diff --git a/launch.ks b/launch.ks
index 6f49322..56059f5 100755
--- a/launch.ks
+++ b/launch.ks
@@ -80,7 +80,6 @@ function launch {
     
     wait until APOAPSIS > target_orbit_altitude.
     lock THROTTLE TO 0.
-    unlock_control().
     
     
     print "--- CIRCULARIZE ---".
@@ -95,7 +94,7 @@ function launch {
     local node is NODE(TIME:SECONDS + ETA:APOAPSIS, 0, 0, 0).
 
     // Burn magnitude in the prograde direction is the difference between the required velocity to acheive circular orbit at apoapsis altitude and our velocity at apoapsis
-    local required_velocity is orbital_velocity_from_ap_pe(APOAPSIS, target_orbit_altitude, target_orbit_altitude).
+    local required_velocity is orbital_velocity_from_ap_pe(APOAPSIS, APOAPSIS, target_orbit_altitude).
     set node:PROGRADE to required_velocity - VELOCITYAT(SHIP, TIME:SECONDS + ETA:APOAPSIS):ORBIT:MAG.
     
     add node.
@@ -118,7 +117,7 @@ function calculate_launch_azimuth {
     local inertial_azimuth is ARCSIN(COS(target_orbit_inclination) / COS(launch_site_latitude)).  // azimuth in inertial space, that is, disregarding the rotation of the body
     
     local equatorial_rotational_velocity is (2 * CONSTANT:PI * BODY:RADIUS) / BODY:ROTATIONPERIOD.
-    local target_orbit_velocity is orbital_velocity_from_ap_pe(APOAPSIS, target_orbit_altitude, target_orbit_altitude).
+    local target_orbit_velocity is orbital_velocity_from_ap_pe(target_orbit_altitude, target_orbit_altitude, target_orbit_altitude).
 
     local launch_vector_x_component is target_orbit_velocity * SIN(inertial_azimuth) - equatorial_rotational_velocity * COS(launch_site_latitude).
     local launch_vector_y_component is target_orbit_velocity * COS(inertial_azimuth).
diff --git a/lib/equations.ks b/lib/equations.ks
index 563bc4e..453d097 100644
--- a/lib/equations.ks
+++ b/lib/equations.ks
@@ -42,9 +42,9 @@ function orbital_velocity {
     //  http://www.orbiterwiki.org/wiki/Front_Cover_Equations
     //  https://en.wikipedia.org/wiki/Vis-viva_equation
     parameter altitude.
-    parameter semi_major_axis is semi_major_axis().
+    parameter sma is semi_major_axis().
     
-    return SQRT(BODY:MU * ((2 / (altitude+BODY:RADIUS)) - (1 / semi_major_axis))).  // add body radius because KSP measures altitude from the surface
+    return SQRT(BODY:MU * ((2 / (altitude+BODY:RADIUS)) - (1 / sma))).  // add body radius because KSP measures altitude from the surface
 }
 
 function orbital_velocity_from_ap_pe {