Another Weapon Reserch

[Purple]

Greetings again forum goers. Here I am again with another one of my questions regarding SF. This time, once again it is a hypothetical design for an infantry weapon. I have recently been researching for a SF rifle. In the process of this I have been reading about various experimental weapons that newer came to be and one thing I hit were flachete rifles. The idea with them was that you have what is effectively a scaled down APFSDS round fired from a rifle.

I had the idea of taking the weapon into SF. The weapon would for all intents and purposes behave, clean, operate, recoil etc. like a normal assault rifle. At least if you have power armor to take care of the recoil. It would be based on a coilgun so that it does not need any propellant (ergo less mass/size/complexity per round) and fire rounds at the enemy at 10 to 50 times the speed of sound. In particular, the projectiles would be 7mm in diameter 7cm long fin stabilized darts. The fins would extend a further 3.5mm to either side and there would be 4 of them giving us a total saboted round width of 14.5mm. The rounds would be manufactured out of a futuristic alloy that has about the density of wolfram. (for the sake of convenience)

Now obviously a full automatic coilgun rifle that behaves like an assault rifle is just plain wank. But that is expected of SF. If people can have plasma rifles or what ever than I can make this. What interests me is assuming such a weapon existed and behaved as I described what its effects would be on a target once the rounds hit.

Some basic calculations on the matter give me the fallowing stats.
Mass: 207.5g
Muzzle Velocity: 3403m/s (low end value) / 17015m/s (high end value)
Kinetic Energy: 1.2MJ (low end) / 30 MJ (high end)

The high end values are for the equivalent principal HMG / light autocanon. The weapon fires the same round but at a much higher velocity.

What I want to know is how this sort of weapon would fare at:

1. Hitting hard armor plates (think futuristic equivalent of modern SAPI plates but also things as high as 40K power armor)
2. Hitting soft armor (think futuristic equivalent of kevlar) or a thick padding of some sort
3. Hitting unprotected flesh (I have a feeling that without the fins the round would just fly through with minimal damage, especially at the high end numbers but with them I don't know)
4. Compared to other SF weapons (Star Wars blasters, 40K lasguns and bolters, what ever weapons Halo and the other SF genres use etc.)
5. What would the more effective variant be. The slower low end (mach 10) or the faster high end (mach 50) version. Assuming all characteristics about the two designs being equal.
6. How much do you think the high and low end rifles would recoil assuming a weight of some 8-10kg for the weapon? Do you think normal humans in non Space Marine power armor could handle it?

[TOSDOC]

Have you read the Honor Harrington books? They have the flechette weapons in use as shipboard weapons, which are devastating to personnel without doing much damage to shipboard systems. Especially Honor of the Queen and In Enemy Hands. And compared to Star Wars weapons, I wouldn't want to think how things would have turned out for Luke and Leia in ANH if the stormtroopers firing across the chasm at them had had flechette guns instead of blasters.

[Simon_Jester]

Frankly, blasters as portrayed here (megajoule-range energy weapons that would probably be able to drill holes in a modern tank given enough time) should have done a lot more damage as it was, from spalling and fragmentation off the surfaces they were shooting. It's not like Luke and Leia were wearing flak jackets.

[Covenant]

You gotta bear in mind that if you're using an absurdwank piece of tech then trying to find out what it would "actually do" is already an exercise in futility.

That said... Depending on the type of flechette it could behave anywhere from being a armor penetrating sabot to being a light pepper of needles. You're best off looking to shotguns for the type of effects caused, since other than ballistic characteristics they're similar. Probably not what you wanted to hear but the fact remains that flechettes are sub-par ammunition for actual warmaking.

This means you're going to shred a lot of tissue, but against an armored target, it's going to suck. Your biggest kill-factor with a kinetic weapon is causing deep wounds, and non-magical flechettes are generally not killing weapons, they're wounding weapons. You can kill people with them when you deploy them from a larger platform, like artillery or a tank, but for small arms flechettes are generally not an optimal load. If you have an assault rifle then firing assault rifle ammunition out of it will be more successful at killing people than firing flechettes.

You also need to take into account that a weapon that has a similar sized cartridge to an assault rifle is not going to do well as a flechette gun because you're only going to fit one flechette into there comfortably. At that point you may as well just use a solid bullet. If you want to use flechettes effectively you want a weapon that can spray an area with them, so you want a wider delivery system. So again, shotgun is your model for success.

The one thing flechettes do well that bullets do not is deliverying a biological payload. Making a 7.62mm dart or needle gun does not improve penetration over a 7.62mm bullet, but it more ably allows you to deliver a poison or toxin. Maybe if your foes are some kind of biowank angry pile of germs or some kind of nanite swarm then delivering a counter-agent then a bullet that delivers kinetic oomph would be "meh" but a flechette with a payload more valuable. But when it comes to killing Life As We Know It, and that includes things like tanks and such, you're better off with a bullet.

[Purple]

You gotta bear in mind that if you're using an absurdwank piece of tech then trying to find out what it would "actually do" is already an exercise in futility.

Why? After all what the weapon does is purely up to the laws of physics. The only thing that is wank is how it does it. To give an analogy. Say I took pixie magic and used it to propel a rifle bullet at the same velocity as a rifle and give it the same spin stabilization. Would the bullet not behave exactly the same?

The reason why I just said take it as is and don't argue is becouse I don't want this thread to end up in a long winded discussion on how it can or can not be achieved that would bury and snuff out the answers that I need.

