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Space Technology

The Engineering and Logistics of Building the Giant Magellan Telescope ( 22

New submitter Kenneth Stephen writes: Astronomers have always wanted bigger and better telescopes. Building such telescopes today come with many challenges that require high precision work to resolve. This story describes the design thinking that is being applied to the construction and deployment of the Giant Magellan Telescope. From the article: "One of the challenges of using a large mirror is that it tends to bend under its own weight and the force of wind. The mirror is exposed to wind like a sail on a yacht, but it can only bend by about 100 nanometers before its images become too blurry. The best way to overcome this problem is to make the mirror as stiff as is practical, while also limiting its weight. We accomplish this feat by casting the mirror into a lightweight honeycomb structure. Each mirror has a continuous glass facesheet on top and an almost continuous backsheet, each about one inch thick. Holding the two sheets together is a honeycomb structure consisting of half-inch-thick ribs in a hexagonal pattern. Our honeycomb mirrors are 70 centimeters thick, making them stiff enough to withstand the forces of gravity and wind. But they’re 80 percent hollow and weigh about 16 tons each, light enough that they don’t bend significantly under their own weight."
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The Engineering and Logistics of Building the Giant Magellan Telescope

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  • by paiute ( 550198 ) on Sunday January 17, 2016 @12:49PM (#51318221)
    As attorney of record for the honeybees, I ask you to stop construction using their proprietary honeycomb technology until such time as the two parties can come to an agreement on licensing fees.
    • I assure you that the honeycomb technology is similar only in name. Ours was derived from computer models and everyone knows that "on a computer" makes similar things novel and unique.

    • Bah! The honeybees didn't invent the hexagon. They copied snowflakes.
  • by 110010001000 ( 697113 ) on Sunday January 17, 2016 @01:21PM (#51318339) Homepage Journal
    If the Astronomers would stop harassing women they would probably get it built faster. - Ethan (StartsWithABang)
  • The Caris Mirror Lab at U of A Tucson, which is building the large mirror segments for this and other large scopes, faced an unusual problem in the Nineties when it was casting the mirrors for the Large Binocular Telescope on nearby Mt Graham. To avoid attack by eco-terrorists who were trying to prevent construction in an early, unsuccessful trial of the protest techniques they are now using in Hawaii, each completed mirror segment had to be sneaked out at a random time in an unmarked vehicle.

    This tactic m

  • by Dr. Spork ( 142693 ) on Sunday January 17, 2016 @01:56PM (#51318485)

    One of the challenges of using a large mirror is that it tends to bend under its own weight and the force of wind.

    I think it's a scandal that we aren't building a massive telescope in space, where you don't have to worry about gravitational sagging or gusts of wind... (or clouds, atmospheric distortions, light pollution, etc.). When we think of near-future space program ambitions, everybody talks about sending people to Mars. But we would learn so much more from building and using a kilometer-scale telescope mirror in orbit. From the article, it's clear that even terrestrial telescope mirrors now consist of a thin glass sheet with scaffolding behind it. Isn't it time to think about how to build that kind of thing in space, where the scaffolding requirements would be much smaller? It's inevitable that for a certain size of mirror, it will actually more expensive to build it on Earth than in space, for the reasons mentioned in the article. So come on, let's get some courageous nerds like Elon Musk on the job and build a telescope that could actually resolve extrasolar planets and see the formation of the first galaxies. Compared to this, people on Mars seems like a vanity project.

    • It's hardly a 'scandal', but a matter of cost. We're still at the stage where space telescopes have to be designed for unattended operation, while the one you envision would have to be manned. Such a scope will be built as a project once there is settlement in the area, just as building Mt Palomar took place after there was settlement and infrastructure in California.

      So our next space telescope will be the Webb. Meanwhile, segmented mirrors allow another generation of large Earh-based instruments to be buil

    • As was seen with Hubble. Building something for space is an entirely different ballgame, building something large scale even more so given the cost of getting every kilo into space and the difficulty of maintaining it afterwards. Would be great if they were looking to build such a telescope in space but we are a long long way from being able to create such a precise piece of engineering on that scale in space and even further from being able to lift something that large into space.
    • by ganv ( 881057 )
      Dr. Spork is on to something here. We still know so very little about our universe and by far the best way forward is to develop very large aperture telescopes. Humans are headed toward building truly massive optical telescopes (100m scale this century, maybe 1km scale in the 2100s or 2200s). Right now we need to succeed in getting the James Webb 6.5m telescope in space and the 30m earth instruments operational. There are several ideas about how to build 100m scale optical telescopes. (See the OWL propo
    • The cost of putting a ton of anything in space is higher than the cost of putting 1000 tons of that thing anywhere on Earth. The LBT cost a hundred million to build, while the Hubble was a couple billion. The LBT's mirrors have 24 times more surface area than Hubble. So how do you propose to put a 30 meter telescope in space?
  • by Teun ( 17872 ) on Sunday January 17, 2016 @03:04PM (#51318779) Homepage
    From the summary: "100 nanometers, about one inch, half an inch, 70 centimeters, 60 tons.

    Now it might 'only' be in the resume of this story but we should have learned many years ago that mixing of units of measurements is almost guaranteeing a failure.

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