscentEnd()
        {
            return AscentSettings.AutoPath ? AscentSettings.AutoTurnStartAltitude : AscentSettings.TurnStartAltitude;
        }

        private double SpeedAscentEnd()
        {
            return AscentSettings.AutoPath ? AscentSettings.AutoTurnStartVelocity : AscentSettings.TurnStartVelocity;
        }

        private bool IsVerticalAscent(double altitude, double velocity)
        {
            _actualTurnStart = Math.Min(_actualTurnStart, AscentSettings.AutoTurnStartAltitude);
            if (altitude < VerticalAscentEnd() && velocity < SpeedAscentEnd())
            {
                _actualTurnStart = Math.Max(_actualTurnStart, altitude);
                return true;
            }

            return false;
        }

        public double FlightPathAngle(double altitude, double velocity)
        {
            double turnEnd = AscentSettings.AutoPath ? AscentSettings.AutoTurnEndAltitude : AscentSettings.TurnEndAltitude;

            if (IsVerticalAscent(altitude, velocity)) return 90.0;

            if (altitude > turnEnd) return AscentSettings.TurnEndAngle;

            return Mathf.Clamp(
                (float)(90.0 - Math.Pow((altitude - _actualTurnStart) / (turnEnd - _actualTurnStart), AscentSettings.TurnShapeExponent) *
                    (90.0 - AscentSettings.TurnEndAngle)), 0.01F, 89.99F);
        }

        private enum AscentMode { VERTICAL_ASCENT, GRAVITY_TURN, COAST_TO_APOAPSIS, EXIT }

        private AscentMode _mode;

        protected override bool DriveAscent2()
        {
            switch (_mode)
            {
                case AscentMode.VERTICAL_ASCENT:
                    DriveVerticalAscent();
                    break;

                case AscentMode.GRAVITY_TURN:
                    DriveGravityTurn();
                    break;

                case AscentMode.COAST_TO_APOAPSIS:
                    DriveCoastToApoapsis();
                    break;

                case AscentMode.EXIT:
                    return false;
            }

            return true;
        }

        private void DriveVerticalAscent()
        {
            if (!IsVerticalAscent(VesselState.altitudeTrue, VesselState.speedSurface)) _mode = AscentMode.GRAVITY_TURN;
            if (Orbit.ApA > AscentSettings.DesiredOrbitAltitude) _mode                       = AscentMode.COAST_TO_APOAPSIS;

            //during the vertical ascent we just thrust straight up at max throttle
            AttitudeTo(90);

            bool liftedOff = Vessel.LiftedOff() && !Vessel.Landed;

            Core.Attitude.SetAxisControl(liftedOff, liftedOff, liftedOff && VesselState.altitudeBottom > AscentSettings.RollAltitude);

            Core.Thrust.targetThrottle = 1.0F;

            if (!Vessel.LiftedOff() || Vessel.Landed) Status = Localizer.Format("#MechJeb_Ascent_status6");  //"Awaiting liftoff"
            else Status                                      = Localizer.Format("#MechJeb_Ascent_status18"); //"Vertical ascent"
        }

        private void DriveGravityTurn()
        {
            //stop the gravity turn when our apoapsis reaches the desired altitude
            if (Orbit.ApA > AscentSettings.DesiredOrbitAltitude)
            {
                _mode = AscentMode.COAST_TO_APOAPSIS;
                return;
            }

            //if we've fallen below the turn start altitude, go back to vertical ascent
            if (IsVerticalAscent(VesselState.altitudeTrue, VesselState.speedSurface))
            {
                _mode = AscentMode.VERTICAL_ASCENT;
                return;
            }


            Core.Thrust.targetThrottle = ThrottleToRaiseApoapsis(Orbit.ApR, AscentSettings.DesiredOrbitAltitude + MainBody.Radius);
            if (Core.Thrust.targetThrottle < 1.0F)
            {
                // follow surface velocity to reduce flipping
                AttitudeTo(SrfvelPitch());
                Status = Localizer.Format("#MechJeb_Ascent_status21"); //"Fine tuning apoapsis"
                return;
            }

            double desiredFlightPathAngle = FlightPathAngle(VesselState.altitudeASL, VesselState.speedSurface) * UtilMath.Deg2Rad;

            if (AscentSettings.CorrectiveSteering)
            {
                double actualFlightPathAngle = Math.Atan2(VesselState.speedVertical, VesselState.speedSurfaceHorizontal) * UtilMath.Rad2Deg;

                /* form an isosceles triangle with unit vectors pointing in the desired and actual flight path angle directions and find the length of the base */
                double velocityError = 2 * Math.Sin((desiredFlightPathAngle - actualFlightPathAngle) / 2);

                double difficulty = VesselState.surfaceVelocity.magnitude * 0.02 / VesselState.ThrustAccel(Core.Thrust.targetThrottle);
                difficulty = MuUtils.Clamp(difficulty, 0.1, 1.0);
                double steerOffset = AscentSettings.CorrectiveSteeringGain * difficulty * velocityError;

                double steerAngle = MuUtils.Clamp(Math.Asin(steerOffset), -Math.PI / 6, Math.PI / 6);

                desiredFlightPathAngle = MuUtils.Clamp(desiredFlightPathAngle + steerAngle, -Math.PI / 2, Math.PI / 2);
            }

            AttitudeTo(desiredFlightPathAngle * UtilMath.Rad2Deg);

            Status = Localizer.Format("#MechJeb_Ascent_status22"); //"Gravity turn"
        }

        private void DriveCoastToApoapsis()
        {
            Core.Thrust.targetThrottle = 0;

            if (VesselState.altitudeASL > MainBody.RealMaxAtmosphereAltitude())
            {
                _mode = AscentMode.EXIT;
                Core.Warp.MinimumWarp();
                return;
            }

            //if our apoapsis has fallen too far, resume the gravity turn
            if (Orbit.ApA < AscentSettings.DesiredOrbitAltitude - 1000.0)
            {
                _mode = AscentMode.GRAVITY_TURN;
                Core.Warp.MinimumWarp();
                return;
            }

            Core.Thrust.targetThrottle = 0;

            // follow surface velocity to reduce flipping
            AttitudeTo(SrfvelPitch());

            if (Orbit.ApA < AscentSettings.DesiredOrbitAltitude)
            {
                Core.Thrust.targetThrottle = ThrottleToRaiseApoapsis(Orbit.ApR, AscentSettings.DesiredOrbitAltitude + MainBody.Radius);
            }

            if (Core.Node.autowarp)
            {
                //warp at x2 physical warp:
                Core.Warp.WarpPhysicsAtRate(2);
            }

            Status = Localizer.Format("#MechJeb_Ascent_status23"); //"Coasting to edge of atmosphere"
        }
    }
}