That said... Depending on the type of flechette it could behave anywhere from being a armor penetrating sabot to being a light pepper of needles.
...
...

Could you explain why? It's not that I disagree but I don't really understand. Do they tend to jaw or something?

You also need to take into account that a weapon that has a similar sized cartridge to an assault rifle is not going to do well as a flechette gun because you're only going to fit one flechette into there comfortably.

The way I came to this was that I wanted a railgun/coilgun type weapon. But as a rule these weapons don't do rifling. So I needed some alternative way of stabilizing it. And that is how I got to the idea of a fin stabilized dart.

[PhilosopherOfSorts]

You gotta bear in mind that if you're using an absurdwank piece of tech then trying to find out what it would "actually do" is already an exercise in futility.

That said... Depending on the type of flechette it could behave anywhere from being a armor penetrating sabot to being a light pepper of needles. You're best off looking to shotguns for the type of effects caused, since other than ballistic characteristics they're similar. Probably not what you wanted to hear but the fact remains that flechettes are sub-par ammunition for actual warmaking.

This means you're going to shred a lot of tissue, but against an armored target, it's going to suck. Your biggest kill-factor with a kinetic weapon is causing deep wounds, and non-magical flechettes are generally not killing weapons, they're wounding weapons. You can kill people with them when you deploy them from a larger platform, like artillery or a tank, but for small arms flechettes are generally not an optimal load. If you have an assault rifle then firing assault rifle ammunition out of it will be more successful at killing people than firing flechettes.

You also need to take into account that a weapon that has a similar sized cartridge to an assault rifle is not going to do well as a flechette gun because you're only going to fit one flechette into there comfortably. At that point you may as well just use a solid bullet. If you want to use flechettes effectively you want a weapon that can spray an area with them, so you want a wider delivery system. So again, shotgun is your model for success.

The one thing flechettes do well that bullets do not is deliverying a biological payload. Making a 7.62mm dart or needle gun does not improve penetration over a 7.62mm bullet, but it more ably allows you to deliver a poison or toxin. Maybe if your foes are some kind of biowank angry pile of germs or some kind of nanite swarm then delivering a counter-agent then a bullet that delivers kinetic oomph would be "meh" but a flechette with a payload more valuable. But when it comes to killing Life As We Know It, and that includes things like tanks and such, you're better off with a bullet.

I don't think any of that is going to matter much. Did you see the size of the darts Purple's gun would be firing? 7 mm diameter, seven centimeters long, and weighing in at 207.5 grams. That's almost half a pound, with a muzzle velocity of mach ten. My layman's gut tells me that's going to be nasty to whatever it hits, regardless of what its shaped like.

[StarSword]

That said... Depending on the type of flechette it could behave anywhere from being a armor penetrating sabot to being a light pepper of needles.
...
...

Could you explain why? It's not that I disagree but I don't really understand. Do they tend to jaw or something?

Lots of different weapons have been called "flechettes" in sci-fi, everything from what most people call a bullet to (much more commonly) weapons designed to create sprays of razor-edged shrapnel.

[Purple]

That said... Depending on the type of flechette it could behave anywhere from being a armor penetrating sabot to being a light pepper of needles.
...
...

Could you explain why? It's not that I disagree but I don't really understand. Do they tend to jaw or something?

Lots of different weapons have been called "flechettes" in sci-fi, everything from what most people call a bullet to (much more commonly) weapons designed to create sprays of razor-edged shrapnel.

But I clearly defined my projectile as a dart 7cm long and 7mm in diameter with a set of 4 fins at the back extending up to 14mm total in the OP. Maybe I should draw an image?

Also, my question relates to his entire post and all the details about how it would not penetrate armor etc.

[Covenant]

Why? After all what the weapon does is purely up to the laws of physics. The only thing that is wank is how it does it. To give an analogy. Say I took pixie magic and used it to propel a rifle bullet at the same velocity as a rifle and give it the same spin stabilization. Would the bullet not behave exactly the same?

I'm just saying that if you want your weapon to hold up under scrutiny, making it based on a wank out concept is going to work counter to that. If you don't care about it holding up to scrutiny, then just set the effects at the level the story demands. IE, if you make a coilgun assault rifle, the concept is already non-realistic enough that nobody will be upset if you just state what the result of being hit by it is.

So you're free to dictate firepower by Author's Fiat once you've crossed from 2001 to 40k, essentially. If you want flechettes just say "it shoots flechettes and it's awesome," is all.

Could you explain why? It's not that I disagree but I don't really understand. Do they tend to jaw or something?

It depends on load is what I mean. A shotgun shell full of flechettes can hurt someone who is unarmored or only using soft armor designed for smaller calibur pistols, but against someone with decent pistol armor, let alone armor with a ballistic plate in it, you're unlikely to do anything more than make them angry and inflict a handful of half inch to one inch punctures. That's for a shotgun load.

Now, for a rifle load, unless the rifle has a massive tube that it's firing out of, you're unlikely to get many flechettes if you want them to have the mass to travel a good long distance accurately and still inflict damage. So in that case you've changed the load. So shotgun is "light pepper of needles" and the rifle is more like "penetrating sabot." Shooting lots of flechettes is needle spray, shooting one flechette is a sabot. See what I mean? In general people only use sabots for firing sprays, because bullets tend to be superior for penetration while also being easier to tool, so when you say "flechette rifle" people generally assume "dart-throwing shotgun-style cone weapon."

