Accelerator guns?

[Epee]

Sorry if this has been covered before but; is there a canonical explanation for how an Accelerator Rifle accelerates?

All I can come up with is a very light conventional gunpowder charge, perhaps utilizing a "High-Low Pressure System", to "bloop" the round out of the barrel at which point a small, solid-fuel rocket motor ignites and speeds the projectile at 900mps toward the target. It would seem that some steadying of the projectile as the rocket ignited would be necessary and result in a device at the muzzle which would look like a muzzle break behind a cage-style flash-hider.

 

[aramis]

The description is a low power conventional round with the firing igniting the booster charge in the projectile. See Bk4, Merc...

Accelerator Rifle: Designed specifically for zero -G combat, the accelerator rifle fires a 6 mm, 5 gram bullet at an initial muzzle velocity of 100 to 150 meters per second which upon leaving the barrel is accelerated by a secondary propelling charge to velocities of 700 to 800 meters per second.

the only possible way for that to work is to be a rocket motor in the projectile.

 

[far-trader]

It always sounded like the old Gyrojet weapon to me:

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

 

[jappel]

What the gents before said.

I have a vague memory of a picture of an accelerator rifle, or perhaps a miniature, showing exhaust slots along the length of the barrel - I guess an additional measure to reduce recoil. Can't for the life of me remember more detail about that, though.

 

[Epee]

It always sounded like the old Gyrojet weapon to me:

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

I've actually had the privilege to fire a Gyrojet, twice! As it is configured it is FAR from recoiless. While the recoil energy is spread out over a long time as the rocket accelerates, there is quite a bit of muzzle-climb; more than a 1911 .45 and the back-blast is harnessed to recock the hammer.

In general though I agree with you. The accelerator must work via rocket and that means accuracy should be somewhat less than conventional guns of the same TL and full power should not be reached at close range (probably not a big problem in EVA combat). Likewise, as a rocket velocity is not determined by the length of the gun's barrel and so, power-wise, an accelerator pisol should be as powerful as an accelerator rifle.

 

[Epee]

The description is a low power conventional round with the firing igniting the booster charge in the projectile. See Bk4, Merc...



the only possible way for that to work is to be a rocket motor in the projectile.

Yep, I have that Book 4 and a rocket is all I can imagine too.

 

[McPerth]

About what does it look, IIRC in Assignement Vigilante (MT) there was a picture of a soldier in Combat armor and with an accelerator rifle.

 

[mike wightman]

As an asideI wonder how small you can miniaturise a grav module and battery pack.

Or how about using a low powered gauss rifle to launch the rocket projectile at TL12+

 

[Omnivore]

Smart bullets (aka miniature tac missiles)

 

[aramis]

As an asideI wonder how small you can miniaturise a grav module and battery pack.

Or how about using a low powered gauss rifle to launch the rocket projectile at TL12+

At the TL range of the game, not THAT small...

And as far as I can see, it's NOT described as a gyroget. It's described as a low-power conventional round that has a small rocket as the projectile. Instead of the 6x10mm ball, it's probably 6x30 ball, with 25mm of that being hollow tube filled with solid rocket.

It's really worth noting that the rocket as described ignites once past the barrel - this is for multiple reasons, I suspect. Not the least of which is the long-slow recoil impulse of the gyrojet, another is that a gyrojet is almost ineffective at 1-2m, while the Accelerator Rifle isn't - it's only as effective as a body pistol by the velocity. A third is that there's less (not no) risk to the hand of the firer, as the round is already receeding at 400m/s by the time it starts throwing backblast, whereas gyrogets typically have lower upon firing.

It also means being able to use low-power 6mm carbine rounds in a pinch...

 

[Epee]

At the TL range of the game, not THAT small...

And as far as I can see, it's NOT described as a gyroget. It's described as a low-power conventional round that has a small rocket as the projectile. Instead of the 6x10mm ball, it's probably 6x30 ball, with 25mm of that being hollow tube filled with solid rocket.

It's really worth noting that the rocket as described ignites once past the barrel - this is for multiple reasons, I suspect. Not the least of which is the long-slow recoil impulse of the gyrojet, another is that a gyrojet is almost ineffective at 1-2m, while the Accelerator Rifle isn't - it's only as effective as a body pistol by the velocity. A third is that there's less (not no) risk to the hand of the firer, as the round is already receeding at 400m/s by the time it starts throwing backblast, whereas gyrogets typically have lower upon firing.

It also means being able to use low-power 6mm carbine rounds in a pinch...

I agree with you on the probable configuration of the projectile.

However, I still think that, parsing the canonical description, there must be some sort of vented tube or rail attached to the muzzle of the rifle; technically the projectile is beyond the barrel but not truely out of the gun. Otherwise tracking shots fired within an atmosphere will begin loosing speed on the vector imparted by the shooter's tracking swing before the rocket boost cuts in. Perhaps I'm overthinking (heck, I'm writing a small novel about an imaginary gun! I know I'm overthinking... )and this just means that the only pressurized place the accelerator is unpenalized is within the rather tight confines of a ship.

I would also think that the accelerator must somehow balance what recoil force it generates so that the shooter experiences a puch directly backward rather than recieving an off-centered puch which will cause a spin as well as a motion vector. This could either be through an adjustable muzzle brake that uses gasses from the inital boost to off-set torque or the stock must be so-designed as to push straight back at roughly waist level. A biased muzzle brake seems the most reasonable but then the shooter must fire from the same position and side of his body for each shot or be spun.

