CMLSsburn 0.2.1

//==CMLS SUICIDE BURN SCRIPT==

SET scriptVersion TO "v0.2.1".

//0.1.0
// - First stable version
//
//0.1.1
//--Major improvements--
// - Experimental PI controller
// - Automatic engine activation and deactivation handling
// - Automatic Kp adjustment based on TWR
//--Minor improvements--
// - Exported initial engine setup to shutdown script
// - Added PILOTMAINTHROTTLE control to ensure that the
//   booster doesn't revert to half or full throttle once
//   the script ends
//
//0.2.0
//--Major improvements--
// - Automatic opMode checking to handle the different
//   types of cores (side booster vs S1)
// - Reverted to P controller for simplicity; PI controller
//   did not improve results and was difficult to tune
// - Automatic handling of occasionally-necessary
//   re-entry burn based on speed and remaining delta-v
//--Minor improvements--
// - Replaced shutdown script with the same CMLSeng script
//   that handles the engine tagging and shutdown for the
//   launch sequence. Updated launch scripts to
//   automatically copy that script to the core/booster
//   computers
// - Added remaining delta-v and booster type readouts
// - Moved altitude triggers outside of control loop
//
//0.2.1
//--Major improvements--
// - Integrated automatic re-entry burn into the terminal
//   guidance control block; each action in the sequence of
//   events is now part of one overall trigger block
//--Minor improvements--
// - Changed delta-v remaining readout to always show sea-
//   level delta-v
// - Further tuning of P controller

//~~~~~SPLASHSCREEN~~~~~

SET TERMINAL:WIDTH TO 50.
SET TERMINAL:HEIGHT TO 25.
CLEARSCREEN.

PRINT "==========COYOTE MLS SUICIDE BURN SCRIPT==========".
PRINT "----------------------" + scriptVersion + "----------------------".
WAIT 1.

PRINT "Initializing...".

RUN CMLSeng.

//~~~~~Variable Declaration~~~~~
SET nextLine TO 7.      //Tracks next line that events should print at in the event log


IF SHIP:PARTSTAGGED("S1Alpha"):LENGTH > 0 {
    SET opMode TO "Core".

} ELSE IF SHIP:PARTSTAGGED("LBAlpha"):LENGTH > 0 {
    SET opMode TO "LeftBooster".

} ELSE IF SHIP:PARTSTAGGED("RBAlpha"):LENGTH > 0 {
    SET opMode TO "RightBooster".

}. //IF-ELSE opMode

FOR eng IN engAll {
    IF eng:GETMODULE("ModuleEnginesFX"):HASEVENT("Shutdown Engine") {       //Shutdown all engines
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Shutdown Engine").
    }.
}.

IF opMode = "Core" {
    S1Alpha[0]:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").     //Activate alpha-group engines
    FOR eng IN S1Bravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").        //Activate bravo-group engines
    }. //FOR eng

} ELSE IF opMode = "LeftBooster" {
    LBAlpha[0]:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").     //Activate alpha-group engines
    FOR eng IN LBBravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").        //Activate bravo-group engines
    }. //FOR eng

} ELSE IF opMode = "RightBooster" {
    RBAlpha[0]:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").     //Activate alpha-group engines
    FOR eng IN RBBravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Activate Engine").        //Activate bravo-group engines
    }. //FOR eng

}. //IF opMode

RCS ON.
GEAR OFF.

SET thrott TO 0.
SET I TO 0.

SET SBSA TO -10000.
SET SBSAmargin TO 10.       //Margin to allow for burns that start a little too late

LOCK dvRemain TO (285 * 9.82) * LN(SHIP:MASS / SHIP:DRYMASS).       //Keeps track of remaining delta-v
LOCK TWR TO SHIP:MAXTHRUST / (SHIP:MASS * SHIP:SENSORS:GRAV:MAG).       //Keeps track of TWR

LOCK vsActual TO SHIP:VERTICALSPEED.
SET radaltOffset TO 18.4.       //Fixed offset amount from probe core to landing legs
LOCK radaltActual TO (ALT:RADAR - radaltOffset).        //Uses offset amount to track distance from bottom of landing legs to ground.

SET vsSetpoint TO -10000.       //Starts out really low so that the PI doesn't try to adjust the vertical speed whilst falling back to the launch site

WAIT 0.5.

//Readout header
CLEARSCREEN.
PRINT "==========COYOTE MLS MK1R SUICIDE BURN============" AT(0,0).
PRINT "TWR: " AT(0,2).          //Readout at 6,2
PRINT "BSA: " AT(16,2).         //Readout at 22,2
PRINT "ARA: " AT(33,2).         //Readout at 39,2

PRINT "OPM: " AT(0,3).          //Readout at 6,3
PRINT opMode AT(6,3).           //opMode readout; static from script start
PRINT "DVR: " AT(33,3).         //Readout at 39,3
PRINT "--------------------EVENT LOG---------------------" AT(0,5).
PRINT "Stage ready for boostback burn" AT(0,nextLine).
SET nextLine to nextLine + 1.

