A passive thermal system for use in a satellite and other aerospace applications includes a container having a heat-pipe working fluid disposed in a first chamber and a Phase Change Material (PCM) disposed in a second chamber that substantially surrounds the first chamber. The first chamber contains a wick for transporting the heat-pipe working fluid. The exterior of the first chamber has fins, etc., that extend into the PCM for heat spreading and increased interface area.

A control method for controlling a momentum wheel device for stabilizing a spacecraft includes: providing the momentum wheel device as a real momentum wheel device having a momentum wheel driven by a motor; providing a simulated momentum wheel device based on an ideal physical model; concurrent feeding of a torque command to both momentum wheel devices, to change a rotational speed of both momentum wheel devices; controlling the motor to change the rotational speed dependent on the fed torque command; detecting a real rotation angle of the real momentum wheel device; calculating a simulated rotation angle of the simulated momentum wheel device by two-fold integration of the fed torque command; comparing the real rotation angle and the simulated rotation angle and generating an error signal corresponding to a deviation between the real and simulated rotation angles; and controlling the motor due to the error signal to reduce the deviation.

An attitude control module is described for providing propellant-free attitude control and momentum desaturation to a spacecraft. The attitude control module includes at least one solar sail comprising a reflective surface for reflecting solar photons; and at least one robotic arm coupled to the at least one solar sail, said at least one robotic arm comprising at least 4 degrees of freedom for positioning and orienting the at least one solar sail relative to the spacecraft. A corresponding method for operating the attitude control module to unload excess momentum from a spacecraft is also described.

Provided is an apparatus for controlling an orbiting satellite by sensing a change in a yaw angle of the orbiting satellite and calculating a ground sample distance (GSD) based on the yaw angle. The apparatus may include a sensor configured to sense a yaw angle corresponding to yaw steering of the orbiting satellite, and a processor configured to calculate, based on the yaw angle, a GSD corresponding to a length of a pixel projected onto a planetary surface scanned by the orbiting satellite.

Methods and apparatus to methods and apparatus for performing propulsion operations using electric propulsion system are disclosed. An apparatus includes a space vehicle including means for performing propulsion operations without using a chemical propulsion system.

A method controls an operation of a spacecraft according to a model of the spacecraft. The method determines control inputs for controlling concurrently thrusters of the spacecraft and momentum exchange devices of the spacecraft using an optimization of a cost function over a receding horizon subject to constraints on a pose of the spacecraft and constraints on inputs to the thrusters. The cost function includes components for controlling the pose of the spacecraft and a momentum stored by the momentum exchange devices. The method generates a command to control concurrently the thrusters and the momentum exchange devices according to at least a portion of the control inputs.

Provided is a three-dimensional rigid ball driving system including: a support frame having a polyhedral shape; a rigid ball positioned at the center of an inner portion of the support frame; a plurality of ball bearings installed at corners of inner sides of the support frame, respectively, and contacting a surface of the rigid ball; and a plurality of electromagnets disposed around the ball bearings and generating magnetic fields to rotate the rigid ball; and a controller controlling the electromagnets to control a rotation direction and a rotation speed of the rigid ball.

Provided is an apparatus for controlling an orbiting satellite by sensing a change in a yaw angle of the orbiting satellite and calculating a ground sample distance (GSD) based on the yaw angle. The apparatus may include a sensor configured to sense a yaw angle corresponding to yaw steering of the orbiting satellite, and a processor configured to calculate, based on the yaw angle, a GSD corresponding to a length of a pixel projected onto a planetary surface scanned by the orbiting satellite.

A method to control a sunlight acquisition phase of a spacecraft with a nonzero angular momentum of an axis D.sub.H. The spacecraft includes a solar generator configured to rotate about an axis Y. The spacecraft actuators are controlled to place the spacecraft in an intermediate orientation in which the axis Y is substantially orthogonal to the axis D.sub.H. The solar generator is controlled to orientate the solar generator towards the sun. The spacecraft actuators are controlled to reduce the angular momentum of the spacecraft. The actuators of the spacecraft engine are controlled to place the spacecraft in an acquisition orientation in which the axis Y is substantially orthogonal to the direction of the sun with respect to the spacecraft.

The present invention provides a method for attitude control based on finite time friction estimation for a flexible spacecraft. The control method includes the following steps: a. introducing spacecraft flywheel friction disturbance into a spacecraft dynamics system, and establishing a flexible spacecraft dynamics system with flywheel friction disturbance; b. converting the flexible spacecraft dynamics system with flywheel friction disturbance into a state-space form; c. constructing a flywheel friction disturbance estimator; d. constructing a flexible appendage vibration disturbance observer; and e. combining the flywheel friction disturbance estimator in the step c and the flexible appendage vibration disturbance observer in the step d with a nominal controller to obtain a compound controller; the compound controller compensating for flywheel friction according to an estimated value of a flywheel friction moment; and the compound controller compensating for flexible appendage vibration disturbance according to an estimated value of flexible appendage vibration disturbance.