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Comments on Profile Post by inverted_helix

  1. Persimmon
    Persimmon
    With cold coupling, they'd exceed grasers in ability to hold a small spot size at long range. Threat range vs manouvering targets is thus light minutes, like other lightspeed weapons.

    I think I'll do a omake/writeup on potential Aliceverse Particle Weapons sometime tomorrow. At the gym right now.
    Jul 18, 2019
  2. inverted_helix
    inverted_helix
    That's very surprising to me, since atomic rockets article about particle beams suggested that their minimum beam angle was much worse than lasers and so would be shorter ranged.
    Jul 18, 2019
    Persimmon likes this.
  3. magic9mushroom
    magic9mushroom
    What's cold coupling?
    Jul 18, 2019
  4. inverted_helix
    inverted_helix
    Hmm interesting, read up on it a bit. I'm basically a layman, but it seems like cold coupling is basically using particles that will form molecules in flight. So a beam of hydrogen atoms that collect into H2 molecules in flight averaging their velocities and thereby reducing beam divergence.
    Jul 18, 2019
  5. inverted_helix
    inverted_helix
    From my reading it seems like particle beams would basically force crafts to deploy plasma and magnetic shields at all sizes instead of just the PD laser and large graser realms, and that they'd wreck unprotected dust barriers allowing RKKV shots to hit the ships directly.
    Jul 18, 2019
    Persimmon likes this.
  6. Persimmon
    Persimmon
    Cold beams are obtained by chilling the ion source and averaging their traverse velocities before feeding into the main accelerator. You can further reduce the temperature of the beam (and thus divergence) via molecular bonding, yes.
    Jul 18, 2019
  7. Persimmon
    Persimmon
    Laser-coupling is using an optical tweezer effect on a particle beam via laser to dramatically reduce divergence, an immense game changer. Most of Atomic Rockets was written pre-PROCSIMA, so I'm not surprised.
    Jul 18, 2019
  8. inverted_helix
    inverted_helix
    Jul 18, 2019
  9. inverted_helix
    inverted_helix
    Overall it doesn't seem that plausible to get a particle beam close to lightspeed with this sort of mechanism either. It seems to get less efficient as speed rises because it's harder to maintain low enough divergence. So you're probably firing beams in the 0.1 to 0.5 c range. Which means that against a moving target your effective range is lower than an RKKV or graser.
    Jul 18, 2019
  10. inverted_helix
    inverted_helix
    Against a stationary target it's better than grasers, but lesser than the hypothetically infinite range of RKKVs.

    Either way though this would offer a much longer ranged option for ships too small to mount an RKKV than conventional mass drivers which tend closer to 0.01c.
    Jul 18, 2019
  11. inverted_helix
    inverted_helix
    Since it's fundamentally normal particles just accelerated to high speed, then I think normal deflector shields should work on them as well as they would against a mass driver round with similar energy put into it. I think it likely penetrates armor better because the energy is more focused than a mass driver similar to an RKKV.
    Jul 18, 2019
  12. Persimmon
    Persimmon
    Laser power required to maintain optical tweezing rises with particle beam throughput/current, not particle energy. To be honest, PROCSIMA is so new we haven't even gotten the results from the first experiments yet.
    Jul 19, 2019
    inverted_helix likes this.
  13. Persimmon
    Persimmon
    But yes, I could see laser coupling requiring dramatically shorter -frequencies- as beam speed approaches C. Which would mean to get graser range you'd need a graser tier FEL, lol.
    Jul 19, 2019
    inverted_helix likes this.
  14. Persimmon
    Persimmon
    But the required throughput of the laser is orders of magnitude less than the particle accelerator, so it would still be useful. And even hard XFELs with decent mirror sizes push the weapon into "easily multiple light minutes" territory.
    Jul 19, 2019
    inverted_helix likes this.
  15. inverted_helix
    inverted_helix
    Doesn't required laser power also rise with particle speed because there's less time to focus the beam before the laser diverges too much to be useful to the focusing, so for a faster particle beam you have to increase the strength of the laser to focus it faster?
    Jul 19, 2019
  16. inverted_helix
    inverted_helix
    I don't think any lasers in aliceverse use focusing mirrors because there's too much light weapons fire flying around for anything that fragile.
    Jul 19, 2019
  17. inverted_helix
    inverted_helix
    I don't see why you'd use a graser enhanced particle beam though since once you could build the effective graser you'd just use it as the weapon instead of the particle beam. The graser seems harder to defend against.
    Jul 19, 2019
  18. Persimmon
    Persimmon
    Aliceverse uses momentum exchange focusers; they're somewhat like cheaty mirrors.

