A new approach for rapid slew and settle of small satellites is based on four single degree-of-freedom control moment gyroscopes with variable speed flywheels (or reaction wheels) in a pyramid configuration, combined with path and endpoint constraint time-optimal control. The path and endpoint constrained time-optimal control can be augmented with momentum management without the use of additional actuators.

A satellite in orbit around a planetary body includes a bus and a drag flap coupled to the bus. The drag flap is used to increase the drag torque applied to the satellite. The bus may house sensors and actuators, such as a star tracker, a gyroscope, a reaction wheel, and a global position system (GPS) receiver to monitor the attitude of the satellite in response to the applied drag torque. The measurements from the sensors and actuators may be used to determine the drag torque applied to the satellite. An estimate of the atmospheric density may be then be determined based on the drag torque. Compared to conventional approaches, the satellite and methods described herein estimates the atmospheric density at comparable, if not better, resolution and bandwidth. The atmospheric density estimates may also be acquired in real-time using a cheaper, lighter, and smaller satellite.

Conductive cooled gimbaled inertial measurement units are disclosed herein. An example apparatus includes an inertial measurement unit, a gimbal assembly in which the inertial measurement unit is disposed, the gimbal assembly having gaps between each gimbal of the gimbal assembly, the gaps including a gas to conduct heat from the gimbal assembly, and an isothermal dome at least partially surrounding the gimbal assembly, the isothermal dome having a cooling tube disposed on an external surface of the isothermal dome to transfer heat from the gimbal assembly via conduction.

Apparatus and methods for controlling a spacecraft for a transfer orbit. The spacecraft includes a momentum subsystem that stores angular momentum relative to a center of mass of the spacecraft, and a propulsion subsystem that includes electric thrusters. A controller identifies a target spin axis for the spacecraft, determines gimbal angles for electric thruster(s) that so that thrust forces from the electric thrusters are parallel to the target spin axis, and initiates a burn of the electric thruster(s) at the gimbal angles. The controller controls the momentum subsystem to compensate for a thruster torque produced by the burn of the electric thrusters. The momentum subsystem is able to produce a target angular momentum about the center of mass, where a coupling between the target angular momentum and an angular velocity of the spacecraft creates an offset torque to counteract the thruster torque.

Apparatus and methods for controlling a spacecraft for a transfer orbit. The spacecraft includes a propulsion subsystem with electric thrusters that are installed with two-axis gimbal assemblies. The spacecraft also includes a controller that identifies a target spin axis for the spacecraft, determines an actual spin axis for the spacecraft during the transfer orbit, determines gimbal angles for the electric thruster(s) that adjust the actual spin axis toward the target spin axis, and initiates a burn of the electric thruster(s) at the gimbal angles.

The present application discloses a propulsion system and method of propulsion which provides thrust without the ejection of propellant, without reaction, and without an external mass to react against. The basic propulsion system comprises; a means for motion, an electric motor, that convey rotary motion to a source of magnetic field, a rotor generating a magnetic field that interact magnetically with a stationary source of magnetic field, a stator, generating a stationary magnetic field. Magnetic interactions between the spinning magnetic field interacting magnetically while moving through the magnetic field space of the stationary magnetic field; generates a gyroscopic force and a Lorentz force without the ejection of propellant; without reliance on an external mass to react against, and without reaction as recognized in the Newton's Third Law Exception in accordance with the established principles of electrodynamics and modern physics.

A method for attitude control of a satellite in inclined low orbit in survival mode is disclosed, the satellite including at least one solar generator, at least one solar sensor, magnetic torquers capable of forming internal magnetic moments in a satellite reference frame having three orthogonal axes X, Y, and Z, and inertial actuators capable of forming internal angular momentums in the satellite reference frame. The at least one solar sensor has a field of view at least 180° wide within the XZ plane around the Z axis, the method including a step of attitude control using a first control law, a step of searching for the sun by means of the at least one solar sensor, when a first phase of visibility of the sun is detected, and a step of attitude control using a second control law.

A rotor assembly for deployment within a momentum control device that enables near-zero revolutions per minute (RPM) sensing, and method for making same, are provided. The provided rotor assembly utilizes a magnet coupled to the rotor shaft and a stationary sensor element to detect magnetic flux from the magnet and derive reliable near zero RPM therefrom.

A hybrid power source and control moment gyroscope (“HPCMG”) is disclosed. The HPCMG includes a control moment gyroscope (“CMG”), a first conductive bearing, and a second conductive bearing. The CMG includes a first transverse gimbal assembly, a central mass that produces a voltage potential, and a second gimbal assembly rotationally connected to the first transverse gimbal assembly. The first transverse gimbal assembly is rotationally connected to the central mass along a first axis of rotation and the central mass is configured to spin about the first axis of rotation and the first transverse gimbal assembly is configured to rotate about a second axis of rotation of the second gimbal assembly. The first conductive bearing rotationally connects the central mass with the first position of the first transverse gimbal assembly along the first axis of rotation.

An operation of a spacecraft is controlled using an inner-loop control determining first control inputs for momentum exchange devices to control an orientation of the spacecraft and an outer-loop control determining second control inputs for thrusters of the spacecraft to concurrently control a pose of the spacecraft and a momentum stored by the momentum exchange devices of the spacecraft. The outer-loop control determines the second control inputs using a model of dynamics of the spacecraft including dynamics of the inner-loop control, such that the outer-loop control accounts for effects of actuation of the momentum exchange devices according to the first control inputs determined by the inner-loop control. The thrusters and the momentum exchange devices are controlled according to at least a portion of the first and the second control inputs.