Self-Regulated Centrifugal Deployment of Passive Space Structures

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Abstract

Large lightweight compliant structures can be spin deployed, utilising centrifugal forces to achieve a compression-free stress distribution. The present research starts from the idea that self-regulating passive centrifugal deployment can be achieved when the spinning motion is driven by an environmental torque that is coupled to the deployment condition. In this thesis, the idea is applied to a deployable atmospheric entry heat shield and a heliogyro-type solar sail. The heat shield is based on a flexible fabric shell that induces aerodynamic roll-torque during descent and thus deploys by autorotating. Deployment leads to shape morphing that varies the aerodynamic roll-torque. Passive self-regulated deployment is thereby achieved as the rate of autorotation is determined by the shape, or in other words the deployment condition of the aeroshell. Active deployment modulation using conventional attitude control devices is also proposed, which can provide structural oscillation suppression as well as downrange manoeuvring of over 300 km during simulated re-entry from LEO for vehicles with 3 kg - 5 ton entry mass. Flight characteristics and structural dynamic behaviours are investigated using analytical analyses and numerical simulations. Low-fidelity experiments including low-speed drop test and wind tunnel test are carried out to verify the simulator and validate the design. Owing to its unique operating principle, the design has shown various advantages over existing solutions including inflatable and mechanically deployable systems. Based on the similar principle, the study also proposes a heliogyro that spins up under a torque generated from a meta-structure reflector and thereby deploys centrifugally. The magnitude of the spin-up torque depends on centrifugal-stress and thus realises self-regulated spin and deployment. Meanwhile, the reflector is based on a self-folding origami that can automatically fold up when exposed to sunlight and thus allows fully passive operation. Critical functions of the meta-structure and the heliogyro are proven by numerical simulations, while the self-folding material is validated through laboratory tests. This concept enables a concise system that prevents the structural dynamic issues faced by existing heliogyro designs, and also provides a practical method to realise multi-functional gossamer structures. In conclusion, the study has shown that self-regulated centrifugal deployment could enable new types of deployable space systems that benefit from being lightweight, compact, scalable, concise and robust.

Keyword(s)

aerodynamic decelerator; deployable space structure; downrange manoeuvre; gossamer structure; heat shield; intelligent system; morphing; self folding; self regulation; smart material; solar sail

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