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Quantum drive (??)

Discussion in 'Environmental Discussion' started by bwilson4web, Nov 6, 2023.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I refer you to Wiki: https://en.wikipedia.org/wiki/Photon

    Source_2: American Scientist

    There are two main ways in which light can exert mechanical forces on atoms: the scattering force and the optical dipole force. In 1933, Otto R. Frisch performed early experiments related to the former and showed that radiation pressure by light from a sodium lamp was able to deflect a beam of sodium atoms. Generally speaking, the scattering force (and the associated light pressure) results from photons "bumping" into atoms, thereby changing their momentum—an effect described by Albert Einstein in 1917. If an atom absorbs a photon it gets a velocity kick in the direction of the laser beam. This interaction both cools and slows the atom (equivalent concepts in physics, as they both involve decreasing the energy level). When many, many photons slam into an atom in this fashion, the effect is significant. Although each individual photon's momentum is minuscule, the rapid, repeated transfer of small amounts of momentum can still lead to atom accelerations 10,000 times stronger than gravity. But the laser must be tuned to a very specific frequency, or the photons will pass right through the atoms as if they were invisible. The frequency needed also depends on the type of atom and how fast it's moving.

    I remain curious but not enthusiastic. My understanding is the 'solar sail' was driven by the solar wind, not photons.

    Bob Wilson
     
  2. tochatihu

    tochatihu Senior Member

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    It is not a new idea that photons can transfer energy to molecules, and that some 'tuning' is required for successful transfers. This is the basis of absorption spectroscopy. All that stuff about CO2 converting infrared photons into thermal energy? Same thing.

    We shine light on one side of a (solar) sail but not the other side. This unilateral process will send the sail thataway. I don't know why this needs a new fancy name.

    Out there in interstellar space, density of molecules is 1 per 10 cubic cm, with some areas much higher. If one were to send a solar sail large surface area, very fast through such, it will encounter many collisions that may eventually be enough to slow it down. Shred it. Whatever. So it may get to another star, or not, also limited by photon flux density we are throwing at it.

    Or, if it arrives at good speed, it will just whiz on by. No means available to illuminate the other side to slow it down, see?

    So I guess if one manages to fire up enough lasers to send it out, a good choice would be to aim at a star surrounded by atoms or dust at high density. That takes care of the stopping part. Now you have sent sail to vicinity of another star. Now what?
     
  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I read but do not claim to fully understand the 'momentum of light.' I was aware of light used to push individual atoms around in a vacuum but again, not really covered in undergraduate classes in 1969-70. In 1971, I switched to Marine Corp studies.

    It might be interesting to calculate the force equivalent of solar light on planets orbiting the sun.

    Bob Wilson
     
  4. tochatihu

    tochatihu Senior Member

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    " In 1971, I switched to Marine Corp studies"

    More to their benefit than yours.

    "It might be interesting to calculate the force equivalent of solar light on planets orbiting the sun."

    No. Sigh it would not. Differential is >6 orders of magnitude compared to gravity. Probably >>6. I decline the work proposed. Other matters ...
     
  5. kenmce

    kenmce High Voltage Member

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    Load it up with sensors and a big dish transmitter. Have it take a look around and report back. Doesn't matter if it stops or just zips on through. Reference "Starwisp"
     
  6. tochatihu

    tochatihu Senior Member

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    Lacking wikipedia I read Forward's 1985 article via

    https://www.semanticscholar.org/paper/Starwisp-An-ultra-light-interstellar-probe-Forward/f77df262458736ec988475a6dfd379a6a7e039d9

    So yes, there are reasons to push with microwaves rather than light of much shorter wavelength. Humans on earth may have enough excess wealth to do it in the future.

    ==
    No one has yet mentioned Breakthrough Starshot here. The current lightsail version. Its plausibility is limited because when all those lasers are built on earth. no one would use them to cook other countries' satellites. Right?
     
  7. tochatihu

    tochatihu Senior Member

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    All of us will be dead when images return to earth, possibly showing continents etc. on an exoplanet. This is a personal problem so to speak, not a fundamental one. But that exoplanet may be completely cloud covered and disappoint whomever does see it.

    Or, it could look great, which would suck in a different way. Because without way more technology, humans will never get there. Look but don't touch. Dang.

    ==
    Humans now have (almost) enough tech to begin hollowing out a metallic asteroid in a suitable solar orbit. That could take a century (or more), but the work would be done. In case anyone later comes up with a way to use it. Including propulsion hundreds of times better than chemical rockets. A great gift for future generations. Their own Oumuamua.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    I haven't yet watched the video, but have always understood solar sails to be driven by photon radiation pressure, not particles of solar wind:

    https://en.wikipedia.org/wiki/Radiation_pressure
    https://en.wikipedia.org/wiki/Solar_sail
    https://www.colorado.edu/faculty/kantha/sites/default/files/attached-files/final_mesloh.pdf

    Skip the planets and large to medium asteroids, where it is negligible. This is much more interesting for artificial satellites and very small bodies. It even causes some thrust vectoring on slowly rotating objects, where the warmer side emits more radiation than the cooler side.

