Physics Question...

[Spee]

Alright.


I, for reasons I will not announce, need to know the effect on the human physiology if the following happened.


A metallic cynlinder, roughly 1 foot long, and posessing a 3" diameter, were propelled at roughly mach 4 towards a human being?

I dont mean the obvious "instagib" answer, I mean, what would the effects, on a much smaller scale be? Massive concussion, and just a hole the width of the cynlinder bored into wherever it hit? The subject literally instagibbing, or, more along the lines of a colossal deagle round?


Be thankful that, while this is rather morbid, it isn't nearly as dumb as my Pancake physics question.

[AztecWarrior]

A: I haven't done collisions yet. I don't know.

B: At Mach 4 (over 2,900 MPH) you're pretty much dead.

[martyr]

at mach four, you are, i'm afraid, looking at instagib. depending on where on the body you apply impact, you'll have the other parts left over, probably shorn fairly cleanly off from the impact area.

more specifically regarding instagib, you're looking at atomization and/or vaporization of the forward, first-impact areas, and an overal trauma mush-up of the far side of the impact area.

edit: upon further consideration, i take back the parts about the shearing-off of bits. maybe the outer extremeties, feet/hands, provided they're extended at time of impact.

the way to look at this problem is to worry less about the surface area of the cylindar, but rather to pay attention to the transfer of force. calculations pending.

edit2:
http://www.giwersworld.org/israel/watermelon.phtml

[Derfud]

I would assume that it would cut right through them, cleanly? I'm not too sure. A foot long tube travelling at 4900 kph has alot of momentum for a human body to stop outright. Depending on where it hit them it could have varying effects. Midsection I would say they are atleast cut in half. Glancing their arm would probably knock them down with a lower risk or losing limbs. Hit in the leg, would probably take a good chunk of their leg, or possibly body off.

[Baneblade]

At mach 4 you could survive depending on how it enters and what it hits, but you will have a hole in you.

People have been skewered before, all the mach 4 part does is make it cleaner.

[Sputty]

It's about half as destructive as me in sex

[Ivan]

Originally Posted by Sobekeus

At mach 4 you could survive depending on how it enters and what it hits, but you will have a hole in you.

People have been skewered before, all the mach 4 part does is make it cleaner.

But the thing is 3" around correct? That's bound to hit something vital.

[Baneblade]

You would be surprised the things people get impaled by. If anything the burn from the friction would cauterize the wound before you knew you had it.

[martyr]

front sfc area: 7.068 ft�
mass: 15,408kg

using my altitude and temperature (sound at 346m/s), i put mach at 1,385m/s (3100mph).

speed: 1385m/s
kinetic energy: 14778005400 N

now dividing that out across the surface of this thing, we see that the pressure it would apply will be a measly...
665,675,918N/m�

for comparison's sake, a .50BMG round (far larger than the one used in the watermelon demonstration) sports 600,909 N/m�
but that force will be applied only over a surface area of 0.0005067m�
(that's a standard 688gr bullet at 2910f/s)


in conclusion, you're all aware that a .50bmg round will happily obliterate any single appendage or at least 1/3 of the trunk of a human body.

this impact you're proposing packs about 11x more energy.
the forces applied to the body at and during impact are going to be astronomical. running these numbers down has solidified my assertion that the victim here will be largely vaporized and atomized by this impact. if anything's left over, it's because it simply fell off before the impact forces propagated through that region of the body. eg, a shoe.

the bullet demonstrated on the watermelon, by the way, runs at about 119,703N/m�

the problem my initial "shearing off" assessment was that i neglected a critical aspect of high-velocity projectile damage (as i currently only have low-velocity projectile weapons, it doesn't occur to me as easily).
at such high speeds, you'll find more than crushing and cavitation, as the impact generates significant and damaging shock waves through the victim's body.

this is a cutaway of the path of a .38 round through clay:

there's no reference on the image, but the caption indicates that the cavity is approximately 3" in diameter - obviously far larger than that of the bullet itself. this is a result of tumbling and cavitation, but shock waves haven't played a factor here, since .38 is a slower, sub-sonic round.

a 7.62x5? round can easily generate shock waves with pressures up around 200atm while passing through - that's 2,066,000kgf/m�


sources:
http://www.mesteel.com/info/conversion.htm (steel data)
http://www.firearmexpertwitness.com/...s/calcnrg.html (.50 comparison)

[ChronoSphere]

LoL, I had done about half the calcs before I noticed Martyr had already calcd it all out. He is correct, there isn't going to be much left.

Put it this way: Yes, the object is small compared to the target, but the massive amount of energy is going to make a major difference. Example? A sabot round from a tank, yes small, yes non explosive, but so damn fast that it can incinerate a tank, even with armor. It's all about the kinetic energy.

[Spee]

Thanks all. Just needed to know how to describe the end of my PC's as a Rail gun sniper owns them all from around 1/2 a mile away.