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Completed TRL 2 (started at 2, targeting 3)
A high fidelity Flexible Reflective Membrane (FRM) solar sail model will be developed to improve mission design and navigation analyses for future solar sail applications. The current mission design practices assume “flat-plate” sail surfaces and solar radiation pressure force based models. These assumptions make it difficult to accurately model environmental torques experienced by the sail. The objectives of developing an improved FRM model will include: improvements to 6- DOF thrust & torque modeling of solar sails, demonstration of guidance and control algorithm capabilities in response to the improved sail dynamics modeling, characterization of solar sails with different sizes and or shapes, and the development of appropriate navigation filters in response to the variations in force modeling. The FRM sail model will be an innovative technology that significantly improves the current state of solar sail propulsive models by handling both force and environmental torque in the presence of complex sail membranes. This development will result in significantly improved designs and therefore reduce risk and schedule for low thrust propulsion in deep space exploration.
All current state of the GN&C simulations and navigation estimation filters for solar sail dynamics behavior assume that the solar sail takes on the shape of a “flat plate”, and that the torque imposed on the solar sail is unpredictable enough to be handled as a “disturbance” torque. However, solar flux causes significant flexing and shape deformation of a solar sail in orbit, leading to discrepancies of delta-v requirements, propellant usage to handle sail torqueing, and trajectory analysis. As an example, there is a significant risk for NASA’s NEA Scout spacecraft that accounts for all of these analysis discrepancies.
A high-fidelity solar sail model was previously formulated and was used for experimentation to see the net force and torque on a solar sail in which the shape/deformation of the solar sail was known before-hand. However, this solar sail thrust/torque model was never implemented into 6-DOF simulations or into estimation filters for navigation purposes, and was only used to compare the resulting net force and torque on pre-defined solar sail shapes.
The objective of this proposal is to start with the previously experimented solar sail model, expand its capabilities to handle more generalized flexibility/solar reflection for different shapes and sizes of solar sails, and implement this model into both 6-DOF simulations and navigation filters, thus replacing the previous flat plate solar sail dynamics models. The name of this expanded generalized model and its associated navigation estimation capabilities will be referred to throughout this document as the Flexible Reflective Membrane solar sail model, or the FRM model. With the implementation of this new FRM model into the 6-DOF tools being used currently for analysis of solar sails, mission-critical requirements (such as required delta-v and thrust characteristics) may be estimated at a much higher level of accuracy. The implementation of the FRM model into estimation filters for navigation will allow the navigation subsystem of GN&C to estimate the current state of the vehicle with much greater certainty. Lastly, the FRM model will allow for a quantifyable representation of the induced torque on a solar sail in a given relative orientation to the sun, which is currently not quantifyable in standard 6-DOF GN&C analysis tools for solar sails.
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