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Rotating Mercury Lunar Observatory
Fraser Cain writes "Universe Today is reporting on a proposal under consideration by NASA from Dr. Robert Angel at the University of Arizona. He wants to build a 100-meter liquid mirror telescope into a crater on the Moon. It would only be able to look at a specific spot in the sky, but the view would bury Hubble's Deep Field Survey." The challenges of off-Earth construction are left as an exercise for the reader.
Is it true that they are saving money by using Lake Erie as the mercury source?
That's no moon...
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Even if they could keep it clean during construction, how would they keep it from getting contaminated with lighter-than-mercury space dust over time?
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I used to imagine a telescope of a pan filled with mercury, spinning, and attached to the lens assembly via rods on top, and the whole device turning to create gravity for the mercury so it stays in the pan, while the whole telescope like a lighthouse scans the skies.
The moon will allow greater sized assemblies, and gravity doesnt have to be induced. The problem is the lack of control, which can be offset by building multiple telescopes at various lattitudes.
So whats difficult? A large container which can carry mercury, even a large plastic bag in a satellite dish mesh can do. The structure will sit on a motor that spins. The motor will not induce any vibrations into the mercury pan, for the former telescope I had a magnetic levitation rotation device, or at least a string that dangles the pan while magnets rotate it. The magnets cannot be in two D structures like regular motors since thats vibration there, so a uniform magnetic field is applied while current is passed between the center of the pan and its sides to allow for a continuous DC motor. If the current can be passed with no contacts, we can achieve real smooth rotations and no frictions or vibrations... again magnetic levitation would be a great idea here since the moon can be cold enough for ceramic superconductors, and clear enough for solar panels to power the thing.
The smaller we make the mercury pan, the more vibration prone it gets as we increase the resolution, so we can expect moon earthquakes to be a problem whenever something hits the surface. Shouldnt be frequent enough to cause a problem...
Unlike Hubble, the structure should be radiation-hardened, low-maintenance, no mechanical parts, no chemical reserves object, except for the mercury container. If spun fast enough, the container can reflect light from greated angles removing the problem of lack of control.
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First off, this far outstrips our present launch capability. Second, we would require a much more reliable method of sending things into space before we decided to send up a significant amount of liquid mercury, given that a failed launch of a rocket carrying a large tank of mercury would be a major ecological disaster. It's a great idea in theory- pouring a bunch of liquid into a bowl would be certainly preferable to the tremendous amount of skill and effort required to properly build and polish large telescope mirrors- but I'm not sure how long it would be before this idea becomes even remotely practical.
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Has any one though of starting with a spinning liquid mecury mirror, letting it freeze, and then using it as a conventional telescope mirror. You could even remelt and respin it should it become contaminated. More complicated yes, but also more useful....
As long as we're suspending disbelief when it comes to building the damn thing, why not pick a bigger crater? C'mon, guys, think big...
How about Tycho? Just think of the view with an 85,000 meter mirror. Or maybe a field of smaller craters in the neighborhood of Tycho...we could call it the Tycho Massive Array #1, or TMA-1 for short. Yeah, thats the ticket...
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These mirrors work by spinning a pan of mercury. The force on the fluid is a function of its distance from the spin axis. The shape formed is a parabola, which is just what you would want for a telescope (collimated ray bundles formed into a point). If you put annular shield say 5 inches from the edge, then the edge of the mirror where the dust collects would be covered and wouldn't affect the image quality so much. There might also be some type of surface duster under that edge that could be used every now and then to lift off the particles. The ripples would die out after a while and you could go back to the astronomy.
Part of the idea with a polar crater is to protect the instrument from temperature variations, something you would get a lot of on a monthly basis with a mirror anywhere else on the Moon. Tycho sits in sunlight for two weeks, then in darkness for two weeks. That's not a stable environment.
Also, a telescope made with a liquid mirror can be aimed in one direction only, towards zenith. Even the slow, monthly rotation of the Moon wouldn't allow for significant exposure times without motion blur, something you don't want when photographing distant galaxies spanning less than an arc second in the sky. The celestial poles are the only two spots in the sky that don't move around (they merely rotate), allowing for arbitrarily long exposures (the article suggests a year) using a camera synchronized with the sky.
If Celestia has the correct orientation of the Moon, the lunar axis points at constellation Draco in the northern hemisphere and at constellation Dorado in the south, the latter including the Large Magellanic Cloud. However, I don't know what particular deep sky objects would be visible using a telescope such as the proposed one at either pole.
With all the com sattelites and GPS sattelites we're sending up, why not just get them to attach small telescopes or somthing similar and build a sattelite array the size of earth's orbit?
I'm sure there are parts of the rotation of some sattelites when these things are operating far under capacity. Is there some way to use that 'down time' to construct an array, or is it too problematic to turn the things to look in the opposite direction?
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They're not using mercury.
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Since any circular section of the parabolic dish would itself be a smaller parabolic dish you could just use a smaller secondary mirror and tilt it to shift the prime focus to any point you wish (within limits). The cost of observing further and farther from the optimum focal point of "straight up" would be in having to use smaller and smaller secondary mirrors and therefore making less magnified observations.
Of course the increased complexity of the system would be a drawback in and of itself but I have to believe it would be worth it. The deep field images would not be endangered since any size secondary could be used right up to the optimum size to take advantage of the entire primary mirror.
300 Standard scopes floating in a hexagonal pattern mounted by cables to the lake floor.Using super computers to syncronize and adjust for distortions.Plus 50 fulltime scientists and 70 illegal laborers woking fulltime cleaning and mixing cocktails(slaves)would be less expensive and more fun than even building a outhouse on the moon.We need to focus more attention on amanda projects also. I am a retard most of the time.
If they're going to send even that much tonnage to space, it would seem more cost effective to just build a space elevator (or other high capacity launch capability) first, either on Earth or the Moon. A lunar space elevator could be "grown" using lunar materials in the direction of Earth without getting too far into Earth's atmosphere or requiring advanced materials. At that point ordinary rockets, shuttles or other vehicles could meet up with the bottom end of it without needing to burn as much fuel as an entire moon trip would require. In the long run, many more projects like this could be done without as much funding required per project.
If you have that much tonnage to throw around then it is also possible to launch enough energy infrastructure up to smelt lunar rocks and produce the needed materials locally.
I could go on, but it just seems like a lot of expense for something that doesn't do much to make future trips more affordable or likely to happen, (even though I also want to find out how far we can peer out into the universe).
We should obviously build it on Mercury.
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How about changing the process of creating optics ?
So far the only viable way has been reduction... IE shape glass add metal, polish metal etc... However with the new advances in ink jet manufacturing how about building optics piece meal by construction rather than reduction?
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