Loosely-displaced geostationary orbits with hybrid sail propulsion

Abstract

To overcome the congestion of geostationary orbit slots, previous work proposed to use vertically-displaced, non-Keplerian geostationary orbits by means of continuous low-thrust propulsion in the form of hybrid solar sail and solar electric propulsion (hybrid sail). This work extends and generalizes that concept by loosening the position constraint and introducing a station-keeping box. Sub-optimal orbits are first found with an inverse method that still satisfy the geostationary position constraint (i.e., no station-keeping box), which will be referred to as ideal displaced geostationary orbits. For these sub-optimal orbits, it is found that the hybrid sail saves propellant mass compared to the pure solar electric propulsion case: for solar sail lightness numbers of up to a value of 0.2 and the most favorable time during the year (i.e., at summer solstice), the hybrid sail saves up to 71.6% propellant mass during a single day compared to the use of pure solar electric propulsion. Subsequently, the sub-optimal orbits are used as a first-guess for a direct optimization algorithm based on Gauss pseudospectral transcription, which loosens the position constraint. This enables a more flexible trajectory around the ideal displaced geostationary orbit and lets the solar sail contribute more efficiently to the required acceleration. It therefore leads to a further propellant savings of up to 73.8%. Finally, the mass budget shows that by using by using far-term solar sail technology, the hybrid propulsion system enables an evident reduction in the required initial mass of the spacecraft for a given payload mass with a relatively long mission duration.

Rapid Algorithm for Generating Entry Landing Footprints Satisfying the No-Fly Zone Constraint

“…We can obtain D″ by (28) and substitute it into (25) to obtain the drag acceleration profile tracking law denoted as…”

“…Fahroo et al [26,27] employed the Legendre pseudospectral method for landing footprints. Other trajectory optimization methods such as the Gauss pseudospectral method [28][29][30] can also be applied to the landing footprint problem. The pseudospectral method has high accuracy, but the calculation takes a long time.…”

Magnetic sail-based displaced non-Keplerian orbits

“…The required thrust cone angle α and characteristic acceleration a c can be written as a function of ψ, ω, and r. To that end, introduce a cylindrical rotating reference frame T C (O; ρ, θ, z) of unit vectors îρ , îθ and îz (see Fig. 6), defined as îρ îr cos ψ − îν sin ψ, , îz îr sin ψ + îν cos ψ , îθ îz × îρ (11) where θ is the spacecraft azimuthal angle, measured from a fixed axis on the displaced orbit plane. Enforcing the balance between the propulsive, gravitational, and centrifugal accelerations, we obtain [31]…”

“…For example, Ceriotti et al [7,8] analyzed the pole-sitter mission concept, whose aim is to place a spacecraft above one of the Earth's poles for observation purposes. MacDonald et al [9] discussed a novel concept for an Earth-Mars interplanetary communication relay and a solar storm warning mission by means of high-specific-impulse low-thrust propulsion systems, while Heiligers et al [10,11] proposed to design new geostationary orbits by means of a hybrid propulsion system, which combines a solar sail with a solar electric thruster.…”

A Convex Approach for Trajectory Optimization of Super-Synchronous-Transfer-Orbit Large Launch Systems with Time-Position Constraints

“…However, in order to avoid interference with other satellites in GEO, and achieve predetermined functions, the satellites should stay above the predetermined point on the earth's equator. In other words, the time and position of orbital injection for GEO satellites are strictly constrained, which is different from the case of general satel-lites [2,3]. Because of the high attitude of the GEO, the scale of the launch system is always very large, and the special situations such as engine failure of large launch systems should be considered.…”