diff --git a/core/src/net/sf/openrocket/simulation/BasicLandingStepper.java b/core/src/net/sf/openrocket/simulation/BasicLandingStepper.java
index 75259962a..a111d1227 100644
--- a/core/src/net/sf/openrocket/simulation/BasicLandingStepper.java
+++ b/core/src/net/sf/openrocket/simulation/BasicLandingStepper.java
@@ -38,8 +38,12 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
 		// Compute drag force
 		double dynP = (0.5 * atmosphere.getDensity() * airSpeed.length2());
 		double dragForce = totalCD * dynP * refArea;
-		double mass = calculateStructureMass(status).getMass();
+
+		// Calculate mass data
+		double rocketMass = calculateStructureMass(status).getMass();
+		double motorMass = calculateMotorMass(status).getMass();
 		
+		double mass = rocketMass + motorMass;
 
 		// Compute drag acceleration
 		Coordinate linearAcceleration;
@@ -122,7 +126,7 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
 		data.setValue(FlightDataType.TYPE_MACH_NUMBER, mach);
 		
 		data.setValue(FlightDataType.TYPE_MASS, mass);
-		data.setValue(FlightDataType.TYPE_MOTOR_MASS, 0.0); // Is this a reasonable assumption? Probably.
+		data.setValue(FlightDataType.TYPE_MOTOR_MASS, motorMass);
 		
 		data.setValue(FlightDataType.TYPE_THRUST_FORCE, 0);
 		data.setValue(FlightDataType.TYPE_DRAG_FORCE, dragForce);
diff --git a/core/src/net/sf/openrocket/simulation/BasicTumbleStepper.java b/core/src/net/sf/openrocket/simulation/BasicTumbleStepper.java
index 97a387976..0c0824dd4 100644
--- a/core/src/net/sf/openrocket/simulation/BasicTumbleStepper.java
+++ b/core/src/net/sf/openrocket/simulation/BasicTumbleStepper.java
@@ -37,8 +37,10 @@ public class BasicTumbleStepper extends AbstractSimulationStepper {
 		double dragForce = tumbleDrag * dynP;
 		
 		// n.b. this is constant, and could be calculated once at the beginning of this simulation branch...
-		double mass = calculateStructureMass(status).getMass();
+		double rocketMass = calculateStructureMass(status).getMass();
+		double motorMass = calculateMotorMass(status).getMass();
 		
+		double mass = rocketMass + motorMass;
 
 		// Compute drag acceleration
 		Coordinate linearAcceleration;
@@ -121,7 +123,7 @@ public class BasicTumbleStepper extends AbstractSimulationStepper {
 		data.setValue(FlightDataType.TYPE_MACH_NUMBER, mach);
 		
 		data.setValue(FlightDataType.TYPE_MASS, mass);
-		data.setValue(FlightDataType.TYPE_MOTOR_MASS, 0.0); // Is this a reasonable assumption? Probably.
+		data.setValue(FlightDataType.TYPE_MOTOR_MASS, motorMass);
 		
 		data.setValue(FlightDataType.TYPE_THRUST_FORCE, 0);
 		data.setValue(FlightDataType.TYPE_DRAG_FORCE, dragForce);
diff --git a/core/src/net/sf/openrocket/simulation/GroundStepper.java b/core/src/net/sf/openrocket/simulation/GroundStepper.java
index 27c50014f..db9ea466d 100644
--- a/core/src/net/sf/openrocket/simulation/GroundStepper.java
+++ b/core/src/net/sf/openrocket/simulation/GroundStepper.java
@@ -60,9 +60,15 @@ public class GroundStepper extends AbstractSimulationStepper {
 		
 		data.setValue(FlightDataType.TYPE_VELOCITY_TOTAL, 0.0);
 		data.setValue(FlightDataType.TYPE_MACH_NUMBER, 0.0);
+
+
+		// Calculate mass data
+		double rocketMass = calculateStructureMass(status).getMass();
+		double motorMass = calculateMotorMass(status).getMass();
 		
-		data.setValue(FlightDataType.TYPE_MASS, calculateStructureMass(status).getMass());
-		data.setValue(FlightDataType.TYPE_MOTOR_MASS, 0.0); // Is this a reasonable assumption? Probably.
+		double mass = rocketMass + motorMass;
+		data.setValue(FlightDataType.TYPE_MASS, mass);
+		data.setValue(FlightDataType.TYPE_MOTOR_MASS, motorMass);
 		
 		data.setValue(FlightDataType.TYPE_THRUST_FORCE, 0.0);
 		data.setValue(FlightDataType.TYPE_DRAG_FORCE, 0.0);