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The math of ground-based telescopes v. space-based telescopes v. interstellar probes

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  • The math of ground-based telescopes v. space-based telescopes v. interstellar probes

    Lately, I've been thinking about the relative advantages and disadvantages of ground-based telescopes, space-based telescopes, and interstellar probes.

    Some of the qualitative stuff is easy to get a sense of. For instance, with adaptive optics to correct for the interference of the atmosphere, ground-based telescopes are getting a new lease on life. Also, scientists have figured out how to put together arrays of telescopes, which increases the relative attractiveness of telescopes v. interstellar probes. NIMBY makes space-based telescopes more attractive. Limited rocket payload diameters make ground-based telescopes more attractive. The time to develop, build, and launch a space-based telescope makes ground-based telescopes more attractive. The long time that it takes an interstellar probe to reach its destination makes telescopes more attractive. And so on.

    However, I have little sense about the math for interstellar probes and would like y'all's thoughts on that and/or links to papers or discussions of it.

    For instance, I want to place a probe payload of a couple thousand pounds into orbit around Alpha Centauri. Let's pretend that we have high-power solid state lasers, such that the transportation system of the probe could be powered on the outbound leg by laser from Earth orbit. Let's also pretend that VASIMR propulsion is available.

    What would be the spacecraft total weight and time to destination? Would it ever make sense, given our current scientific outlook to do interstellar probes?
    I came upon a barroom full of bad Salon pictures in which men with hats on the backs of their heads were wolfing food from a counter. It was the institution of the "free lunch" I had struck. You paid for a drink and got as much as you wanted to eat. For something less than a rupee a day a man can feed himself sumptuously in San Francisco, even though he be a bankrupt. Remember this if ever you are stranded in these parts. ~ Rudyard Kipling, 1891

  • #2
    Heh, Heh, Heh... Dan said probe...

    [/beavis]
    Try http://wordforge.net/index.php for discussion and debate.

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    • #3
      Re: The math of ground-based telescopes v. space-based telescopes v. interstellar probes

      Originally posted by DanS
      What would be the spacecraft total weight and time to destination?
      I have no idea.

      But...you forgot to mention balloon telescopes in your analysis. These are being use, and at 1% the cost of a space launch, can get about 95% of the atomosphere.

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      • #4
        A balloon is going to have a difficult time getting to another star, Zkrib.

        NIMBY makes space-based telescopes more attractive.


        Why? You never put them near people anyway, 'cause of the light pollution.

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        • #5
          Believe it or not, that's where native burial sites and such stuff are at. At least in the US, this is a big consideration. See, e.g., Mt. Graham.

          I came upon a barroom full of bad Salon pictures in which men with hats on the backs of their heads were wolfing food from a counter. It was the institution of the "free lunch" I had struck. You paid for a drink and got as much as you wanted to eat. For something less than a rupee a day a man can feed himself sumptuously in San Francisco, even though he be a bankrupt. Remember this if ever you are stranded in these parts. ~ Rudyard Kipling, 1891

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          • #6
            Believe it or not, that's where native burial sites and such stuff are at.


            Bah

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            • #7
              For the sake of argument, we could pretend that adaptive optics have advanced so much that we no longer need to use mountaintops for astronomy. I allow it for this discussion.
              I came upon a barroom full of bad Salon pictures in which men with hats on the backs of their heads were wolfing food from a counter. It was the institution of the "free lunch" I had struck. You paid for a drink and got as much as you wanted to eat. For something less than a rupee a day a man can feed himself sumptuously in San Francisco, even though he be a bankrupt. Remember this if ever you are stranded in these parts. ~ Rudyard Kipling, 1891

              Comment


              • #8
                the answer is too depressing

                It's why I don't work at places like JPL anymore. I went for the money instead and am much happier.
                “It is no use trying to 'see through' first principles. If you see through everything, then everything is transparent. But a wholly transparent world is an invisible world. To 'see through' all things is the same as not to see.”

                ― C.S. Lewis, The Abolition of Man

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                • #9
                  with adaptive optics to correct for the interference of the atmosphere, ground-based telescopes are getting a new lease on life


                  Often overstated. Corrective optics don't work all that well yet, and there is some doubt that they'll ever be able to help all that much.
                  12-17-10 Mohamed Bouazizi NEVER FORGET
                  Stadtluft Macht Frei
                  Killing it is the new killing it
                  Ultima Ratio Regum

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                  • #10
                    pchang: Are interstellar probes several orders of magnitude from making sense?
                    I came upon a barroom full of bad Salon pictures in which men with hats on the backs of their heads were wolfing food from a counter. It was the institution of the "free lunch" I had struck. You paid for a drink and got as much as you wanted to eat. For something less than a rupee a day a man can feed himself sumptuously in San Francisco, even though he be a bankrupt. Remember this if ever you are stranded in these parts. ~ Rudyard Kipling, 1891

                    Comment


                    • #11
                      Originally posted by DanS
                      For the sake of argument, we could pretend that adaptive optics have advanced so much that we no longer need to use mountaintops for astronomy. I allow it for this discussion.
                      I don't think you have a real sense for just how difficult, if not impossible that would be.
                      12-17-10 Mohamed Bouazizi NEVER FORGET
                      Stadtluft Macht Frei
                      Killing it is the new killing it
                      Ultima Ratio Regum

                      Comment


                      • #12
                        Originally posted by DanS
                        Are interstellar probes several orders of magnitude from making sense?
                        Yes.
                        12-17-10 Mohamed Bouazizi NEVER FORGET
                        Stadtluft Macht Frei
                        Killing it is the new killing it
                        Ultima Ratio Regum

                        Comment


                        • #13
                          Won't we always need some space-based just because of the atmosphere filtering out parts of the spectrum?

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                          • #14
                            what Krazyhorse said
                            “It is no use trying to 'see through' first principles. If you see through everything, then everything is transparent. But a wholly transparent world is an invisible world. To 'see through' all things is the same as not to see.”

                            ― C.S. Lewis, The Abolition of Man

                            Comment


                            • #15
                              Originally posted by KrazyHorse
                              with adaptive optics to correct for the interference of the atmosphere, ground-based telescopes are getting a new lease on life


                              Often overstated. Corrective optics don't work all that well yet, and there is some doubt that they'll ever be able to help all that much.
                              That's good to know. I'm also interested in arrays of telescopes. For instance, the diameter of the Hubble mirror (~2 meters) was in part constrained by the diameter of the payload bay of the Shuttle. I could imagine multiple mirrors unfold on orbit to create an array. In addition, we could use the proposed new NASA exploration rocketry, which has much larger diameters.
                              I came upon a barroom full of bad Salon pictures in which men with hats on the backs of their heads were wolfing food from a counter. It was the institution of the "free lunch" I had struck. You paid for a drink and got as much as you wanted to eat. For something less than a rupee a day a man can feed himself sumptuously in San Francisco, even though he be a bankrupt. Remember this if ever you are stranded in these parts. ~ Rudyard Kipling, 1891

                              Comment

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