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Bullet Catching

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A set of machine guns at the base of a very high cliff, at the top of which is a scenic viewing area. The machine guns fire all at once, and being set at an almost 90 degree angle, fire up the cliff, reach their maximum height about ten feet above the viewing area, then clatter uselessly to the ground. Tourists can visit, claim to have caught a bullet fired straight from a gun, and be technically correct in that misleading statement.

Multiple machine guns are used to make it more likely that the bullets will make it, and you prolly can't do this on a windy day.

notmarkflynn, Sep 08 2007

Handy-dandy diagram http://i37.photobuc...tmarkflynn/GUNS.jpg
LOOK I CAN DRAW! [notmarkflynn, Sep 08 2007]

THE SECRET OF THE BULLET CATCH http://www.foreworks.com/bullet2.html
[nuclear hobo, Sep 09 2007]

Bullets fired up http://en.wikipedia...Bullets_Fired_Up.22
[shapu, Sep 10 2007]

A Cannon using bullets coil_20gun_20canon
Kinda Similar, but more a shameless plug. [bleh, Sep 10 2007]

Why this is a risky plan http://www.youtube....watch?v=0ABGIJwiGBc
Guy just misses his date with St. Pete [elhigh, Sep 12 2007]

[link]






       A bullit fired from a gun up in the air and you try to catch it? Better have the ambulance standing by. Objects falling through air to earth come down at about 200 kph, if I'm not mistaken.
zeno, Sep 08 2007
  

       I changed it to make it a bit clearer. The maximum height the bullets reach is only a bit more than the height of the cliff, so they're not going too fast when they hit the ground.
notmarkflynn, Sep 08 2007
  

       Cool idea. Unless of course you are Chuck Norris.
the dog's breakfast, Sep 08 2007
  

       I know this is the Halfbakery, but isn't this something not so wise to do?
normzone, Sep 08 2007
  

       //Objects falling through air to earth come down at about 200 kph, if I'm not mistaken//
But only if they fall back to their starting point. This idea makes the bullets fall about three metres (ten feet for the metrically-challenged), so they'll barely be going faster than walking pace. [+]
AbsintheWithoutLeave, Sep 08 2007
  

       You'll probably want a very low tracer ratio too.
AbsintheWithoutLeave, Sep 08 2007
  

       <nemesis>No, notmarkflynn, you cannot draw. You may also wish to write fewer ideas incorporating weapons, given that they will inevitably bring about your demise once I get to them.</nemesis>
dbmag9, Sep 08 2007
  

       //Tourists can visit, claim to have caught a bullet fired straight from a gun//
You could even catch them in your teeth, assuming you don't stumble over the edge in the process.
ldischler, Sep 08 2007
  

       Now bungee bullet bobbing would be fun.   

       Right, so no danger whatsoever? hmm-
zeno, Sep 09 2007
  

       You know how far a buttet shot straight up in the air would travel? well lets just say that there aren't many tourist spots thats high.
shinobi, Sep 09 2007
  

       Slugs out of a shotgun might work... much shorter range, so the catching platform wouldn't need to be quite so high. Plus, slugs are pretty big, which would make them easier to catch.
gus_webb, Sep 09 2007
  

       Well then how about sub-machine guns? Or just bullets with less powder.
notmarkflynn, Sep 09 2007
  

       Sure, the tourists would be perfectly safe, but the operators...
croissantz, Sep 09 2007
  

       I was picturing them firing it remotely from a bunker a short distance away. Also, warning lights would flash and all that.
notmarkflynn, Sep 09 2007
  

       You could adapt this to use ninja stars, and have the tourists try to catch them with chopsticks. I pity the operators when the tourists aren't up to scratch though. [+]
jtp, Sep 09 2007
  

       Mythbusters tested something similar to this.   

       Bullets fired directly straight up, or reasonably directy straight up, reach a velocity of zero and then begin to tumble. Thus, they come back to earth at a much-less-than-original velocity, owing to their lack of aerodynamics.   

       Bullets fired at an angle will maintain their ballistic trajectory as they arc downward, due to their conserved forward travel. Thus, they will kill people.   

       This idea is foolish, but not fatally so - more bruisingly so.   

