Extraplanetary Exploration Using Electric Solar Wind Sail

This doctoral research investigates the problems in the dynamics and control of extraplanetary exploration using an electric solar wind sail (E-sail). The E-sail is a novel propellantless propulsion technology that harvests energy by repelling the charged particles in solar wind. It consists of a spinning central spacecraft connected by kilometer-long and thin positively charged tethers with remote units at their tips. Three dynamic models of E-sail are developed: the high-fidelity tether dynamic model, the generalized E-sail model, and the reduced-order analytical E-sail model. The coupling effects of orbital and self-spinning motions of the E-sail, the elastic deformation of tethers, the rigid-flexible coupling effect on the attitude dynamics and spin control of E-sail, and the stability control of the flexible E-sail are thoroughly investigated based on these models. Meanwhile, the controllability of E-sail spin rate and the attitude of the E-sail are demonstrated, and the trajectory tracking problems in extraplanetary exploration missions are studied. Finally, the main contributions of this dissertation are introduced

Extraplanetary Exploration Using Electric Solar Wind Sail

This doctoral research investigates the problems in the dynamics and control of extraplanetary exploration using an electric solar wind sail (E-sail). The E-sail is a novel propellantless propulsion technology that harvests energy by repelling the charged particles in solar wind. It consists of a spinning central spacecraft connected by kilometer-long and thin positively charged tethers with remote units at their tips. Three dynamic models of E-sail are developed: the high-fidelity tether dynamic model, the generalized E-sail model, and the reduced-order analytical E-sail model. The coupling effects of orbital and self-spinning motions of the E-sail, the elastic deformation of tethers, the rigid-flexible coupling effect on the attitude dynamics and spin control of E-sail, and the stability control of the flexible E-sail are thoroughly investigated based on these models. Meanwhile, the controllability of E-sail spin rate and the attitude of the E-sail are demonstrated, and the trajectory tracking problems in extraplanetary exploration missions are studied. Finally, the main contributions of this dissertation are introduced

Flight Dynamics and Control Strategy of Electric Solar Wind Sails

This paper studies the flight dynamics and control strategy for electric solar wind sails based on the nodal position finite element method, where the coupling effects between tether dynamics and the electrical field are considered. A modified throttling control strategy is proposed to control the attitude of electric sails by modulating individual tether voltage synchronously with the spinning motion of the sails. The effects of four critical physical parameters (tether numbers, tether length, sail spin rate, and mass of remote units) are investigated. The results show that the effect of the relative velocity of the solar wind has a significant effect on the spin rate of the sail in attitude maneuvering, which in turn affects the attitude dynamics and orbit motion of the sail. Numerical results show that the proposed control strategy work successfully stabilizes the spin rate of sail when the new type sail is adopted

Stability and control of radial deployment of electric solar wind sail

The paper studies the stability and control of radial deployment of an electric solar wind sail with the consideration of high-order modes of elastic tethers. The electric solar wind sail is modeled by combining the flexible tether dynamics, the rigid-body dynamics of central spacecraft, and the flexible-rigid kinematic coupling. The tether deployment process is modeled by the nodal position finite element method in the arbitrary Lagrangian–Eulerian framework. A symplectic-type implicit Runge–Kutta integration is proposed to solve the resulting differential–algebraic equation. A proportional–derivative control strategy is applied to stabilize the central spacecraft’s attitudes to ensure tethers’ stable deployment with a constant spinning rate. The results show the electric solar wind sail requires thrust at remote units in the tangential direction to counterbalance the Coriolis forces acting on the tethers and remote units to deploy tethers radially successfully. The parametric analysis shows the tether deployment speed and the thrust magnitude significantly impacts deployment stability and tether libration, which opens the possibility of successful deployment of tethers by using optimal control. Finally, the analysis results show that radial deployment is advantageous due to the isolated deployment mechanism, and a jammed tether can be isolated from affecting the deployment of rest tethers.Natural Sciences and Engineering Research Council of Canad

Preparation and biomedical application of a non-polymer coated superparamagnetic nanoparticle

We report the preparation of a non-polymer coated superparamagnetic nanoparticle that is stable and biocompatible both in vitro and in vivo. The non-polymer, betaine, is a natural methylating agent in mammalian liver with active surface property. Upon systemic administration, the nanoparticle has preferential biodistribution in mammalian liver and exhibits good reduction of relaxivity time and negative enhancement for the detection of hepatoma nodules in rats using MRI. Our data demonstrate that the non-polymer coated superparamagnetic nanoparticle should have potential applications in biomedicine

The Effects of Coordinated Molecules of Two Gly-Schiff Base Copper Complexes on Their Oxygen Reduction Reaction Performance

In this study, two simple Schiff base copper complexes [Cu(H2O)2(HL)]·2H2O (Complex 1) (H3L = 2-OH-4-(OH)-C6H2CH=NCH2CO2H) and [Cu(py)2(HL)] (Complex 2) (Py = pyridine) were initially achieved and authenticated by single-crystal X-ray structure analyses (SXRD), powder X-ray diffraction analyses (PXRD), FT-IR spectroscopy, and elemental analyses. The SXRD reveals that the Cu2+ center in Complex 1 exhibited a distorted square pyramidal geometry, which is constructed based on phenolate oxygen, water molecules, carboxylate oxygen, and imine nitrogen from a deprotonated H3L ligand in an NO4 fashion. The Cu2+ atom in Complex 2 had distorted square pyramidal geometry, and was coordinated with two pyridine molecules and one Gly-Schiff base ligand, exhibiting an N3O2 binding set. Additionally, the free water molecules in Complex 1 linked independent copper complexes by intermolecular hydrogen bond to form a 2D framework. However, the one-dimensional chain supramolecular structure of Complex 2 was formed by the intermolecular O–H…O hydrogen bonds. The oxygen reduction performance of the two complexes was analyzed by cyclic voltammetry (CV) and the rotating disk electrode (RDE) method. Both complexes could catalyze the conversion of oxygen to water through a predominant four-electron pathway, and the Cu–NxOy moieties might be the functional moieties for the catalytic activity. The catalytic pathways and underlying mechanisms are also discussed in detail, from which the structure–activity relationship of the complexes was obtained