There's other fin-stabilized rounds. But in general, for the weapon you're talking about stability is a non-issue. It's firing at a huge velocity and most "successful" combat is done at exceedingly close range. A weapon like this will not need to be air stabilized unless it's being fired by tanks. I assume when you say "rifle" you mean a man packed small arm used for shooting at other people, right? You called it an infantry weapon. Regular infantry are not good weapon platforms for super accurate weapons, so really, once you're firing something THAT FAST it becomes functionally point-and-shoot for the engagement ranges that humans successfully fight at.

The way I came to this was that I wanted a railgun/coilgun type weapon. But as a rule these weapons don't do rifling. So I needed some alternative way of stabilizing it. And that is how I got to the idea of a fin stabilized dart.

Well, you could just do it the way normal railguns do it and have a discarding sabot with a fin stabilzed penetrator inside. It achieves the same result but it's not usually referred to as a flechette. It works and it's significantly less effort to explain. But if you want you can still call it a flechette, or you could change the load to a rocket propelled version. Giving the thing an internal servo or CO2 pocket could let it adjust itself in-flight if someone is spotting or the thing has a laser targetting array, but now we're talking smartgun tech instead of an infantry weapon.

I don't think any of that is going to matter much. Did you see the size of the darts Purple's gun would be firing? 7 mm diameter, seven centimeters long, and weighing in at 207.5 grams. That's almost half a pound, with a muzzle velocity of mach ten. My layman's gut tells me that's going to be nasty to whatever it hits, regardless of what its shaped like.

I'm not even going to address that yet. Any weapon firing a slug that size is not an infantry weapon, so first I want to address issues of function, then we can move onto making the thing not fire buicks at a high rate of fire.

Also, my question relates to his entire post and all the details about how it would not penetrate armor etc.

They're generally not armor defeating weaponry because firing a flechette into a target means you've traded quite a bit of powder and mass for a special shape. Whereas a powerful shotgun can fire a flechette spray that penetrates poorly through armor, that same shotgun firing a slug will cause pretty horrific damage on target with a solid slug--let alone one designed with a penetrator.

The same applies to rifles. Rifles that fire armor defeating ammunition do not benefit from retooling them into flechettes. The ideal penetrator design is a bullet, not a dart, so any target with armor that can resist your rifle ammo will be able to laugh at your dart ammo. Any target with armor that cannot survive dart hits will be obliterated by rifles.

[StarSword]

But I clearly defined my projectile as a dart 7cm long and 7mm in diameter with a set of 4 fins at the back extending up to 14mm total in the OP. Maybe I should draw an image?

Also, my question relates to his entire post and all the details about how it would not penetrate armor etc.

So it's a fin-stabilized bullet, like the rounds used by UNSC sniper rifles in Halo. As I said, people were likely thrown off by the use of the word "flechette". (And, looking at the OP, not once do you say "flechette." That was an addition by TOSDOC and a red herring.)

Answering the questions you actually asked (I'm looking at you, TOSDOC) requires somebody with actual knowledge of ballistics. That's something that's unfortunately not part of an electrician's training, so I can't help there.

[Covenant]

So it's a fin-stabilized bullet, like the rounds used by UNSC sniper rifles in Halo. As I said, people were likely thrown off by the use of the word "flechette". (And, looking at the OP, not once do you say "flechette." That was an addition by TOSDOC and a red herring.)

Most small fin-stabilized rounds are going to be classed as flechettes no matter what. Wikipedia sucks but it's right on there: "Sabots are used to fire the flechettes that form anti-armour kinetic energy penetrators."

A discarding sabot is required unless it's a slug box. And a small dart is going to be, essentially, a flechette. Therefore a fin-stabilzed small arms dart is going to be a flechette by definition even if it's not exactly the word you'd use. If you mean to say it's not a flechette or a dart because the fins are going to extend much farther up the thing's body than normal, then all you've done is designed inferior ammunition. You don't need much of a tail on something to give it good flight, and having a bigger one will make it less stable. You want it to be a fin that keeps it on target, not a sail to let air currents blow it sideways.

[PhilosopherOfSorts]

I'm not even going to address that yet. Any weapon firing a slug that size is not an infantry weapon, so first I want to address issues of function, then we can move onto making the thing not fire buicks at a high rate of fire.

Well, he also mentions that you need power armor to use this weapon, so I don't think he's thinking of standard infantry anyway.

[Purple]

I'm just saying that if you want your weapon to hold up under scrutiny, making it based on a wank out concept is going to work counter to that. If you don't care about it holding up to scrutiny, then just set the effects at the level the story demands. IE, if you make a coilgun assault rifle, the concept is already non-realistic enough that nobody will be upset if you just state what the result of being hit by it is.

So you're free to dictate firepower by Author's Fiat once you've crossed from 2001 to 40k, essentially. If you want flechettes just say "it shoots flechettes and it's awesome," is all.

I want the effect to be realistic in relation to the description of how it is achieved. I can justify railguns magically working becouse that is a SF convention that all readers suspend disbelief on. But it would look very stupid if someone was to read my text 10 years later on a forum and do some math only to realize that my made up damage was way wrong and the thing would work way differently. As for the rest I explained it in my last post. I just can't work on two discussions at once.

