3 ms·

Do they expect to outdo the sun?

h2odragon 5y ago
In one very specific frequency band, at one comparatively small place, yes. by a large amount. Ocean vs firehose. Or, better: In the same way every "daytime headlight" you see is outdoing the sun.
- hereforphone 5y ago
  Which 'frequency band'? https://www.researchgate.net/figure/Spectral-power-density-of-solar-radiation-5_fig1_268822609 https://www.researchgate.net/figure/Spectral-power-density-o...
  - rrss 5y ago
    microwave
    - hereforphone 5y ago
      Brilliant answer
  - h2odragon 5y ago
    > Achieving a beam that narrow (1/2000000 rad) from the Earth would require a phased array spaced out over a much larger area, at least 200 km at 5 Ghz (6cm). I doubt they'd want a very large band but in microwave work I dunno what counts as "large". and i'm a little afraid to go look deeper into this because i'll wind up tearing up junkyard microwave ovens and building something i shouldn't.
    - hereforphone 5y ago
      The headlight vs. sun comparison (which I think was an edit?) is irrelevant because we're comparing the amount of energy deliverable over distance. The energy delivered by the sun (at a tenable band) vs. the energy delivered by the remote transmitter on earth, after the 'link budget' has been applied (taking into account distance, atmospheric attenuation, and so on) are the two things that need to be compared.
      - h2odragon 5y ago
        I beg you pardon, im not arguing for the idea of a earth to moon microwave power link as viable. or sensible. I think it's beautifully insane, i have severe doubts about the actual practicality of such a thing, etc. But thats the thing: now i want to do a mad max maser on a truck with maybe dozens of magnetrons if i could tow a generator... It fits with my "Orbital Slingshot" project so well, too.
        hereforphone 5y ago
        What is your Orbital Slingshot project?
        h2odragon 5y ago
        I'm glad you asked :) It's a totally silly idea to built a big ass slingshot that throws things as high as possible. I figure calling it an "Orbital Slingshot" makes it at least as viable and investment worthy as some of the other efforts [1] and [2] forex. If I can get my daughter to do some artwork I might fire up a web page for it finally. [1] https://www.space.com/23015-slingatron-reusable-launch-system.html https://www.space.com/23015-slingatron-reusable-launch-syste... [2] https://www.nextbigfuture.com/2018/02/spinlaunch-is-using-large-centrifuges-to-accelerate-to-payloads-into-space-target-500000-per-launch.html https://www.nextbigfuture.com/2018/02/spinlaunch-is-using-la...
      - deleted 5y ago
        [deleted]
      - rrss 5y ago
        Ok, check my math. basics: solar constant: 1.36 kW / m^2 earth-to-moon range: 400 km parameters from the article: frequency: 5 GHz -> wavelength: 6cm earth antenna array linear dimension: 200 km transmit power density: 100 W/m^2 Let's assume that the earth antenna array elements are 50m wide, and spaced out such that they cover 1% of the total 200km * 50m area, for a total antenna aperture of 1e5 square meters (10% of the SKA). Combining the stated transmit power density of 100 W/m^2 with the antenna area, we get a total transmit power of 10 MW. Throw it at Friis: power density at moon = transmit power * earth antenna area / (range^2 * wavelength^2) = 10e6 watts * 1e5 m^2 / ( 400e3^2 m^2 * 0.06^2 m^2) = 1.73 kW / m^2 Atmospheric attenuation at 5 GHz is pretty minimal. If we conservatively assume 20% loss, I think we still end up with a higher power density at a single frequency than from the sun across the entire spectrum. I don't think anything like this will ever be built, but I don't see why it is impossible. Where's the mistake?
    - hereforphone 5y ago
      It won't let me reply to your response to my response to this comment. But just let me say that as an engineer with tons of RF experience, you're full of shit.
      - TigeriusKirk 5y ago
        This thread would be interesting if you would show your work. I'm here for interesting ideas, not people declaring their expertise without educating us. Educate me.
        hereforphone 5y ago
        I'm not the one making the wacky assertions. Ask the parent posts to demonstrate their claims first.
        macintux 5y ago
        One of you is performing some mildly interesting speculation out of confessed limited knowledge. One of you is being rude, insulting, claiming to be the expert, but offering no new information. One of you is contributing to the thread, at least. It's not you.
        h2odragon 5y ago
        The only assertions I've made are that im interested in this idea. The assertions the blog post made included a link to another post [1] under the text "I have written more than once about how silly this idea is". referring to "the space-based solar power trope." You're arguing against ... what then? [1] https://caseyhandmer.wordpress.com/2019/08/20/space-based-solar-power-is-not-a-thing/ https://caseyhandmer.wordpress.com/2019/08/20/space-based-so...
      - IggleSniggle 5y ago
        At least one person here is exploring an idea and trying to learn. I don’t get how that makes a person “full of shit”
      - 5y ago
  - jhgb 5y ago
    The one that the receiver is the most sensitive to. The fact that sunlight comprises many wavelengths is the reason why single-junction cells have comparatively low efficiency.

