What-If 0021: "Machine Gun Jetpack"

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project2051
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Re: What-If 0021: Machine Gun Jetpack

Postby project2051 » Tue Nov 20, 2012 7:30 pm UTC

gmalivuk wrote:Considering 1W lasers have serious accidental blinding potential, I'd say it happens too fast to close your eyes or move out of the beam. But of course going without eye protection into a fight where you know people will be shooting lasers is a seriously stupid thing to do.

My Eyes! The goggles do noth.... wait I think they actually worked this time!

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Re: What-If 0021: Machine Gun Jetpack

Postby neremanth » Tue Nov 20, 2012 7:35 pm UTC

gmalivuk wrote:Considering 1W lasers have serious accidental blinding potential, I'd say it happens too fast to close your eyes or move out of the beam. But of course going without eye protection into a fight where you know people will be shooting lasers is a seriously stupid thing to do.

That's a good point. Although I wonder if it's possible to construct any kind of eye protection that simultaneously provides enough shielding to prevent a battle-strength laser from blinding you, and still lets enough light through that you can see where the other combatants actually are. Maybe opaque goggles with a small hole in the middle? You'd still be able to be blinded if the person firing at you managed to hit the hole and get the angle right, but it'd be harder. You'd be giving up your peripheral vision of course; but then if everyone's wearing similar goggles at least you're not at a disadvantage compared to them. Or I guess you could have completely opaque goggles with cameras on the outside and video displays on the inside - although you still have to protect the cameras then which seems to me to present the same problem as protecting the eyes.

On the other hand, I know very little about physics, so maybe it turns out that it's like glass windows protecting you from sunburn yet still allowing you to see out, and there's some kind of material that will block the laser beam but let in normal light?

ahammel wrote:Lasers would also be presumably be better weapons in a space combat setting where if you get a hole of any size in your space car or your space clothes you are having a bad problem and it may be a bad thing that you are in space today.

:lol:

That actually sounds like a much more sensible strategy. I shall have to remember that if I'm ever in a laser battle in space: aim for the enemy's oxygen tank. (Hey, I guess it'd work for deep-sea laser battles too, right? Wow, this tip is so versatile!)

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Re: What-If 0021: Machine Gun Jetpack

Postby RuneWarden » Tue Nov 20, 2012 8:48 pm UTC

My god, how has nobody brought up Cave Story yet? LVL 3 Machine Gun + Turbocharge = Infinite flight of DOOM.

(If you don't know, the machine gun at LVL 3, the max, will propel you up if you fire down. The turbocharge speeeds up ammo regen enough that pulsing the machine gun will give you more ammo than you use.)

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Re: What-If 0021: Machine Gun Jetpack

Postby Rattler » Tue Nov 20, 2012 8:54 pm UTC

Just in case no-one else mentioned it, this idea is the basis of 'King David's Spaceship', a novel published in 1980 by Jerry Pournelle. The ship of the title, intended to exploit a legal loophole in the laws of a conquering Imperium, is propelled by numerous rapid-fire machine guns and manages to get into a low orbit before running out of ammunition.

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Re: What-If 0021: Machine Gun Jetpack

Postby JJH » Tue Nov 20, 2012 8:55 pm UTC

Would a jet-pack AK still need the barrel or is it just dead weight? I assume you’d need at least a bit to properly accelerate the bullet.

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Re: What-If 0021: Machine Gun Jetpack

Postby Barstro » Tue Nov 20, 2012 9:12 pm UTC

neremanth wrote:I wonder if it's possible to construct any kind of eye protection that simultaneously provides enough shielding to prevent a battle-strength laser from blinding you, and still lets enough light through that you can see where the other combatants actually are. Maybe opaque goggles with a small hole in the middle? You'd still be able to be blinded if the person firing at you managed to hit the hole and get the angle right, but it'd be harder. You'd be giving up your peripheral vision of course; but then if everyone's wearing similar goggles at least you're not at a disadvantage compared to them. Or I guess you could have completely opaque goggles with cameras on the outside and video displays on the inside - although you still have to protect the cameras then which seems to me to present the same problem as protecting the eyes.


