Control of Lagrange Point Orbits Using Solar Sail Propulsion
- Paper number
IAC-05-C1.6.03
- Author
Mr. John Bookless, University of Glasgow, United Kingdom
- Year
2005
- Abstract
Solar sailing is an emerging form of propulsion which utilises solar radiation pressure to provide a useful thrust. The sail is a thin reflective film with a thickness of order 2 µm, with a large reflective area in order to intercept a flux of photons. A key advantage of solar sails over conventional propulsion systems is that missions are not constrained by the Δv available from stored reaction mass. This enables many new and exciting high-energy mission concepts. Planetary and small body sample returns can be achieved which require large Δv. Alternatively, the solar sail can be orientated normal to the Sun-line, which produces thrust in the anti-Sun direction to generate displaced non-Keplerian orbits at planets or small bodies.
This paper investigates utilising solar sails to generate non-Keplerian orbits in the Earth-Sun three-body problem. Artificial libration points can be generated Earthwards of the L 2 Lagrange point and Sunward of the L 1 Lagrange point. Hill’s equations will be adapted to model the dynamics of the problem including acceleration due to solar radiation pressure. Solutions which lead to quasi-periodic orbits will be identified using eigenvalue methods. A Jacobi integral can be derived from Hill’s equations to produce a series of Hill surfaces, which represent trapped orbits. In order to reduce the required Δv for insertion to a non-Keplerian orbit, invariant manifolds which pass near to the Earth will be identified.
Due to the instability of these orbits, station-keeping is required to prevent escape after orbit insertion. Applying trims to the solar sail area or sail pitch and yaw angles provides complete controllability at the nominal orbit. A linear quadratic regulator will be designed to enable optimal control after insertion to a non-Keplerian orbit. A comparison between solar sail and solar electric propulsion control techniques will be conducted for orbits near the L 1 and L 2 Lagrange points.
After inserting a solar sail into an orbit at L 1 or L 2, slow sail deployment can be used to spiral inward along the Sun-line. NASA has proposed the Geostorm mission to deliver a solar sail with science payload onto an orbit sunward of L 1. The aim is to provide advance warning of Earthbound CMEs (coronal mass ejections). The warning time would be improved over the ACE spacecraft (Advanced Composition Explorer) which is limited by the need to orbit the L 1 point. A possible mission trajectory will be outlined utilising a slow sail deployment to spiral sunwards after initial insertion to a halo orbit at L 1. The launch Δv and sail loading requirements will be considered for each stage of the mission.
- Abstract document
- Manuscript document
IAC-05-C1.6.03.pdf (🔒 authorized access only).
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