In one very specific frequency band, at one comparatively small place, yes. by a large amount. Ocean vs firehose. Or, better: In the same way every "daytime headlight" you see is outdoing the sun.

hereforphone 5y ago
Which 'frequency band'? https://www.researchgate.net/figure/Spectral-power-density-of-solar-radiation-5_fig1_268822609 https://www.researchgate.net/figure/Spectral-power-density-o...
- rrss 5y ago
  microwave
  - hereforphone 5y ago
    Brilliant answer
- h2odragon 5y ago
  > Achieving a beam that narrow (1/2000000 rad) from the Earth would require a phased array spaced out over a much larger area, at least 200 km at 5 Ghz (6cm). I doubt they'd want a very large band but in microwave work I dunno what counts as "large". and i'm a little afraid to go look deeper into this because i'll wind up tearing up junkyard microwave ovens and building something i shouldn't.
  - hereforphone 5y ago
    The headlight vs. sun comparison (which I think was an edit?) is irrelevant because we're comparing the amount of energy deliverable over distance. The energy delivered by the sun (at a tenable band) vs. the energy delivered by the remote transmitter on earth, after the 'link budget' has been applied (taking into account distance, atmospheric attenuation, and so on) are the two things that need to be compared.
    - h2odragon 5y ago
      I beg you pardon, im not arguing for the idea of a earth to moon microwave power link as viable. or sensible. I think it's beautifully insane, i have severe doubts about the actual practicality of such a thing, etc. But thats the thing: now i want to do a mad max maser on a truck with maybe dozens of magnetrons if i could tow a generator... It fits with my "Orbital Slingshot" project so well, too.
      - hereforphone 5y ago
        What is your Orbital Slingshot project?
        h2odragon 5y ago
        I'm glad you asked :) It's a totally silly idea to built a big ass slingshot that throws things as high as possible. I figure calling it an "Orbital Slingshot" makes it at least as viable and investment worthy as some of the other efforts [1] and [2] forex. If I can get my daughter to do some artwork I might fire up a web page for it finally. [1] https://www.space.com/23015-slingatron-reusable-launch-system.html https://www.space.com/23015-slingatron-reusable-launch-syste... [2] https://www.nextbigfuture.com/2018/02/spinlaunch-is-using-large-centrifuges-to-accelerate-to-payloads-into-space-target-500000-per-launch.html https://www.nextbigfuture.com/2018/02/spinlaunch-is-using-la...
    - deleted 5y ago
      [deleted]
    - rrss 5y ago
      Ok, check my math. basics: solar constant: 1.36 kW / m^2 earth-to-moon range: 400 km parameters from the article: frequency: 5 GHz -> wavelength: 6cm earth antenna array linear dimension: 200 km transmit power density: 100 W/m^2 Let's assume that the earth antenna array elements are 50m wide, and spaced out such that they cover 1% of the total 200km * 50m area, for a total antenna aperture of 1e5 square meters (10% of the SKA). Combining the stated transmit power density of 100 W/m^2 with the antenna area, we get a total transmit power of 10 MW. Throw it at Friis: power density at moon = transmit power * earth antenna area / (range^2 * wavelength^2) = 10e6 watts * 1e5 m^2 / ( 400e3^2 m^2 * 0.06^2 m^2) = 1.73 kW / m^2 Atmospheric attenuation at 5 GHz is pretty minimal. If we conservatively assume 20% loss, I think we still end up with a higher power density at a single frequency than from the sun across the entire spectrum. I don't think anything like this will ever be built, but I don't see why it is impossible. Where's the mistake?
  - hereforphone 5y ago
    It won't let me reply to your response to my response to this comment. But just let me say that as an engineer with tons of RF experience, you're full of shit.
    - TigeriusKirk 5y ago
      This thread would be interesting if you would show your work. I'm here for interesting ideas, not people declaring their expertise without educating us. Educate me.
      - hereforphone 5y ago
        I'm not the one making the wacky assertions. Ask the parent posts to demonstrate their claims first.
        macintux 5y ago
        One of you is performing some mildly interesting speculation out of confessed limited knowledge. One of you is being rude, insulting, claiming to be the expert, but offering no new information. One of you is contributing to the thread, at least. It's not you.
        h2odragon 5y ago
        The only assertions I've made are that im interested in this idea. The assertions the blog post made included a link to another post [1] under the text "I have written more than once about how silly this idea is". referring to "the space-based solar power trope." You're arguing against ... what then? [1] https://caseyhandmer.wordpress.com/2019/08/20/space-based-solar-power-is-not-a-thing/ https://caseyhandmer.wordpress.com/2019/08/20/space-based-so...
    - IggleSniggle 5y ago
      At least one person here is exploring an idea and trying to learn. I don’t get how that makes a person “full of shit”
    - 5y ago
- jhgb 5y ago
  The one that the receiver is the most sensitive to. The fact that sunlight comprises many wavelengths is the reason why single-junction cells have comparatively low efficiency.