Add node execution code.

lib/navigation.ks

@@ -1,6 +1,30 @@
+// functions for calculating steering values.
 @lazyglobal off.
 
 function GetPitch {
   parameter v is SHIP:FACING:FOREVECTOR.
   return 90 - vectorangle(SHIP:UP:FOREVECTOR, v).
 }
+
+function CreateCircularizationNode {
+  parameter usePeriapsis is false.
+  local target is SHIP:ORBIT:APOAPSIS.
+  local t is SHIP:ORBIT:ETA:APOAPSIS.
+  if usePeriapsis {
+    set target to SHIP:ORBIT:PERIAPSIS.
+    set t to SHIP:ORBIT:ETA:PERIAPSIS.
+  }
+  local n is Node(t, 0, 0, 0).
+
+  // move fast until we pass our target.
+  until (usePeriapsis and n:ORBIT:APOAPSIS < target) or n:ORBIT:PERIAPSIS > target {
+    set n:PROGRADE to n:PROGRADE + 1.
+  }
+
+  // now bring it back in real slow until we come back.
+  until (usePeriapsis and n:ORBIT:APOAPSIS > target) or n:ORBIT:PERIAPSIS < target {
+    set n:PROGRADE to n:PROGRADE - 0.01.
+  }
+
+  return n.
+}

lib/throttle.ks

@@ -1,4 +1,4 @@
-// Functions for calculating navigational and guidance values.
+// Functions for calculating thrust values.
 @lazyglobal off.
 
 // Returns the throttle value you should use to achieve the
@@ -42,15 +42,16 @@ function SensorCheck {
   set HAS_GRAV_SENSOR to false.
 }
 
-// adapted from https://github.com/sporadisk/KSP-KOS-scripts/blob/master/modules/GravityTurn.ks
-// todo: I don't think I actually like this code...
-function GravityTurn {
-  parameter TargetDirection is 90.
-  parameter TargetApoapsis is 80000.
-  parameter Factor is 1.
+function BurnTime {
+  parameter dV.
 
-  local remFactor is (2 / Factor).
-  local remHeight is (SHIP:APOAPSIS/TargetApoapsis).
-  local angle is (90 * (1 - (remHeight ^ remFactor))).
-  return heading(TargetDirection, angle, 90).
+  list ENGINES in en.
+
+  local f is en[0]:MAXTHRUST * 1000.  // Engine Thrust (kg * m/s²)
+  local m is SHIP:MASS * 1000.        // Starting mass (kg)
+  local e is CONSTANT():E.            // Base of natural log
+  local p is en[0]:ISP.               // Engine ISP (s)
+  local g is 9.80665.                 // Gravitational acceleration constant (m/s²)
+
+  return g * m * p * (1 - e^(-dV/(g*p))) / f.
 }