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Lunar Lens Takes A Step Forward
palewook writes "A recent breakthrough increased NASA's interest in a lunar-based space telescope. Researchers combined an ionic liquid surface and a layer of silver which produced a favorably reflective mirror."
The Lunar chicks are just gonna love this.
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Meldroc, Waster of Electrons
The question I would ask is: would not this mirror have a very short lifespan as lunar dust covers/mixes with the liquid surface?
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Lunar ant civilization takes two steps back.
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Actually, I took a physics class a few years ago given by the lead researcher (Ermanno Borra) here at Laval U., and I remember him describing that for ionic liquids the damping can be extraordinarily high, so there are almost no image distortions coming from vibrations.
Not that old canard again. Glass is an amorphous solid, it is not a liquid (at ordinary temperatures). (And no, thickness differences in medieval stained glass windows don't prove anything - the pieces were installed thick side down for stability, and they didn't have the technology for uniform-thickness glass).
They're talking about real liquids, spun to form a curved surface. Early liquid mirror experiments involved mercury.
-- Alastair
This is actually a very old idea. American Scientist's May-June issue had a interesting piece on a liquid (mercury) telescope, and focused on some of the engineering challenges a team in Birtish Columbia tried to address. There is no rigid coupling - air cushions and a ring of permanent magnets serve to support and drive the mirror. (via a rotating magnetic field, produced by three stationary field windings). The other major issue was speed variations from the air currents and interfaces -- they ended up using a mylar film for one problem and a precise (2500 pulses/360 degrees) dynamic correction of rotational velocity. A 4 meter and 8 meter instruments are being built in Chile. The big advantage of building on the moon is gravity. There first numbers seem to indicate a diameter of about 100 meters could be possible with these ionic liquids (mercury would freeze). (Lack of) atmosphere problems could be addressed by using superconductors as a supporting base.
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Science -- Sealed, Delivered.
The telescope works with gravity, there's no gravity in space. More precisely, there is, but you are continuously falling so you don't feel it. However, you could use a telescope that slowly falls towards the sun and use the solar wind to stop it from falling and also create a weak gravity force. Could be enough to build your telescope in space.
Launch say 5 to start out so that four become the array and one transmits the data back.
Of course this now has me wondering if Bluetooth will work on the moon...
"Bah!" - Dogbert
Static electricity is one thing that keeps moving dust around on the moon. And then there's ejected material from meteor impacts (with gravity that low, stuff kicked up by meteors can travel quite far)
Visible light interferometry is damned difficult because of the small wavelengths involved. Also, even though and interferometer gives you the same angular resolution as a similar sized single element telescope it doesn't give you the same sensitivity to faint objects because of the smaller overall surface area of the objective. Plus, really big telescopes are inherently cooler.
You are so boring that when I see you my feet go to sleep.
"Yes, launch tons and tons of highly toxic quicksilver on a rocket to Moon. What could go wrong?"
Well I suppose killing all life on the Moon would violate the Prime Directive.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
They do have existing spinning liquid mirrors in service, one of which is in Whistler BC. At this time I don't remember the name of the observatory. The article I read outlined the stringent engineering requirements both to prevent vibrations as well as turbulence generated by the motion of the water.
How that would be applied on a lunar observatory is another story.
Would the freezing of the mercury really be that much of a problem? How about a system where the mirror is formed of molten metal, then allowed to freeze (requiring no additional energy to hold its shape). If it gets scratched, chipped, warped, or otherwise marred, heat it up and shape it again.
The down side of such a system would be that you would lose the ability to change mirror dimensions "on the fly", but I'm not sure they're doing that anyhow. Also the mirror makers would have to account for the contraction of the metal on freezing, but at least they have the ability to retry if they don't get it quite right, or if the secondary mirrors (which presumably will be the standard glass type) turn out to be imperfect.
I also believe a telescope with a liquid mirror would have to be a "transit telescope", always pointed straight up relative to the local pull of gravity. Transit telescopes can track objects by moving their secondaries around, but not very far off-axis, and at the cost of focus and sensitivity. A solid-Hg mirror would remove this restriction, though it would possibly be too massive to reasonably move it around. Without this ability, observations would be at the mercy of whichever way the scope was pointed at any given time, give or take a few degrees.
It also seems to me the dust problem is relatively easy to solve using a positive pressure system. Any amount of gas in the telescope enclosure will be positive pressure compared to what's outside. Either the enclosure will not leak (and dust will have no way in), or it will leak slightly, forcing dust away from the leaks anyhow. Then maintaining a clean mirror is as simple as pumping in replacement gas.
Mal-2
How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.
UBC has a telescope whose primary reflector is a spinning liquid mercury mirror http://www.astro.ubc.ca/LMT. It forms a paraboloidal reflective surface, which is one of the optimal reflector shapes, but can only be aimed at the zenith. A larger (6m diameter) version is being constructed for installation at the same facility near Vancouver.
Smaller liquid-mirror telescopes were designed in the late 19th century, and a 51cm diameter example was built in the early 20th century (by Robert Wood) http://en.wikipedia.org/wiki/Robert_W._Wood. Wood's design suffered from intermittent ripples on the surface, but performed well at other times.
At least Canada is closer than the Moon, and easier to get to (not necessarily less inhospitable, of course).
Those who can make you believe absurdities can make you commit atrocities. - Voltaire