Gyrojet Weapons

[Purple]

We all seen them in 40K and they exist in real life. So I have to ask, just how effective (if the cost aspect is disregarded) would Gyrojet rounds be.

http://en.wikipedia.org/wiki/Gyrojet

Is there any other SF universe that uses them and how effective would they be in real life compared to regular projectiles.


Also would it be possible to combine them with a regular round to create a projectile that only fires its engine after leaving the barrel or after a certain range to create a high accuracy, high speed long range projectile while negating the inherit short range weakness of the Gyrojet? I am talking larger calibers here like the 30mm round. (I think you know where this is going.)

[adam_grif]

They're inferior to conventional weaponry. The primary advantage is lacking recoil, but they're drastically inferior (i.e. crap) at close ranges because they have to build up speed. Making a compromise design is just going to make it worse overall. If you're packing enough gunpowder to do significant short range damage, then you have the recoil that you were trying to eliminate in the first place by using a rocket. It also makes ammunition larger and heavier.

The other main downside is that it's costly to produce ammunition for it. Building small rockets costs much more than building regular ammo, not least because infrastructure already exists for conventional ammo.

[Temujin]

Its conceivable with more advanced technology you could improve upon them enough to make a viable weapon, but those advances in technology will also allow for more conventional firearms to be improved as well, ultimately negating any advantage an improved gyrojet design offers.

[Purple]

Hm.. I see.

How about this thou.
With a normal round, maximum speed is achieved the moment it leaves the barrel.
But could a combined round be made that adds a rocket buster to a regular round? The buster would fire over the duration of the flight to effectively increase the range and keep it from loosing speed. Effectively giving the round a much greater range and keeping it at near muzzle velocity on impact.
Would this work?

Also, cost is not that big of an issue since it would be a specialist weapon at best. Not something for wide deployment.

[Lord of the Abyss]

Its conceivable with more advanced technology you could improve upon them enough to make a viable weapon, but those advances in technology will also allow for more conventional firearms to be improved as well, ultimately negating any advantage an improved gyrojet design offers.

I disagree. Recoil puts an upper limit on how much velocity a conventional bullet can have fired from a handheld weapon, no matter how powerful your propellant or strong the materials you make the weapon out of. If you want higher projectile velocities conventional handheld weapons can't produce them.

My idea of a future gyrojet weapon is that the rocket rounds would be electromagnetically fired from a gun using the coilgun principle or something similar; unlike the classic Gyrojets, they would start out by traveling as fast as conventional bullets and accelerate from there. That would eliminate their close range weakness; and at longer ranges they would hit even harder. It has also occurred to me that such a weapon could perhaps fire ramjet bullets instead of rocket bullets since they'd leave the muzzle traveling very fast.

The other main downside is that it's costly to produce ammunition for it. Building small rockets costs much more than building regular ammo, not least because infrastructure already exists for conventional ammo.

"I don't shoot very many people."

"At those prices, I should think not."

From Larry Niven's The Meddler IIRC. The protagonist had a gyrojet pistol.

Is there any other SF universe that uses them and how effective would they be in real life compared to regular projectiles.

Classic Buck Rogers had rocket pistols I think. And the power armored marines in Crusade by Weber/White use something like a rapidfire rocket gun.

[Feil]

40k bolters appear to be a combination type, using an explosive charge to give the round a formidable velocity, then kicking in the rocket a few meters after it clears the muzzle. Perhaps their (quite implausible) 'mass reactive' detonators depend on the rocket to function, or something of that sort. Then again, this is 40k. They have chainsaw swords and space elves. 'Because I want my automatic rifle to shoot rockets, goddammit!' is the only justification they need. Techno(sorcery)babbling how and why they work in universe is an afterthought at best.

[Purple]

Well I was thinking more of a tank gun than a machine gun... but no one yet has commented on my idea.

