Propellantless Pointing and Momentum Management Technology for Deep Space Science Missions

Project Objective  

Utilizing reflectivity control devices (RCDs) developed for solar sail missions, RCDs can be used for conventional spacecraft missions to aid in momentum management or utilized as part of space telescope requiring fine pointing control. 

Project Description 

One of the technologies as developed part of Solar Cruiser, a discontinued 1653 square meter solar sail, are reflectivity control devices or RCDs. These RCDs work like glass opacity controls where they switch between opaque and transparent. By placing them away from the center of mass of a spacecraft, they can be used to generate small changes in solar torque by switching states. If reaction wheels are used to steer a spacecraft, these torques can be used to keep their speeds under control without consuming any propellant. If a spacecraft requires minuscule steering torques, like a large space telescope, RCDs may be able to provide control with more precision than reaction wheels or electric propulsion. RCDs are easily scaled to the torque required by changing their size, moment arm, and time they are turned on. These RCDs enable fine pointing control (approximately 15 micro arcseconds is possible in theory) and propellantless momentum management to extend mission lifetimes which were previously limited with conventional reaction control systems.

Project Results and Conclusions 

Currently the project is in a research and development stage focused on the fine pointing control. Utilizing custom tools in MATLAB/Simulink, the team has been able to develop a fine pointing control system utilizing banks of RCDs with near complete field coverage. This fine pointing control exceeds Habitable World Observatory fine pointing requirements in its current configuration on a large telescope operating in the Earth-Sun L2 operating environment. 

Future development will look at conventional spacecraft in Earth orbit and determine the feasibility and configuration of conventional spacecraft utilizing RCDs for momentum management. Utilizing RCDs instead of propulsion will help extend mission lifetimes while utilizing the Sun's radiation pressure to dump momentum from the reaction wheels.

This project can benefit future deep space telescopes, such as Habitable World Observatory, while offering a new actuator for ultra-fine pointing control with current results measuring in the tens of micro arcseconds. Additionally, being utilized for satellites whose primary momentum management actuator are thrusters, this technology can provide a limitless supply of momentum management capabilities and greatly extend mission lifetimes.

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