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The US Air Force lab in Albuquerque, New Mexico, is patenting a new way of designing folding parabolic mirrors for space telescopes (US 2003/223135.) The new mirror can be collapsed for launch, and unpacked and expanded at its destination. To make the mirror, water is spun rapidly in a vertical cylinder to form a concave curve in its top surface. Fast-curing liquid polymer is then poured on the water, which sets to form a curved membrane a few micrometres thick. The membrane is coated with an optically reflective material and an ultrathin layer of a “shape memory” alloy. The mirror…