Lightsabers: "Sheath" of Energy?

[Lord Poe]

In ROTS, Yoda throws his lightsaber into the chest of a clonetrooper, where it sticks halfway out.

Why didn't it go all the way in to the hilt? Why didn't it immediately drop and bisect the trooper?

Perhaps there is a "sheath" of energy surrounding the blade, almost like a forcefield, that allows cutting, but no major thermal damage unless contact is more than momentary?

Thoughts?

[Teleros]

Off the top of my head, could Yoda have used the Force to hold it in place?

[Lord Poe]

Off the top of my head, could Yoda have used the Force to hold it in place?

Well yeah, but....why?

[CaptHawkeye]

In ROTS, Yoda throws his lightsaber into the chest of a clonetrooper, where it sticks halfway out.

Why didn't it go all the way in to the hilt? Why didn't it immediately drop and bisect the trooper?

Perhaps there is a "sheath" of energy surrounding the blade, almost like a forcefield, that allows cutting, but no major thermal damage unless contact is more than momentary?

Thoughts?

The same thing happened to Durge in the Clone Wars cartoon with Obi Won's lightsaber. It didn't fall through him when he was impaled by it. Even as he moved around and tried to punch Kenobi it didn't fall or move until Obi called it with the force. Perhaps lightsabers do impart some kind of friction on the surface they are contacting? Qui Gon Jinn seemed to be putting a fair amount of effort into the TradeFed Bridge door when he was cutting through it.

Maybe the blade's energy output just goes really low during a contact period, but the magnetic field stays engaged or increases power. This is interesting, I was thinking about it just the other day. It would make sense, lightsabers supposedly use battery power when they are activly slicing through something. A "sheath" is probably meant to conserve power in some way.

[Lord Pounder]

Perhaps it's a setting on the lightsaber for ocassions when you know you're gonna be throwing it? When Vader fights Luke on the DS 2 he seems to twist the handle before he throws it at the catwalk.

[Darth Yoshi]

I thought he was simply locking the lightsabre on so that it wouldn't deactivate while midflight.

[Stark]

People are wondering why it didn't cut down through the body, not turn off.

Since sabre blades do have resistance and do need force to cut things, perhaps the weight of the hilt isn't enough to push the blade downwards through a body. Durge in particular was in rigid metallic armour, and even the Clones had armour.

[Darth Tanner]

I'd imagine it's that the blade needs force behind it to cut, as shown with the TPM example of it taking considerable time and effort to cut through the blast doors. I'd actually find it pretty strange if it just cut through substances with no effort behind it although clone trooper armour is considerably weaker than those blast doors so the relative force difference should have just cut through the trooper like paper.

-
Although not very clear the blade is pretty much upto the hilt, theres only a few centimeters of blade showing our side of the insertion point.

Also Yoda spins the blade into him rather than javelining it in, so another argument is why it just dosnt cut sideways out the other half of the trooper and why it cuts straight into him rather than slashing in from the side.

It looks like 'the force' is the only real answer to these issues.

[Anguirus]

Or that armor just imparts a fair-to-middling amount of resistance. The prequels have consistently debunked the uber-ness of lightsabres. You might as well ask why it can't cut the MagnaGuards' staves. Its' not that they have special properties (like cortosis), it's just really dense metal (phrik).

Even when a clone is slashed full on in the chest, it doesn't tend to bisect him totally. This behavior seems consistent wih the spinning lightsabre sticking into the chestplate.

Anyway, even the blast door wasn't really sliced at all in TPM. Qui-Gon was burning through it.

[Stark]

Yeah, it'd be nice if people noticed and we didn't have to put up with silly cortosis stuff, since you don't need such game mechanics to protect or fight against lightsabres. I doubt it, though.

[Molyneux]

I was under the impression that lightsabers burn or melt through materials, rather than cutting (as shown by the effects on the blast door in TPM); perhaps Durge's armor and the Clonetrooper armor are sufficiently heat-resistant to 'hold' the blade where there's only a small area of contact, and no more force pressing on it than the handle's own weight?