    Radiation pressure can even be used for attitude control of artificial satellites, e.g. with adjustable boom-tip vanes:

    https://arc.aiaa.org/doi/10.2514/3.61784
    https://link.springer.com/article/10.1007/s42064-019-0062-0
    Fault tolerant satellite attitude control using solar radiation pressure based on nonlinear adaptive sliding mode - ScienceDirect
     
    #8 fuzzy1, Nov 27, 2023
    Last edited: Nov 27, 2023
  9. fuzzy1

    fuzzy1 Senior Member

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    After watching the video, I failed to see how it had any connection to what you wrote. Or how any of the included video had any connection to the narrator's alleged topic. And was disappointed that once the fluff was done, he quit talking and didn't proceed to any substance.
     
  10. Trollbait

    Trollbait It's a D&D thing

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    Remember the Martian probe that crashed cause of unit unit conversion error? The use of a single extended solar panel meant it had to make corrections during the trip out to compensate for the panel side being pushed around.
     
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  11. fuzzy1

    fuzzy1 Senior Member

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    Not remembering that particular 'one' at the moment, there were numerous examples of each element you mention. But I certainly believe it, as it took the space industry quite a few mission failures before this and other factors were adequately accounted for.
     
  12. kenmce

    kenmce High Voltage Member

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    You would build them in space so that when you boost something you don't have to stop and wait while your planet gets in the way. There is a considerable problem that anything capable of delivering that much energy that far, with that much precision, would also readily serve as a weapon.
     
  13. kenmce

    kenmce High Voltage Member

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    If you can get your probe up to 10% of C you can visit the Centauri system in just 40 years. No guarantee they'll be anything interesting though.

    Venus is 100 percent cloud covered. We just use radar to look at it.

    The necessary technologies exceed what we can do right this minute, but they don't require violating the rules of physics, so with a little luck, we should get there.

    If you send in guys with pick axes, yeh, it could run a century, I'd suggest you run a shaft along the long axis, stuff it with ice, use reflectors to heat up your rock until it melts, let the expanding gas blow it up like a balloon.


    "Build it and they will come."
     
  14. tochatihu

    tochatihu Senior Member

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    Hmmm. Star-shooting with a synthetic aperture radar instead (or added to) optical imaging might make sense. If the device is large enough to accommodate. Starshot people seem to be thinking about tiny cameras on a tiny rig. But yeah, much more data from radar scan. Anyone 'there' is more to realize they are being looked at. Depending on tech level. That may or may not be a good thing.

    ==
    Hollowing out an asteroid is what the purported trillion dollar mining industry is about. The metals get sold on earth, and the remaining shell becomes somebodys' starship someday maybe.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    Getting those metals from solar orbit to the Earth's surface, for less than the cost of mining the stuff already here, will be quite a challenge. And don't forget that if they succeed in great volume, market prices will collapse.
     
  16. tochatihu

    tochatihu Senior Member

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    OK, largest tech challenge ever faced. Could very well be. But let's call it a three-fer:

    Manufacture photovoltaics and other structures up there without dealing with earth's gravity well and crossing the atmosphere.

    Make 'blobs' to transfer to earth surface in the familiar 'reentry capsule' shape. Aim them at deserts (or enemies !). Some loss by ablation, sure. But what remains is profit. Let us agree that metal mining in earth's crust also has issues. Like for those platinum miners in S Africa.

    Finally there remains a big hollow metal shell up there, that someone may find a use for later.

    NASA mission to Psyche launched in October. That M-class asteroid may not be ideal choice, but hey, take a look while assessing alternatives.

    ==
    Earth has a differentiated core, which brings all kinds of wonderfulness for us and biology in general. But, it puts much of the metals any proper spacefaring civilization needs out of reach. My assertion is that any developing civilization would come to face a decision:

    a) stay home. other stars are soooo far away

    b) find an M-class asteroid and begin the long process
     
  17. tochatihu

    tochatihu Senior Member

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    As of 2010, 19 M-class asteroids were known:

    A radar survey of M- and X-class asteroids II. Summary and synthesis - ScienceDirect

    Dun no if Arecibo later 'radared' more later, but they lost their tentpoles.

    A matter of interest is whether any M-class are in orbits suitable for this superbig mining project. Or if one needs to be 'adjusted', how to select.

    ==
    The whole 'protect earth from asteroid hit' is a worthy goal, but far from the full story. Big metal rock project is descendants' way out of here.
     
  18. fuzzy1

    fuzzy1 Senior Member

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    For space-faring purposes, leaving Earth and migrating to the outer solar system here or to other solar systems, these metal resources don't need to be brought down to Earth's surface. Refining and building with them 'up there' will save vast amounts of energy. For such purposes, these would eventually become excellent resources.
     
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