Semi-Realistic Lightsaber Technology?

[Samloyal23]

According to physics a lightsaber, as described, is just not possible. Lasers cannot be made solid and will not end at a point. But how close can we get?

• Lightsaber Traits
  Lightsabers project a blade from a hilt.
  The blades are solid but weightless.
  The blades can cut cleanly through most materials.
  The blades are super-heated and can melt metal.

How can we simulate these traits with realistic technology or at least without actually breaking known laws of physics?

 

[Mishihari Lord]

Niven's variable sword are close. A monomolecular filament held stiff by a forcefield, IIRC. You could make it more realistic by dropping the forcefield and putting a bow behind it like a giant cheese slicer. Or postulate that you can charge the thing and it stays stiff by electric self-repulsion. This could even produce some St Elmo's fire as the light part of the light saber. You get extruded but not projected from a hilt, solid but weightless, cuts cleanly through most materials, and light. You don't get heat.

 

[Umbran]

A monomolecular filament held stiff by a forcefield, IIRC.

A Slaver stasis field, actually. Which means it isn't viable with anything near current tech.

Or postulate that you can charge the thing and it stays stiff by electric self-repulsion.

Except that won't work - the charge will arc to anything grounded nearby, and leave you with a monofilament whip, not a sword.

Make it a (room temp) superconducting monomolecular wire, and you keep it stiff with magnetic fields. Not that we can make such powerful fields right now, but the idea probably works in theory.

You don't get the super-heating (though you get to cut through most things). The ability to duel with them is... sketchy. Interacting magnetic fields get funky fast.

 

[Mishihari Lord]

A Slaver stasis field, actually. Which means it isn't viable with anything near current tech.



Except that won't work - the charge will arc to anything grounded nearby, and leave you with a monofilament whip, not a sword.

Make it a (room temp) superconducting monomolecular wire, and you keep it stiff with magnetic fields. Not that we can make such powerful fields right now, but the idea probably works in theory.

You don't get the super-heating (though you get to cut through most things). The ability to duel with them is... sketchy. Interacting magnetic fields get funky fast.

Well of course it will arc. I was thinking of a large power source that can keep it continuously charged despite the frequent loss. Nothing we can do today but it's SF. Taser effects on a hit and scary sparks are a bonus. Thinking about it now, it shouldn't actually take much charge considering the near negligible mass of the thing, and if it's superconducting like your idea then keeping it charged along the whole length isn't a problem.

The magnetic idea is neat too, especially if one wants to work through the math and see what happens when two weapons interact. A touch of reality in SF can make SF combat more complex and interesting, like in the Jack Campbell books I'm currently reading.

 

[Umbran]

Well of course it will arc.

You realize that the user of the sword is probably the closest thing to arc to, right?

I was thinking of a large power source that can keep it continuously charged despite the frequent loss.

Since we are talking about plausible tech - you can't carry a power pack that large.

Thinking about it now, it shouldn't actually take much charge considering the near negligible mass of the thing

The mass of the thing isn't the issue. The mass of what it hits is. Monomolecular or not, it will meet resistance, and that will tend to bend it. And it would take monumental charge to keep it from bending due to exterior force. Even enough charge to keep it stiff under force of gravity is going to be significant - torque can be a bit of a pain sometimes.

 

[MarkB]

A Slaver stasis field, actually. Which means it isn't viable with anything near current tech.



Except that won't work - the charge will arc to anything grounded nearby, and leave you with a monofilament whip, not a sword.

Make it a (room temp) superconducting monomolecular wire, and you keep it stiff with magnetic fields. Not that we can make such powerful fields right now, but the idea probably works in theory.

You don't get the super-heating (though you get to cut through most things). The ability to duel with them is... sketchy. Interacting magnetic fields get funky fast.

Variable-swords had a red bead at the end to let the user know where the blade was, since it was invisibly thin. So, rather than trying to run any sort of charge through the filament itself, maybe work on something to repel the bead from the hilt, thus stretching the filament between them.

The tricky part would be making the repulsion directional relative to the hilt - otherwise the blade will just dangle from the hilt like a pendulum.

 

[Mishihari Lord]

You realize that the user of the sword is probably the closest thing to arc to, right?

Insulated gloves and boots fix that, but you'll still have to be careful. Bring an uninsulated portion of your body near something grounded and you're in trouble.

Since we are talking about plausible tech - you can't carry a power pack that large.

Plausible is a pretty subjective word. We're talking SF, not something that can be built today. I think it's plausible that someday supercapcitors could store enough juice to pull off something like this.

The mass of the thing isn't the issue. The mass of what it hits is. Monomolecular or not, it will meet resistance, and that will tend to bend it. And it would take monumental charge to keep it from bending due to exterior force. Even enough charge to keep it stiff under force of gravity is going to be significant - torque can be a bit of a pain sometimes.

Already thought of that. Physical resistance isn't going to be much, and even though it bends on a hit I would still expect a deep cut. On a hit you're pretty much guaranteed to drop your charge anyway, which as you said turns it into a whip. As long as it can build up a sufficient charge quickly afterward to restore stiffness, it shouldn't be much of a problem.

 

[Mishihari Lord]

Variable-swords had a red bead at the end to let the user know where the blade was, since it was invisibly thin. So, rather than trying to run any sort of charge through the filament itself, maybe work on something to repel the bead from the hilt, thus stretching the filament between them.

The tricky part would be making the repulsion directional relative to the hilt - otherwise the blade will just dangle from the hilt like a pendulum.

Directionality is tricky but doable with current technology. I'm a controls engineer, and I've built controllers for flexible membrane telescopes that are similar in principle but not specifics. I think the harder problem is making sure your don't attract or repel other items. Having your sword stick to a metal car at a critical point would be more than inconvenient. On the other hand that would address a SW feature of light sabers. Blaster are supposed to shoot plasma bolts, and if the plasma is charged it would be reasonable that it could be attracted and grounded by the sword without having to invoke the Force to predict shot trajectories.

 

[MechaPilot]

According to physics a lightsaber, as described, is just not possible. Lasers cannot be made solid and will not end at a point. But how close can we get?

• Lightsaber Traits
  Lightsabers project a blade from a hilt.
  The blades are solid but weightless.
  The blades can cut cleanly through most materials.
  The blades are super-heated and can melt metal.

How can we simulate these traits with realistic technology or at least without actually breaking known laws of physics?

Lightsaber is probably just a nickname. The blade is likely not made of light: if it were, a lightsaber fight would be like fighting with flashlight beams. Instead, the beam is probably an electromagnetic field that contains plasma. The most problematic question that arises from this concept of the lightsaber is that of temperature: why wouldn't the plasma heat the air or the handle so much that no one could stand to be in the vicinity of an active lightsaber (plasma, if I recall correctly, is several thousand degrees).

I have no answer for that question. However, I do know that heat is a form of radiation. Perhaps the same field that constrains the plasma also contains the radiation.

 

[Morrus]

They're not lasers.

Lightsabers are contained plasma. That's well established. The word "light" is just a word.

Beyond that, yeah, it's probably not possible.

I guess the Force helps. Magic makes stuff work! Though Han Solo used one. So I guess that theory's out.