• MsPenguinette@lemmy.world
    link
    fedilink
    English
    arrow-up
    4
    ·
    3 months ago

    If photon hitting a surface can impart momentum, does generating photons also impart momentum? Like, if you put a solar powered laser pointer in space, would it move?

    • OrganicMustard@lemmy.world
      link
      fedilink
      English
      arrow-up
      5
      ·
      edit-2
      3 months ago

      Yes, but that would be a lot less efficient. With a dielectric mirror you can get easily 99.9% of the maximum momentum gain from the light, while with a solar powered laser you would get for the emission the compounded efficiency of the solar panel + storage + laser, so way below 10%. So you would gain around 10 times more impulse from your solar panel absorbing light than from the actual laser.

      The final momentum gain is a bit different as the maximum you can gain from a photon is double its momentum (because you can reflect it back with opposite direction).

    • ch00f@lemmy.world
      link
      fedilink
      English
      arrow-up
      4
      arrow-down
      1
      ·
      3 months ago

      Sure, but it would be less efficient than a sail, and since the incoming radiation would impart inertia on the solar panels, you would still be limited on where you could steer.

      • SchmidtGenetics@lemmy.world
        link
        fedilink
        English
        arrow-up
        1
        ·
        edit-2
        3 months ago

        Sail absorbs power while also acting as a sail, and you can use the lasers to steer?

        It would also be like steering a boat more or less no?

        • ch00f@lemmy.world
          link
          fedilink
          English
          arrow-up
          1
          arrow-down
          1
          ·
          3 months ago

          The solar sail reflects light instead of absorbing it so you get to double dip on photon momentum.

          And sure, you can steer with the laser I suppose, but with that kind of super weak deltaV, you’re not going to be exactly doing donuts in the solar system.

          Even the massive solar sail only imparts a super small amount of force. It’s only useful because it does so for free over a long period of time with no air resistance.

          You’d be better off using a conventional thruster to do whatever steering you needed to do before letting the sail take over. It’s not like you need to steer around any obstacles.