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Death by Shockwave

  1. Nov 28, 2007 #1
    I'm not in the medical field and it has been a long time since my college physics courses so I turn to you folks for a possible answer and further explanation. It has been brought up on another forum concerning naval battles in the age of sail about the phenomena of sailors being killed or injured by cannon shot passing close to, but not striking, an individual. I presume this was due to the supersonic shock wave (1130 ft/sec) of the projectile hitting the individual. We're talking about Nelsonian era battles (1800's) with solid, non-explosive, shot of 18, 24, or 32 pound cannon balls and the victim at least 50 yards from the muzzle blast of the cannon. Does anyone have further knowledge of this effect? How far out from the cannon ball would the wave project and would it be sufficient to cause blunt force trauma to internal organs?
     
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  3. Nov 28, 2007 #2

    stewartcs

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  4. Nov 28, 2007 #3

    Integral

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    I find it hard to believe that Napoleonic era cannons generated that much of a shock wave. Consider that that the usual practice was to "skip" the cannonball across the battle field. The projectile may have bounced off the ground once or twice before reaching the opposing forces. They did this simply because the balls did no good if they were more then 2m off the ground. They had to use a low angle trajectory to keep the ball low.

    Several factors indicate a low muzzle velocity. The balls themselves were not precise enough, the cannon barrels were not precise enough, the powder was not good enough.

    I have read extensively about 17th and 18th century warfare and have never encountered such a claim. I remain very skeptical and would like to know about the source of this story.


    To compare the guns on an Iowa class battleship with Napoleonic era cannon is to compare a horse and buggy to a Ferrari.
     
  5. Nov 28, 2007 #4

    Chris Hillman

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    The photograph posted by stewartcs illustrates the 16''/50 Mark 7 rifled cannon mounted on U.S.S. Wisconsin. From a naval gunnery fansite and this WP article, these fire the Mark 8 armour piercing shell weighing 2,700 pounds, with a muzzle velocity of 2690 ft/s. The black sleeves (called Blast Bags) visible in the picture are designed to shield the gun crew from the blast effects, and indeed the entire deck had to be cleared before firing to avoid serious injury to crew members. (In Movietone newsfootage from WWII, you can hear a warning klaxon sounding shortly before firing large caliber naval cannon, similar to common practice in mining operations.)

    But as Integral said, this is a completely different type of gun from Napoleonic War era naval cannon! From a H.M.S. Victory fansite, the 32 pounder cannon achieved a muzzle velocity of about 1600 ft/s. This page also says that on British ships, which used shorter cannon than French vessels, "the most common injury to gun crews was abdominal rupture" (from the blast of their own gun), and I recall reading that in some published accounts. I am not sure about possible shock wave effects from a cannon ball fired at close range passing very close to a person, but a contemporary account of a death "without a visible mark" on the rebel side, of a person almost struck by a cannonball fired by the British at the Battle of Bunker Hill, suggests this might have been possible.

    Hmm... WWII shell about 80 times as massive as cannon ball, and ratio of kinetic energy as projectile leaves muzzle something like 236. Using nonrelativistic theory :wink:

    [EDIT: warning! Just discovered there is a controversy over the notion of hydrostatic shock, and that biomedical companies selling lithotriptor devices have a huge financial stake in pushing the naysaying side, say by hiring a PR firm willing to engage in forum shilling. I did spot a misstatement in the WP article which suggests an attempt to mislead. Not that I think that's what's going on here, but it illustrates the dangers in taking anything you read on the web at face value. 1oldman, no offense, I hope.]
     
    Last edited: Nov 29, 2007
  6. Nov 28, 2007 #5

    Integral

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    Chris,
    It also occured to me that the gun crews and friendly troops would have been in more danger from such a shock wave then the enemy. I doubt that in the heat of battle that the crews did little more then step behind the muzzel before firing, needless to say I'll bet the lot of them were nearly deaf after a few months as gunners.
    Wonder what they used for hearing protection?
     
  7. Nov 28, 2007 #6

    Chris Hillman

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    It pains me to say it, but AFAIK, earplugs or nothing. And indeed many books mention that gunners tended to suffer permanent hearing loss. The human ear is a delicate organ.
     
  8. Nov 28, 2007 #7

    LURCH

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    Also, we must be clear that the blast wave seen in the photo is from the muzzle of the cannon, not from the projectile. If Chris's datum is correct, a 32-lb ball would be travelling 1600 ft/s, just a tad over 1000 mph, right? That's a very small object going less than Mach 2; I don't think it killed anybody with its sonic boom. However, (speaking of hydrostatic shock), maybe these stories are from people in the water. A cannon ball striking water at high speed could do all kinds of damage to a person emersed in that water. Shockwave would hit like a sledgehammer.
     
