Satellite launches experience approximately one deployment failure every two years. These failures include a solar array or antenna that fails to deploy because it is stuck due to a mechanism failure, or is snagged by a cable or thermal blanket. Knowledge of the exact circumstances of the deployable failure is limited. Ground commanding of the spacecraft is conducted in an attempt to free the stuck deployable.
Prior art relies on the satellite ground operator’s ability to induce loads on the solar array or antenna by changing the local environment, i.e. spacecraft attitude control loads, thermal environment, etc., thereby overcoming the forces preventing full deployment. This approach may be limited by the loads the spacecraft can apply to the deployable.
Robotic servicing of a satellite in geosynchronous Earth orbit (GEO) requires advanced systems capable of meeting the harsh environments of space. To support this effort, techniques and processes were developed by which repairs to satellites may be performed. For the work described here, repairs refers to the process of freeing a spacecraft mechanism, such as a solar array or antenna that failed to deploy after launch.
During robotic servicing of a client satellite, the servicer spacecraft performs a variety of tasks through the robotic manipulation of a variety of tools. The purpose of these innovations is to provide satellite servicers with options for performing repairs on failed deployable components. By performing the repair task, the satellite servicer will attempt to bring the solar array, antenna, or other deployable into its proper configuration and enable it to function as planned. Servicers initiate repair tasks by gathering information using the onboard situational awareness cameras and close-in inspection cameras to inspect the stuck solar array, antenna, reflector, or other deployable.
Depending on the situation, they may use one or more of the available concepts below to release the stuck deployable. The Infrared Reflector Heater Tool is attached to the Advanced Tool Drive System (ATDS), which is attached to the robot arm. The tool is maneuvered to the stuck deployable and is used to raise the temperature of the deployable’s components whose stiffness has increased dramatically due to the low temperatures in space (i.e. frozen wire harnesses, etc.), thus preventing deployment due to the decrease of torque margin. The heater tool consists of a small parabolic or concave reflector dish with an infrared heater located at its focal point, and a laser to ensure the tool is pointed in the right direction and at the intended component. Since infrared has a relatively long wavelength, the dish can be made out of polished aluminum.
The Ultrasonic Friction Reduction Tool is attached to the ATDS, which is attached to the robot arm. The tool is maneuvered to the stuck deployable. The tool is capable of reducing the friction on the deployable’s components that are stuck due to excessively high friction between surfaces in contact. The tool is placed in contact with the stuck component to introduce a sinusoidal forcing function of low amplitude, forcing frequency in the ultrasonic frequency range of 20 to 50 kHz. The low-amplitude large accelerations generated by high-power ultrasonics separate the surfaces of the parts in contact under high friction as each part begins to vibrate relative to each another. The resulting effect is the reduction or elimination of friction. The tool includes a piezoelectric actuator driven by a sinusoidal voltage and configured to generate vibrations at an ultrasonic frequency.