       [+] for the art.
shapu, Sep 10 2007
  

       /Bullets fired at an angle will maintain their ballistic trajectory as they arc downward, due to their conserved forward travel. Thus, they will kill people./   

       Within the context of guns being fired upwards at steep angles, there are some generalisations made here that don't stand up to mathematical scrutiny.
Texticle, Sep 10 2007
  

       "Hey kids! Let's try this in reverse"
skinflaps, Sep 10 2007
  

       Um, the bullets, if fired from a rifled barrel, are still going to be spinning/rotating when they reach their apex. I can't do the math to figure out how many RPM will be happening, but I'd not grab the damn things with my bare hands.
baconbrain, Sep 10 2007
  

       Just how high of a cliff are you proposing? Oh wait, I actually see the solution to that problem: less gunpowder for less velocity.
Noexit, Sep 10 2007
  

       [baconbrain] The bottom of the bullet is flat. While they will still be rotating, the flat bottom will exhibit FAR more air restistance than the pointed front. If they are fired STRAIGHT up, then when they reach zero velocity, they will begin to come down, flat end first, and begin to tumble. Thus, there is no ballistic concern - it's just a few dozen grams of lead or steel falling from great height. It will hurt, yes, but it will not kill.   

       I am supplying a link.   

       EDIT: [Texticle]: I am not sure how bullets fired forward, at a non-90-degree angle, will lose their ballistic properties. I vaguely recall that battleships used to do that sort of thing all the time on a grander scale.
shapu, Sep 10 2007
  

       hi, [notmark]! i didn't know you were a halfbaker! i gave this idea a bun on the merits that even stupid people should have fun. +
k_sra, Sep 10 2007
  

       // The bottom of the bullet is flat. While they will still be rotating, the flat bottom will exhibit FAR more air restistance than the pointed front//
But the now pointed rear end of the bullet will create far less turbulence behind the bullet, and hence less drag, and so therefore, paradoxically, the bullet may actually go further.
coprocephalous, Sep 10 2007
  

       Haha. Awesome idea, but yes, if you angle it, it will still be lethal. Sorry mate :P
Runtman, Sep 10 2007
  

       //if you angle it, it will still be lethal.//
How so, [runtman]?
AbsintheWithoutLeave, Sep 10 2007
  

       lets run the math. (i'll probably screw it up, so check me if you're bored.)   

       say we use a sub sonic pistol with a muzzle velocity of 330 m/s   

       if we fire it nearly straight up at a 89 deg angle it will travel to a height of   

       max H @ Vy= 0   

       Vy= Voy + At; where Voy is the initial velocity up and a is -9.8m/s, and t is time so...   

       t= (Voy/A) = (330m/s*sin(89))/(9.8m/s^2) = 33.66seconds ~33 s   

       the height at 33 seconds is y=Yo + Voyt - 1/2 At^2= 0+ 330(sin(89))(m/s)(33s) - .5(9.8m/s^2)*(33^2)=~ 5554 meters (edited I left off the square of the time in my calculator)   

       at that point it will temporarily have a vertical velocity of zero.   

       It will have traveled   

       x= Xo + Voxt -1/2At^2 = 0+ 330*cos(89)(33)- 0 = 190 m along the horizontal. (edit forgot t)   

       If the platform (*really high platform!) was 7 meters below the peak,   

       Y= 7m = Yo+ Voy*t+ At^2 = 0+0+9.8t^2   

       t= 7/9.8^2= .07s   

       V= Voyt+ At = 0+9.8*.07= .714 m/s =   

       very catchable [+]   

       Of course this assumes an ideal frictionless system with no wind or outside forces.
bleh, Sep 10 2007
  

       I think just catching a falling bullet would not be cool enough. The very top of its trajectory should be at chest-height. You'd see the bullet reach the top of its flight, slow to a standstill for a fraction of a second (ok, an infinitesimal fraction of a second) and could be plucked out of the air.
MaxwellBuchanan, Sep 10 2007
  

       ok, then a platform at 215.5 m (assuming chest height to be around 1.5m.)   

       alternatively, if the path terminated its vertical velocity 1 meter above the user's head, the bullet will only be going 1 m/s up when passing the catcher's head allowing the catcher the snag it while still on the up leg of its travel. I do suggest fluorescent bullets though.   

       p.s. This would make for a spectacular suicide. Jumping off a cliff onto machine guns rapidly firing fluorescent bullets.
bleh, Sep 10 2007
  

