Charlotte Lücking

Electrochromic orbit control for smart-dust devices

Recent advances in MEMS (micro electromechanical systems) technology are leading to spacecraft which are the shape and size of computer chips, so-called SpaceChips, or ‘smart dust devices’. These devices can offer highly distributed sensing when used in future swarm applications. However, they currently lack a feasible strategy for active orbit control. This paper proposes an orbit control methodology for future SpaceChip devices which is based on exploiting the effects of solar radiation pressure using electrochromic coatings. The concept presented makes use of the high area-to-mass ratio of these devices, and consequently the large force exerted upon them by solar radiation pressure, to control their orbit evolution by altering their surface optical properties. The orbital evolution of Space Chips due to solar radiation pressure can be represented by a Hamiltonian system, allowing an analytic development of the control methodology. The motion in the orbital element phase space resembles that of a linear oscillator, which is used to formulate a switching control law. Additional perturbations and the effect of eclipses are accounted for by modifying the linearized equations of the secular change in orbital elements around an equilibrium point in the phase space of the problem. Finally, the effectiveness of the method is demonstrated in a test case scenario.

Solar Radiation Pressure-Augmented Deorbiting: Passive End-of-Life Disposal from High-Altitude Orbits

A deorbiting strategy for small satellites is proposed that exploits the effect of solar radiation pressure to increase the spacecraft orbit eccentricity so that the perigee falls below an altitude where atmospheric drag will cause the spacecraft orbit to naturally decay. This is achieved by fitting the spacecraft with an inflatable reflective balloon. Once this is fully deployed, the overall area-to-mass ratio of the spacecraft is increased; hence, solar radiation pressure and aerodynamic drag have a greatly increased effect on the spacecraft orbit. An analytical model of the orbit evolution due to solar radiation pressure and the J2 effect as a Hamiltonian system show the evolution of an initially circular orbit. The maximum reachable orbit eccentricity as a function of semimajor axis and area-to-mass ratio is found analytically for deorbiting from circular equatorial orbits of different altitudes. The analytical planar model is then adapted for sun-synchronous orbits. The model is validated numerically...

Micro-to-Macro: Astrodynamics at Extremes of Length-scale

This paper investigates astrodynamics at extremes of length-scale, ranging from swarms of future ‘smart dust’ devices to the capture and utilisation of small near Earth asteroids. At the smallest length-scales families of orbits are found which balance the energy gain from solar radiation pressure with energy dissipation due to air drag. This results in long orbit lifetimes for high area-to-mass ratio ‘smart dust’ devices. High area-to-mass hybrid spacecraft, using both solar sail and electric propulsion, are then considered to enable ‘pole-sitter’ orbits providing a polar-stationary vantage point for Earth observation. These spacecraft are also considered to enable displaced geostationary orbits. Finally, the potential material resource available from captured near Earth asteroids is considered which can underpin future large-scale space engineering ventures. The use of such material for geoengineering is investigated using a cloud of unprocessed dust in the vicinity of the Earth-Sun L1 point to fractionally reduce solar insolation.