Abstract: Mass properties of liquid-filled spacecraft are important for flight dynamics modeling and control design. However, measuring devices for mass properties are usually applicable to measure the spacecraft mass properties of dry weight only. Mass properties of liquid-filled spacecraft can only be obtained by computational methods. How to take into account the inertial tensor of liquid in each tank is the difficult point in such engineering computation. Theoretical expressions for mass properties of liquid in an arbitrary shaped tank were derived in a general sense. The derivation was conducted for a fully filled liquid tank with no free liquid surface and a partially filled liquid tank with a free sloshing liquid surface of small amplitude respectively. A numerical method for computing the mass properties of liquid was proposed using 3D finite elements. As a verification example, the numerical solutions and the analytical solutions of mass properties of the liquid in a rectangular tank were compared, which confirmed the accuracy of the proposed method. As an application research, mass properties of a liquid-filled spacecraft were computed using different computational methods. Studies show that the traditional computational method which solidifies the liquid obtains obviously larger moments of inertia, while the proposed method is more correct in theory and more applicable in engineering.

Key words: liquid-filled spacecraft, mass properties, inertial tensor, liquid sloshing, numerical computation