fixed burn time calculations for multi stage burns

library/lib_vessel_utils.ks

@@ -16,8 +16,8 @@ declare function GetDragDir{
 }
 
 declare function AnyEngineActive{
-	list engines in allEngines.
-	for eng in allEngines{
+	list engines in egs.
+	for eng in egs{
 		if eng:ignition {
 			return true.
 		}
@@ -26,11 +26,11 @@ declare function AnyEngineActive{
 }
 
 declare function GetIsp{
-	LIST ENGINES IN allEngines.
+	LIST ENGINES IN egs.
 	declare local totalThrust is ship:maxThrust.
 	local sum is 0.
 	local weights is 0.
-	for eng in allEngines{
+	for eng in egs{
 		if eng:IGNITION and not eng:flameout{
 			local w is  eng:AVAILABLETHRUST / totalThrust.
 			local ispW is eng:isp * w.
@@ -42,15 +42,18 @@ declare function GetIsp{
 }
 
 declare function GetIspForStage{
-	parameter engineState.
+	parameter engineStage.
 	parameter pressure is 0.
-	LIST ENGINES IN allEngines.
-	local totalThrust is GetThrustOfStage(engineState).
+	LIST ENGINES IN egs.
+	local totalThrust is GetThrustOfStage(engineStage, pressure).
+	if totalThrust = 0{
+		return 0.
+	}
 	local sum is 0.
 	local weights is 0.
-	for eng in allEngines{
-		if eng:stage = engineState {
-			local w is eng:POSSIBLETHRUST / totalThrust.
+	for eng in egs{
+		if eng:stage = engineStage {
+			local w is eng:POSSIBLETHRUSTAT(pressure) / totalThrust.
 			local ispW is eng:ispat(pressure) * w.
 			set sum to sum + ispW.
 			set weights to weights + w.
@@ -60,9 +63,9 @@ declare function GetIspForStage{
 }
 
 declare function GetMaxMassFlow{
-	LIST ENGINES IN allEngines.
+	LIST ENGINES IN egs.
 	local sum is 0.
-	for eng in allEngines{
+	for eng in egs{
 		if eng:IGNITION and not eng:flameout{
 			set sum to sum + eng:maxmassflow.
 		}
@@ -70,6 +73,18 @@ declare function GetMaxMassFlow{
 	return sum.
 }
 
+declare function GetMaxMassFlowForStage{
+	parameter engineStage.
+	LIST ENGINES IN egs.
+	local sum is 0.
+	for eng in egs{
+		if eng:stage = engineStage {
+			set sum to sum + eng:maxmassflow.
+		}
+	}
+	return sum.
+}
+
 
 
 
@@ -86,9 +101,12 @@ declare function CalculateBurnDuration
 	parameter initialMass.
 	parameter massFlow.
 
+	if burnIsp = 0 {
+		return 0.
+	}
 	set dv to abs(dv).
 	local exp is -dv / (burnIsp * constant:g0).
-	local massRatio is ApproximateExp(-exp).
+	local massRatio is constant:e ^ (-exp).
 	local finalMass is initialMass / massRatio.
 	local fuelUsed is initialMass - finalMass.
 
@@ -151,67 +169,43 @@ declare function CalculateTimeToImpact{
 
 function CalculateMultiStageBurnDuration{
 	parameter dv.
-	if ship:deltav:current >= dv {
-		print "one stage" at (0, 5).
-		return GetBurnTime(dv, ship:maxthrust, ship:mass).
+	if ship:STAGEDELTAV(ship:stagenum):current >= dv {
+		return CalculateBurnDuration(dv, GetIsp(), ship:mass, GetMaxMassFlow()).
 	}else{
-		print "multi stage" at (0, 5).
 		local burnTime is 0.
 		local remDv is dv.
-		from {local s is ship:stagenum. } until s = 0 step { set s to s-1.} do {
+		from {local s is ship:stagenum. } until s = -1 step { set s to s-1.} do {
 			if remDv <= 0 {
 				return burnTime.
 			}
 			local cdv is ship:stagedeltav(s):current.
 			local cmass is GetMassOfStage(s).
-			local cthrust is GetThrustOfStage(s).
+			local cflow is GetMaxMassFlowForStage(s).
 			local cisp is GetIspForStage(s).
+			local sdv is 0.
+			print cdv.
 			if cdv >= remDv {
-				set burnTime to burnTime + GetBurnTime(remDv, cmass, cthrust, cisp).
+				set sdv to remDv.
 			}else{
-				set burnTime to burnTime + GetBurnTime(cdv, cmass, cthrust, cisp).
+				set sdv to cdv.
 			}
+			set burnTime to burnTime + CalculateBurnDuration(sdv, cisp, cmass, cflow).
 			set remDv to remDv - cdv.
 		}
 		return burnTime.
 	}
 }
 
-// Burn time from rocket equation
-function GetBurnTime {
-    parameter deltaV.
-	parameter stagethrust is 0.
-	parameter stagemass is 0.
-    parameter isp is 0.
-    
-    if deltaV:typename() = "Vector" {
-        set deltaV to deltaV:mag.
-    }
-    if isp = 0 {
-        set isp to GetIsp().
-    }
-	if stagethrust = 0 {
-		set stagethrust to ship:thrust.
-	}
-	if stagemass = 0 {
-		set stagemass to ship:mass.
-	}
-    
-    local burnTime is -1.
-    if stagethrust <> 0 {
-        set burnTime to stagemass * (1 - CONSTANT:E ^ (-deltaV / isp)) / (stagethrust / isp).
-    }
-    return burnTime.
-}
 
 function GetThrustOfStage {
 	parameter st.
+	parameter pressure is 0.
 
 	local totalThrust is 0.
-	LIST ENGINES IN allEngines.
-	for eng in allEngines{
+	LIST ENGINES IN egs.
+	for eng in egs{
 		if eng:stage = st {
-			set totalThrust to totalThrust + eng:POSSIBLETHRUST.
+			set totalThrust to totalThrust + eng:POSSIBLETHRUSTAT(pressure).
 		}
 	}
 	return totalThrust.
@@ -219,12 +213,11 @@ function GetThrustOfStage {
 
 function GetMassOfStage {
 	parameter st.
-	
 
 	local total is 0.
 	LIST PARTS IN allP.
 	for p in allP {
-		if p:stage <= st {
+		if p:stage <= st and p:DECOUPLEDIN < st {
 			set total to total + p:mass.
 		}
 	}