[Wyrm]

Thermal conductivity and vaporization (or lack of it). Those are the two factors that I think explain the differences in the way lightsabers are behaving in the instances of the TPM bulkhead-melt and the clonetrooper stab.

First, heat conductivity. We see the bulkhead doors of TPM conducting heat rather quickly. Blast doors, among other things, are supposed to protect against large influxes of heat and pressure without failing (at least until the pressure subsides), and one of the factors controlling material strength is the temperature — melted material have no structural strength to speak of, after all. There are two ways of satisfying the temperature requirement: insulate the structural members, or try to sink as much of the heat as possible into the mass of the door, making the average temperature as low as possible. Given the relatively high thermal conductivity, blast doors obviously opt for the latter method. The result is that when the lightsaber stabs into the door, more heat is drawn away from the contact area, so more of the door melts and less of it vaporizes.

This brings us to point two, vaporization. Have you ever seen that neat physics experiment where liquid nitrogen is dumped on a hot plate, but it remains darting about for several seconds, much longer than you'd expect liquid nitrogen to remain? What happens is that the small amount of liquid nitrogen that comes in contact with the plate instantly boils, forming an insulating, supporting cushion of gaseous nitrogen. (Gasses are notorious for having low rates of heat conduction.)

Because the higher thermal conductivity of the blast doors, this vapor cushion does not form, and more area of the door is in contact with the lightsaber. This increases the heat flux and speeds the doors' destruction.

On the other hand, the properties that work so well for a blast door (for it's intended use) does not serve well for personal armor. Armor should not be allowed to get as hot as a bulkhead may. You can step away from a red-hot bulkhead; you can't really step away from red-hot armor you are wearing. But armor has to be carried, so it has a weight limitation, and therefore a heat capacity limitation. That means that given the same influx of energy, personal armor will probably achieve a higher average temperature than a bulkhead. Therefore, armor can't simply take the heat and spread it around — that would result in serious burns that would kill the wearer as surely as a blaster bolt. Instead, it has to keep the heat from penetrating the armor, and it can do that by having a low thermal conductivity. Indeed, for large influxes of energy, you would rather have the armor ablate away energy that way than to expose the wearer to even a small fraction of that energy. A low heat conductivity would insure that the heat remains concentrated, causing the small patch of armor taking the blast to quickly heat up and vaporize, carrying away the energy of the blast.

When this armor is penetrated by the lightsaber blade, a small gap quickly opens up between the lightsaber surface and the armor, with an insulating layer of gasses between the two. Human flesh, which is mostly water, does the same thing. Like in the liquid nitrogen demonstration, there would be a water vapor cushion between the searing human flesh and the lightsaber. After the initial vaporization, the actual rate of vaporization to maintain the vapor cushion can actually be quite small.

Is it enough? Well, if the seal between the lightsaber and the flesh is tight enough, then it could. But flesh isn't rigid, so I have a fair amount doubt that we can get away with the amount of vaporization we see.

Thoughts?

[Molyneux]

Sounds good to me, Wyrm. On a note: Even if the flesh around the lighsaber blade is too flexible for the vapor to shield it from the heat, it just needs to be held in place for a second or two by the armor (with the clonetrooper).

With Durge, he can literally shift his body mass away from the lightsaber blade - it probably only burned him as it penetrated, then caused no further damage to him, and was held only by his (extremely heat-resistant) armor.

[Darth Wong]

It's all well and good to say that lightsabres might have resistance to movement when cutting through something, because that makes theoretical sense. The problem is that there is absolutely no detectable slowdown in the blade movement when someone cuts off a limb or a head with a lightsabre. So this resistance must be very light, at least when cutting through human flesh.

I suppose you might argue that the blade encounters more resistance when cutting through the stormtroopers' body armour. I believe that most cuts against body-armoured opponents go through at one of the joints, where it would only have to cut through the black body-glove rather than the presumably strongest, thickest area which would be the chestplate.

[General Zod]

Perhaps there is a "sheath" of energy surrounding the blade, almost like a forcefield, that allows cutting, but no major thermal damage unless contact is more than momentary

Don't some of the books mention that early lightsabers were created as a way of holding blaster bolts in place via force field technology? It'd make sense if 'modern' lightsabers worked on similar principles and were simply a miniaturized refinement of the originals.

