Rare Gyrojet Firing

[kilemall]

This youtube shows a very rare firing of both the gyrojet pistol and the carbine with authentic ammunition, so this should help quite a bit with visualization of the accelerator rifle and snub pistol.


https://www.youtube.com/watch?v=cJAXpyt8-oQ


Obviously 50-year old ammunition that was handmade was going to not be reliable- presumably by the higher TL those problems would be resolved.

 

[whartung]

What a fascinating device. The hammer and firing process alone.

 

[JimMarn]

The big complaint I remember is the slow acceleration. Close targets, it supposedly wouldn't hurt.

 

[Enoki]

Two take aways:

The rounds are slow. Yes, they accelerate further out, but even then, they are slow.

The accuracy is terrible.

On the whole, this is a pretty pathetic weapon even if it has something of a high curiosity and wow! factor.

If I were making a snub pistol, I'd opt for a high - low pressure round instead.

https://en.wikipedia.org/wiki/High–low_system

This is used on the US 40mm round for example.

The advantage is that the snub pistol would have little or no recoil, could use a larger caliber round to compensate for the velocity, and would allow for a compact design.

 

[Straybow]

Well, I don't think a hi-low round would be low enough recoil for zero-g use. Logically, a rocket round of some sort could serve. This particular implementation is flawed, but I think several innovations could fix those flaws.


First is 3D printing, which could solve the nozzle and propellant variability and production bottlenecks. What we have today is primitive compared to what we should expect in a Travelleresque venue 3 centuries to 3 millennia in the future.


Second, refinement in the design could yield much better performance. The shape and materials of the shell are somewhat arbitrary in this design. I'm sure the power of the propellant could be improved.



Third, at some point technology could allow a microscopic controller to make it a guided projectile. It might be merely inertial correction to make it more precise, or have IR seeking, or target designated guidance, or maybe even onboard proximity radar. The missile could save the final burst of acceleration until properly aligned on the target.


For example, one port could have a fast-acting valve to modulate thrust to turn the round for increased control. Multiple valves could make more dramatic turns. A corner-rounding shot might not be able to turn 90° since it wouldn't have the energy to completely negate it's original vector, but it could still hit some targets behind cover. A fully programmable target solution could make almost any course change, given enough room to maneuver.


It could even be a slug gun, though it would need a different description of effects. Very close targets would suffer the propellant burning while the shell is embedded in armor or flesh.

 

[MThompson016]

What I see as the issues are the horrible accuracy and expense of the ammo. When a group of gun hobbyists can't hit a man-sized target at 10 yards, there's an issue for actual combat. I'm a horrible marksman, but I know at the 10 yard line, an aimed shot I make with a pistol will go more or less where I want it to from a standing position. When those guys, shooting in testing conditions, are having issues, it was not a ready for use weapon with 1960's tech.

Also, when the ammo all had to be hand made, there's a huge quality problem there. Again, it's an issue with manufacturing technology. I think now, it could be mass produced, especially with additive manufacturing to make the nozzled baseplates.

It's feasible for an advanced technology society, but as it exists, Gyrojets fail my new-stuff adaption test: Does it offer better performance to my existing gear, including reliability?

 

[aramis]

... it was not a ready for use weapon with 1960's tech.

Also, when the ammo all had to be hand made, there's a huge quality problem there. Again, it's an issue with manufacturing technology. I think now, it could be mass produced, especially with additive manufacturing to make the nozzled baseplates.

The issue was that the design team didn't think it through....

• It needs to spin to function accurately.
• the launcher is a rail system
• The ammo needs to be cast or milled for consistency...
• the ammo needs to be easily handled.
• short run ammo was hand made; if it were to be reliable, it must be easily assembly lined for minimum human skill.

The ammo as developed uses a centerfire primer - no problem there - BUT... the primer is attached to the crimped in baseplate, and the baseplates were hand drilled.

A mass manufacture version should be cast in two pieces with a minimum 3 part mold each.