In this hypothetical world, I think your best bet would be a lens that blocks only that particular laser's wavelength. Much like the small goggles you wear in a tanning bed; some of the lights don't even look like they are turned on because they produce only UV and the goggles block all UV, but you can see everything else just fine (with a reddish hue, for my pair).

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Re: What-If 0021: Machine Gun Jetpack

Postby nyrath » Tue Nov 20, 2012 9:49 pm UTC

atomfullerene wrote:It's like the Kzinti lesson in reverse....the better a weapon is, the more efficient a reaction drive it makes...


Well spotted.
However, TV Troupes suggest that this is not an example of the Kzinti lesson so much as it is an example of an "exhaustized weapon". Go to the tvtropes.org website and look up Weaponized Exhaust.

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Re: What-If 0021: Machine Gun Jetpack

Postby airdrik » Tue Nov 20, 2012 10:56 pm UTC

JJH wrote:Would a jet-pack AK still need the barrel or is it just dead weight? I assume you’d need at least a bit to properly accelerate the bullet.

Quite the inverse, actually - the length of the barrel determines how much the bullet accelerates, so sawing off the barrel will actually decrease the resultant acceleration.
So, if you want to alter the barrel to increase the amount of acceleration you need to make it longer. As for how much longer and still be practical, I imagine that there is a length where the pressure from the expanding gases behind the bullet reaches the pressure from the (rapidly compressing) air in front of the bullet, at which point there is no more net gain for increasing the length of the barrel.

On the other hand, there probably are other parts of the AK that could be discarded as dead weight - like the handle and the arm rest.

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Re: What-If 0021: Machine Gun Jetpack

Postby gmalivuk » Tue Nov 20, 2012 11:02 pm UTC

Barstro wrote:
neremanth wrote:I wonder if it's possible to construct any kind of eye protection that simultaneously provides enough shielding to prevent a battle-strength laser from blinding you, and still lets enough light through that you can see where the other combatants actually are. Maybe opaque goggles with a small hole in the middle? You'd still be able to be blinded if the person firing at you managed to hit the hole and get the angle right, but it'd be harder. You'd be giving up your peripheral vision of course; but then if everyone's wearing similar goggles at least you're not at a disadvantage compared to them. Or I guess you could have completely opaque goggles with cameras on the outside and video displays on the inside - although you still have to protect the cameras then which seems to me to present the same problem as protecting the eyes.
In this hypothetical world, I think your best bet would be a lens that blocks only that particular laser's wavelength. Much like the small goggles you wear in a tanning bed; some of the lights don't even look like they are turned on because they produce only UV and the goggles block all UV, but you can see everything else just fine (with a reddish hue, for my pair).
Yeah, while you won't be able to see full-color images of everything, it's not terribly difficult to make goggles that block particular colors. Of course, you'd still run into problems if the enemy, likely knowing a few things about the state of goggle-making technology, used lasers of a few different colors.
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Re: What-If 0021: Machine Gun Jetpack

Postby ahammel » Tue Nov 20, 2012 11:05 pm UTC

gmalivuk wrote:Yeah, while you won't be able to see full-color images of everything, it's not terribly difficult to make goggles that block particular colors. Of course, you'd still run into problems if the enemy, likely knowing a few things about the state of goggle-making technology, used lasers of a few different colors.
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Re: What-If 0021: Machine Gun Jetpack

Postby bmonk » Tue Nov 20, 2012 11:51 pm UTC

atomfullerene wrote:It's like the Kzinti lesson in reverse....the better a weapon is, the more efficient a reaction drive it makes...

Get out of my head!
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Re: What-If 0021: Machine Gun Jetpack

Postby bmonk » Tue Nov 20, 2012 11:54 pm UTC

Whizbang wrote:The damage from a bullet is not always from the size of the entry point. Bullets often bounce around inside the body, ripping organs to shreds. A "through and through" is usually not very serious, unless it is through an organ. A laser would always be a through and through, and so require more accuracy. You'd always have to hit the heart, lungs, or head. A gut shot would be messy, and probably lead to death eventually, but would give the victim plenty of time (assuming they tolerate the pain) to shoot back at you.

