Combat Physics

[sungkono]

Hello everyone, I am Hans from Indonesia. I am really fascinated by what everyone here at ARMA has accomplished. Great work! I was wondering if anyone has studied the physics and science that happens during a close quarter combat. I tried searching the net but found very little on this subject. For instance the mass and velocity of an object translates to the kinetic energy that the object imparts upon impact. k=1/2 mv2(thats squared not 2), so if you double the mass you get twice the energy, but if you double the velocity you get 4 times the energy!

This is simple physics, but I was wondering if it is possible to translate this study into something more useful, say on how much energy is required for a sword to pierce through a steel armor or how much force is really required to cut through muscle and bone. Perhaps all these data can be used to run a simulation on a computer to see what actually happens during combat.

Thanks everyone!

[Randall Pleasant]

Sungkono

Check out George Turner's ground breaking article Sword Motions and Impacts: An Investigation and Analysis here on the ARMA site. This is a must read for understanding what actually happens when you cut with a sword. Beware of some of the "junk theories" on sword cutting & performance that you might run into out on the web -the stuff about harmonics and vibrations mostly grew out of marketing rather than the Laws of Physics.

[JeffGentry]

Hey guy's

Do you mean something like what they do with bullet's and bullistic gelatin? That would be interesting i know with bullet's it is some amazing stuff with secondary wound channel's and such ge little diffrent look at how a sword does it's damage other than through archeology/patheology/forensic's(not sure what it would be) it would be interesting none the less.

Jeff

[Webmaster]

Welcome to the forum, Hans. Definitely check out George Turner's mind-altering, side-splitting work of genius, and please also reread our forum rules and register under your real name, as we do not allow aliases here. We haven't had a good physics discussion here in a while, nice to see somebody new who's interested.

[Douglas S]

"if you double the mass you get twice the energy, but if you double the velocity you get 4 times the energy!"

That's interesting, it explains why heavy swords are not better than fast swords.

[Mike Habib]

George Turner's report was awesome; I thoroughly enjoyed it.

Interestingly, many of the principles he uses (such as basic beam theory) are also applicable to what happens to targets when they are struck by a weapon (as opposed to what happens to the weapon, which was Turner's focus).

One thing that is especially interesting to me, using George Turner's impact model, is that we should consider the possibility of bone tissue failure (ie. breakage) from sword impacts, even in armored targets where the armor is not penetrated. If the armor does not dissipate the force sufficiently, a strong bending moment can still be transmitted to the arm, and though it will not be cut or sliced, it may snap or shatter. To get an idea of how tranmission of force can be important, consider that someone who falls from a window may break their legs and not their feet (or likely both), despite the fact that it is only their feet that hit the ground at impact.

This does not mean a sword should be especially heavy or blunt (common misconceptions about Euro. swords, as we all know), but more that it should move quickly and focus force well (ie. have a good edge).

Of course, I say this without having tested the force dissipation by plate mail, so take it with a grain of salt.

Cheers,
--Mike Habib

[Mike Habib]

I decided to split this into a separate post, for sake of keeping each post shorter...

I find it additionally intriguing that the advantage of a curved blades seems so nebulous. As G. Turner points out, it probably is not enormous either way, but I had an idea I would love to get feedback on:

As pointed out in the report, draw cuts are not as potent as they are often thought, and certainly not very good at slicing armor. But suppose for a moment that you are aiming for joints or fighting relatively unarmored targets, and thus use a draw cut (which slices meat very nicely).

The cut you make on a draw cut is partly a product of how well your edge cuts and how long you cut. If more edge passes over the point of contact (actually line of contact), you will do more cutting. Now, having a curved blade might add some more cutting edge length (I have heard this claimed before), but I doubt that would matter much. What does matter is human anatomy; specifically how we swing a sword...

To make a cut last (ie. to have as much of the blade slice through the line of contact as possible) you draw the blade along its axis. So, for a straight blade, you draw in a straight line (assuming, again, that you are maximizing slicing; you can draw cut in an arc with a straight blade and you will give up some slicing for additional cutting because you rotate the blade into the target).

A curved blade, however, has a curved axis, and thus draws the longest on an arc. This would not matter except that human arms have a better (ie. wider) range of motion swinging in an arc.

Just a thought.

Cheers,
--Mike Habib

[JeffGentry]

hey Mike
that is my thinking too i guess i will have to teach myself some physics to look at this further i know JC has done research on battle wound's from Euro weapon's, i myself do not have the knowledge of physics to something of this nature, would love to see the stat's and such on this type of thing.

Jeff

[Casper Bradak]

For a curved blade to get any significant amount of extra edge out of the curvature, it would have to be ridiculously curved. Swords like the japanese katana get no extra edge from their curvature. And if you did have a longer edge, you would still need to get it all on the target in practice for any added effect.
No sword was ever designed as a primarily slicing weapon, not katanas, not anything, and a slice alone will never be as effective as a true percussive cut.
Also, in practice, a curved blade does not draw through any more than a straight one in a slice. It just doesn't make much difference when it comes down to the physical reality of it.
Draw cuts are 100% ineffective vs armour, not just "Not very good."
Chances are, if you were to slice at most armour joints, the armour or the padding underneath would render it ineffective (this holds true in training, and you never see it or hear it mentioned in the manuals). But assuming you worked it onto bare flesh without the armour impeding you, it'd be great.
Slices are very effective within their proper context. If used in place of a swords primary function, you'll be defeated in short order.

