Space telescopes play a key role in the exploration of our universe, from imaging planets to gathering spectra of distant stars. To date, all space telescopes are manufactured on Earth and launched into orbit, with their size constrained by the diameter of the launcher’s payload fairing. This approach sets a hard limit on the telescope light collection ability, which determines its resolution and contrast. The Fluidic Telescope (FLUTE) project proposes to overcome launch constraints through the in-space creation of large liquid mirrors by utilizing interfacial physics under microgravity conditions. We present the design of experiments for the creation and measurement of spherical liquid mirrors under microgravity and their successful execution in parabolic flights. We describe the design of the mechanical apparatus and experimental methods used to pin, constrain, and control liquid gallium alloy and ionic liquid, as well as the optical technique used to reconstruct their surfaces in situ using Shack–Hartmann wavefront sensing. The results validate our experimental approach and show that the surfaces obtained under microgravity are indeed spherical, as expected from theory, though parabolic flight conditions prohibit optical-grade liquid surfaces. This set of experiments is a key milestone in maturing the FLUTE approach toward future extremely large liquid space telescopes.
We present experiments performed in parabolic flights and in space, demonstrating the use of Fluidic Shaping to create optical components in microgravity. By injecting optical liquid into a circular bounding frame in microgravity, surface tension drives the liquid to a minimum energy form of a spherical lens with sub-nanometric surface roughness. We will discuss the engineering challenges encountered in such experiments, and provide details and insights towards the future implementation of similar experiments in microgravity.
We view this set of experiments as the first milestones in expanding in-space manufacturing capabilities to also include optical components. Due to its simplicity, low power consumption and essentially zero waste, Fluidic Shaping can serve as a fabrication infrastructure for future long-duration space missions that must be self-sufficient. Due to its scale invariance, the method could potentially be used for the creation of large space telescopes, thus overcoming launch constraints.
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