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Exoscientist

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    Mathematics, physics, science, futurism, spaceflight, science fiction

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  1. I get your irony, but with the simplicity of both a liquid mirror optical telescope or grid-wire Arecibo-type radio telescope they might be something constructible by self-assembly. Robert Clark
  2. Astronomers want to plant telescopes on the Moon. The lunar surface offers advantages for infrared and radio astronomy, despite the challenges. By Ramin Skibba, Inside Science | Published: Tuesday, January 19, 2021 Astronomers want to plant telescopes on the Moon | Astronomy.com (See the link there to a journal special issue exploring the idea.) I speculated about the possibility of detecting exo-civilizations optically in this Kerbal forum post: How large a space telescope do we need to see exo-civilizations? - Science & Spaceflight - Kerbal Space Program Forum
  3. Yes, that is a good question. Here's a NASA page showing the full disk at night of some regions on Earth. The lighting is pretty spotty. https://earth.app.goo.gl/rDX9W5 Bob Clark
  4. Thanks for that. Perhaps we could just observe the variation in light between the day and night side as a point source. Say, for reasonable surface materials for a rocky planet, the night side brightness is too high and would be best explained by artificial illumination. Bob Clark
  5. To be able to directly image an exoplanet the space telescope would not need to be especially large; the James Webb Space Telescope could do it. What would be key though is a starshade to block the stars light. See the discussion here: https://en.wikipedia.org/wiki/New_Worlds_Mission The animation illustrating a proposed starshade is pretty cool on that page. The starshade also would not need to be particularly large, perhaps 10 meters across. But the issue with the nightside city lights is that it likely would be much less than the full daytime reflected light of the planet,
  6. A team of scientists is investigating ways of detecting exo-civilizations aside from just radio signals as with SETI: JUNE 19, 2020 Does intelligent life exist on other planets? Technosignatures may hold new clues. by University of Rochester https://phys.org/news/2020-06-intelligent-life-planets-technosignatures-clues.html Two methods of detection mentioned in the article are detection from reflected light from solar panels or detection or pollution such as CFCs. However, even on our planet the number of solar panels would not be such that they would add appreciably to the E
  7. This article suggests you will be able to see the full disk Earthrise from the lunar surface: Earth Rising Earth as seen from the Moon is always in the same place – true or false? It depends. By Paul D. Spudis MAY 15, 2014 https://www.airspacemag.com/daily-planet/earth-rising-180951474/ While most locations on the Moon's surface would only be able to see partial disk Earthrises, at the lunar terminator (separator between far side and near side of Moon) and at the lunar poles, you'll be able to see the full disk Earthrise. Anyone want to do a try in Kerbal Realism mode to
  8. Right. Let me redo that calculation: Use equation x=1/2 a t2, and round off 1 g acceleration as 10 m/s2. Then 2x1016 m = (1/2)*10*t2. So t = 63x106 s. That's 730 days. The speed reached is v = at =10*63x106 = 630,000 km/s. This is double lightspeed of 300,000 km/s. Then you would have to consider relativistic effects. At some point as you approached light speed you would need to expend a huge amount of energy to maintain that speed, still without actually reaching lightspeed. Perhaps someone will do the calculation about how long it would appear to take for shipboard time compa
  9. The time is actually shorter, and it doesn't quite reach light speed. It's surprising how fast and how far you can go by just 1 g acceleration: A nice way to remember the distance of a lightyear is that it's about 10 trillion km, which equals 1x1015 meters. Use equation x=1/2 a t2, and round off 1 g acceleration as 10 m/s2. Then 2x1015 m = (1/2)*10*t2. So t = 2x107. That's 231.5 days. The speed reached is v = at =10*2x107 = 200,000 km/s, less than lightspeed of 300,000 km/s. Bob Clark
  10. I would have loved to have seen a true microscope sent to Mars. After more than half a dozen landers there still has not been sent a true optical microscope sent. The best resolving power has been at no better than that of a geologists hand lens. This would have importance for the search for possible life, but also for geological samples. Bob Clark
  11. Yes. They could use sea level engines for all six engines. You would lose on delta-v or payload though because you wouldn't get the high vacuum Isp of the vacuum engines. By the way, it is not well known that with altitude compensation you improve both sea level thrust and vacuum Isp for the sea level engines. So you would get better takeoff thrust actually than just 6 sea level engines. The vacuum Isp part is well known. But sea level thrust is also improved because sea level engines with fixed nozzles are a compromise. Even for sea level engines a large portion of the flight of that fi
  12. Elon on Twitter said hopefully the Starship will fly this week:https://www.cnet.com/google-amp/news/el ... -fly-soon/Presumably this will be a short hop test. But running the numbers the Starship could get a surprisingly high delta-v.The latest version has 3 level and 3 vacuum engines. Presumably only the 3 sea level ones will be used at launch. So this will mean 3 x 200 tons = 600 tons of launch thrust. I’ll take the propellant load as 400 tons to allow for payload at later tests. But launching the bare rocket could get 354*9.81Ln(1 + 400/120) = 5,100 m/s delta-v, past Mach 16.This though is
  13. Odd, that this didn’t occur to me earlier, but this idea for the Starship used as a first stage means it wouldn’t be the stage going to orbit. Then the payload loss for reusability would be less since you wouldn’t have the greater weight for thermal protection for reentry from orbit. In fact, the Falcon 9 booster has minimal thermal protection weight. But this is also due to the fact it slows down to minimize thermal heating on reentry from suborbit. Intriguingly, the payload loss for the Starship used for this purpose may be less than with the F9 because it is higher temperature steel rath
  14. The weight estimate is not new. It was the original weight estimate. How easy it would be is relative to taking another approach. The triple-core Falcon Heavy only cost 50% more in development cost than the Falcon 9 at triple the payload. In contrast, based on size, the 3 times larger SuperHeavy booster would cost 3 times more in development cost. Bob Clark
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