    So the photons, after coupling with the particles, not only induce a gradient in the particle beam, but are in turn focused by the particles in the beam, which lets the NASA's proposed 60GW beam hit a sub 100 meter sail at 500AU (theoretically).
    Jul 19, 2019
  19. Persimmon
    Persimmon
    Even a partial optical tweezer effect (without the particle stream focusing the laser) would still massively decrease divergence, though there is the potential for particle beam instability if the photons are not coupled to the particles.
    Jul 19, 2019
  20. inverted_helix
    inverted_helix
    Are you putting together your post about particle beams in the aliceverse?

    What do you see as their weaknesses? How would you defend against them? How small could you make one that would be effective?
    Jul 19, 2019
    Persimmon likes this.
  21. Persimmon
    Persimmon
    In progress.
    Jul 19, 2019
  22. magic9mushroom
    magic9mushroom
    I think there is an issue with the laser/particle-beam coupling idea when weaponised; because the laser moves faster than the particle beam, the two will separate and lose cohesion after some amount of time and distance. For PROCSIMA's use case this is less relevant due to the beam being fired at the same spot for a long period, but for a weapon which may need to change targets this can be an issue.
    Jul 19, 2019
  23. magic9mushroom
    magic9mushroom
    Simply continuing the laser after the particle beam has changed targets wouldn't work, because without the particle beam it'll spread out before it can catch up.

    Basically, it would be important to push the particle beam into the ultrarelativistic region in order to make an effective long-range weapon.
    Jul 19, 2019
  24. inverted_helix
    inverted_helix
    The laser doesn't need to be continuous, most of the focusing effect is in the first thousand kilometers. After that the particle beam can continue without the laser.

    This does mean the laser arrives well before the beam.
    Jul 19, 2019
  25. magic9mushroom
    magic9mushroom
    I do not believe you, IH - I'm not accusing you of lying, but if you're calling it "focussing" I don't think you understand what beam divergence actually is.
    Jul 19, 2019
  26. inverted_helix
    inverted_helix
    The laser isn't a significant damage source in a laser coupled particle beam. The laser is just used to decrease the divergence of the particle beam. It has most of that effect in the first thousand kilometers. This lets you get a tight enough particle beam to go millions of kilometers while keeping tight enough for use as a weapon.
    Jul 19, 2019
  27. inverted_helix
    inverted_helix
    At that range the laser will be spread out into uselessness, and will arrive significantly before the particle beam, but the particle beam will still be tight and effective.
    Jul 19, 2019
  28. magic9mushroom
    magic9mushroom
    As I said, you don't seem to understand what's going on here - certainly, not well enough to be telling me what I'm doing wrong.
    Jul 19, 2019
  29. magic9mushroom
    magic9mushroom
    Focussing creates *systematic* convergence of a beam. It is useful for converting a parallel beam into a focussed beam that comes to a near-point. It is *not* useful for counteracting *random* spreading, such as that of a particle beam (or that which prevents a non-laser light source from being focussed down to a point).
    Jul 19, 2019
  30. magic9mushroom
    magic9mushroom
    The reason optical tweezing works is not because it cools the beam, but because it is generating a force pulling all the particles together.

    They won't *stay* together once the laser's no longer there, because they still have those random individual motions. That's like saying that if you put air in a box (with the outside of the box in vacuum), the air will stay there once the box is removed.
    Jul 19, 2019
  31. inverted_helix
    inverted_helix
    If you've cooled the air in the box to near absolute zero the air *will* stay there though. The random motion is dependent on temperature, at extremely low temperatures the random motion is extremely low.
    Jul 19, 2019
  32. Persimmon
    Persimmon
    I did it, and I am very tired now. Hopefully ShaperV appreciates it.

    You can cool the transverse motion of the beams dramatically (using a low velocity/multipass loop) before feeding into accelerator, you can use a very high quality ion source, and heavy beams diverge less proportionally.
    Jul 19, 2019
    inverted_helix likes this.
  33. magic9mushroom
    magic9mushroom
    IH: To extend the metaphor a little further, if the air was at absolute zero, you wouldn't have needed a box in the first place.
    Jul 19, 2019
  34. magic9mushroom
    magic9mushroom
    Yes, obviously, there are ways that you can actually cool the beam and those will reduce divergence in the case where there is not a laser beam there. But that's not related to my point - that the laser itself will only stop the beam spreading out while it is there, and once it is gone the beam will continue spreading at whatever rate it was doing so before the laser was applied.
    Jul 19, 2019
  35. magic9mushroom
    magic9mushroom
    Again, IH, I do not believe you know what you're talking about enough to pick holes in what I say. I can tell you're in parrot mode here and Persimmon is not (some of this is a bit beyond my level, but a lot of it isn't).
    Jul 19, 2019
  36. magic9mushroom
    magic9mushroom
    (Parrot, or "script kiddie" mode is enough for most things - we can't all be specialists in everything - but part of self-awareness is knowing when you're in that mode and that you shouldn't debate from it.)
    Jul 19, 2019