Bullets, FTW.

Go, Firefly!
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Re: What-If 0021: Machine Gun Jetpack

Postby Trasvi » Wed Nov 21, 2012 1:16 am UTC

On the 'flying by firing guns', I submit the recent A-Team movie: http://www.youtube.com/watch?v=8ErI9SyHSEM


As for laser wounds... this is from TVTropes so take it with a truckload of salt, but I don't have a better reference atm:
Frickin Laser Beams wrote:There actually are "real lasers" in weapons research and development — like the Airborne Laser and THEL. These lasers are supposed to burn through targets (like missiles) and cause their fuel/warhead to explode or their airframe to disintegrate when it hits, although this is also a continuous beam and requires some time to work. Solid-state pulsed lasers are also in development, which fire bursts of energy and are lighter than fluid-based lasers, but harder to cool. Not to mention that the heat from a powerful laser wouldn't just burn through clothing or make a neat, bloodless, pin-sized hole. There's a common misconception that laser beams cauterize wounds, but real laser wounds are every bit as bloody as knife wounds. It can also cause the water in the body to boil, expand and rip the surrounding tissues apart, much like a high velocity bullet impact. There are also electrolasers under development, which ionize the air so that electric current can be sent along the beam's path. Ironically, all of these characteristics make lasers far more effective as weapons than their portrayal in most fiction, which is in fact the main reason that the military is developing them in the first place. It's also probably the main reason we're not likely to see realistic laser weapons in children's shows.

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Re: What-If 0021: Machine Gun Jetpack

Postby thkng » Wed Nov 21, 2012 1:33 am UTC

neremanth wrote:
gmalivuk wrote:Considering 1W lasers have serious accidental blinding potential, I'd say it happens too fast to close your eyes or move out of the beam. But of course going without eye protection into a fight where you know people will be shooting lasers is a seriously stupid thing to do.

That's a good point. Although I wonder if it's possible to construct any kind of eye protection that simultaneously provides enough shielding to prevent a battle-strength laser from blinding you, and still lets enough light through that you can see where the other combatants actually are. Maybe opaque goggles with a small hole in the middle? You'd still be able to be blinded if the person firing at you managed to hit the hole and get the angle right, but it'd be harder. You'd be giving up your peripheral vision of course; but then if everyone's wearing similar goggles at least you're not at a disadvantage compared to them. Or I guess you could have completely opaque goggles with cameras on the outside and video displays on the inside - although you still have to protect the cameras then which seems to me to present the same problem as protecting the eyes.

On the other hand, I know very little about physics, so maybe it turns out that it's like glass windows protecting you from sunburn yet still allowing you to see out, and there's some kind of material that will block the laser beam but let in normal light?

ahammel wrote:Lasers would also be presumably be better weapons in a space combat setting where if you get a hole of any size in your space car or your space clothes you are having a bad problem and it may be a bad thing that you are in space today.

:lol:

That actually sounds like a much more sensible strategy. I shall have to remember that if I'm ever in a laser battle in space: aim for the enemy's oxygen tank. (Hey, I guess it'd work for deep-sea laser battles too, right? Wow, this tip is so versatile!)


If you have the technology to block the lasers, why not build an entire suite using that, making the laser completely useless. If you were having trouble seeing through them, you may as well leave only the eyes exposed so the enemy has to get a perfect shot at your eyes. Although the idea of blindfolded soldiers trying to shoot each other with lasers does seem funnier.

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Re: What-If 0021: Machine Gun Jetpack

Postby MahouShoujoMaruin » Wed Nov 21, 2012 1:45 am UTC

thkng wrote:
neremanth wrote:
gmalivuk wrote:Considering 1W lasers have serious accidental blinding potential, I'd say it happens too fast to close your eyes or move out of the beam. But of course going without eye protection into a fight where you know people will be shooting lasers is a seriously stupid thing to do.

