Liquid-mirror space telescope
A liquid-mirror space telescope is a concept for a reflecting space telescope that uses a reflecting liquid such as mercury as its primary reflector. == Design == There are several designs for such a telescope: Twirled pail: A pair of objects, one the mirror assembly and the other a counterweight possibly containing a camera assembly, are spun up to induce centripetal acceleration on the surface of the mirror assembly.
Source: Wikipedia — Liquid-mirror space telescope (CC BY-SA 4.0)