  9. Nov 28, 2007 #8

    Chris Hillman

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    Agreed, water is basically incompressible while air is compressible. For example, many books mention the effect of depth charges exploding near survivors from a torpedoed ship who were floating in the water. Not nice. However, as I understand the OP's question (after several rereadings), he was asking about alleged muzzle blast effects on the gun crew, not people in the water. In Napoleonic times, sailors who went into the water quickly drowned, BTW, since as many sources attest, most of them were unable to swim.

    Wow! This is getting grim--- let's discuss something cheerful, like the prospect of destroying the universe with a gravitational wave. Which, you know, you wouldn't see coming :wink:
     
    Last edited: Nov 28, 2007
  10. Nov 28, 2007 #9
    Stewartics, thanks for the reply but that's way overkill to the question at hand.

    Integral, the documented acounts I'm refering to are in naval battles, and after about 1800 when cannon boring technology had improved, the muzzle velocities would have been in the 1000 ft/sec to 1600 ft/sec. The speed of sound at sea level is 1130 ft/sec. A 32 pound cannon ball is roughly 5.5 inches in diameter.

    Chris Hillman, thanks for the reply. Here what a supersonic shock wave looks like:
    http://en.wikipedia.org/wiki/Shock_wave.
    So the question is; How far out from the cannon ball would it project and could it cause blunt force trauma?
     
  11. Nov 28, 2007 #10

    Integral

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    1oldman,
    Yeah, I have realized that. In 18th century land battles the range of cannon fire was generally greater then 50yds, inside that range gun crews became easy targets. OTOH sea battles were generally fought inside of that range, it may well be that at less then 15 - 20 yds just the muzzle blast could be disabling, this may be the shock wave causing injury, more then simple passage of a cannonball.
     
  12. Nov 28, 2007 #11
    Integral, I don't really think so. The one instance that I can think of, the individual was standing with others on the quarterdeck and keeled over dead at the passing of a cannon ball. Non of the others were affected.
     
  13. Nov 28, 2007 #12

    Integral

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    Interesting, of course given the state of pathogy of the day, one has to wonder if that is really what killed him. There were so many hazards, one can only speculate.
     
  14. Nov 28, 2007 #13
    Well, that's true but I'm trying to get beyond the speculation. I can do plenty of that on my own.:smile:
     
  15. Nov 28, 2007 #14
    As others have pointed out, it is highly unlikely that the pressure wave killed them. That said, there is a common battlefield phenomena that might explain some of these deaths. Too wit, the pressure wave surrounding a projectile is a small, but powerfull, shockwave. In an environment like, say, the human squash, the danger is not the power of the wave itself, but the cavitation it causes. Simply put, if a big enough shockwave passes through a human skull, whether by massive projectile moving relativly slowly at a distance, or a high speed bullet missing by millimeters, the shockwave, by nature of moving faster in some media (bone, dense grey matter etc.) than in others ( encephalic fluid, blood ) creates a discontinuity in internal pressures that leads to a cavitation of the blood vessels. As anyone with any experience in hydrostatics can tell you cavitation in a pressure system is a bad thing...lol. It leads immediately to unpredictable pressure spikes in the system. In a system such as blood flow in the brain, I believe it is safe to say this is a bad thing.

    In short, I think the shockwave itself is of small physical impact, but the cavitation it can cause might lead to sudden and perhaps life ending stroke, without leaving a mark on the cadaver as to the cause.
     
  16. Nov 29, 2007 #15
    Wysard, thank you, that is one of the best explanations I've recieved on this topic so far. I actually have the question out on several forums, including military medical, and so far I haven't had a whole lot of interest. :approve:
     
  17. Nov 29, 2007 #16

    Chris Hillman

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    We need a new whiffle bat icon!

    I proclaim a rule: every time anyone gives a link to WP without solemnly intoning

    they get bopped with a whiffle bat.

    Wikipedia, the website anyone can edit at any time in any way they please using any "identity" they please... what does that tell you the stability and reliability of things you read or images you find at Wikipedia? To be sure, the same point is valid for many websites put up by persons who may or may not have some idea what they are talking about.

    Better say speculation, not explanation! More or less wild speculation: that's all you're getting from anyone here, including me, as I hope you know!

    It's quite possible that no-one really knows a scientifically sound answer to your question, because no-one in the 21st century has conducted a really careful scientific investigation of the effects of early 19th century artillery.
     
    Last edited: Nov 29, 2007
  18. Nov 29, 2007 #17
  19. Nov 29, 2007 #18
    I just spoke to one of the elders here at the Army Research Lab.

    He says that he has never heard of any case of a projectile whether it be from cannon, tank, rpg, mortar, or naval gun, etc. killing or injuring personnel solely due to it's shockwave.
     
  20. Nov 30, 2007 #19
    Thought you guys might find this interesting, especially the part where Dr Frysinger gets knocked on his keister by the sonic shock wave. :rofl:
     
  21. Nov 30, 2007 #20
    Seycyrus, most of my military sources say the same thing so I think this is probably just a myth out of the history books.
     
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