//~~~~~Boostback completion~~~~~
WAIT UNTIL vsActual < 0.        //Wait until apogee
WAIT 30.        //Wait another 10 seconds to allow for late/extended boostback burns

FOR eng IN S1Bravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Shutdown Engine").        //Shutdown bravo-group engines, this leaves the single alpha engine running
}.

FOR eng IN LBBravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Shutdown Engine").
}.

FOR eng IN RBBravo {
        eng:GETMODULE("ModuleEnginesFX"):DOEVENT("Shutdown Engine").
}.

PRINT "Stage prepared for re-entry." AT(0,nextLine).
SET nextLine TO nextLine + 1.

//~~~~~Burn control~~~~~

WHEN ALTITUDE < 40000 THEN {        //Check performed at 40km
    IF dvRemain >= 500 AND VELOCITY:SURFACE:MAG > 1400 {        //If the velocity is high and enough dv remains...
        PRINT "Re-entry velocity high;" AT(0,nextLine).
        SET nextLine TO nextLine + 1.
        PRINT "Performing re-entry burn" AT(0,nextLine).
        SET nextLine TO nextLine + 1.
        SET SHIP:CONTROL:PILOTMAINTHROTTLE TO 0.5.      //...set the throttle to half...

        WHEN dvRemain < 500 THEN {
            SET SHIP:CONTROL:PILOTMAINTHROTTLE TO 0.        //...and burn until 500dv remains
            PRINT "Re-entry burn complete" AT(0,nextLine).
            SET nextLine TO nextLine + 1.
        }. //WHEN dvRemain

    } ELSE IF dvRemain < 500 AND VELOCITY:SURFACE:MAG > 1400        //If there's not enough dv left, don't burn. Just pray.
        PRINT "Re-entry velocity high;" AT(0,nextLine).
        SET nextLine TO nextLine + 1.
        PRINT "Delta-V margin below threshold; no re-entry burn" AT(0,nextLine).
        SET nextLine TO nextLine + 1.

    }. //IF-ELSE

    WHEN ALTITUDE < 10000 THEN {
        LOCK SBSA TO (((vsActual^2) / (2 * (SHIP:MAXTHRUST / SHIP:MASS) - SHIP:SENSORS:GRAV:MAG)) + SBSAmargin).        //Determines suicide burn start altitude
        SET SHIP:CONTROL:PILOTMAINTHROTTLE TO 0.        //Stops re-entry burn if it's still going
        PRINT "Atmospheric re-entry complete" AT(0,nextLine).
        SET nextLine TO nextLine + 1.

            WHEN radaltActual < (SBSA + 250) THEN {     //Waits until 250m above SBSA
            SAS ON.     //Vehicle should be completely vertical and with no horizontal velocity at this point
            PRINT "Prepare for suicide burn." AT(0,nextLine).
            SET nextLine TO nextLine + 1.

                WHEN radaltActual < SBSA THEN {     //Waits until SBSA
                    LOCK vsSetpoint TO -5.      //Stage will burn fully until 5m/s descent
                    LOCK THROTTLE TO thrott.
                    GEAR ON.
                    PRINT "Suicide burn initiated. Gear down." AT(0,nextLine).
                    SET nextLine TO nextLine + 1.

                    WHEN radaltActual < 3 THEN {        //Below 3 meters, it switches to 1m/s descent
                        LOCK vsSetpoint TO -1.

                    }. //WHEN < 3
                }. //WHEN < SBSA
            }. //WHEN < 250 + SBSA
    }. //WHEN altitude
}. //WHEN surf velocity

SAS OFF.
LOCK Kp TO MAX(0.001,((TWR * -0.1) + 1.1)).     //Adjusts the gain based on the TWR
LOCK P to (vsSetpoint - vsActual).      //Error - difference between desired VS and actual VS
LOCK dthrott TO Kp * P.

//~~~~~P Loop/Readouts~~~~~

UNTIL STATUS = "LANDED" {       //Loops until touchdown

    SET thrott TO MIN(1, MAX(0,thrott + dthrott)).

    PRINT ROUND(TWR,1) + "    " AT(6,2).        //Prints TWR
    PRINT ROUND(SBSA,1) + "    " AT(22,2).      //Prints suicide burn start alt
    PRINT ROUND(radaltActual,1) + "    " AT(39,2).      //Prints the radar altitude adjusted for the landing legs

    PRINT ROUND(dvRemain) + "    " AT(39,3).        //Prints remaining DV

    WAIT 0.001.

}. //UNTIL

PRINT "Touchdown!" at (0,nextLine).
SET nextLine TO nextLine + 1.
UNLOCK THROTTLE.
SAS OFF.
RCS OFF.
SET SHIP:CONTROL:PILOTMAINTHROTTLE TO 0.
WAIT 3.
CLEARSCREEN.