[Mike Habib]

I actually agree, overall. My point was not that extra edge is added (I mentioned that I thought that difference would be slight, despite the persistent rumors). I am also not arguing that a curved blade draws through any more than a straight blade.

What I am arguing (apparently confusingly, my apologies), is that it is easier to get a full draw from a curve blade than a straight blade. A full draw on a straight blade requires more foot work because hyperflexion in the arm is a much shorter path than deltopectoral swinging (ie. an arc cutting motion).

That being said, I have to agree that it is unlikely that any swords were designed primarily to slice.

Good point on the padding at joint regions, I should not have neglected that aspect. I have not practiced with draw cuts much myself (for several reasons), so it was a purely theoretical argument.

Cheers,
--Mike Habib

[Randall Pleasant]

Mike Habib wrote:
What I am arguing (apparently confusingly, my apologies), is that it is easier to get a full draw from a curve blade than a straight blade. A full draw on a straight blade requires more foot work because hyperflexion in the arm is a much shorter path than deltopectoral swinging (ie. an arc cutting motion).

Mike

This may or may not be true. I can see where this is most likely true with a waster or blunt sword against a hard target such as a pell because throughout the slice your edge stays at the same place in relationship to the target - ie. the edge does not cut into the target. However, with shard swords a against a cutable target this might not be true because during the slice the edge will move not only past the target but also into the target. It might actually be that the stright edge will place more pressure against the target during the slice. In any case this is clearly testable through test cutting on realistic targets such a large peice of meat. Got meat?

[Stacy Clifford]

It's my understanding that those swords used primarily from horseback such as sabres were curved mainly because it allowed the blade to slide free of the target more easily in a ride-by attack. Any extra slicing action would be a nice side benefit, but not having my sword ripped from my hand because it's stuck in the guy going the other way would be a bigger concern for me. The curvature would probably also discourage thrusting from horseback, which could be a very easy way to disarm yourself in a cavalry battle.

[Casper Bradak]

That doesn't stand up to the physics. People aren't made of superglue and I can't imagine that making a difference in real life.
On the other hand, it's a common belief now, and maybe it was back then as well.
It needs two kinds of varification. Verification of that belief and verification that it holds up physically. The physical proof that it is a false idea is easy enough from test cutting.
The actual cut would not be performed in a different fashion (another instance of some people I've met believing curved swords were primarily for slicing, especially from horseback; see how well you can slice at that speed, and compare the results to cuts), and regardless of the blade type, if it embedded in the enemie's body, if you wanted it to simply slide free and the footman had simply not just fallen (as tended to happen), you let your sword go to a point back hammer grip as you pass (if it were still in the enemy anyway).
And don't forget, tucks were common cavalry weapons in eastern europe. The last incarnation of cavalry swords in the US were basically rapiers, and taught only to use the thrust.
If they didn't have a problem with stuck weaponry, why would a cutting blade? But the same thing happens, the blade passes out of the victim on the ride by, or they simply fall off the blade, or both, in the instances where the blade is still in them, which may not have been very much, by letting the point drop and point to the rear as they pass. It's the same technique taught to lancers (as lances were not usually one shot shatter sticks).
I know cutting a dead dear and not fully passing through doesn't cause the slightest stickyness. Not even bone sticks. But then some people believe live humans have some kind of super strong vacuum suction of blades within their bodies that isn't equalized by perforation.
Here's what I usually tell people to visualise in order to see if their weapon would stick. Put a knife (blunt, if they really want to do it) blade in someone's mouth. Tell them to bite as hard as they can, close their mouth and suck in as hard as they can. That's about as bad as it could get. Now yank it out and see how hard that is.
Don't forget the lubrication ability of blood, tissue, fluids and fat (trust me).

[Stacy Clifford]

Good points Casper. I didn't know that tucks were used as cavalry weapons. I never thought people were made of glue, I was thinking more of momentum in opposite directions possibly shocking the blade out of your hands before you have the opportunity to drop the point back and slide through. Also, live flesh may not pose stickiness problems, but what about heavy clothing, thick leather, metal armor? If these are penetrated by the edge, will they let go as easily? Probably not too different, I imagine, but perhaps this is a subject for some test cutting? We do know you don't want to get stuck in a wooden shield, and curvature won't help there. Anyway, somebody had to bring it up.

[Casper Bradak]

I didn't assume you thought people were that sticky, but I think it's an annoying myth on sword types so I try to make a strong point for people in general.
I understand the possibility of a hard, sudden impact on your sword, but that would not be effected by sword type in the least, obviously.
Heavy clothing would cause no difficulty for withdrawal if penetrated.
Armour grade leather is probably the heaviest stuff likely to be penetrated by a blade, and therefore the most likely to grab, but I still don't think it would get stuck at all.
Metal could post the biggest shock to the weapon, but it won't be cut.
Another point it that what we're really assuming is a charging warrior cutting horizontally or towards his opponent. In manuals and contemporary art, it's mostly forward downright cuts, which would pose less of a problem if there were a problem, and make for an even easier pass.
And another point, is don't forget lanyards, that often even attached a man at arm's sword to his body armour, so if it did get shocked or caught up somehow, he'd at least drag his weapon and retain it.
Assuming it were caught somehow in his foes body, even if his foe were unharmed, and gripped the weapon, the knight's position, with the help of his saddle designed for such things, would more likely take the footman with him than vice versa.