h a l f b a k e r y"My only concern is that it wouldn't work, which I see as a problem."
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Consider the hero who must jump from an incapacitated plane at great height, because it is going to blow up,or crash, or has monsters on board or all 3. The hero has no parachute. How to avoid a hard impact?
Some machine guns must be mounted on a vehicle or otherwise fixed because the recoil produced
is so great it would throw a person to the ground. I propose that the hero could grab two such large caliber weapons, or perhaps one of those Vulcan quad-guns on his way out of the plane. He would allow himself to reach terminal velocity. Then as he neared the earth, he would begin firing both guns straight down, ideally into massed crowds of monsters. Could the recoil slow his descent enough to allow him to hand on his feet, unharmed? I assert that it could, and so be a useful technique for an action hero.
If this was in a Vin Diesel movie already I apologize. If it was not, then I would like compensation in the form of a bit part in the movie where it will appear.
FN MAG
http://en.wikipedia.org/wiki/FN_MAG
The GPMG. Ah, bless ... [8th of 7, Apr 08 2010]
GAU-8 avenger
http://en.wikipedia...AU-8_Avenger#Recoil
10,000 pounds of recoil [bungston, Apr 08 2010]
Wikipedia: Metal Storm
http://en.wikipedia.org/wiki/Metal_Storm
Weapons capable of highest rates of fire. [rcarty, Apr 09 2010]
It works, apparently
https://www.youtube...watch?v=EK2eV6KEgko
[MaxwellBuchanan, Jan 01 2017]
[link]
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Sorry to disappoint you, [bungs]. A GPMG (L5) firing 7.62mm NATO ammunition pointed vertically down does not produce enough thrust to lift its own weight. Yes, there is recoil, but not enough. And the GPMG is fairly light, a mere 12Kg. |
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Practical tests have also shown that an experienced paratrooper* equipped with an unloaded GPMG can exit a C-130 and, after automatic chute deployment, have sufficent time to engage the belt, cock the weapon and deliver acceptably accurate suppressive fire. The use of the weapon does not have any noticeable effect on the paratrooper's rate of descent. |
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*Note: These people are completely insane, so no meaningful conclusions can be inferred from their behaviour. |
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Also......this won't work in a movie, because the audience
won't understand why the guy is plummeting to earth,
shooting straight down, and comes to a gentle halt. You'd
have to have explanatory subtitles. |
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Nice idea, though. I guess you could design something
with sufficient recoil to do this. All you need is that the
total mass x velocity of the bullets is greater than the
total mass x velocity of the falling person. (This assumes
that all the bullets are fired in such rapid succession that
the faller does not gain any additional downwardth motion
between shots.) |
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I guess a typical bullet weighs 10 grams, and travels at
1000m/s. It would therefore slow a 100kg falling person by
0.1m/s. |
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Terminal velocity for a person is something like 50m/s, so
they'd have to fire about 500 such bullets in very rapid
succession to come to rest. |
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A GPMG can fire at 1000 - 1200 rounds per minute, but the belts are much shorter than that - maybe 300 rounds. And you have to add the mass of the unfired ammunition to the overall mass to be decelerated. It's a second-order differential equation, albeit a well-documented and soluble one. |
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As to terminal velocity, that's for a human falling chest-down with outspread arms and legs. Falling feet first, higher descent velocities are (briefly) attainable. |
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OK so the 50 monsters all fire upwards each with two big machine guns in each of its 4 arms, and the bullets all ricochet off out hero's oversized steel-soled boots. Would that work? |
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Maybe ... what size boots do you take, [pom] ? |
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//1000 - 1200 rounds per minute// |
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So, this would take 30 seconds to arrest the faller. However,
that ignores the effect of gravity *during* those 30 seconds,
and in reality there will be no significant slowing. (As for the
mass of the unfired bullets, yes, but that's only going to be a
few kg). |
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Best option would be for something that can fire, say, fifty
100gram bullets. |
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// the mass of the unfired bullets, ... only going to be a few kg // |
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HAH ! Plus the steel box they come in. No problem then, Mister Big Biceps, you're patently highly experienced in the specialised area of lugging SAA around in bulk. |
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(We are only saying this to keep you distracted so that [MikeD] can sneak up behind you, nd give you a right ding alongside the earhole, which you deserve). |
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That was a cartoon, [21Quest]. It's not like the News, or the Weather, or Star Trek. It's not actually real. |
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I linked this Avenger. 10,000 pounds of recoil seems like a fair bit. The wikipedia article comments that the thing slows its plane down slightly when firing. I do not have the calculus to determine if I strapped this thing on with a harness whether I could use it as a rocket pack. |
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This idea accurately predicts the future of combat. The days of coordinated attacks, with discriminate shooting are soon to be over. It's very likely that in the near future battles will be fought by a single vehicle like a helicopter that propels itself simply by spraying bullets everywhere. |
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/the audience won't understand why the guy is plummeting to earth, shooting straight down, and comes to a gentle halt/ |
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Thinking more about not whether this is possible (as it clearly is) but how the movie will make clear what is going on. I think the protagonist must not only slow but reverse course on nearing the ground (possibly because he noted massed monsters) and instead go upwards and laterally to land atop a handy building. The gun could then be used for a series of jumps building to building until he exhausted the ammo. |
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An enormously long belt of ammo falling behind him might be useful but it would continue to the ground when he reversed course and there get grabbed by a monster, using it to jerk the gun from the hand of the flying hero. |
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A fine sight gag would be for the (sentient) monster to turn the gun around and point it at the hero, but on firing the gun drives the monster downwards thru the surface it is standing on. |
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SyFy channel I hope you are collecting these gleaming gems. |
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<drops [bung]'s chute on scales> |
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<returns with pallet truck loaded with liquorice bootlaces> |
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<flurry of surreptitious activity> |
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<exits loft stage right whistling cheerfully, with empty pallet truck and armful of severed shroud lines> |
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This whole firing-guns-downward thing in order to slow a descent was done in a documentary I saw about a group of technical innovators. I think they were called "the A-Team", and they showed that a tank could be brought to a safe descent by firing artillery shells downward. |
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One hero falling from plane, one very long belt of.50 calibre, and that phenomenon like curtain beads string recoiling back.. |
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A quick perusal of Youtube finds Max correct about the A team. And my horror: did I somehow borrow this concept from the movie? But redemption: this idea was posted 2 months before the movie came out. |
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They must have moved very fast to film it and add it in. |
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