I rather doubt the ability of the accelerator to use 6mm ammo from either the carbine or assault rifle; 10rds carbine=125g, 30rds assault rifle=330g, 15rds accelerator=500g. While the carbine and assault rifle are in line with one another velocity-wise and very close weight-wise (allowing for the assault rifle magazine to have fewer parts per number of rounds), the rounds of the accelerator or over 2.5 times as heavy.

 

[aramis]

Thing is, the Accelerator Rifle isn't "imaginary" - it was an ARPA project in the 70's. No "rails" - it's a conventional weapon with an unconventional projectile. (It was also unreliable as hell, but more reliable than a gyroget... because it had pistol velocities even if the rocket failed to ignite.)

The thing is, the design concept for the Accelerator Rifle dates back to the 1930's...
http://blog.modernmechanix.com/machine-gun-fires-rocket-bullets/

Noting the "very little recoil" in the article, and that it's a machinegun, not electric fired, and appears to have a recoil-spring chamber much like a certain pistol I've fired...

 

[Blue Ghost]

Sorry if this has been covered before but; is there a canonical explanation for how an Accelerator Rifle accelerates?

All I can come up with is a very light conventional gunpowder charge, perhaps utilizing a "High-Low Pressure System", to "bloop" the round out of the barrel at which point a small, solid-fuel rocket motor ignites and speeds the projectile at 900mps toward the target. It would seem that some steadying of the projectile as the rocket ignited would be necessary and result in a device at the muzzle which would look like a muzzle break behind a cage-style flash-hider.

We discussed these back in 2005 I think. I started the thread thinking about the "rocket guns" from "You Only Live Twice" with Sean Connery, and someone here had actually used them. Their history goes back to Vietnam where I think they were used by low ranking commissioned officers.

 

[aramis]

We discussed these back in 2005 I think. I started the thread thinking about the "rocket guns" from "You Only Live Twice" with Sean Connery, and someone here had actually used them. Their history goes back to Vietnam where I think they were used by low ranking commissioned officers.

Those are slightly different - they are purely tube launched electric fired rockets. Muzzle velocities of 30mps or so.

 

[Carlobrand]

... technically the projectile is beyond the barrel but not truely out of the gun. ...

Uh, what???o:

 

[aramis]

Uh, what???o:

He's talking about an extended rail - an idea put forward for extending the accuracy of Gyrojets - but not needed if you have a pre-ignition speed of 300m/s....

 

[BlackBat242]

IThe accelerator must work via rocket and that means accuracy should be somewhat less than conventional guns of the same TL.

Smart bullets (aka miniature tac missiles)

Precisely... accuracy should not suffer with the "electronic sights" (laser-pointer sight with image magnification) and rounds with a simple quadrant detector (such a quadrant photodiode can be less than 2mm in diameter) linked to guidance fins in the rocket exhaust.

Note that TL10+ propellants likely have a faster/higher-energy burn than anything we have now, so that it might well be able to reach "normal" rifle speeds within 20 yards or so... which is the point inside which you should be using something OTHER than a rifle!


http://www.eosystems.com/quadrant.htm

http://www.pacific-sensor.com/pdf/quadrant.pdf

http://www2.bioch.ox.ac.uk/oubsu/ebjknight/q4d.html

 

[Omnivore]

No longer a contributor to this board.

 

[Epee]

He's talking about an extended rail - an idea put forward for extending the accuracy of Gyrojets - but not needed if you have a pre-ignition speed of 300m/s....

Book4 says 150mps;where is the 300mps figure from?

The idea of "rails", perforated tube or any kind of "guide" in front of the barrel is so that the round is steadied as the rocket motor cuts in and so that any lateral vector supplied by the shooter swinging the barrel tracking a target. No matter how good TL9 or 10 gunpowders are there is going to be some delay between the time the projectile exits the barrel and the rocket motor cuts-in; there has to be in order for the backblast of the rocket charge not to push against the muzzle of the gun. This will result in at least some delay in firing at distant targets, possibly some disruption of the path if the round is not spun by rifling and perhaps even more if it is (I would suspect that the rocket would be venturi-spun at the same rate as the barrel's rifling). 150mps by itself, especially if the round included some form of warhead, would probably be adequate in zero-G unless the ranges were much over 150 meters and this would be because of flight time rather than bullet "drop". However in a gravity field these weapons would suffer greatly. The bullet will drop, as soon as it exits the muzzle, and then, no matter how much the rocket boosts it, it will suffer in accuracy at long range simply because the bullet wasn't pointing at the point of aim when the rocket cut-in.

If Traveller incorporates "smart bullets" we can take them into account; however, there is no mention of those or any other form of guided projectile, heads-up display, or correcting gunsight in the canonical discription.

I'm not trying to be an a** about it; there are a number of good ideas floating around. But I'm just wanting to be sure that, as far as Traveller is concerned, I haven't missed any elaboration on how the accelerator rifle works. It would seem that as described and only as described it's a pretty limited and unlikely weapon (especially considering other potential weapons available) and something extra is needed for it to work as advertised.

 

[Epee]

We discussed these back in 2005 I think. I started the thread thinking about the "rocket guns" from "You Only Live Twice" with Sean Connery, and someone here had actually used them. Their history goes back to Vietnam where I think they were used by low ranking commissioned officers.

Some Gyrojet handguns were issued on a trial basis to a few Special Forces NCOs during the Vietnam War.