That's a good point. Although I wonder if it's possible to construct any kind of eye protection that simultaneously provides enough shielding to prevent a battle-strength laser from blinding you, and still lets enough light through that you can see where the other combatants actually are. Maybe opaque goggles with a small hole in the middle? You'd still be able to be blinded if the person firing at you managed to hit the hole and get the angle right, but it'd be harder. You'd be giving up your peripheral vision of course; but then if everyone's wearing similar goggles at least you're not at a disadvantage compared to them. Or I guess you could have completely opaque goggles with cameras on the outside and video displays on the inside - although you still have to protect the cameras then which seems to me to present the same problem as protecting the eyes.

On the other hand, I know very little about physics, so maybe it turns out that it's like glass windows protecting you from sunburn yet still allowing you to see out, and there's some kind of material that will block the laser beam but let in normal light?

ahammel wrote:Lasers would also be presumably be better weapons in a space combat setting where if you get a hole of any size in your space car or your space clothes you are having a bad problem and it may be a bad thing that you are in space today.

:lol:

That actually sounds like a much more sensible strategy. I shall have to remember that if I'm ever in a laser battle in space: aim for the enemy's oxygen tank. (Hey, I guess it'd work for deep-sea laser battles too, right? Wow, this tip is so versatile!)


If you have the technology to block the lasers, why not build an entire suite using that, making the laser completely useless. If you were having trouble seeing through them, you may as well leave only the eyes exposed so the enemy has to get a perfect shot at your eyes. Although the idea of blindfolded soldiers trying to shoot each other with lasers does seem funnier.


I wonder if speedglass welding masks would work? The glass somehow senses the increased light and in a small fraction of a second turns the glass opaque. Not sure if it's quick enough to avoid eye damage from a high-power laser though.

http://en.wikipedia.org/wiki/Welding_helmet
Recently helmets have been developed that use an electronic LCD shutter that darkens automatically when exposed to the bright welding arc so the welder can see to work under normal ambient light while wearing the helmet. With the development of electronic auto-darkening helmets, the welder no longer has to get ready to weld and then nod their head to lower the helmet over their face. However, these electronic auto-darkening helmets are significantly more expensive.



As for weapons in space, are there any other wavelengths or ways to use electromagnetic waves as as weapon other than laser that might be effective?

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Re: What-If 0021: Machine Gun Jetpack

Postby ijuin » Wed Nov 21, 2012 1:45 am UTC

Rattler wrote:Just in case no-one else mentioned it, this idea is the basis of 'King David's Spaceship', a novel published in 1980 by Jerry Pournelle. The ship of the title, intended to exploit a legal loophole in the laws of a conquering Imperium, is propelled by numerous rapid-fire machine guns and manages to get into a low orbit before running out of ammunition.


To elaborate a bit on said legal loophole for the benefit of people who haven't read the story, basically the Empire's laws say that a society capable of spaceflight is considered advanced enough to deserve representation in their Parliament and automatic citizenship for their people when it is absorbed by the Empire, while pre-spaceflight societies are considered "primitives", and are treated as colonies. By launching a crewed orbital flight of their own construction before the annexation treaty is signed, the people of the planet in question are thus able to get proper membership in the Empire instead of being merely subjugated. It's sort of a twisted variant on Star Trek's Prime Directive, which divides societies based on whether they have achieved Warp Drive yet.

As far as the idea of the A-10's gun affecting its flight, the other problem is that the plane can only carry about a thousand rounds of ammunition--there's nowhere to mount a larger ammo drum or to feed ammunition from an externally-mounted drum into the gun. The plane will run out of ammunition before it drops below stall speed if the engines are running at full thrust.

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Re: What-If 0021: Machine Gun Jetpack

Postby Rotherian » Wed Nov 21, 2012 2:23 am UTC

thkng wrote:If you have the technology to block the lasers, why not build an entire suite using that, making the laser completely useless. If you were having trouble seeing through them, you may as well leave only the eyes exposed so the enemy has to get a perfect shot at your eyes. Although the idea of blindfolded soldiers trying to shoot each other with lasers does seem funnier.


