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7-8 meter diameter mirror in outer space would be too small? Should be possible to put into orbit in one starship launch. And a system of big mirrors could be p

7-8 meter diameter mirror in outer space would be too small? Should be possible to put into orbit in one starship launch. And a system of big mirrors could be probably assembled and aligned together, without gravity and outside vibrations.

p_l 6y ago
Try 39 meters, weighing 400 tons for just the first mirror in sequence of 5, and that's without supports and actuators and everything else.
- beambot 6y ago
  I assume you're talking about the ELT. It's composed of something like 800 individual segments with their own position-adjusting actuators. I'm not intimately familiar with its construction (and the tolerances!), but I presume it would be possible to launch individual segments for space-based or moon-based construction... The big, monolithic secondary mirror is entirely within Starship's payload volume (4.2m diameter) and mass (3.5 tonnes). Bonus: Space-based radio astronomy will achieve much higher SNR! Edit (since reply is slow): You probably benefit on your mass-related support structure costs due to the lower-gravity (or zero gravity) environments.
  - p_l 6y ago
    ELT pretty much would require space manufacturing base - for the mass involved, you could probably furnish a small moon town. The problem is that the ones making the mess aren't going to pay for that, and I shudder at the costs involved in just space assembly of something the size of ELT... Edit to the slow reply ;) - the 400 tons is just the estimate zerodur mirror segments for the main mirror, nothing of the support structures... and didn't include ~65 tons of spare segments (ELT plans to replace two daily or something like that).
    - maccam94 6y ago
      Starship will be an incredible game changer for space economics. Look at this progression: - $50,000/kilogram for 27,500kg of payload (Space Shuttle, 1981-2011) - $2,500/kg for 22,800kg of payload (SpaceX Falcon 9, 2010-present) - $20/kg* for 100,000kg of payload (SpaceX Starship, 2022??) *: This is the estimated operational cost, not the price of a launch For a ballpark launch cost estimate, assuming that the mirror segments would be mass constrained rather than volume, it would cost $8M (plus however far off the cost estimates are, plus profit) just to get the mass into space. Maybe say $20M just to pad it a bit? There would almost certainly need to be more money spent on designing the whole thing to work in space, of course. But these projects have long planning horizons, there's no way anyone would have considered building something large in space before Starship was announced (other than nation-state level prestige projects). I suspect we'll see a flood of small to medium sized projects announced once Starship completes its first commercial LEO launch, then larger projects tentatively announced in the following couple of years. Sources on costs: https://ntrs.nasa.gov/citations/20200001093 https://ntrs.nasa.gov/citations/20200001093 https://en.wikipedia.org/wiki/SpaceX_Starship https://en.wikipedia.org/wiki/SpaceX_Starship
- nine_k 6y ago
  Let's admit, this telescope is also one of a kind, and it (ELT) is not online yet, too. If we care about telescopes which are built by hundreds, their mirrors are an order of magnitude smaller. OTOH with the massive launch capacity SpaceX is building, we could put a dozen 5m telescopes in various high orbits around Earth. With orbital assembly, very large diameter mirrors can be formed; even if these mirrors had a relatively small area (many holes between mirror elements), the angular resolution could be higher than anything reasonably achievable on the planet surface.
- iso1631 6y ago
  "List of largest optical reflecting telescopes" 8.2 m (323 in) https://en.wikipedia.org/wiki/List_of_largest_optical_reflecting_telescopes https://en.wikipedia.org/wiki/List_of_largest_optical_reflec...

p_l 6y ago

Try 39 meters, weighing 400 tons for just the first mirror in sequence of 5, and that's without supports and actuators and everything else.

beambot 6y ago
I assume you're talking about the ELT. It's composed of something like 800 individual segments with their own position-adjusting actuators. I'm not intimately familiar with its construction (and the tolerances!), but I presume it would be possible to launch individual segments for space-based or moon-based construction... The big, monolithic secondary mirror is entirely within Starship's payload volume (4.2m diameter) and mass (3.5 tonnes). Bonus: Space-based radio astronomy will achieve much higher SNR! Edit (since reply is slow): You probably benefit on your mass-related support structure costs due to the lower-gravity (or zero gravity) environments.
- p_l 6y ago
  ELT pretty much would require space manufacturing base - for the mass involved, you could probably furnish a small moon town. The problem is that the ones making the mess aren't going to pay for that, and I shudder at the costs involved in just space assembly of something the size of ELT... Edit to the slow reply ;) - the 400 tons is just the estimate zerodur mirror segments for the main mirror, nothing of the support structures... and didn't include ~65 tons of spare segments (ELT plans to replace two daily or something like that).
  - maccam94 6y ago
    Starship will be an incredible game changer for space economics. Look at this progression: - $50,000/kilogram for 27,500kg of payload (Space Shuttle, 1981-2011) - $2,500/kg for 22,800kg of payload (SpaceX Falcon 9, 2010-present) - $20/kg* for 100,000kg of payload (SpaceX Starship, 2022??) *: This is the estimated operational cost, not the price of a launch For a ballpark launch cost estimate, assuming that the mirror segments would be mass constrained rather than volume, it would cost $8M (plus however far off the cost estimates are, plus profit) just to get the mass into space. Maybe say $20M just to pad it a bit? There would almost certainly need to be more money spent on designing the whole thing to work in space, of course. But these projects have long planning horizons, there's no way anyone would have considered building something large in space before Starship was announced (other than nation-state level prestige projects). I suspect we'll see a flood of small to medium sized projects announced once Starship completes its first commercial LEO launch, then larger projects tentatively announced in the following couple of years. Sources on costs: https://ntrs.nasa.gov/citations/20200001093 https://ntrs.nasa.gov/citations/20200001093 https://en.wikipedia.org/wiki/SpaceX_Starship https://en.wikipedia.org/wiki/SpaceX_Starship
nine_k 6y ago
Let's admit, this telescope is also one of a kind, and it (ELT) is not online yet, too. If we care about telescopes which are built by hundreds, their mirrors are an order of magnitude smaller. OTOH with the massive launch capacity SpaceX is building, we could put a dozen 5m telescopes in various high orbits around Earth. With orbital assembly, very large diameter mirrors can be formed; even if these mirrors had a relatively small area (many holes between mirror elements), the angular resolution could be higher than anything reasonably achievable on the planet surface.
iso1631 6y ago
"List of largest optical reflecting telescopes" 8.2 m (323 in) https://en.wikipedia.org/wiki/List_of_largest_optical_reflecting_telescopes https://en.wikipedia.org/wiki/List_of_largest_optical_reflec...