Flux-pinning mechanisms for improving cryogenic segmented mirror performance

Abstract

Although large cryogenic space telescopes may provide a means of answering compelling astrophysics questions, the required increase in the primary mirror diameter presents technical challenges. Larger primaries are more flexible, and cryogenic mirrors are typically very lightly damped-the material damping is negligible, and common damping methods break down. To address these challenges, we propose placing flux-pinning mechanisms along the edges of adjacent mirror segments. These mechanisms consist of a collection of magnets and superconductors, and like flexures, they preferentially allow motion in specific degrees of freedom. Motion in nonpreferred degrees of freedom is resisted by a force analogous to a damped spring force, and the stiffness and damping can be adjusted independently. As an example, we consider simple mechanisms consisting of an inexpensive magnet and a single superconductor. These mechanisms provide increasing resistance as the magnet and superconductor-or mirror segments attached to each-come closer to colliding. These mechanisms, with typical stiffness and damping values on the order of 5000 N∕m and 5 kg∕s, respectively, also provide modest improvements to the mirror performance. Greater gains can be achieved by using stronger magnets or smaller separations, or by placing nonmagnetic conductive materials near the mechanism.

Overview and accomplishments of advanced mirror technology development phase 2 (AMTD-2) project

“…In anticipation of the contrast leakage effect of segment rigid-body motion in a segmented aperture, AMTD funded Jessica Gersh-Range to investigate mitigation strategies. In FY 2014/15, she published her PhD research [17][18] which indicates that connecting segments along their edges with damped spring interfaces provides potentially significant performance advantages for very large mirrors (Figure 8). With no edgewise connection, the segments behave independently.…”

Piece‐wise control of constant electromagnetic moments for spacecraft self‐ and soft‐docking exploiting dynamics conservation

“…However, the thrust approach relies heavily on propellant consumption and results in limited spacecraft mission life, which is worse for regular on-orbit servicing. Therefore, the approach of no propellant consumption has attracted significant attention, such as inter-spacecraft force/torque produced by the electrostatic [5,6], the electromagnetic [7][8][9], and the magnetic flux pinning effects [10][11][12]. Inter-spacecraft electromagnetic actuation consumes no propellant and produces no plume contamination, while providing high-precision, continuous, reversible, synchronous, and non-contacting control capability, which has potential advantages for spacecraft docking and separation application.…”