I will admit that I could be wrong, but I would think that a suit made from material that could successfully block a weapon-grade laser would be too rigid to actually be feasible. For the helmet, the only supple area you would likely need would be the neck region (if the suit is designed to allow turning the head without turning the body - if it is not, the neck area could be rigid as well). The rest of the suit, at the very least, would need non-rigid joints or the person inside wouldn't be able to move easily,
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Re: What-If 0021: Machine Gun Jetpack

Postby JustDoug » Wed Nov 21, 2012 2:36 am UTC

LittleMikey wrote:The bit that intrigues me is the fact that the GAU-8 mounted on an A-10 produces so much recoil.

What I'd like to know is how much this can slow the plane down while it's flying. I'm guessing that the plane already lowers it's speed for a strafing run, but if the gun was fired in a sufficiently long burst would it be enough to cause the plane to loose so much speed it would stall? Or can the A-10 maintain flight even at very low speeds?

If anyone knows I'd be delighted to find out the answer!


As someone that worked on the beast... No, it won't stall. It will slow down some. The normal firing attitude is a diving run, throttled back to let the SAS stabilization system help out in maintaining aim (which is eyeballed, BTW, unless there's been a LOT more changes since I last walked the factory floor).

PIlots are universally "surprised" by the gun's performance when they make their first live firing run and let 'er rip. Early users had the benefit of two selectable firing rates, but they decided that 'puree' was all that was needed, and dropped the 'chop' setting.

There was some talk that, with enough ammunition, you might get the aircraft to stall in level flight by continuously firing the gun and throttling back some, but you'd have to carry more weight in ammo than there was total lift.

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Re: What-If 0021: Machine Gun Jetpack

Postby Mikeski » Wed Nov 21, 2012 3:01 am UTC

rmsgrey wrote:Meanwhile, back at the article, I'm not sure why the cop pulled Cueball over either - speeding, reckless endangerment, aggravated property damage, manslaughter, possession of an illegal weapon...

Thus the answer.

"Do you know why I pulled you over?"

(I can think of several reasons, but I don't know which one(s) you have in mind currently...) "No."

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Re: What-If 0021: Machine Gun Jetpack

Postby aewgliriel » Wed Nov 21, 2012 5:37 am UTC

Rattler wrote:Just in case no-one else mentioned it, this idea is the basis of 'King David's Spaceship', a novel published in 1980 by Jerry Pournelle. The ship of the title, intended to exploit a legal loophole in the laws of a conquering Imperium, is propelled by numerous rapid-fire machine guns and manages to get into a low orbit before running out of ammunition.

Rattler


The only thing I have to say about that is that Jerry Pournelle is a dick. Had to work with him a few years ago, wanted to strangle him within 15 minutes of meeting him and I had to put up with him for three days.

These threads are always so educational, though a good lot of what you guys discuss is at least a mile over my head . . .

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Re: What-If 0021: Machine Gun Jetpack

Postby J Thomas » Wed Nov 21, 2012 12:53 pm UTC

aewgliriel wrote:The only thing I have to say about that is that Jerry Pournelle is a dick. Had to work with him a few years ago, wanted to strangle him within 15 minutes of meeting him and I had to put up with him for three days.


Pournelle isn't so bad provided you always agree with him about everything.
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Re: What-If 0021: Machine Gun Jetpack

Postby jay35 » Wed Nov 21, 2012 3:59 pm UTC

Beltayn wrote:"An AK-47 clip holds 30 rounds.""

It's a magazine, not a clip.

-A magazine is an insertable container filled with rounds that can be removed, refilled, and re-used when it runs empty. An AK-47 and M-16 use magazines.
-A clip is a disposable attachment of several rounds together that simply gets ejected automatically when the last round is fired, following which you just insert a new one. There is nothing to remove or reuse. An M-1 Garand, such as was used in WW2, used clips. The clip being ejected was what made that distinctive CA-CHING noise when you ran out of ammo.

Also, there's some nominclature confusion in the article between "rounds" and "bullets". The two are not interchangable.
The bullet is just the projectile, the lead slug that is shot out of the rifle. The casing and charge, along with the bullet, all add up to being a round.

