Passive Spin-Stabilised Solar Sailing for CubeSat Heliocentric Escape

Project Svarog is a student-led initiative at Imperial College London aiming to reach the heliopause using a CubeSat-class spin-stabilised solar-sail demonstrator. Small spacecraft are increasingly being considered for missions to extreme heliocentric distances, including NASA’s Solar Gravitational Lens concept at a starting 550 AU focal line. Recent missions have also highlighted the difficulty of maintaining stable sail attitudes within small satellite mass and power constraints, motivating simple and robust propulsion and control architectures.

This paper evaluates a spin stabilised solar sail architecture capable of achieving heliocentric escape with positive C3, utilising minimal attitude actuation compatible with near term CubeSat implementations. Coupled attitude orbit dynamics under solar radiation pressure are used to characterise feasible operating regions under passive stability and navigation tracking constraints, defining limits on achievable sail attitudes.

These passive stability limits are enforced within a constrained trajectory optimisation problem to identify heliocentric escape trajectories achievable without sustained active attitude control. A control strategy based on slow slewing via controlled centre of pressure to centre of gravity offsets is used, with small quasi static trim shifts generating weak solar radiation pressure torques that gradually reorient the spin axis and adjust mean cone and clock angles while minimising bounded nutation. Nutation behaviour is explicitly considered through a discussion of mitigation strategies and the use of stability maps to avoid unstable attitude regions.

The constrained control design problem spanning spin axis orientation, cone and clock selection, allowable trim offsets, and slew rates is benchmarked against fixed attitude and constant cone assumptions. A thermal and optical degradation assessment establishes conservative design margins, overall demonstrating that heliocentric escape can be made more feasible for small satellites using passive sail dynamics and low authority trim control rather than high delta v injection or continuous attitude control.