It depends on load is what I mean. A shotgun shell full of flechettes can hurt someone who is unarmored or only using soft armor designed for smaller calibur pistols, but against someone with decent pistol armor, let alone armor with a ballistic plate in it, you're unlikely to do anything more than make them angry and inflict a handful of half inch to one inch punctures. That's for a shotgun load.

Now, for a rifle load, unless the rifle has a massive tube that it's firing out of, you're unlikely to get many flechettes if you want them to have the mass to travel a good long distance accurately and still inflict damage. So in that case you've changed the load. So shotgun is "light pepper of needles" and the rifle is more like "penetrating sabot." Shooting lots of flechettes is needle spray, shooting one flechette is a sabot. See what I mean? In general people only use sabots for firing sprays, because bullets tend to be superior for penetration while also being easier to tool, so when you say "flechette rifle" people generally assume "dart-throwing shotgun-style cone weapon."

But I clearly defined my round as early as the first post. A single very nasty dart.
Here is an exact image of the round in question. It is encased within a discarding sabot made of a magnetic material and fired one at a time like you would a bullet. The sabot is mostly just used becouse it makes the round easier to store and load.


All measurements are in mm.

There's other fin-stabilized rounds. But in general, for the weapon you're talking about stability is a non-issue. It's firing at a huge velocity and most "successful" combat is done at exceedingly close range. A weapon like this will not need to be air stabilized unless it's being fired by tanks. I assume when you say "rifle" you mean a man packed small arm used for shooting at other people, right? You called it an infantry weapon. Regular infantry are not good weapon platforms for super accurate weapons, so really, once you're firing something THAT FAST it becomes functionally point-and-shoot for the engagement ranges that humans successfully fight at.

So what you are saying is that the speed alone will make sure the round stays stable at the kind of ranges I will be engaging no mater it's shape and the presence or lack of fins? Cool. I newer thought about that.

Well, you could just do it the way normal railguns do it and have a discarding sabot with a fin stabilzed penetrator inside. It achieves the same result but it's not usually referred to as a flechette. It works and it's significantly less effort to explain.

That was what I meant from the start. See post #1:

Greetings again forum goers. Here I am again with another one of my questions regarding SF. This time, once again it is a hypothetical design for an infantry weapon. I have recently been researching for a SF rifle. In the process of this I have been reading about various experimental weapons that newer came to be and one thing I hit were flachete rifles. The idea with them was that you have what is effectively a scaled down APFSDS round fired from a rifle.

But if you want you can still call it a flechette, or you could change the load to a rocket propelled version. Giving the thing an internal servo or CO2 pocket could let it adjust itself in-flight if someone is spotting or the thing has a laser targetting array, but now we're talking smartgun tech instead of an infantry weapon.

I am sure I can find some use for a weapon like that one. The art of assassination just became way more cool.

I'm not even going to address that yet. Any weapon firing a slug that size is not an infantry weapon, so first I want to address issues of function, then we can move onto making the thing not fire buicks at a high rate of fire.

But that is the whole point of it. To fire massively heavy darts over 1500m and kill people.
The hope is that at mach 10 (the infantry held version) the dart would fly fast enough to punch through a space marine and kill him. And that at mach 50 the HMG version the round would be even nastier. But that one would be strictly used as a vehicle mounted weapon.

This said, and I can not stress this point enough. If physics disagrees with my projectile fired at those speeds doing the kind of damage I need I will just think of a new weapon type. I don't want to just let this become a case of rule of cool.

They're generally not armor defeating weaponry because firing a flechette into a target means you've traded quite a bit of powder and mass for a special shape.

This being a special case in that there is no propellant.

The same applies to rifles. Rifles that fire armor defeating ammunition do not benefit from retooling them into flechettes. The ideal penetrator design is a bullet, not a dart, so any target with armor that can resist your rifle ammo will be able to laugh at your dart ammo. Any target with armor that cannot survive dart hits will be obliterated by rifles.

So are you saying I should shape my projectiles like normal bullets and hope the speed stabilizes them sufficiently?

Also, the power armor I am talking about is not Space Marine grade. But it does bust the users strength by a factor of 2-3 and lets people carry around 500kg and stuff.

[Eleventh Century Remnant]

Can't quite get my head round the math for this myself- but can anyone who can tell me if my gut instinct is correct, and a projectile moving at 17kps at sea level atmospheric pressure is going to superheat from air friction and burn up in very short order?

3-4kps should be doable, but there has to be a limit somewhere, and I suspect the HMG version is way on the other side of it. Also, the recoil of these things is going to be up in tank gun range, especially for the heavier versions. Enough to shake a 60+ton vehicle with multiple m2 contact with the ground may be enough to floor a human shaped being, power armour or not.

Thinking about this, an idea emerges- heavier projectiles at atmosphere- enduring velocities yes, but how about a combination of laser/projectile, use a laser to evacuate a tunnel in the air for the bolt to pass through, as would be the idea for a charged particle beam- and then launch the bolt at moderate velocity, on the beam, accelerating it as if it were a lightcraft? http://en.wikipedia.org/wiki/Lightcraft

The energy requirements of the coilgun are going to be massive anyway, this might not be much worse; "dry-firing" the beam alone might be a useful weapon in itself, possibly as a less-lethal setting. At least that might get you enormous velocity without enormous recoil and atmospheric heating.

[Covenant]

I want the effect to be realistic in relation to the description of how it is achieved.