Did you also cringe when he categorized the AK as a "machine gun"? :)

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Re: What-If 0021: Machine Gun Jetpack

Postby ahammel » Wed Nov 21, 2012 4:12 pm UTC

aewgliriel wrote:The only thing I have to say about that is that Jerry Pournelle is a dick.
So I gathered from reading his books. Why did you have to work with him?
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Re: What-If 0021: Machine Gun Jetpack

Postby JeromeWest » Wed Nov 21, 2012 6:02 pm UTC

thkng wrote:If you have the technology to block the lasers, why not build an entire suite using that, making the laser completely useless. If you were having trouble seeing through them, you may as well leave only the eyes exposed so the enemy has to get a perfect shot at your eyes. Although the idea of blindfolded soldiers trying to shoot each other with lasers does seem funnier.


Or why not have the suit entirely blocked-off from the outside including the eyes, then have some kind of camera pass a visual feed through to a heads-up display. Of course, then the camera will become the point of attack for the enemy, so camouflaging the camera, randomising its location, and having multiple or replaceable cameras would become the arms race du jour. Much (all?) of this is brought up by Iain M. Banks in various novels, most notably (if my memory serves) in the big scrap at the end of Consider Phlebas.

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Re: What-If 0021: Machine Gun Jetpack

Postby Beltayn » Thu Nov 22, 2012 2:19 am UTC

jay35 wrote:
Beltayn wrote:"An AK-47 clip holds 30 rounds.""

It's a magazine, not a clip.

-A magazine is an insertable container filled with rounds that can be removed, refilled, and re-used when it runs empty. An AK-47 and M-16 use magazines.
-A clip is a disposable attachment of several rounds together that simply gets ejected automatically when the last round is fired, following which you just insert a new one. There is nothing to remove or reuse. An M-1 Garand, such as was used in WW2, used clips. The clip being ejected was what made that distinctive CA-CHING noise when you ran out of ammo.

Also, there's some nominclature confusion in the article between "rounds" and "bullets". The two are not interchangable.
The bullet is just the projectile, the lead slug that is shot out of the rifle. The casing and charge, along with the bullet, all add up to being a round.

Did you also cringe when he categorized the AK as a "machine gun"? :)


Meh, that one is not so bad, since it is a fully automatic weapon. We don't really use the term "machine gun" much in the military, "automatic weapons" is preferred.
What civilians typically think of when they say "machine gun" we'd call a "crew served weapon", though not all of those are machine guns either (for example, the MK-19 is an automatic 40mm grenade launcher; it is basically a big machine gun that fires grenades. And that is absolutely 100% as awesome as it sounds.)

Technically, the AK-47 is an assault rifle. But yeah.

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Re: What-If 0021: Machine Gun Jetpack

Postby Technical Ben » Thu Nov 22, 2012 9:39 am UTC

I'm so using this for a sci-fi. Either a space gun able to move craft as well as fire, or a rail gun to do similar. :P
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Re: What-If 0021: Machine Gun Jetpack

Postby nyrath » Thu Nov 22, 2012 10:00 pm UTC

Technical Ben wrote:I'm so using this for a sci-fi. Either a space gun able to move craft as well as fire, or a rail gun to do similar. :P

Yes, this is called a "mass driver." You generally encounter in in sci-fi associated with asteroid mining. The rock-rat asteroid miners find an asteroid with valuable minerals and want to move it to another more convenient location. Instead of a rocket engine they use a mass driver.

This takes the form of a nuclear reactor, and a linear accelerator with buckets. You fill the buckets with rocks, they accelerate to the end, the buckets stop but the rocks keep flying, the bucket returns to the start and is re-loaded.

It is a way to use plentiful rocks as rocket propellant.

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Re: What-If 0021: Machine Gun Jetpack

Postby bmonk » Thu Nov 22, 2012 10:48 pm UTC

nyrath wrote:
Technical Ben wrote:I'm so using this for a sci-fi. Either a space gun able to move craft as well as fire, or a rail gun to do similar. :P

Yes, this is called a "mass driver." You generally encounter in in sci-fi associated with asteroid mining. The rock-rat asteroid miners find an asteroid with valuable minerals and want to move it to another more convenient location. Instead of a rocket engine they use a mass driver.

