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 SPACE.com, 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.
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