Moon dust.  Image credit:  NASA

Recipe for Giant Lunar Telescopes

4 Jun , 2008 by

Someone has finally figured out something useful for all the dust on the moon’s surface: mix it with some epoxy and a pinch of carbon to create giant telescope mirrors. “We could make huge telescopes on the moon relatively easily, and avoid the large expense of transporting a large mirror from Earth,” said Peter Chen at a press conference today at the American Astronomical Society meeting. “Since most of the materials are already there in the form of dust, you don’t have to bring very much stuff with you, and that saves a ton of money.”

Chen and is team had been working with carbon-fiber composite materials to produce high-quality telescope mirrors. But then they decided to try an experiment. They substituted tiny carbon nanotubes for the carbon-fiber composites, and mixed in epoxies with crushed rock that has the same
composition and grain size as lunar dust, they discovered to their surprise that they had created a very strong material with the consistency of concrete. This material can be used instead of glass to
make mirrors.

Then they spun their concoction at room temperature to create a 12-inch-wide telescope mirror form, which they then coated with aluminum to create a highly reflective surface.

“Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter,” said collaborator Douglas Rabin. Currently the world’s largest optical telescope is the 10.4-meter Gran Telescopio Canarias in the Canary Islands, so this would be quite a step up.

Like liquid mirror telescopes, these large telescopes on the moon have definite advantages. With a stable platform, and no atmosphere to absorb or blur starlight, the monster scope could record the spectra of extra solar terrestrial planets and detect atmospheric biomarkers such as ozone and methane. Two or more such telescopes spanning the surface of the Moon can work together to take direct images of Earth-like planets around nearby stars and look for brightness variations that come from oceans and continents.

“Constructing giant telescopes provides a strong rationale for doing astronomy from the moon,” says Chen. “We could also use this on-site composite material to build habitats for the astronauts, and mirrors to collect sunlight for solar-power farms.”


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Sili
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Sili
June 4, 2008 2:30 PM

I seem to recall that the lunar soil is rich in He-3 (because of the solar wind, presumably). Am I misremembering? If we ever get fusion to work there might be a further incentive in mining that, right?

Adam
Guest
June 4, 2008 2:40 PM

Hope it can handle the thousands of sand grain sized meteorites hitting it all the time… maybe they should go with a liquid mirror so it can get it’s shape back after an impact.

Another Drew
Member
Another Drew
June 4, 2008 10:15 PM

Oops. Area of a circle is πr^2, not 2πr. Duh! wink Try 1963 square feet.

Peace

Excalibur
Member
Excalibur
June 4, 2008 4:06 PM

You are probably correct in that the mirror will take conciderable damage from dust meteorites, but a spun mirro made on location could be replaced by another once it have degraded to much, so the concept is still very good.

john
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john
June 4, 2008 5:52 PM

Interesting, this sounds like a step on the way to finding a good solution to what has seemed an insurmountable problem. Keep on working it.

trux
Guest
June 4, 2008 7:04 PM

I am not quite sure if microsopic meteorits would be of a considerably higher risk for a telescope on the Moon, than they are for example for the Hubble. Well, the gravitation of the Moon may attract little bit more of them, but I wonder if it is really that bad.

Another Drew
Member
Another Drew
June 4, 2008 7:33 PM
How is building a telescope on the Moon a _good_ idea? Don’t get me wrong, I fully support a lunar observatory, but building the telescope in situ probably doesn’t make much sense. Instead of carting up the mirror from Earth, you’d have to cart up the machines and equipment to _make_ the mirror, and that would be considerably more costly than assembling a multi-facetted mirror built on Earth to give the equivalent diameter of a single piece. Think about it. You’d have to send up the machines to collect the lunar regolith. You’d have to send up the machines to hold the regolith in place. You’d have to send up the epoxy. You’d have to send up a… Read more »
Brad
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Brad
June 4, 2008 7:42 PM

I agree with Drew. What has Hubble cost us? Isn’t it something like seven billion and counting. When you could have built OWL on earth and used adaptive optics to remove atmospheric interference. The result would be an order of magnitude better at a fraction of the cost. Plus its a helluva lot easier to upgrade and maintain!!

Flaming Pope
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Flaming Pope
June 4, 2008 7:54 PM
man power for dust collection (which even for a machine wouldn’t weigh more than a mirror, doesn’t even have to be big, just have the machine run on solar and let it run for a month if necessary), machine to spin = less mass than actual 50 foot lens, which is 50 feet in at least 2 orthogonal directions, don’t even know how your going to fit at on a shuttle. Molds are light weight and can be pieced together from scratch. Melting aluminum = solar power once again (you fail to realize that its about 1 Au from the sun and no atmosphere to weaken solar rays). But why just optical? I would like to see multi… Read more »
Another Drew
Member
Another Drew
June 4, 2008 10:12 PM
@Flaming Pope: Man power for dust collection?! What a waste! Consider how big a 50′ mirror is. That’s 150 square feet of surface area. Imagine collecting enough sand to cover 150 square feet to a depth of a couple inches. Now do that on the Moon wearing a suit with limited air, limited time, and multiple priorities. Would you really spend valuable time sending astronauts out on errands to collect dust in buckets?! I was ignoring power production (except for a few select places like the rim of Shackleton Crater, solar power on the Moon only works 14 out of 28 earth-days) because the power requirements are moot – operating the telescope and support equipment will require power,… Read more »
Chuck Lam
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Chuck Lam
June 5, 2008 5:43 AM