This takes the form of a nuclear reactor, and a linear accelerator with buckets. You fill the buckets with rocks, they accelerate to the end, the buckets stop but the rocks keep flying, the bucket returns to the start and is re-loaded.

It is a way to use plentiful rocks as rocket propellant.

Or as bombs, if your railgun is mounted on the moon, and controlled by a large, self-aware computer.
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Re: What-If 0021: Machine Gun Jetpack

Postby JPatten » Fri Nov 23, 2012 2:02 pm UTC

Back on the topic of the damage a laser would cause vs. Bullets. If you can tune the laser, or probably maser for water you can do as much damage. Dump the beam energy into the flesh and the water will flash vaporize. I would think a 'steam explosion' would like do a fair amount of tissue damage.

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Re: What-If 0021: Machine Gun Jetpack

Postby Condor70 » Fri Nov 23, 2012 3:26 pm UTC

peewee_RotA wrote:This has been explored in video games as well. There are laser jumps in halflife (1), megaman 9 has a level where you move around in gravity by firing the buster. I'm sure there's more examples but I know that this is something I try routinely in FPS's to try to get higher jumps. Although rocket jumping is more common, every so often you get lucky with kickback.


Rocket jumping works in real life too, at least according to freddiew: http://www.youtube.com/watch?v=7XzdZ4KcI8Y.

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Re: What-If 0021: Machine Gun Jetpack

Postby ijuin » Sat Nov 24, 2012 6:47 am UTC

JPatten wrote:Back on the topic of the damage a laser would cause vs. Bullets. If you can tune the laser, or probably maser for water you can do as much damage. Dump the beam energy into the flesh and the water will flash vaporize. I would think a 'steam explosion' would like do a fair amount of tissue damage.


A "steam explosion" would be certain destruction to the body parts that it affected, but it might take more energy overall than simply burning open some major blood vessels and letting him bleed to death, since you have to flash-boil several grams (possibly a dozen or more grams) of water, which takes about three kilojoules per gram of water (slightly more in the body than in free air because the surrounding flesh can endure 20-30 kPa of internal gas pressure before anything seriously ruptures).

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Re: What-If 0021: Machine Gun Jetpack

Postby Carlington » Sat Nov 24, 2012 10:45 am UTC

ijuin wrote:
JPatten wrote:Back on the topic of the damage a laser would cause vs. Bullets. If you can tune the laser, or probably maser for water you can do as much damage. Dump the beam energy into the flesh and the water will flash vaporize. I would think a 'steam explosion' would like do a fair amount of tissue damage.


A "steam explosion" would be certain destruction to the body parts that it affected, but it might take more energy overall than simply burning open some major blood vessels and letting him bleed to death, since you have to flash-boil several grams (possibly a dozen or more grams) of water, which takes about three kilojoules per gram of water (slightly more in the body than in free air because the surrounding flesh can endure 20-30 kPa of internal gas pressure before anything seriously ruptures).


I feel like this depends on whether it's easier to generate smaller pulses of energy. If we can dump, say, 5kJ of energy per pulse, and we can efficiently generate repeated pulses of the same power at a fast rate, then we would end up with the classic sci-fi "pew pew pew" blaster laser model. Short "bolts" of laser energy, rapidly repeating fire, with each bolt vapourising approximately 1mL of water.
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Re: What-If 0021: Machine Gun Jetpack

Postby mishka » Sat Nov 24, 2012 8:58 pm UTC

Isn't the recoil distributed over time through the use of a recoil mechanism?

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Re: What-If 0021: Machine Gun Jetpack

Postby RobIrr » Sat Nov 24, 2012 10:20 pm UTC

bmonk wrote:Or as bombs, if your railgun is mounted on the moon, and controlled by a large, self-aware computer.