[Anguirus]

I suppose you might argue that the blade encounters more resistance when cutting through the stormtroopers' body armour. I believe that most cuts against body-armoured opponents go through at one of the joints, where it would only have to cut through the black body-glove rather than the presumably strongest, thickest area which would be the chestplate.

Makes sense to me. Also, I would note that the few times we see Jedi taking on stormtroopers (all in RotS IIRC) they use very powerful shoulder or backhand strokes to cut through the chest armor.

A lightsabre slash and a blaster shot both seem able to pierce armor and kill whoever's wearing it, while leaving the armor more or less intact (as opposed to blowing open the chest/cutting through flesh without slowing down).

Oh, and also note that the resistance of metal armor to lightsabres isn't even new. In Empire, Vader's armor protects him from what should have been a crippling hit to the shoulder. (Seems to me that that's when Vader realized Luke was a threat, because he next presses his attack and takes off Luke's hand a few strikes later.)

[General Zod]

Oh, and also note that the resistance of metal armor to lightsabres isn't even new. In Empire, Vader's armor protects him from what should have been a crippling hit to the shoulder. (Seems to me that that's when Vader realized Luke was a threat, because he next presses his attack and takes off Luke's hand a few strikes later.)

The EU shows that Vader's armor was specially treated using Sith alchemy to help deflect lightsaber blows, iirc.

[Darth Wong]

Perhaps there is a "sheath" of energy surrounding the blade, almost like a forcefield, that allows cutting, but no major thermal damage unless contact is more than momentary

Don't some of the books mention that early lightsabers were created as a way of holding blaster bolts in place via force field technology? It'd make sense if 'modern' lightsabers worked on similar principles and were simply a miniaturized refinement of the originals.

That implies that blaster bolts are some kind of confined energetic gas, which is the old "plasma bolt" interpretation and which is quite obviously wrong for many reasons. To give just one example, any plasmoid of that size and energy would have to be so hot that it radiates like an arc welder, and looking at the bolt would cause permanent eye damage.

I think a lot of people think that you could look at intense high-energy plasma and just squint, like in Babylon 5. Anyone who's ever had the misfortune of coming around a corner and seeing an asshole welder working without a curtain would know that nothing could be further from the truth. You can't see shit after just glimpsing something like that. It actually feels like there's sand in your eyes.

[Anguirus]

The EU shows that Vader's armor was specially treated using Sith alchemy to help deflect lightsaber blows, iirc.

Sounds like post hoc uber-lightsabre bullshit to me. I suppose the clone troopers had magical Sith armor too.

[Cykeisme]

Look, regardless of whether the lightsaber directs heat into the material its cutting, or whether it breaks the intermolecular/atomic bonds through some method we don't yet understand, it takes a certain amount of energy to break the bonds in a plane of a certain surface area.
There's a hard minimum quantity of energy that will be needed to make a cut of specific area through a specific material.

The lightsaber obviously cannot have infinite power, so it an object is hard and dense enough, it's going to take time to make the cut.. just as with the TradeFed blast door, Vader's metal armor and the clonetrooper's chest.

That much is obvious.

However, I also theorize that even if material was torn apart through some mechanism we don't know about yet, it also generates heat as a by-product at the point fo a cut.
Materials tend to have much weaker structural properties when their temperature increases. Hence, some of this inefficiency (heat) can be taken advantage of if the wielder simply pushes the blade, thus actually physically pushing the blade through the softened material.
When the blade is stuck through two layers (chestplate and backplate) of thermally resistant armor, the hilt of the saber isn't heavy enough to cut through it.


Also, as has also been pointed out by some others, it's possible that some sort of "field" surrounds the blade (possibly similar in nature to "deflector shield" on droidekas and starships), and lightly repels it from surfaces.

Thus, if the blade is simply sitting stuck into an object, the volume of the blade that actually cuts is not in contact with an object, and it's held in place by the "field" around the blade.


If there's any problems with any of my ideas, feel free to point them out.