We don't know enough about how hypersonic projectiles actually function except for the fact that they tend to impart a lot of energy. Presumably this thing will just do that. If you want actual descriptions of how it'll function... you're probably best at looking at modern tanks. The weapon you're describing is, propellant aside, just a tank gun with some of the numbers squiggled around but achieving the same kinds of results. Heavier, slower slugs tend to smash armor better, but lighter, faster ones tend to make little melted-metal jets that blast through it. Depending on what your objective is, generally they both achieve the same result once you're talking about weaponry of this size.

So what you are saying is that the speed alone will make sure the round stays stable at the kind of ranges I will be engaging no mater it's shape and the presence or lack of fins? Cool. I newer thought about that...
...that is the whole point of it. To fire massively heavy darts over 1500m and kill people.

Yeah. At high speeds and at conventional human engagement ranges, the weapon will not need fins to be stable, because the amount of time it takes to 'wobble' will have put it at such an extreme distance that it'll already have hit the target. This is assuming that the rail it's being fired through is going to be accurate enough. If you're only shooting 1500m or so, I don't think fins will be necessary. Would be nice, but not worth compromising the design further for it. 1500m is going to be point blank for something like this because of the speed, it will be hard for the thing to miss--assuming the thing has a barrel of course.

For the record, a 50cal can obliterate targets at 1800m, and has killed humanlike targets at 2200m and above. Similarly large conventional ammunition can kill human targets at 2700m and so forth, so 1500m is a fine distance but it's nothing alarming. The biggest concern will be achieving a stable firing platform, accurate and fine articulation of said platform (so you can aim the thing properly at long range) and having a degree of sighting, rangefinding, and targetting required to deliver the shells on-target. Human visual acuity is not great enough to really see things well at around 1000 meters, so what you're still talking about is fitting a tank gun to a tank chassis and using tank targetting equipment to aim it. At this point "powered armor" is sounding like the conventional "powered armor" we have rolling around on treads.

The hope is that at mach 10 (the infantry held version) the dart would fly fast enough to punch through a space marine and kill him. And that at mach 50 the HMG version the round would be even nastier. But that one would be strictly used as a vehicle mounted weapon.

This said, and I can not stress this point enough. If physics disagrees with my projectile fired at those speeds doing the kind of damage I need I will just think of a new weapon type. I don't want to just let this become a case of rule of cool.

Right now you're just struggling with the numbers. Physics is going to weep at the idea of a Mach 50 HMG. Laying aside ANY of the technical questions, as I have been so far, about manufacture and energy/materials questions... that projectile is basically going to flash into gas the moment you fire it. I don't know of anything that can survive a rapid acceleration to that speed in atmosphere without melting right off the bat. And that's assuming Act Of Q actually lets you fire a projectile at Mach 50 from something that'll fit on a vehicle. Even the normal "power armor infantry" weapon is basically a naval rail cannon.

Also, the power armor I am talking about is not Space Marine grade. But it does bust the users strength by a factor of 2-3 and lets people carry around 500kg and stuff.

It would need to be Battlemech grade. While a Space Marine has increased strength and so forth, this weapon would put a Heavy Bolter to shame.

What we're describing is something more suited be being mounted on a Naval platform, or a space-based delivery system. It's an absolutely massive slug being fired at an astoundingly huge speed. The recoil from the thing would be grotesque, and since it's a coilgun it's got to have a huge and astoundingly heavy set of impellers to fire the sucker. That also means a big ol' stanky battery pack and an equally huge amount of ammunition feed.

Power armor wouldn't cut it. It's basically a vehicle weapon. If you want a good model for a weapon that could be fired by a man from "powered armor" you're looking at a browning 50cal or something similar. This thing in it's current state just kicks way too hard. It's not useful as an infantry weapon because of those drawbacks, and you certainly wouldn't need it for firing at other "power armor."

[Purple]

We don't know enough about how hypersonic projectiles actually function except for the fact that they tend to impart a lot of energy. Presumably this thing will just do that. If you want actual descriptions of how it'll function... you're probably best at looking at modern tanks. The weapon you're describing is, propellant aside, just a tank gun with some of the numbers squiggled around but achieving the same kinds of results. Heavier, slower slugs tend to smash armor better, but lighter, faster ones tend to make little melted-metal jets that blast through it. Depending on what your objective is, generally they both achieve the same result once you're talking about weaponry of this size.

Ok, thanks. Will do that.

Yeah. At high speeds and at conventional human engagement ranges, the weapon will not need fins to be stable, because the amount of time it takes to 'wobble' will have put it at such an extreme distance that it'll already have hit the target. This is assuming that the rail it's being fired through is going to be accurate enough. If you're only shooting 1500m or so, I don't think fins will be necessary. Would be nice, but not worth compromising the design further for it. 1500m is going to be point blank for something like this because of the speed, it will be hard for the thing to miss--assuming the thing has a barrel of course.

Cool.

For the record, a 50cal can obliterate targets at 1800m, and has killed humanlike targets at 2200m and above. Similarly large conventional ammunition can kill human targets at 2700m and so forth, so 1500m is a fine distance but it's nothing alarming. The biggest concern will be achieving a stable firing platform, accurate and fine articulation of said platform (so you can aim the thing properly at long range) and having a degree of sighting, rangefinding, and targetting required to deliver the shells on-target. Human visual acuity is not great enough to really see things well at around 1000 meters, so what you're still talking about is fitting a tank gun to a tank chassis and using tank targetting equipment to aim it. At this point "powered armor" is sounding like the conventional "powered armor" we have rolling around on treads.