How about this thou.
With a normal round, maximum speed is achieved the moment it leaves the barrel.
But could a combined round be made that adds a rocket buster to a regular round? The buster would fire over the duration of the flight to effectively increase the range and keep it from loosing speed. Effectively giving the round a much greater range and keeping it at near muzzle velocity on impact.
Would this work?

[Lord of the Abyss]

Seems workable. I imagine something like that as being a two stage bullet; a first stage that fires like a normal bullet, then a second stage that works as a rocket.

[Temujin]

Well I was thinking more of a tank gun than a machine gun... but no one yet has commented on my idea.

How about this thou.
With a normal round, maximum speed is achieved the moment it leaves the barrel.
But could a combined round be made that adds a rocket buster to a regular round? The buster would fire over the duration of the flight to effectively increase the range and keep it from loosing speed. Effectively giving the round a much greater range and keeping it at near muzzle velocity on impact.
Would this work?

I assume you're referring to something like this: Rocket-Assisted Projectiles (RAP)

[Purple]

Seems workable. I imagine something like that as being a two stage bullet; a first stage that fires like a normal bullet, then a second stage that works as a rocket.

Exactly, and presumably it would contain either a KE penetrator or a heavy AP round to hit enemy tanks with at ranges way beyond their effective retaliation. (would probably mounted on aircraft or helicopters too).


Also, what would be the effectiveness of such a round? For example, since I expect that it would hold its speed for much longer, it would presumably have a much longer range right? Also, more damage when it does hit the target? Greater accuracy?


Would it be useful for an air to air canon role? I presume that it would give aircraft a much longer gun range and accuracy, thus requiring less rounds and lower rates of fire to achieve the same effect.


All in all, percentage wise how much do you people think one could increase the range of such a round compared to a normal round (using a standard 30mm projectile as an example) with modern technology?


PS. Edit becouse of the above post:

I assume you're referring to something like this: Rocket-Assisted Projectiles (RAP)

I guess nothing is original any more. Oh well, just gives me more to justify it with than. Thanks.

Still, as I would deploy it on much smaller shells my question stands about its air to air and general direct fire utility.

[Sarevok]

Is normal bullets ineffective against infantry body armor ? A gyrojet bullet or any other kind of enhanced ammunition would make sense only if infantry started becoming more durable.

[Zixinus]

There are two avenues I can see for rocket-bullet type rounds: one is long-range shooting, ie, sniping. A gyrojet bullet has the advantage that it doesn't cause as much noise and flash when fired (plus, it only penetrates the sound barrier mid-way rather than from the start). Also, the bullet keeps a flatter course due to rocket mechanics.
If you are clever, you might even make stealth-bullets better with this, if you manage to keep the rocket-bullets below sound barrier speeds.

The other is, and I am not sure of this, is underwater bullets. I am not sure whether hydrodynamics favor this, but a slightly but constantly accelerating bullet might work better than a suddenly but only once accelerating bullet.

What I wonder, is what happens when such a bullet, with still fuel burning in it, hits someone, with or without body armor. Does the still accerelating bullet do anything nasty? Can you vary the bullet-head type to make use of the remaining fuel?

[Sea Skimmer]

Hm.. I see.

How about this thou.
With a normal round, maximum speed is achieved the moment it leaves the barrel.
But could a combined round be made that adds a rocket buster to a regular round?

That already exists for artillery for the last 65 years. It’s called RAP. Accuracy sucks crap and the rockets burn out the barrel quickly but this is accepted because its one of only few ways to substantially extend the range of existing artillery tubes. For small arms rocket assist is just really stupid. Even if everything worked well you would end up making the gun action much larger to accommodate longer rocket assisted ammo. This forces up the total size of the gun very quickly. You could just fire a larger conventional cartridge. Artillery can use RAP more easily because the ammo is separate loading.

