Abstract: The balance of a spin-balanced spacecraft may be dynamically adjusted by moving a liquid between or among containers spaced about the spin axis. The transfer of liquid is accomplished by controllable heaters associated with each container, for heating that container from which liquid is to be transferred to increase the pressure and drive out liquid. A spacecraft for accomplishing this method includes a balance sensing arrangements such as a gyroscope and logic for determining which container or containers are to be emptied and for controlling the heaters. Weight is minimized by accomplishing the transfer of liquid among fuel containers by way of manifolds which also supply fuel to thrusters.

Abstract: An attitude control system using magnetic torquing is enhanced using a momentum wheel which is pivoted if the sensed error signal about the roll axis exceeds a given threshold. The momentum wheel is pivoted under control of a stepping motor through a first angle proportional to the detected average roll error, and one-half nutation period later through an equal angle in the same direction. Alternatively, the momentum wheel is pivoted over first and second angles of different values wherein the difference is related to nutation.

Abstract: A method and system is described for simultaneously precessing and nutation damping a spinning spacecraft that includes a computer, thrusters for precession and nutation damping and gyros aligned with or parallel to each of three orthogonal axes with the x-axis being the spin axis. The gyro information from three orthogonal axes is used to compute the momentum vector and target vector. The error vector is computed from the computed momentum vector and target vector. When the error vector's component along a given axis orthogonal to the x-axis changes sign, the thrusters are fired to apply corrective torques according to a computed control error.

Abstract: A nutation damping control for a dual-spin satellite is provided by tilting the axis of the rotor relative to the normal spin axis of the satellite and back a half nutation period later. The tilting is in the direction of the angular momentum vector component that is transverse to the rotor's spin axis.

Abstract: An improved system and method for ejecting and stabilizing a satellite/perigee stage assembly from a shuttle or orbiter type craft in space where the satellite includes gyros aligned parallel to three orthogonal axes, a computer, and spin and attitude control thrusters is described. The method comprises the steps of orienting the shuttle such that the perigee motor is pointing in the desired firing attitude, initializing said gyros and initializing the attitude determination algorithm in the spacecraft's computer, ejecting the spacecraft/perigee stage assembly without spin, after ejecting, slowly spinning the assembly about a desired spin axis, damping the assembly's nutation and precessing the assembly to the initial attitude while slowly spinning, and when at the initial attitude, spinning up the assembly for perigee motor firing.

Abstract: A preselected axis other than the axis of maximum moment of inertia of a momentum stabilized spacecraft is oriented for alignment with the total angular momentum vector of the spacecraft by rotating one or more rotors to a critical rate of rotation. The rotation of the rotor or rotors is maintained at the critical rate to effect the desired rotation. The axis of the rotor or the effective angular momentum vector of the resultant momentum of a plurality of rotors is aligned with the axis of the desired spacecraft orientation. Energy dissipation assures stability by dissipating energy on the spacecraft body at a faster rate of dissipation than the rate of energy dissipation on the rotor.