Hey Alf!

Yeah, I am the author of the MindSpring site, aka "Harald", only I forgot my old password and so created a new ID. Haven't posted in ages.

You pose a mountain of questions, so let me try to respond efficiently.

QUOTE: What happens on microscopic level with tissue cells subjected to a pressure wave? Would you agree that if you apply pressure to a closed cell it would burst if the physical limitations of the cell wall is exceeded by the pressure wave?

Yeah, there can be a lot of masceration due to the pressure wave.

QUOTE: Do you not state and is it understood that when a projectile passes through tissue it generates a pressure wave, that this wave magnitude is directly related to the velocity of the projectile and that the wave is ultimately the cause of how tissue reacts and the reaction is actually the wound?

Agreed

QUOTE: From your website: "The phenomenon from which this misunderstanding arises is simply trauma to the central nervous system (typically the upper or thoracic spinal region, but also the brain in special instances) resulting from the violent pressure wave that accompanies a bullet passing nearby."
Then something that I find difficult to comprehend:
"In terms of terminal ballistics, "work" involves all aspects of the bullet-target interaction event; but not all of this kinetic energy is applied to effective work. Some of the energy is lost to heat, some to friction, some is tied up in the rotational velocity of the bullet, some lost to elastic displacement, and some is usually spent on deforming the bullet. The only work which is effective work is that which causes damage to the target, by penetration and cavitation."

I am not sure what you're asking, Alf, but let me guess that you are questioning why I seem to say that only direct damage is effective work in one place and yet allow that pressure waves can paralyze an animal? The temporary paralysis phenomenon is not an effective lethal mechanism. It can be helpful since it saves us the trouble of tracking, but it won't kill big game in itself. Now, there is another, distinct instant death (not paralysis) phenomenon, but it seems to result from hits lower on the thorax that would be otherwise fatal, only in these cases the death is not due to hemorrhage.

QUOTE: But is penetration and cavitation not directly related to a form of energy or energy transfer?

All work (damage) done is due to kinetic energy.

QUOTE: The higher the kinetic energy, all things being equal the bigger the penetration and the higher the kinetic energy the bigger the cavity due to the pressure wave? ( as long as the projectile remains stable, does not deform etc)

"All things being equal" is a dangerous clause. I don't know what you include in your thought. All kinetic energy is not the same. Joules are not joules. The energy associated with a high velocity does a different kind of damage than the same amount of energy delivered by a low velocity. That is a crucial point for understanding.

QUOTE: In fact the good Dr Norbert hansen bases his whole theory of penetration on the generating of a pressure wave and the cavity that it forms as the bullet passes. ( this only valid for fluid containg tissue as a cavity cannot be induced in solids such as bone at normal working rifle velocities ----- it would work if you could fire the bullet at say 10,000 fps and the bullet stayed together for at these velocities the pressure wave creates cavitiation in steel or bone for that matter)

Supercavitation has some application in homogeneous fluid media for some solids. The military is looking at this for advanced torpedoes. I doubt if flow separation works to the benefit of expanding bullets.

QUOTE: As for energy lost to deformation? how does this happen? Exactly what transpires between tissue and projectile that causes the projectile to deform or is it simply some random happening?

Well, it certainly isn't a random happening. Energy transfer occurs in many forms since energy exists in many forms. We have mainly kinetic energy, strain energy and heat to be concerned with. Almost all of the bullet's energy is converted to strain energy and other forms of kinetic energy (i.e., imparted to the target material) from contact. The bullet contacts tissue, producing a high pressure region. The tissue is damaged (strained) and accelerated away from the region of high pressure. Eventually everything comes back to rest and the energy assumes the form of heat. The projectile may exit, carrying a bit off into the countryside.

QUOTE: A projectile that posesses no kinetic energy cannot deform, not so?

Well, a projectile with no kinetic energy is not much of a projectile. But yeah, it needs energy to be deformed and to deform (unless something hits it).

QUOTE: So in order to deform it must possess kinetic energy.

Something has to hit something else, yes.

QUOTE: Secondly it must interact with the medium through which it travels. There must be resitance from the side of the tissue, energy is "lost" from one medium, the bullet to the medium (target) for this to happen. So what does this physically look like?

As described above the energy transfer process takes the form of strain and acceleration (imparted motion).

QUOTE: You further claim that "energy dump" is a myth, do you not concede that some of the energy of the projectile is lost to the tissue? I mean what happens to a bullet travelling at 3000 fps, it hits the target, say for arguement sake a simple piece of wet living muscle and skin and the bullet exists the target at a velocity lower than the initial 3000 fps, say now it's 2000 fps, what happened to the 1000 fps, did it simply vanish in thin air? Or say its a big piece of flesh and the 3000 fps bullet comes to dead stop ? what happened here in phyiscal terms?

What I am countering in my arguments against the "energy dump" school of thinking is the idea that if I have 3000 ft-lbs of KE, then that will kill an elk or a kudu. Really, you don't know anything by simply looking at a calculation of the kinetic energy other than there is some quantity of potential work there which might produce an effective wound if were delivered at a certain velocity by a particular type of bullet. As I said earlier, not all energy is the same. 3000 ft-lbs is not capable of doing any discrete, quantifiable amount of killing. It depends greatly on the velocity and the projectile. Now, to be fair, most bullets operate in a range that is what can be termed high velocity. Where this becomes important is when you start comparing things that are very different, like an ultra-high velocity varmint load with an old blackpowder load with a massive bullet but low velocity. I give an example on my web site. The very high velocity energy will result in extremely high local pressures on impact, destroy the bullet, cavitate a huge hole, but deliver very shallow penetration. The old blackpowder load will produce very low pressures on impact that will not deform the soft lead bullet appreciably and will create a very deep penetration of a diameter close to that of the projectile. Same amount of energy, but very different character of work done. So talking quantities of ft-lbs or J in isolation doesn't mean anything. It is very misleading.