Also, something odd.. we've observed that cuts make significant amounts of heat, judging by the glow of the TradeFed blast door.
How come the lightsaber wasn't shot out of the clonetrooper's chest in a jet of superheated steam after such prolonged contact with his innards?

[Connor MacLeod]

There probably is some friction or motion element tied to lightsaber and the thermal effects - Else why would Qui-Gon bother twisting or grinding his saber hilt into the blast door? But I'm not sure how much.

Speaking of the blast door and resistance of lightsabers, looking at that scene again, it is pretty obvious the blast door presented hardly any resistance. In fact it rather rapidly melted the door to orange-yellow temp quite readily, and the longer it was stuck in there, the hotter and more molten the door got (and quite in a large radius, in fact)

It is worth noting that this differs in contrast to how the lighstaber reacted with the stormtrooper armor. Certainly, the outputs were probably different (I doubt they need to punch 100+ MJ into stormtrooper armor to penetrate) but the effects didn't seem to be radiating much around the armor - no melting or anything (again, unlike the blast door.) Not even any glowing. (The trooper inside, however, may be another story. From what little I could see of the wound, it looked extensively charred/cauterized, even cremated, to quite a large area.)

Its also worth noting the damage did look comaprable to the redirected blaster Yoda hit one of the last Stormies with (A fist sized, ,blackened hole in the armor.)

The OT Visual Dictionary and the ANH novelization hint very heavily at storm trooper armor having some sort of energy-dissipation system or "shileding" It may very well be that we didnt see a glow for this very reason.

As a side note, we SAW stormtrooper armor (well shock trooper armour) walking around comfortably and without problem outside in the open on Mustafar, which to all indications looks to be simialr to conditions inside a volcano (the temps look quite high.) Shouldn't that speak to some fairly substnatial thermal resilience (if not active measures protecting the occupants) in the armor?

[Connor MacLeod]

I'm not really sure if any sort of "field" surrounds the blade. The blade itself seems to be some sort of "field" if you want to think of it in those terms(nevermind the plasma crap.) whether its massless or has some sort of mass to it, the effect.

As far as the blade "sticking" in the Clone trooper, maybe Yoda held it there to facilitate further damage (even if the armor could absorb or dissipate the energy, the person inside would probably get crisped pretty badly considering he's basically impaled onit.)

Alternately, and equally possible, its some property of the armor resisting. This might very well be explained by the apparent lack of "heating" in the same way the blast door is heated. IIRC shatterpoint covers the heating issue and how superconducting armour can hamper or defeat a lightsaber blade (in the short term, anyhow.) Same could be true of stormtrooper armor.

[Darth Wong]

I think you've got that backwards. The rapid heating of the blast door implies that its thermal conductivity is much higher than the stormtrooper armour. Conversely, the lack of apparent heating of the stormtrooper armour suggests that it doesn't really conduct heat that well.

[Aquatain]

I simply think it's a combat move from Yoda's side , he trows the Lightsaber in order to kill the trooper , he could then stop and use the Force to retrieve the saber from the ground or he could continue his motion - jump to the trooper (while keeping the saber in place though the Force) and retrieve it that way.

[Cykeisme]

I simply think it's a combat move from Yoda's side , he trows the Lightsaber in order to kill the trooper , he could then stop and use the Force to retrieve the saber from the ground or he could continue his motion - jump to the trooper (while keeping the saber in place though the Force) and retrieve it that way.

I find it implausible that if Yoda were using telekinesis, that the saber would remain perfectly in place in the trooper's chest, even as the trooper fell to his knees and began to keel over.
That is, of course, unless the lightsaber blade actually imparted reaction force to the armor/torso and vice-versa, in which case it would not be neccessary to hold the saber in place with the force anyway.


Btw, please note that the blade being able to apply force on objects is not the same thing as the blade having mass. It can both apply force and be massless.
I mean, if it can parry and push a super-dense Phrik staff, and Qui-Gon puts his weight on the cut into a blastdoor, why's it so hard to believe that it can stick in an armored chestplate?
Besides, SoD aside, this is obviously the intention of the event.