This paper provides a preliminary end-to-end mission design for NASA's Sunjammer solar sail mission, which is scheduled for ground test deployment in 2015 with launch at a later date and targets the sub-L 1 region for advanced solar storm warning. The artificial equilibrium points (AEPs) in the sub-L 1 region accessible by the Sunjammer sail as well as solar sail Halo orbits are investigated. Subsequently, the fly-out from an Earth GTO into either a selected sub-L 1 AEP or Halo orbit is optimized for a trade-off between the 飦刅 to be provided at GTO perigee and the time of flight. In addition, interesting, time-optimal extended mission scenarios are presented to underpin future solar sail mission applications, e.g. transferring to an AEP high above the ecliptic plane for high-latitude Earth observation. All analyses are carried out both for an ideal Sunjammer sail performance as well as for a realistic performance derived from a detailed sail structural analysis. A comparison of the results shows that non-ideal sail properties increase the time of flight of the trajectories by 2.4 -7.9%.
This paper presents families of libration point orbits in the Earth-Moon system that originate from complementing the classical circular restricted three-body problem with a solar sail. Through the use of a differential correction scheme in combination with a continuation on the solar sail induced acceleration, families of Lyapunov, halo, vertical Lyapunov, Earth-centred, and distant retrograde orbits are created. As the solar sail circular restricted three-body problem is non-autonomous, a constraint defined within the differential correction scheme ensures that all orbits are periodic with the Sun's motion around the Earth-Moon system. The continuation method then starts from a classical libration point orbit with a suitable period and increases the solar sail acceleration magnitude to obtain families of orbits that are parametrised by this acceleration. Furthermore, different solar sail steering laws are considered (both in-plane and out-of-plane, and either fixed in the synodic frame or fixed with respect to the direction of Sunlight), adding to the wealth of families of solar sail enabled libration point orbits presented. Finally, the linear stability properties of the generated orbits are investigated to assess the need for active orbital control. It is shown that the solar sail induced acceleration can have a positive effect on the stability of some orbit families, especially those at the L 2 point, but that it most often (further) destabilises the orbit. Active control will therefore be needed to ensure long-term survivability of these orbits.
The static deflection profile of a large spin-stabilized space reflector because of solar radiation pressure acting on its surface is investigated. Such a spacecraft consists of a thin reflective circular film, which is deployed from a supporting hoop structure in an untensioned, slack manner. This paper investigates the use of a variable reflectivity distribution across the surface to control the solar pressure force and hence the deflected shape. In this first analysis, the film material is modelled as one-dimensional slack radial strings with no resistance to bending or transverse shear, which enables a semi-analytic derivation of the nominal deflection profile. An inverse method is then used to find the reflectivity distribution that generates a specific, for example, parabolic deflection shape of the strings. Applying these results to a parabolic reflector, short focal distances can be obtained when large slack lengths of the film are employed. The development of such optically controlled reflector films enables future key mission applications such as solar power collection, radio-frequency antennae and optical telescopes.
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