NASA Envisions Huge Lunar Telescope
A 12-inch parabolic moondust mirror made by spincasting. The mirror consists of a bottom layer of lunar soil simulant JSC-1A Coarse mixed with a small quantity of carbon nanotubes and bonded with thinned epoxy.
Credit: Peter Chen/NASA/GSFC

Telescope mirrors made from lunar dust could help realize dreams of stargazing from the far side of the moon.

Creating gigantic lunar telescopes would normally carry an astronomical price tag, but NASA researchers used a mix of epoxy, simulated lunar dust and carbon nanotubes to demonstrate how to use materials already found on the moon.

?You can go to the moon with a few buckets, and build something far larger than anything a rocket can carry,? said Peter Chen, a physicist at the NASA Goddard Space Flight Center in Greenbelt, Md.

Orbiting vs. moon-based

Astronomers have argued about which is better in the future: building additional orbiting space telescopes such as Hubble or setting them up on the moon. Both types of telescopes would be beyond the interference of Earth?s atmosphere, although the moon has the added advantages of being a stable platform with a far side shielded from Earth?s cluttered radio background. On the other hand, getting to the moon represents more of a challenge than simply launching a space telescope.

However, the debate so far has been ?limited by launching from the ground,? Chen told, because Earth?s gravity places both size and cost limits on what rockets can carry into space or to the moon.

The solution: Get much of the needed building material from the moon itself. Chen had already started working with epoxy and carbon nanotubes to create ?smart? materials that can flex or change shape when an electric current passes through, but ended up adding simulated lunar dust called JSC-1A Coarse Lunar Regolith Simulant to the mix.

Chen used the resulting lunar concrete as the foundation of a foot-long disk, and poured more plastic epoxy on top of it. Then he spun the mirror at a constant speed that formed the epoxy into a parabolic, slightly bowl-like shape as it hardened. The mirror?s finishing touch came with a thin layer of reflective aluminum applied inside a vacuum chamber.

Making a Hubble-sized mirror would require bringing 130 pounds (60 kg) of epoxy to the moon with 3 pounds (1.3 kg) of carbon nanotubes and less than 1 gram of aluminum, according to Chen?s calculations. Meanwhile, 1,300 pounds (600 kilograms) of lunar dust could provide the bulk of the material. The moon?s lack of atmosphere also suits the vacuum conditions needed to make the mirror.

Base considerations

Astronomers may imagine telescope mirrors half the size of a football field, but realizing such dreams depends heavily on whenever NASA returns human explorers to the moon and sets up a moon base.

Other challenges include getting the necessary manufacturing equipment to the moon, such as the spinning table on which the mirror gets created. Future astronauts would also have to ensure that none of the free-floating lunar dust contaminates the mirror.

"It?s a great idea in principle, but nothing is simple on the Moon," said James Spann, physicist heading the Space and Exploration Research Office at Marshall Space Flight Center, in a NASA statement.

Chen and his colleagues will try to scale up their demonstration by creating 1.64-foot (0.5 meter) and 3.28-foot (1 meter) mirrors using the simulated lunar dust. They also plan to figure out ways to hone the quality of the finished mirror?s surface, and are already speculating about ways future explorers and robots could build even larger telescope mirrors on the moon — perhaps within an impact crater.

?It?s totally out-of-the-box, but it?s fun to think about,? Chen said.