Anyway, a normal projectile follows a ballistic arc; this is consistent and predictable. When you throw a rocket onto a projectile you now have a constant thrust source which is constantly changing the trajectory in flight, creating inaccuracy and greatly magnifying every other source of inaccuracy. You don’t have a nice long barrel guiding the acceleration. Aiming a projectile which had a constant rocket burn would quickly become insane. Rocket weapons have never been known for accuracy, dispersion on rockets fired by MLRS for example is about 40 times worse then 155mm tube artillery firing normal ammo. This is why prior to the latest guided rockets, MLRS was always used enmass with cluster warheads with the target being an entire kilometer by kilometer grid square. The rockets literally could not hit anything smaller.

The buster would fire over the duration of the flight to effectively increase the range and keep it from loosing speed. Effectively giving the round a much greater range and keeping it at near muzzle velocity on impact.
Would this work?

No it certainly won’t work worth a damn to make the rocket burn for the entire length of flight. That would suck on many levels and require a rocket motor so large you aren’t going to fit it in a reasonable small arm. Real rocket assist burns out as quickly as possible because the rocket has to be a reasonable size, and the longer the rocket burns the worse accuracy becomes. In reality rocket assist is only really useful when combined with guidance systems to turn the projectile into a gun launched missile. RAP artillery shells are not much used. Ideally rocket assist would burn out before the projectile left the barrel, but that places a pressure limit on how powerful an assist it can be.

There are two avenues I can see for rocket-bullet type rounds: one is long-range shooting, ie, sniping. A gyrojet bullet has the advantage that it doesn't cause as much noise and flash when fired (plus, it only penetrates the sound barrier mid-way rather than from the start). Also, the bullet keeps a flatter course due to rocket mechanics.

If you wanted rocket assist to such a degree that the bullet starts out subsonic, it would be more rational to just have a pure rocket weapon and throw away the gun. Secondly while the trajectory might be flatter on paper you will still need to lob the round a great deal, and overall accuracy will become worthless because of cross winds. A constant source of thrust magnifies any slight wobble.

If you are clever, you might even make stealth-bullets better with this, if you manage to keep the rocket-bullets below sound barrier speeds.

Ever seen a mortar? That’s what your subsonic sniper rifle trajectory is going to look like at any significant range. The British and Russians already have subsonic sniper rifles, effective range is tiny but they have uses in urban fighting. Rocket assist isn’t going to help this at all. The rocket assist exhaust is going to be supersonic, defeating any notion of stealth, or else the rocket assist will be very sucky and worthless. This is besides accuracy issues.

The other is, and I am not sure of this, is underwater bullets. I am not sure whether hydrodynamics favor this, but a slightly but constantly accelerating bullet might work better than a suddenly but only once accelerating bullet.

Underwater rocket guns have already been made. They suck but they do work. This is maybe the only place that rocket assisted small arms ammo makes any sense.

[Sea Skimmer]

Seems workable. I imagine something like that as being a two stage bullet; a first stage that fires like a normal bullet, then a second stage that works as a rocket.

Exactly, and presumably it would contain either a KE penetrator or a heavy AP round to hit enemy tanks with at ranges way beyond their effective retaliation. (would probably mounted on aircraft or helicopters too).

Been done, you can look up Tank Extended Range Munition if you want. But as ever guidance was required to make it effective, so we are back to the shell being a pseudo gun launched missile. The Russian and Israeli solution is even easier, fire anti tank missiles straight out of the gun barrel. The US likes its guided shell concepts because they can fire over hills. But the rocket isn't about increasing speed so much as it is about compensating for the drag of the guidance system control fins required to make indirect anti tank fire work. If the drag penalty didn't exist they wouldn't bother with the rockets.

All in all, percentage wise how much do you people think one could increase the range of such a round compared to a normal round (using a standard 30mm projectile as an example) with modern technology?

A damn lot? Rocket assist can scale up until you are finally stopped only by the exhaust velocity of the rocket itself. You can’t go faster then that. But your gun will also probably weigh as much as the whole aircraft by that point.

[Purple]

I am well aware that for small arms use such a projectile would be overkill.