Well presumably the weapon would be fitted with some sort of optics like any modern rifle. And moder sniper rifles are rated at 800m or so at least so I don't see your point. Yes, it would require optics and a bypod for stabilization but I don't quite think I would need tank grade stabilization and firing computers.

Right now you're just struggling with the numbers. Physics is going to weep at the idea of a Mach 50 HMG. Laying aside ANY of the technical questions, as I have been so far, about manufacture and energy/materials questions... that projectile is basically going to flash into gas the moment you fire it. I don't know of anything that can survive a rapid acceleration to that speed in atmosphere without melting right off the bat. And that's assuming Act Of Q actually lets you fire a projectile at Mach 50 from something that'll fit on a vehicle. Even the normal "power armor infantry" weapon is basically a naval rail cannon.

Ok, consider the heavy version terminated.

It would need to be Battlemech grade. While a Space Marine has increased strength and so forth, this weapon would put a Heavy Bolter to shame.

Is it that much overkill? I assumed it would be barely enough to penetrate SM armor? I was even scared I had undershot by a huge margin.

Can any 40K expert confirm this?

[Covenant]

BTW, Starsword, he DID call them flechettes:

In the process of this I have been reading about various experimental weapons that newer came to be and one thing I hit were flachete rifles. The idea with them was that you have what is effectively a scaled down APFSDS round fired from a rifle.

Anyway...

Well presumably the weapon would be fitted with some sort of optics like any modern rifle. And moder sniper rifles are rated at 800m or so at least so I don't see your point. Yes, it would require optics and a bypod for stabilization but I don't quite think I would need tank grade stabilization and firing computers.

Well, a bipod is only useful if you're going to lay down and let the thing be stabilized by it, and how are you going to do that with power armor on? I suppose if your power armor is incredibly articulated you could manage it, but otherwise you're creating a nasty problem here. You say it's like an assault rifle, but you don't usually put sniper optics and a bipod on an assault rifle. You could, but for marksmanship purposes you'd be better off using a better bipod-equipped weapon than your general rifle.

Being able to move and shoot with a weapon like this will be hard enough. Using a bipod makes it impossible to move around much, since then you're not using the bipod, and having "normal rifle optics" makes no sense. You wanna put a red dot sight on a weapon firing hypersonic projectiles? You're not using this thing for room clearing. Now, depending on some of the doodads built into this thing, it could be not that dissimilar to the naval railgun designed for the next-gen destroyers, a weapon rated at somewhere between 50 and 100 miles when fired at a ballistic trajectory. If you're simply using this thing to fire at another dude, it's huge overkill. You may as well fire nuclear bazookas at each other, or make sure you're not fighting within 10 miles of a city you don't want to be fragged by missed fire.

Is it that much overkill? I assumed it would be barely enough to penetrate SM armor? I was even scared I had undershot by a huge margin.

Can any 40K expert confirm this?

For the record, a Heavy Bolter is firing what essentially amounts to a rocket propelled grenade with a solid penetrator. It's acceleration is nearly entirely granted by the rocket motor, with the initial charge being relatively low impact. This gives the bolters a very smooth firing because their recoil is so low compared to the on-target kick, and the penetration (while quite good) is actually secondary to the explosive aspect. Soft targets like people can be entirely penetrated, but they're designed to pop once they penetrate. Bolters are, in general, not that effective against heavy armor.

[Whiskey144]

Bolters are, in general, not that effective against heavy armor.

Just thought I'd chime in on this, as, depending on munition, and close range, bolters can penetrate armor very well; at borderline hand-to-hand ranges, they penetrate Astartes warplate quite easily- and there are specialized rounds designed specifically for armor penetration, namely the Kraken and Vengeance rounds.

Soft targets like people can be entirely penetrated, but they're designed to pop once they penetrate.

This, IMO, is so that the bolts don't overpenetrate and can actually kill the target. It doesn't really hurt that the Orks, which spurred the development and deployment of the bolter AFAIK, generally tend to have very poor personal armor- but have very high individual resilience.

Is it that much overkill? I assumed it would be barely enough to penetrate SM armor? I was even scared I had undershot by a huge margin.

Can any 40K expert confirm this?

While not a 40K expert, from the reactions/descriptions of other posters in this thread, the weapon you describe is far closer to a naval gun system- and therefore will fairly easily punch through Astartes warplate.

[Nephtys]

You know, the high end of your specs (~17000 m/s, .2kg projectile) has more than double the kinetic energy that the M1 Abram's cannon puts out. It seems a little ridiculous if you're even considering such ludicrous weapons to be 'man-portable', instead of vehicle or small warship mounted armaments.

[Purple]

Anyway...

erhem...

In the process of this I have been reading about various experimental weapons that newer came to be and one thing I hit were flachete rifles. The idea with them was that you have what is effectively a scaled down APFSDS round fired from a rifle.

Description > name. But anyway...

Well, a bipod is only useful if you're going to lay down and let the thing be stabilized by it, and how are you going to do that with power armor on? I suppose if your power armor is incredibly articulated you could manage it, but otherwise you're creating a nasty problem here.