QUOTE: You conceded to a pressure wave, well everybody who knows what happens when you drop a stone into water or fire a bullet into thin air knows a pressure wave is created. The stone slows down, so does the bullet cause energy has been trnasferred to the water It has to for if it doesnt there would be no wave.

Yes, there is energy transfer between any projectile and the medium through which it passes. All moving bodies in contact exchange energy. It can be elastic strain energy, plastic strain energy (permanent damage) or friction, motion, etc.

QUOTE: Now did this bullet in the large piece of flesh not just "Dump" all of it's energy? and was the wave thus created not absorbed or better countered by the elasticity of the tissues.

Dump is not a scientific depiction of the energy transfer process, but if it is brought to rest then you would say that all of the original KE of the projectile ended up in the projectile or the body as heat.

QUOTE: Also how do you propose to explain energy loss and the physical events when a projectile is fired, say a round ball, it only has kinetic energy as forward motion, no spin, no yaw a perefctly round little steel pellet and after it hits the target the hole looks exactly like that created by your bullet fired from a rifled barrel. How did this come about ? What if any different is the pshysical event that happens here. And by the way when this baby hits living flesh it vaporises cells and tissues with a pressure pulse that blows the confines of the vacuum tank apart.

I don't know what the question is here. It works the same way for smoothbores and rifled bullets. Is that what you're asking?

The general drift of these questions seems to be argued on the premise that I have questioned the validity of KE or its role in terminal ballistics. I have never done that. I have only tried to clarify what that role is. Some folks want to speak of momentum, and other things, but let's be clear: all terminal ballistics is about energy. Strain energy and kinetic energy. That's it. Momentum is a quantity we use to describe kinetics, but in terminal ballistics the useful expressions are hydrodynamic and energy relations. Conservation of momentum in a simplistic algebraic sense doesn't get you anywhere in situations where plastic strain dominates the event. The trick with energy is understanding that you need to know its characteristics. In thermodynamics, that character is given by temperature. In terminal ballistics the character is given by velocity.

Is that any clearer, or only worse?

Alf,

Norbert's SuperPenetrator design is actually an application of cavitation theory, in this case cavitation at the front edge of the missile in the medium produces a boundary layer in the flow around the missile (here obviously a bullet). As long as the cavitation induced boundary conditions are intact, the bullet is shielded from the forces trying to upset its physical structure and result in the bullet turning (deviating from a straight trajectory). The meplat is necessary to induce cavitation. This application was first applied developed in Soviet torpedo research, and its application there produced significantly higher velocities of the torpedo than could be achieved with normal flow (hence drag) around it.

I know Fackler's work, and have read it before.
(The music on the current linkpage I think is intended as punishment for the reader). It does not contradict when I allege to be true.

The second paper is beyond my ability to suspend disbelief. I remember when the "shock reflex" theory was popular in Europe and cartridges such as the 5.6X61 Vom Hofe Super Express were designed so that velocity at the target was above the theorized critical threshhold for the shock phenomenon to occur. It fell away because it could not be verified.

I started studying slowing down theories in 19(mumble) when I was 19 years old, and examining the analytical theory of slowing down neutrons in various media as part of reactor theory. That is a relatively simple system, as complex as it is. The theory of terminal ballistics has never had a similar analytical theory -- the non-linearities of the system are to difficult for closed-form solution.

The mechanics of bullet damage are straight-forward. The bullet crushes all in its path (as long as its structure is intact), and it deflects small pieces of tissue and whatever radially away from its path. The bullet's course is the permanent wound channel, and the radial deflection is responsible for the temporary cavity. By the way things such as clay blocks show more temporary cavity than animals do.

If you regard the bullet as something carrying energy, and calculate how much the temperature of the struck body's temperature would rise by transferring all the bullet's kinetic energy, the result is a fraction of a degree.

If you believe in hydrostatic shock, you believe in action at a distance without an intervening physical mechanism. Sonic shock waves certainly exist, else the demonstrated ability of medical people to destroy kidney stones with them would not exist. However, these waves do not damage the body's tissue.

jim

Jim,
The last thing I want to do is get involved in championing HS in bullets, but the reaction at a distance that is postulated from what I've heard is similar to the concussive shock that one sees if you toss a stick of dynamite into a farm pond and fish on the other side of the pond come belly up. The reaction at a distance does have an intervening mechanism which is water, and a shock wave is transmitted via a relatively rigid material - water being more or less rigid when those sorts of velocities are involved.

Brent

Alf is the medical professional here and should answer this, but I don't think that any technical definition of shock ever kills an animal that is shot (unless we consider one that dies hours later from a lousy shot). It bleeds to death as the primary cause. Yes, in a state of shock, medically speaking, but that actually helps it survive (that's why your body drops your heart rate, blood pressure and temperature). You bleed out slower in shock than otherwise. Maybe I've overstated the case here. Alf can correct me.

Shock in the engineering/physics sense just doesn't play at all.

I've already talked about some other things that can happen, paralysis from high pressure near the spine (but that is not fatal) and the weird "lights out" thing that happens sometimes with hits near the heart. Nobody really understands that and yes, it does happen more frequently with violently expansive impacts, but all bullets hits are in the extremely violent category. I've had some physicians try to explain it and the theory seems to be that the impact disrupts some neurological signal governing cardio-pulmonary function. But its unpredictable.