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3 reasons you’d kill yourself with a lightsaber

Fri, 06/13/2014 - 11:02am
JF Stackhouse, Engineerjobs.com

JF StackhouseWhen I was eight years old, there was only one thing I wanted more than for someone to invent the lightsaber. I wanted one to fall off the back of a truck and land in my front yard.

Fortunately, neither occurred; lightsabers are dangerous, poorly designed, and unstable. Here are three of the many reasons they should be preemptively outlawed.

Lightsaber Plasma Containment Failure

According to Star Wars canon, a lightsaber’s blade is composed of plasma contained by an energy field. The field arcs up from one side of a magnetic stabilizing ring circling the top of hilt, up to a meter away, and then back down into “negatively charged” ring surrounding the plasma emitter. A superconducting wire back to the power source would supposedly provide a completed circuit.

 

Image Credit: Wookieepedia

There are a few problems with this, of course, though no one would categorize Star Wars as hard SF. For our purposes, let’s grant the Jedi the ability to create plasma with nothing more than a stream of electrons passing through an array of one to three focusing crystals, with atmospheric air as the carrier gas. Perhaps it’s a Force ability.

We know the resulting plasma is hot enough to cut through just about any known material, with a few exotic exceptions (cortosis, Mandalorian iron, and the ultrachrome come to mind). This suggests a “hot” plasma, with the heavy particles and electrons at similar temperatures. While electron temperatures can comfortably reach several thousand degrees Celsius in a non-thermal plasma, no one is likely to cut through a blast door with your plasma screen television. That ‘blade’ is seriously hot and energetic, confined only by the electromagnetic field contained in the saber’s hilt.

And that’s how you’ll get yourself killed.

Image Source: Star Wars Aficionado MagazineWe use electromagnetic fields to contain plasma by steering its charged particles along a desired path. Rather than a vessel, it’s more of a track: biasing the plasma to travel along a specific path allows you to determine its volume. So long as the field maintains its shape, the plasma is safely contained.

But what if another object – such as your estranged son’s wrist, or the field containing another lightsaber blade – intersects the field? Similarly, what if you walk under a high-tension electrical wire with an active lightsaber?

Bad things happen.

First, your containment field will warp in response to these new influences. It may collapse entirely, or simply interact with the larger field. In either case, the superheated electron fog of your lightsaber blade will be free to arc along newly-chosen paths – with a little help from any moving electrons in the neighboring field. In the best case, you’ve invented the Jedi thermal plasma cutter and suffered permanent eye damage. Slightly worse options include generating a lightning bolt (an average of 300 kA) with its origin point less than a meter from your face, or – if the energies involved in lightsaber blade plasma are high enough – a minor firestorm, with you at its center.

Wielding a lightsaber beneath high tension electrical lines would call down lightning. Not nifty Dark Jedi lightning, but the kind that kills you.

In any case, the release of high-energy plasma along an unpredictable path while you hold the emitter is likely to create an occupational fatality. For your own safety, do not activate a lightsaber in atmosphere, near conductive materials, or in the presence of competing electromagnetic fields.

Lightsabers Transmit Minimal Haptic Feedback

Two aspects of lightsaber design compound the chances of fatal user error. One is the relatively weightless nature of the blade itself, and the other is the gyroscopic effect created by its plasma containment system. Separately, they each present a hazard. Together, they would almost certainly get you killed.

When we primates use a tool, our proprioceptive sense includes the device into its locative map of our limbs, body, balance, and so forth. You experience a similar effect when you’re driving a car, or balancing a heavy object; part of your brain keeps track of the tool as though it were part of your body. The exact mechanism of human proprioception is unknown, though it’s believed to incorporate inner ear feedback with tactile sensation, forces measured through touch, the degree to which your muscles are stretched, and the positions of your joints. In unconscious or reflexive proprioception, aggregation takes place in the cerebellum, via the posterior column-medial lemniscus pathway. A human may consciously model this information, at reduced speed, in the cerebrum.

Image Credit: Wikimedia Commons

As a contained electron cloud transmits far less feedback than, say, a stick, modeling a precise haptic image of your blade is non-trivial. With little more to go by than tracking wrist angles and visually confirming location (at some risk to your eyesight), avoiding your own blade during the whirling gymnastics of a lightsaber duel may prove impossible.

Gyroscopic Precession in Lightsabers?

If maintaining a haptic image of the lightsaber blade is difficult, due to the lack of feedback, then this next bug could arguably be a feature. Of course, it’s just as likely to kill you dead.

As we discussed above, the blade’s particle fog is contained via an electromagnetic field projected from the lightsaber’s hilt. (We’ll leave aside, for the moment, the fatal deformations which could result from whipping a field emitter around in circles.) Containing thermal plasma is less a matter of “pouring” it into an appropriate vessel than it is generating and guiding it onto a track within an electromagnetic field. Lorentz forces guide its charged particles into a helical path around the field lines, effectively confining the plasma to a determined volume.

Where this presents an issue for aspiring Jedi is if gyroscopic precession occurs within lightsaber blades.

Canon Star Wars tech babble suggests it does, though I’m not certain gyroscopic precession occurs in real-world plasmas under rotation. Plasma physics – not my specialty by the longest of long shots – appears to have much more in common with fluid dynamics than solid-body mechanical physics. Determining whether a charged particle cloud, in motion along containment field lines, acts in aggregate as a gyroscope is decidedly out of my league. My gut says it might, but a (very) casual reading of the literature appears to suggest otherwise.

While I encourage you to weigh in with your analysis in the comments, for now we’ll accept the Star Wars hand-waving as settled physics: the rotation of charged particles within a lightsaber blade exerts precession effects when the user changes the orientation of the blade. This could, on one hand, counter the haptic imaging difficulties we’ve mentioned, previously. On the other, it creates a situation where the lightsaber exerts small-f force in proportional opposition to the movements of its wielder.

An attempt to rotate the spin axis of a gyroscope produces equal force along a perpendicular axis. In wheels and fixed stabilizing gyroscopes, this angular momentum is exploited to maintain balance along an axis perpendicular to the rotation of the spin axis; this is how you ride a bicycle. In the specific case of lightsaber blades, however, this could cause the saber to either twist relative to the wielder’s hand or arc away from the center of his dueling stance.

If the latter occurs, your opponent is better-positioned to drill you in the chest with their own lightsaber. The former case, combining gyroscopic precession with the lack of haptic feedback, creates a dangerous situation to the novice wielder: the plasma you’re waving around bends perpendicular to wherever you attempt to steer it, tries to twist along the axis of your grip, and is quite difficult to keep track of.

Truly, novice Jedi are more dangerous to themselves than to their opponents.

Box of Saber PartsLightsabers: Defective By Design

While our inner eight-year-olds want lightsabers, one would be hard-pressed to find a more dangerous, poorly-designed, or unstable weapons system. The prospect of containment failure and a high risk of user error combine to make lightsabers far more dangerous to their wielders than to an opponent.

Emperor Palpatine’s near-total restriction of lightsaber technology during his reign was a boon to public safety and humane practices in warfare. More so than blasters, unregulated autonomous robots, or planet-busting energy weapons, lightsabers are a serious public safety hazard.

This blog was originally posted on www.engineerjobs.com.

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