Hey NASA! I believe it in the best interest of main street America that you put Drew and Brad on your payroll as senior science advisors. Why you ask? Well, both gentlemen exhibit more common sense in their posts than the team working on this “lunar telescope” folly. My gawd! What are these NASA “lunar telescope” guys smoking when spending our tax dollars?

jayem4646
Member
jayem4646
June 5, 2008 8:23 AM
@Drew I’m not quite sure if the scientists are suggesting to produce a 50-metre diameter mirror that could then be spun inside a ~ 50-metre diameter spinning-type machine as this would require huge, huge amounts of machinery (so I agree with you on that count). Before I go on, just a note about your corrected calculations which seem, I think, to suggest you’ re looking at 50 foot diameter mirrors, but as far as I know they’re talking about ~ 50-metre diameter mirrors (and upwards). This would then make the overall area using Ï€r^2 as ~ 1963 sq. metres not 1963 sq. feet (1963 sq. metres is much, much greater than 1963 sq. feet). I think, however, that… Read more »
Excalibur
Member
Excalibur
June 5, 2008 3:24 AM

…and projected size is 50 meters, not 50 feet.

Chuck Lam
Guest
Chuck Lam
June 5, 2008 12:29 PM

Hello Dude, Wow! You figured it out! However, wouldn’t it make more economic and technical sense to manufacture a segmented mirror on earth and transport it to the surface of the moon for assembly? Why screw around with transporting lens making machinery! OK, so maybe NASA’s science engineers may not be smoking what-ever it is they might smoke. Those guys are misguided and not thinking clearly. It’s frustrating to see our tax dollars “go up in smoke”, err . . . wasted.

Dude
Guest
Dude
June 5, 2008 6:17 AM

Wow, you guys realize that transporting 1 set of machines means you can manufacture any number of mirrors right? Oh and the same machines that manufacture the mirrors are the SAME machines that manufacture other regolith “concrete”. The only difference is the form and the coating.

Who are the ones smoking crack?

Think before you open your pie holes.

Flaming Pope
Guest
Flaming Pope
June 5, 2008 10:38 AM
Back @ Drew: Your still thinking like a down to earth human, when you should be thinking space man. I referred to spin like a concrete mixer, (which is quite small no matter how you look at it)- this along with molds instead of one gigantic fabricator. And I’m saying small since you can have the machines run for any length of time. 14 out of 28 days is plenty, either have panels on both sides of the moon, a back up storage unit, or simply build two telescopes with the equipment at hand. And size is of no matter where it be micro meters, feet, kilo meters, just let machines run for any indefinite amount of time… Read more »
Alex
Guest
June 5, 2008 11:35 AM

I like a radio telescope on the far side of the moon. It would be protected from the earth (communication via satt. would be required), and would use the natural shape of a crater to form a large (100 meter for example) collector. I wonder if a simple metal mesh could be placed in a crater to create such a telescope? One could roll it up and send it to the moon. Optical telescopes on the moon seem very hard to construct, the technology seems a ways off that is.

Richard Kirk
Member
Richard Kirk
June 6, 2008 4:53 AM
Some of the posters seem to be talking as though the whole mirror was going to be cast in one go. I would assume the 50 meter telescope would be built out of small segments. At that sort of scale, a 10 cm square segment is within a quarter of a wave of being flat. Perhaps they would use larger tiles – say spinning hexagons 1 meter across. I don’t see any problem with making these. What I do see is the problem making something that supports and points all of this the size of the Jodrell Bank radio telescope. Unless we are just finding some convenient crater and polishing up the sides like Arecibo. Have a look… Read more »
Ross
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Ross
June 6, 2008 7:09 AM
One thing some of the posters might be forgetting is that they won’t just be building mirrors on the moon – they intend to actually build a space colony there, so whatever equipment they need to do that, can be used to build the mirrors. I’m sure the smart folks at nasa realize what it will take to build these things, and are considering that when making these proposals. If there is a colony on the moon, it makes sense to have those in the colony doing useful things, like building and maintaining telescopes for one thing. If putting a colony on the moon makes sense (I’m not sure it does), then so does making telescopes.
publius
Guest
June 7, 2008 9:43 AM

Sure, if ALL you are going to be doing is setting up ONE astronomical telescope, it makes sense to transport it from Earth & assemble it either on the lunar surface or in free space. On the other hand, if you are interested in a real observatory with multiple instruments, or if you are going to the Moon for (God forbid!) some extended period, or with multiple goals, transporting materials-processing & manufacturing equipment rapidly becomes more economical than transporting finished parts and supplies.

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