Why would it not be articulated? I envision my suits of PA looking like medieval knights armor with articulated overlapping plates covering the joints and solid body plates covering the limbs and torso. The whole thing is than surrounded by padding and an outed coat. It should really not be any harder to move in it than it was for medieval knights. And they could do things like somersault and athletics. But I will have a separate thread for that.

You say it's like an assault rifle, but you don't usually put sniper optics and a bipod on an assault rifle.

G36 anyone?
http://en.wikipedia.org/wiki/Heckler_%26_Koch_G36
Standard sights include a scope. And any modern assault rifle can mount a rail attached bipod.

You could, but for marksmanship purposes you'd be better off using a better bipod-equipped weapon than your general rifle.

Well that is probably what I would do. But the operating principals being the same there is no need to make such distinctions.

Being able to move and shoot with a weapon like this will be hard enough. Using a bipod makes it impossible to move around much, since then you're not using the bipod, and having "normal rifle optics" makes no sense. You wanna put a red dot sight on a weapon firing hypersonic projectiles?

I was thinking more along the lines of a reflex sight tied to a camera that puts a crosshair on the users visor. But yea, the analogy fits.

You're not using this thing for room clearing.

Why not?

Now, depending on some of the doodads built into this thing, it could be not that dissimilar to the naval railgun designed for the next-gen destroyers, a weapon rated at somewhere between 50 and 100 miles when fired at a ballistic trajectory. If you're simply using this thing to fire at another dude, it's huge overkill. You may as well fire nuclear bazookas at each other, or make sure you're not fighting within 10 miles of a city you don't want to be fragged by missed fire.

Ok, point taken.

For the record, a Heavy Bolter is firing what essentially amounts to a rocket propelled grenade with a solid penetrator. It's acceleration is nearly entirely granted by the rocket motor, with the initial charge being relatively low impact. This gives the bolters a very smooth firing because their recoil is so low compared to the on-target kick, and the penetration (while quite good) is actually secondary to the explosive aspect. Soft targets like people can be entirely penetrated, but they're designed to pop once they penetrate. Bolters are, in general, not that effective against heavy armor.

Hm... did not know that.

You know, the high end of your specs (~17000 m/s, .2kg projectile) has more than double the kinetic energy that the M1 Abram's cannon puts out. It seems a little ridiculous if you're even considering such ludicrous weapons to be 'man-portable', instead of vehicle or small warship mounted armaments.

Ok... point definitively taken.

Project Canceled


This said, I still want to make some use of this topic for other things if you guys don't mind. In particular, I need to ask one question. What do you people think of the 40K lasgun? I tried reading the thread linked to from the sticky but I have to admit that it only confused me even more and answered none of my questions. So like help.

[StarSword]

BTW, Starsword, he DID call them flechettes:

In the process of this I have been reading about various experimental weapons that newer came to be and one thing I hit were flachete rifles. The idea with them was that you have what is effectively a scaled down APFSDS round fired from a rifle.

Sorry, missed that part.

[Covenant]

Why would it not be articulated? I envision my suits of PA looking like medieval knights armor with articulated overlapping plates covering the joints and solid body plates covering the limbs and torso. The whole thing is than surrounded by padding and an outed coat. It should really not be any harder to move in it than it was for medieval knights. And they could do things like somersault and athletics. But I will have a separate thread for that.

Because power armor isn't just a series of interlinking plates. Being able to carry an onboard power system that allows for strength-boosting is complex enough that we've got some modern strength-boosting armatures that are feasible but it's not power armor. Now, if you want to continually upscale the suit until it's capable of shrugging off substantial enough small arms that you'd need a hypersonic rail gun to be effective (because there is no equal powers warmaking effect on ridiculous overkill except to lose the war due to economics) then you're crafted a walking tank.

Walking tanks are generally not very mobile or highly articulated, since all the servos, gears, pneumatic muscles and swivel bits required to replicate humanesque arm and leg movements are expensive both in terms of space, weight, and cost. It's hard to have not only an onboard power system, extreme lifting capacity, resistance to small and large arms, and to do all that while retaining full human articulation. It's basically impossible, it's like asking why Japanese Gundams aren't realistic, but that's the fact of it. Your reward for forcing people to design and manufacture such a hideous contraption is the hilarity of watching these toy soldiers get paralyzed every time something gets hit and breaks a gear or a bone or something. It's easy to armor a turret up but it's freakishly hard to armor a giant robotic arm.

Your opponent would basically counter your walking tanks with non-walking tanks and win.

Knights could move around in armor because the armor itself, while cumbersome, simply didn't weigh all that much and they weren't being asked to do an awful lot while in full armor. They had to sit on their horsie and slap people with swords. Doing much more than that, or being unhorsed, would typically spell doom for you. You can do a somersault but you'd have a dickens of a time trying to go prone, fire a sniper rifle, then get up and move to a new target before enemy fire came in. They DO use artillery to take out snipers afterall. Doubly so if your target is a highly expensive piece of power armor with a railcannon assault rifle. Drop a cheapo bomb on that sucker and he's toast.

Knights also contain their own power source, us, and that power source and articulation was already 'onboard'. Once you're adding more gear than a human chassis can carry, yet you're requiring a complex bit of robotics to carry it in the same way as we do, you're increasingly screwed. Magic or physics defying nonsensescience are the only ways to justify that stuff. This is not a problem for 40k, because they're quite happy to just be silly.

