From 429a1d5302951d2fcbad295443ae98024838166b Mon Sep 17 00:00:00 2001
From: annabunches <annabunches@gmail.com>
Date: Thu, 5 Aug 2021 21:45:19 -0400
Subject: [PATCH] Improvements to node execution, including attempt at better
 node time calculations and automatic staging.

---
 lib/node.ks | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/lib/node.ks b/lib/node.ks
index 335ad2d..ba5acc3 100644
--- a/lib/node.ks
+++ b/lib/node.ks
@@ -11,8 +11,16 @@ function ExecNode {
   local leadT is BurnTime(NEXTNODE:DELTAV:MAG / 2).
   local t is BurnTime(NEXTNODE:DELTAV:MAG).
 
+  if willStage(NEXTNODE:DELTAV:MAG) {
+    print "WARNING: kOS will stage during this node execution. Safe cancellation requires reboot.".
+    when flameOut() then {
+      print "Flameout detected. Staging.".
+      stage.
+    }
+  }
+  
   print "Adjusting heading".
-  lock STEERING to NEXTNODE:DELTAV.
+  lock STEERING to LookDirUp(NEXTNODE:DELTAV, SHIP:FACING:TOPVECTOR).
   wait until VAng(SHIP:FACING:FOREVECTOR, STEERINGMANAGER:TARGET:FOREVECTOR) <= 0.1.
 
   print "Warping to node.".
@@ -34,12 +42,16 @@ function ExecNode {
 // Calculate the time required to burn a given dV.
 // Assumes a perfectly spherical Kerbal in a vacuum.
 function BurnTime {
-  parameter totaldV, m is SHIP:MASS, s is STAGE:NUMBER.
+  parameter totaldV, s is STAGE:NUMBER.
   local totalT is 0.0.
 
-  until totaldV <= 0 {
+  local lastStage is false.
+  // We allow a small tolerance to deal with potential floating point errors.
+  until totaldV <= 0.001 {
     local F is stageThrust().
     local Isp is stageISP().
+    local m is stageMass(s).
+    // TODO: handle node execution in atmosphere?
     local dV is min(totaldV, SHIP:StageDeltaV(s):VACUUM).
     local t is calcBurnTime(dV, m, Isp, F).
     print "DEBUG: " + dV + " m/s^2 in stage " + s + ", in " + t + " seconds.".
@@ -48,6 +60,7 @@ function BurnTime {
     set totalT to totalT + t.
   }
 
+  print "DEBUG: Total Burn Time: " + totalT + " s.".
   return totalT.
 }
 
@@ -104,3 +117,41 @@ function stageThrust {
 
   return sum.
 }
+
+// Determine mass at start of target stage.
+// This can handle Delta V-style launchers but
+// only if the central rocket remains in the stack
+// for exactly two stages, one of which is the current stage.
+// More complex staging with partially depleted tanks may produce
+// undefined behavior.
+function stageMass {
+  parameter s is STAGE:NUMBER.
+
+  local m is SHIP:MASS.
+  if s = SHIP:STAGENUM { return m. }
+
+  local ps is List().
+  list PARTS in ps.
+  for part in ps {
+    if part:DECOUPLEDIN <= s {
+      set m to m - part:MASS.
+    } else if part:HasSuffix("AVAILABLETHRUST") and part:AVAILABLETHRUST > 0 {
+      // This is an engine and it is currently active. Subtract the fuel
+      // it will burn before the next stage.
+      set m to m - (part:MAXMASSFLOW * SHIP:StageDeltaV(SHIP:STAGENUM):DURATION).
+    }
+  }
+
+  return m.
+}
+
+function flameOut {
+  local ens is List().
+  list engines in ens.
+  for en in ens {
+    if en:FLAMEOUT {
+      return true.
+    }
+  }
+  return false.
+}