       Classy.
notmarkflynn, Sep 10 2007
  

       <ahem>   

       Vf^2 = Vi^2 +2*A*D
Vi = 330m/s (1 degree off vertical is a negligile difference)
Vf = 0
A = 9.81m/s^2
  

       ~ D = 5550m   

       sadly your answer is probably closer to reality <not intentionally> because we have conveniently ignored air resistance which is *by far* the greatest factor affecting the vertical distance a bullet will reach.   

       to everyone that thinks a bullet cannot return base-first. You are conveniently ignoring gyroscopic stabilising forces from the spinning bullet. Under the right conditions, they can return base first.   

       Personally, I like the idea. I suggest air cannons (much more control of velocity and repeatability shot-shot) and you could be launching catcher-friendly projectiles - 1" or more bore.
Custardguts, Sep 11 2007
  

       damnit. I knew I'd screw up the maths. I still dont see where though. (edit: now I do.)   

       Ke1+ Pe1= Ke2 + Pe2   

       assuming bullet weight is 1 (something)   

       Ke1= 1/2 mv^2= 1/2(330^2)   

       Pe1= 0   

       Ke2= 0   

       Pe2= mgh= g(h)   

       gh= 1/2* 330^2 = 54450   

       h= ~ 5556   

       energy methods confirm your results. do you see a glaring error in my calculations?   

       edit: I found the errors in my initial calculations. anno has been edited accordingly.
bleh, Sep 11 2007
  

       //do you see a glaring error in my calculations?//   

       <wonders if 'kepekepeghh' is a word>
k_sra, Sep 11 2007
  

       //wonders if 'kepekepeghh' is a word//   

       It may not be, but its fun to say. :)
bleh, Sep 11 2007
  

       You could quite easily measure the muzzle velocity of every round leaving the barrel with timing coils built into the flash eliminator.
This information could then be relayed to hydraulic jacks under the catching platform, to raise or lower it the appropriate amount.
AbsintheWithoutLeave, Sep 11 2007
  

       Plexiglass umbrellas should adequately protect ground level personnel.
GutPunchLullabies, Sep 11 2007
  

       //to everyone that thinks a bullet cannot return base-first. You are conveniently ignoring gyroscopic stabilising forces from the spinning bullet. Under the right conditions, they can return base first.//   

       Thank you, [Custardguts]. That spinning is what I was referring to earlier. It is something that everyone seems to ignore, in almost all cases,for some reason.   

       To clarify and to make obvious, the rifling of a rifle barrel makes the bullet spin on its long axis, like a pencil rolled between your hands. This is for stability, supposedly, but more properly for accuracy.   

       In my earlier annotation, I was pointing out that while a cliff-top RIFLE bullet may pause in front of the eager tourist as a result of perfect aiming and power, it's still going to be spinning like a rabid top.
baconbrain, Sep 11 2007
  

       <Assumed it wouldn't actually be a problem, checked Wikipedia>For example, the .220 Swift, at 4,000 ft/s (1200 m/s), spins the 50 grain (3 g) bullet at 240,000 rpm.<AIWABAPCW>   

       Hard to catch.
GutPunchLullabies, Sep 11 2007
  

       OOoooooh! You could point the base of the bullet, and then it could land on the observation deck, spinning and spinning like a top until it finally fell over!
GutPunchLullabies, Sep 11 2007
  

       Thanks, [GP].   

       Mind, I have no problem with the basic premise of the idea. Catching or stopping things at the top of a trajectory is a neat trick.
baconbrain, Sep 11 2007
  

       //And before you ask, no, I don't know what the muzzle velocity of a small yappy type dog would be.//   

       using an 8 pound dog, 800 lbs of weight, a 10 ft lever fulcrumed at 2 ft from the weight, with a 7 foot rope going to the sling- about 60 f/s
bleh, Sep 11 2007
  

       The cliff idea is risky as hell. I've added a link to a youtube video of a guy shooting at a solid - i.e. not backstop putty - target about 200 yards away, and his shooting day comes to an abrupt end.   

       Shooting with a weak powder charge to the top of a cliff is a neat idea. The guns have to be automatically controlled or fired from within a bunker, because I can't think of anyone who would want to be under all the shots that came back down on top of them.
elhigh, Sep 12 2007
  
      
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