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."

Comments

The interesting part

[meldroc]

Borra envisions a telescope with a liquid mirror measuring 66 feet to 328 feet wide.

Anyone with any knowledge of telescopes will immediately see why astronomers are drooling right now.

Re:dust?

[Octorian]

And what environmental factors could possible cause that on the moon, which has no atmosphere or tectonic activity?

Freezing metal mirrors

[Mal-2]

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