Spinning Membrane Space Telescopes Would Be Big, Cheap and Easy

Robert Zubrin has proposed using rotating membranes to create Enormous Space Telescopes (ESTs) that can scale to over 1000 meter diameter or match current space telescopes for thousands of time lower cost. They would also not require the construction of large structures.

A demonstration cubesat EST could have an aperture larger than the Webb Space Telescope. The Webb Space Telescope has a 6.5-meter mirror and costs over $10 billion.

The EST employs a hoop to deploy a slack reflector membrane, such as solar sail material or radio dish. The EST is simultaneously rotated around its center and accelerated along its axis of rotation, the membrane will assume a parabolic shape, thereby creating a reflector for a very large aperture telescope. The EST reflector can be accelerated along its linear axis by tethering its deployment hoop to a tug spacecraft.

Linear acceleration will shape the telescope membrane into a parabola.

A little demonstration EST, with a total mass less than 20 kg, including optics that would be positioned along or suspended from the tether at the parabola focal point, would have four times the light gathering capacity of Webb (about thirty times that of Hubble), while costing on the order of 1/1000th as much.

A 50 kWe argon-ion drive spacecraft would weigh 1000 kilograms and could deploy a 130-meter diameter EST telescope. The 65-meter radius operational EST would have a mass of about 2000 kg.

A single SpaceX Super Heavy Starship could deploy a 120 ton EST space telescope with a diameter of 1000 meters.

If there was a multi-decade nuclear power source, then the 20 kilogram systems could be deployed to the gravititional lensing points twenty times further than Pluto.

Making lighter but highly capable cubesat space telescopes would make it more affordable to send thousands of these telescopes out to the gravitational lensing point. The gravity of the sun would then enhance the images by millions of times. A 1-meter space telescope at the gravitational lensing point would be like an 80-kilometer diameter regular space telescope. A 12-meter diameter space telescopes at the gravitational lensing point would be able to image like a regular 1000 kilometer space telescope.

SpaceX has mass produced krypton fed hall effect thrusters for the Starlink satellites.

The SpaceX Starlink satellites cost less than $1 million each.

We could get space telescopes out to the gravitational lens point using near term technology within 8 to 15 years using a slightshot around the sun.

The earlier plan would be first create the cubesat demos of the spinning membrane telescopes and then scaling up to the 1-kilometer space telescopes over the next 5 years. In 5-10 years, we would perfect long-duration nuclear power source cubesat EST and then send those out to the gravitational lens points. The gravitational lens telescopes would reach their observation points in the 2040s.

Other Attempts to Get a Breakthrough for Larger and Cheaper Telescopes

There have been attempts to make large ground based telescopes that are a hundred times cheaper than the traditional approach.

The Large Zenith Telescope (LZT) was a 6.0-meter diameter liquid-mirror telescope located in the University of British Columbia’s Malcolm Knapp Research Forest, about 70 km (43 mi) east from Vancouver, British Columbia, Canada. It was one of the largest optical telescopes in the world, but still quite inexpensive. The telescope was completed in the spring of 2003 and decommissioned by 2019. The Large Zenith Telescope is now decommissioned and all its liquid mercury stored for other projects.

This mirror was a test, built for $1 million, but it was not suitable for astronomy because of the test site’s weather. The University planned a larger 8-meter liquid-mirror telescope named ALPACA for astronomical use at an estimated first-light cost of $5 million, $3 million contingency, $10 million for the camera, $5 million for a spectrograph, and $0.3 million operating costs per year. A larger project is planned, called LAMA, with 66 individual 6.15-meter telescopes with a total collecting power equal to a 55-meter telescope, resolving power of a 70-meter scope.

SOURCES- Centauri Dreams, Robert Zubrin
Written by Brian Wang, Nextbigfuture.com