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Re: What-If 0021: Machine Gun Jetpack

Postby Brace » Sat Nov 24, 2012 11:05 pm UTC

You could get a better thrust-to-weight ratio by using Draco AK pistols converted to automatic, and if you had access to the right machinery you could also create custom synthetic furniture to reduce the weight further, which you would probably have to do anyway to mount the guns to a jetpack. Shorter barrel means less velocity though, I wonder if the trade-off would be worth it.
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Re: What-If 0021: Machine Gun Jetpack

Postby nyrath » Sun Nov 25, 2012 2:05 am UTC

ijuin wrote:A "steam explosion" would be certain destruction to the body parts that it affected, but it might take more energy overall than simply burning open some major blood vessels and letting him bleed to death, since you have to flash-boil several grams (possibly a dozen or more grams) of water, which takes about three kilojoules per gram of water (slightly more in the body than in free air because the surrounding flesh can endure 20-30 kPa of internal gas pressure before anything seriously ruptures).


According to Dr. John Schilling, a laser weapon would need about one kilojoule to incapacitate a human target, divided into 1 joule pulses at 5 microsecond intervals. This will make a tunnel about 30 cm long in soft tissue, 15 cm in bone or plastic, 5 cm in brick or concrete, and 2.5 cm in steel or ceramic. 5 microsecond pulses is optimal for soft tissue, other materials need different intervals. It will be difficult to make the tunnel longer than 30 cm in soft tissue.

Pulse #1 hits the hapless target's skin. It makes a hole 1 mm in diameter, but steam expansion will widen it to up to 4 cm. The 5 microsecond delay is to allow the steam and tissue debris to clear the beam path, otherwise beam power is wasted and penetration suffers. Pulse #2 hits the bottom of the 4 cm crater and makes a new crater. Rinse, lather, repeat. Past about 30 cm, enough time has elapsed for the entire tunnel to collapse.

Go to the Atomic Rocket website under Sidearms Energy for details. I would post the link but it keeps marking my message as spam.

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Re: What-If 0021: Machine Gun Jetpack

Postby slimeone » Sun Nov 25, 2012 7:18 am UTC

Why is it Cue Ball on the GAU-8 powered car? I would have thought that BHG would be the one to try it. In which case we can pretty much guess the reason he was pulled over.

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Re: What-If 0021: Machine Gun Jetpack

Postby niky » Sun Nov 25, 2012 1:06 pm UTC

JeromeWest wrote:
thkng wrote:If you have the technology to block the lasers, why not build an entire suite using that, making the laser completely useless. If you were having trouble seeing through them, you may as well leave only the eyes exposed so the enemy has to get a perfect shot at your eyes. Although the idea of blindfolded soldiers trying to shoot each other with lasers does seem funnier.


Or why not have the suit entirely blocked-off from the outside including the eyes, then have some kind of camera pass a visual feed through to a heads-up display. Of course, then the camera will become the point of attack for the enemy, so camouflaging the camera, randomising its location, and having multiple or replaceable cameras would become the arms race du jour. Much (all?) of this is brought up by Iain M. Banks in various novels, most notably (if my memory serves) in the big scrap at the end of Consider Phlebas.


Was wondering why it took so long for someone to mention cameras. All you need is compact wide-spectrum wide-angled camera mounted on eye-shields This would give the soldiers more peripheral vision, some night vision and IR, and built-in protection against laser blinding.

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Re: What-If 0021: Machine Gun Jetpack

Postby Someguyfromcrowd » Sun Nov 25, 2012 5:45 pm UTC

I envision a day when our jets have a bank of miniguns facing upwards on their noses and a bank of miniguns facing downwards on their tails

Then they could just hover over the enemy front line, spraying bullets everywhere whilst spinning like out-of-control pinwheels.

slimeone wrote:Why is it Cue Ball on the GAU-8 powered car? I would have thought that BHG would be the one to try it. In which case we can pretty much guess the reason he was pulled over.


I was kind of expecting that too.

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Re: What-If 0021: Machine Gun Jetpack

Postby peewee_RotA » Mon Nov 26, 2012 12:20 pm UTC

Technical Ben wrote:I'm so using this for a sci-fi. Either a space gun able to move craft as well as fire, or a rail gun to do similar. :P


They found out how useful this is as a propulsion method when they mounted a railgun on a submarine. It surfaced and fired directly port. The submarine spun around in circles several times and ended capsized. The entire crew threw up.
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