Project StarShot - 20% speed of light to Alpha Centuri

Discussion in 'The Watering Hole' started by XolveJohn, Mar 9, 2017.

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  1. Mar 9, 2017 #1

    XolveJohn

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    This is a year old, but I just heard of it. A tiny circuit board probe with a solar sail, powered with a TeraWatt laser on earth!

    My physics and propulsion pals insist it will work. Would only need a few hours to get to 1/5 the speed of light, 20 years for the trip.

    Such a strong laser might zap satellites, probably Russian or Chinese, and make them mad. Or vaporize the moon.

    They are talking about sending flocks of them. They communicate with laser beams, and have a camera.

    The main problem is that when far away I don't see how a tiny laser beam from them could be detected on Earth.

    Is this project viable, or just another way to waste money, and perhaps alert aliens to our world?

    http://www.space.com/32546-interstellar-spaceflight-stephen-hawking-project-starshot.html

    https://breakthroughinitiatives.org/Initiative/3

    https://phys.org/news/2016-08-breakthrough-starshot-interstellar-probe-highlights.html laser.jpg
     
  2. Mar 9, 2017 #2

    Incongruent

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    How will the probe not melt?
     
  3. Mar 10, 2017 #3

    markkoelsch

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    I think it is an interesting idea, but not practical. How big is the probe, and will they actually be able to target it at range? Hitting anything with that much power would likely vaporize it. Sounds like the main weapon of the Death Star.
     
  4. Mar 10, 2017 #4

    Incongruent

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    Angling the solar sail should allow steering. Unless, of course, the solar sail no longer exists as a solid...
     
  5. Mar 10, 2017 #5

    Charles_McG

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  6. Mar 10, 2017 #6

    XolveJohn

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    Incongruent: I did not consider the lasers could melt the probe. Perhaps shielding. I will ask my phD buddy tonite.

    I never heard of Starwisp, but Geoffrey A. Landis was a model rocketeer back in the day, now at nasa. Lasers will go farther than microwaves and still hold their power,

    I think, less divergence. Starwisp was a lot bigger.
     
  7. Mar 10, 2017 #7

    aerostadt

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    You can read more about this in the latest issue of Scientific American. The sail is fairly small and must be 99.9 percent or more reflective. The payload per sail is a small small electronic chip and weighs only a few grams. There may be very many of these sails. The sail accelerates for just a few minutes at 60,000 g's. It takes about 20 years to arrive at Alpha Centauri and 4 years for the radio signal to come back. There are many technical issues. One issue is how to get such a small transmitter to have enough power to transmit back a distance of 4 light-years. Perhaps, a relay network with many sails in-between us and Alpha Centauri. I wonder about how precise can the aiming of the trajectory can be. If the final velocity vector after a short boost is a tiny bit off the sail-probe could miss Alpha Centauri by a huge amount.
     
  8. Mar 10, 2017 #8

    XolveJohn

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    Yes, unlike most probes there are no thrusters for course updates. Need a tiny ion engine with RTG power supply. I think it may have a tiny RTG. Hard to use solar cells in the middle of nowhere. How are they going to aim the lasers onboard to send back data? This may be a pie in the sky idea, but I wish them well. At least cheaper than sending people to Mars. The concept of the one way trip cracks me up. I have a long list of suggestions, starting with that NK nut with the missiles.
     
  9. Mar 10, 2017 #9

    Incongruent

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    That's still a gigawatt not being reflected and thus absorbed.
     
  10. Mar 10, 2017 #10

    Charles_McG

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    You would need to know the watts/m^2 at the sail to say that. You don't know how much of the beam the sail intersects.
     
  11. Mar 10, 2017 #11

    Rex R

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    one does not start with one tw you start with lower power and add power as the sail accelerates/gets further away to maintain a constant power on the sail.
    Rex
     
  12. Mar 10, 2017 #12

    Igotnothing

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    Also, use energy fields as a sail so that you don't melt the sail, and it can be located some distance from the probe so that the probe doesn't get melted. Also, use the Sun for propulsion.

    Don't laugh. There is a PhD Physicist, who also is a member of Tripoli, who is working on this.
     
  13. Mar 10, 2017 #13

    Charles_McG

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    I've always thought the mini-magnetosphere concept was cool. Blow a magnetized plasma bubble, ride the solar wind. You can even shape the bubble to generate lift, and so tack and steer.

    But it only works in the heliosphere. Good for Kuiper, maybe Oort probes. The local flow of the interstellar medium would take over before you get to the Oort Cloud, and it's thin, to boot. Less to sail on.

    That's more of an ion sail, than a photon sail.
     
  14. Mar 10, 2017 #14

    XolveJohn

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    Mike M. says it does not absorb that much power, 99.9% reflective. The sail does not pull the board, it pushes it, so the board is shielded. There is a steering system using light sources. And perhaps a star tracker. And RTG.

    If a photon is reflected, you get twice the pushing power than if it was absorbed. Force = 2 x Power of laser/ speed of light. A terawatt laser will provide a force of one ton. Must not rip sail apart! Photons do not have mass, but do have momentum. Need to understand quantum mechanics for that.
     
  15. Mar 11, 2017 #15

    Incongruent

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    If all of the laser beam hits the sail, it will be absorbing a gigawatt of energy (assuming 99.9% reflection). In a few minutes, that could theoretically raise the temperature of a metric tonne of water to roughly 60,000 degrees if spread evenly. Note that the energy is not distributed evenly nor will the mass of the satellite be anything close to a metric tonne.

    You'll rip that sail apart, if not from the force, then atomically from the energy absorbed.

    In my cursory research I found articles about reflective surfaces that can reflect 100% of a specific wavelength. If this is true, red shifting still gets us.
     
  16. Mar 11, 2017 #16

    XolveJohn

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    That is all true, but just engineering problems, the physics is well understood. We can play some tricks to make it work.

    Like starting with just a few of the lasers, not all of them. As it gathers speed, more would be activated and aimed at the sails. If there are multiple craft, certain lasers could be dedicated to specific sails.

    It should be possible to shift the laser output light freq to compensate for the doppler shift.

    The dark side of the sail could have a nanoscale heatsink/black body radiator, to keep it cool.

    I am still worried that the Borg or Klingons will catch some, and back calculate the transit path. We could be assimilated!
     
  17. Mar 11, 2017 #17

    Peartree

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    I think I've also heard mention of pulsing the lasers so that the sail can cool between pulses.
     
  18. Mar 12, 2017 #18

    XolveJohn

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    Yes, pulsing can control the power level. Classic pulse width modulation. With solid state lasers, should be no problem.

    Even though there is some risk, I would rather see this funded than the SLS. Just read they are only going to launch every year at a BILLION DOLLARS A LAUNCH. The old school boys are still at it. Gold plated vehicles that go around the moon.

    Maybe Trump will straighten them out. Send a tweet: HOW SAD THIS IS, THE RUSSIANS ARE DOING MORE WITH LESS.

    Hail Putin. :kill:
     
  19. Mar 13, 2017 #19

    Charles_McG

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  20. Mar 14, 2017 #20

    XolveJohn

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  21. May 18, 2019 at 2:53 AM #21

    aerostadt

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  22. May 18, 2019 at 2:27 PM #22

    boatgeek

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    A terawatt-scale laser that can be targeted that accurately (especially through the atmosphere) is also an enormously powerful offensive and defensive weapon. I believe the Pentagon has only gotten into the tens or hundreds of kilowatts. Even if this was intended for peaceful purposes, it would be weaponized in short order.
     
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  23. May 18, 2019 at 2:39 PM #23

    Charles_McG

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    ”A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive."
     
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