What I was thinking about is essentially creating a rocket assisted bullet for the 30mm autocannon used on aircraft. The idea would be to create some sort of long range sniper weapon for a fighter-bomber.

I see now that I was mistaken as it would more or less ruin the accuracy at the cost of incresing the range. Unless I add some method of stabilisation like the gyrojet suposedly had.

Spin stabilization of the Gyrojet was provided by angling the four tiny rocket ports rather than by forcing the projectile through a rifled barrel

Do you think that would work?

[Simon_Jester]

Another problem is that the ballistic trajectory of a rocket can be tricky to compute, which makes it very hard to use the "rocket bullets" for long range shots.

[Purple]

Who said anything about a ballistic trajectory?

[Stark]

They arc in flight. What do you think they do? As Skimmer says they arc differently, are unconstrained and thus erratic, etc. How long are you expecting this magical gyrojet to burn and how much energy are you expecting it to add to the weapon? Note that this technology is like forty years old.

[Purple]

No idea honestly.
I mean, after a little thought and some math I figured out that to make it effective I would have to add some sort of stabilization and a reasonably sized engine. And when it comes to that, I might as well just make it a guiled missile and just stick it under the airplanes wing and be done with it.

All in all, idea is canceled.

[Simon_Jester]

There's something to be said for the idea of a missile with a high initial velocity, but the key is to recognize that it's a missile (expensive, delicate, and thus something that had better count when it hits the enemy), rather than a bullet (cheap, rugged, and able to be used in great numbers).

Unguided rocket weapons are looking to be the wave of the past in any case, as electronics improve to the point where it's seldom worthwhile to not include guidance.

[adam_grif]

My idea of a future gyrojet weapon is that the rocket rounds would be electromagnetically fired from a gun using the coilgun principle or something similar; unlike the classic Gyrojets, they would start out by traveling as fast as conventional bullets and accelerate from there. That would eliminate their close range weakness; and at longer ranges they would hit even harder. It has also occurred to me that such a weapon could perhaps fire ramjet bullets instead of rocket bullets since they'd leave the muzzle traveling very fast.

In your first paragraph, you talk about recoil being crippling for people, and in your second, you talk about making projectiles go even faster via coilguns for rocket assists. Are you aware that Newton's Third applies to coilgun projectiles as well, and if you're firing something larger and faster than a conventional round, it also has significantly more recoil?

[Lord of the Abyss]

My idea of a future gyrojet weapon is that the rocket rounds would be electromagnetically fired from a gun using the coilgun principle or something similar; unlike the classic Gyrojets, they would start out by traveling as fast as conventional bullets and accelerate from there. That would eliminate their close range weakness; and at longer ranges they would hit even harder. It has also occurred to me that such a weapon could perhaps fire ramjet bullets instead of rocket bullets since they'd leave the muzzle traveling very fast.

In your first paragraph, you talk about recoil being crippling for people, and in your second, you talk about making projectiles go even faster via coilguns for rocket assists. Are you aware that Newton's Third applies to coilgun projectiles as well, and if you're firing something larger and faster than a conventional round, it also has significantly more recoil?

My point is that the projectile wouldn't be going any faster until after it left the barrel, since unlike a bullet it would keep on accelerating.

[Sea Skimmer]

I am well aware that for small arms use such a projectile would be overkill.

Overkill is questionable, as Gyrojet proved underkill is a damn lot more likely. You end up with a bulky impractical inaccurate weapon.

What I was thinking about is essentially creating a rocket assisted bullet for the 30mm autocannon used on aircraft. The idea would be to create some sort of long range sniper weapon for a fighter-bomber.

A sniper weapon for an aircraft? Sorry we have a solution to that already, it’s called a guided missile. Plus it’s already highly unrealistic to use the max range of existing aircraft guns, because the target is not going to be cooperative enough to let you line up for a shot. If it is cooperative like a UAV, then you don’t need more range anyway.

