Kerbal Space Program

I have no idea what it's actually returning, but it's wrong, based on comparing the values for a vessel when it is loaded and then when it is unloaded

This has been an error for a long time

The following code does return the correct values, feel free to use it or just to compare to what you have:

private double GetUnloadedVesselMass(string name, ProtoVessel protoVessel)
        {
            double num = 0.0;
            for (int i = 0; i < protoVessel.protoPartSnapshots.Count; i++)
            {
                ProtoPartSnapshot protoPartSnapshot = protoVessel.protoPartSnapshots[i];
                num = (double)protoPartSnapshot.mass;
                for (int j = 0; j < protoPartSnapshot.resources.Count; j+)
                {
                    ProtoPartResourceSnapshot protoPartResourceSnapshot = protoPartSnapshot.resources[j];
                    if (protoPartResourceSnapshot != null)
                    {
                        if (protoPartResourceSnapshot.definition != null)
                        {
                            num += protoPartResourceSnapshot.amount * (double)protoPartResourceSnapshot.definition.density;
                        }
                        else
                            Debug.Log("Vessel: " + name + ", resource: " + protoPartResourceSnapshot.resourceName + ", no definition");
                    }
                }
            }
            return num;
        }