The Balloonscope

A balloonscope, or kiloscope, is a telescope created in space by blowing up a large transparent balloon that can be kilometres in diameter then spinning it to create an oblate ellipsoid (ie flattening it a bit), and hardening it with ultraviolet light.

A mirror surface is then sprayed onto a patch of the flatter side, and a detector unit placed at the focal point of the mirror. The width of the mirrored surface, or usable reflective area (URA) over which the surface is close to the ideal parabolic curve for a mirror, is limited by the ability of the optics at the detector unit to correct for divergence of the curvature from parabolic.

In addition to their conventional astronomical use for detecting and studying distant exoplanets they will also be used as communications receivers, eventually establishing a network through known space.

Recent prototypes increase the URA by adding a stretch-ring of thicker material around a larger circle, pre-hardening that, then partially venting the balloon before completing the hardening of the remainder of the balloon. The extra rigidity of the stretch-ring allows the unused area of the balloon to be cut away after venting, thus removing the need for it to be transparent.

New, simpler balloon materials are being developed that will not only allow much larger balloons to be created but also allow kiloscopes to be constructed from scratch in other solar systems.