G36 anyone?
http://en.wikipedia.org/wiki/Heckler_%26_Koch_G36
Standard sights include a scope. And any modern assault rifle can mount a rail attached bipod.
I was thinking more along the lines of a reflex sight tied to a camera that puts a crosshair on the users visor. But yea, the analogy fits.

Reflex sights do not count when your projectile can travel 10 miles. You also cannot use a reflex sight to target something 1500 meters away successfully. Sniper rifles use more complex gear than that. And sure, a modern rifle CAN mount a bipod. I can put a bipod on a shotgun. I could put a bipod on a derringer with a bit of tape. But you're still not getting much from it, and it defies the point of having an assault rifle setup.

There's a difference between a weapon being flexible, like having pictanny rails to swap on a scope and bipod for your marksmen, and designing a weapon that cannot do it's job as stated. A G36 is a battle rifle, but you'd not be sending your average soldier with the bipod attached. Extra weight for no value? Bipods are good for a squad support role when you want a stabler firing platform and you don't intend to move much, so you can reduce fatigue and increase stability yadda yadda, but does not solve the problem of "your weapon's muzzle energy is thrice a tank cannon" and "it may have 50 mile effective range."

Why not?

Because it's a hypersonic railgun! You don't clear rooms with this thing, you shoot down aircraft or ICBMs or you blow up aircraft carriers. Not only would your power-armored trooper probably be the size of a tank, carrying a weapon of relatively similar size, but if you fire this thing at a target... well, hit or miss, you're going to be sending a massive hypersonic shell rocketing through the target, through the wall, and out into who knows where. You could very easily level an entire neighborhood with such a weapon just while exchanging fire on a stairwell. It's called overpenetration. Modern rifles can go through walls and kill people quite a distance away, even through other stone/mud/masonry walls. When you upgrade that thing to something akin to a naval cannon, you're going to be lucky not to just destroy everything around you.

I don't want to be mean, but you've clearly got no sense of what this thing would be doing to people. Each time you fire it, due to muzzle friction, there would be a tremendous roaring explosion of red and white flame that erupts from the barrel of this thing. The air around you would literally explode, not only from the muzzle flash but from the intense pressure your projectile is creating as it hits Mach 10 in a fraction of a second. The kickback would be extreme, sending anything but a several-dozen ton unit flipping backwards wildly or crushing them into paste as the gun attempts to accelerate ITSELF away from the slug at roughly mach 3 or so. And when it finally hits something it would probably explode, the slug that is, turning into white-hot splatters of metal that spray the area and shred surrounding structures and people.

So that's why you wouldn't use it for room clearing. You'd be better off clearing rooms with an automatic grenade launcher.

Anyway, I know you canceled the project, I just wanted to explain stuff further. Hypersonic railcannons are cool, but they are not man-packed weaponry.

[Winston Blake]

First let me shamefully admit that I haven't bothered reading the thread in detail, since it's fairly large and complex. I would just like to point out that the mass in the OP is way too high - by about 4 times as much, since Purple has mistaken diameter for radius.

Further, except for the Mach 50 speed, those specs are roughly similar to existing autocannon rounds in the 25mm ~ 40mm range. E.g. a real 200g APFSDS round:

The 40 mm L/70 APFSDS-T is a fixed round, with the projectile assembly rigidly crimped to the brass cartridge case by two 360º crimping bands. The single drive band is a plastic material. The subprojectile is a tungsten-alloy rod penetrator, which weighs 200 g, is 200 mm long and has a diameter of 11 mm. It can be fired at automatic fire rates and is stabilised in flight by four tailfins. Before firing, the penetrator is held in position in the cartridge case and barrel by a three-segment sabot assembly. A segmented sloping windshield covering the forward part of the penetrator gives protection during handling and mechanical loading. The sabot and windshield are discarded once the projectile leaves the gun muzzle and once the drive band also ruptures. The relatively high weight of the arrow-shaped penetrator and its high initial velocity provide the penetrator with a relatively flat trajectory. The kinetic effect on the target ensures good penetration, which is enhanced by the fragmentation effects of the penetrator inside the target.The 40 mm L/70 APFSDS-T muzzle velocity has been quoted as 1,470 to 1,480 m/s. The penetrator is stated to be able to pierce 100 mm of armour at 1,000 m, but test firings have demonstrated the possibility of defeating 135 mm of armour with significant terminal effects in witness plates behind the armour.

[Darth Wong]

Can't quite get my head round the math for this myself- but can anyone who can tell me if my gut instinct is correct, and a projectile moving at 17kps at sea level atmospheric pressure is going to superheat from air friction and burn up in very short order?

Of course. Keep in mind, too, that air resistance power scales with the cube of velocity, so the rate of heating (in watts or some other suitable unit of power) for a projectile moving at 4 kps would be eight times the rate of heating for a projectile moving at 2 kps. Do the math: if an object moving at five times the speed of sound (1.7km/s) were accelerated to 10 times that speed, it would be heating up a thousand times as quickly.

17 km/s is similar to the impact velocity of Earth-crossing asteroids. At that kind of velocity, the rule of thumb for rock is that it will be vapourized by the time it passes through a column of air roughly equal to its own mass. A projectile made of various super-materials could last longer, of course, but one should make no mistake that we're dealing with a huge amount of heat.

[JointStrikeFighter]

[quote="Winston Blake"]40mm Bofors/quote]


Said guns are of course quite large in themselves;



Good luck even getting the barrel into a room for clearing.