The Russians however did do work on a rocket boosted 45mm aircraft gun. The reason was that they wanted improved anti tank performance and you can not use discarding sabot from an aircraft. This weapon never worked well and was abandon because guided anti tank missiles made overwhelmingly more sense then a better gun. Kill rates which be far higher and so was aircraft survivability. The result was they rolled out a dedicated anti tank variant of the Su-25 with Vikhr missiles.

In fact guns always sucked for air combat, hit rates are very low and kill rates even lower because one or two hits just aren’t going to cause that much damage. Today designers want the lightest possible gun because it is purely an emergency snap shot weapon in the rare case you get into a dogfight. Adding rocket assisted ammo would substantially force up gun size in ordered to chamber the much larger ammo. No one is going to do that to get more range. Long range air to air gunnery is almost hopeless, so much so that in WW2 people experimented with time fuse air bursting ammo to try to improve hit rates. This against bomber targets going no more then 350mph. Against jets you run into serious problems with the ability of a near sonic jet to literally fly in-between the bullets. That’s why the US and certain communist block designs did accept a certain weight penalty in ordered to use gating guns. More velocity will not solve this problem.

I see now that I was mistaken as it would more or less ruin the accuracy at the cost of incresing the range. Unless I add some method of stabilisation like the gyrojet suposedly had.

No. Look it is very simple. If an unguided projectile is subject to thrust without a barrel to guide it along, accuracy will suffer. End of story. Stabilization helps; it does not and can not eliminate this problem, rather such efforts must exist just to keep accuracy remotely credible as a usable weapon. RAP artillery rounds are spin stabilized and indeed use a slight bit of rocket thrust to help maintain the spin, so are MLRS rockets, accuracy is still much lower then conventional artillery projectiles. Air to air rockets were fielded with both spin and fin stabilization, accuracy was so bad that even a simultaneous 108 rocket salvo could not be relied upon to hit a bomber the size of a B-36 or B-52! The US fielded an air to air rocket with a nuclear warhead as a solution to that problem.

This is why everyone rushed so quickly to completely ditch guns in the 1950s as absolutely soon as any kind of guided air to air missile was available. Guns suck, even if they did come back in a reduced form and are now dieing out again. Now if you want a small rocket assisted guided projectile on the plane, I suggest hanging a pod of Stingers under the wing. You could have several of them for the weight of one Sidewinder.

Do you think that would work?

No, I mean, we already damn well know it doesn’t work which is one of many reasons why Gyrojet didn’t just fail as a program, no one has even tried the technology again in a small arm.
What’s more by venting rocket impulse to provide stability, you are loosing impulse for forward thrust which means the ammo has to grow even larger to provide the same velocity. Burning gunpowder inside of a close piston, the gun barrel, is inherently more efficient. It’s the same reason why a diesel gets better specific fuel economy then a jet engine afterburner.

Sure, you can use some subrockets to add a spin or try to stabilize the flight path, it will never work very well without some kind of control mechanism. Such control mechanisms are plausible, but only with a quite large bullet which is bound to already have more then ample range. Max ballistic range for a .50cal round is as much as 7km and it will defeat most any body armor at any range it can reach. Why not make the .50cal rifle smaller then with rocket assist? Well if you did that then you could only use rocket assisted guided ammo which would downright suck, and its questionable how much weight would be saved since a shorter barrel is counter balanced by requiring a larger firing chamber and larger moving parts.

The only way I can see a rocket assisted bullet making sense is if you need a really high terminal impact speed, in which case rationally the rocket would ignite only just before impact anyway and would not be used to extend range. But long range guided anti tank rifles firing time delay rocket assisted ammunition make about as much sense as 5 megaton hand grenades. You could in any case also simply increase anti armor performance by using a very small shaped charge.

[Simon_Jester]

Skimmer, calm down, he pretty much already conceded it was a bad idea.

[Purple]

Skimmer, calm down, he pretty much already conceded it was a bad idea.

Indeed I did. Here is the proof.

All in all, idea is canceled.