Part 1: The capsule.
Mold piece one: interior, forming female screw coupling
Mold pieces 2 & 3: form the exterior.
Hardest issue: Have to unscrew it from the mold
Without increasing mold complexity, one can use a friction belt to unscrew the case casting from the screw/interior form.
With an extra part, mold piece one becomes the center bore, and a screw on/off screw face. Cast, rotate back the thread form, then open the sides, then air-eject the casing. Well within 1960's capabilities.

Part 2: Base plate. This needs multiple nozzles, a primer bay, and a male-thread exterior. Sounds like milling, no? Well....
Again, we can go with decent multi-part molds. A 4-part sounds right in this case:

1. interior - has wells to receive and lock to the cones for the nozzles; also has part of the primer firepaths.
2. Back has the primer well and spike, and touches to the ends of the firepaths. Also has the cones. Designed to unscrew from the mold.
3. exterior die with threads

Pressure mold the copper. Unscrew the back, which withdraws the cones from their lock into the inside. Spin the core while advancing the part out of the threads (note that the threads for mating the baseplate should be wider than the threads formed by the exterior die); the firepaths provide the needed torque.

Station 3: Cast the fuel slug - 2 or 3 part mold.
station 4: fill the cooled case with the precast slug of fuel.
Station 5: primer the plate
Station 6: using a Thrust-cones-shaped driver, drive the baseplate into the threads, then retreat the driver.
Station 7: package.

The inherent instability can be reduced by (1) more nozzels, and (2) casting a couple nubs on the exterior case to increase handleability in screw-fitting, as well as engaging in rails in the weapon to give increased initial spin.

None of this is beyond 1960's casting and machining. It's much easier now, but it was doable then.

 

[Enoki]

I still think the hi-low system coupled with systems that negate any residual recoil would work better.

For example, you have a muzzle brake on the gun, the barrel and firing system (seer / breech mechanism) take up the recoil to make it as near recoilless as possible.

That would make the ammunition easier to manufacture and avoid the lower velocity and slow acceleration of the rocket round.

 

[aramis]

I still think the hi-low system coupled with systems that negate any residual recoil would work better.

For example, you have a muzzle brake on the gun, the barrel and firing system (seer / breech mechanism) take up the recoil to make it as near recoilless as possible.

That would make the ammunition easier to manufacture and avoid the lower velocity and slow acceleration of the rocket round.

In zero g, the only thing that's going to matter that you've mentioned is the muzzle brake.

The energy absorbed by the sere, bolt, and breech are all transferred to the wielder. When the wielder can dissipate via traction, the duration of the kinetic impulse matters; in zero G, that's not practical, and so the duration is far less important.

The muzzle brake, in normal gravity, is usually calibrated to reduce kick and to reduce muzzle climb; muzzle climb is due to off-axis force on rifles. Part of kick reduction is simply diverting the force of the gas expansion to the sides rather than straight out the barrel - the angular change creates a forward force.

A zero-G muzzle brake must account for a proportionally different muzzle-climb — given the lack of significance of the gravity term, the brake must devote MORE moment (energy • arm of motion) to reducing the muzzle climb.

The user must likewise adapt to firing such that the muzzle-force is in axis with his center of mass.

The only way to generate a true "no spin-inducing recoil in 0-G" is to have an equal adjusted charge fired in the opposite direction - the muzzle brake can reduce the unadjusted charge needed to counter.

Felt recoil is nearly a single-instant force; spin-induction is a force over time situation, and springs, bolt movement, sere movement, and all that are, in fact, still using the same force, but are distributing it over more time.

Shoulder injury from shooting is about instantaneous force; the elastic recoil of the flesh is what is overcome by the instantaneous force to cause tissue injury... reduce the instantaneous force, and the elasticity can convert that to heat and body motion instead of tissue damage. Transferring the very short (near-instant) pulse of the detonation to the spring backed bolt spreads that impulse out over the duration of bolt travel, but still puts more than 99.99% of the force through the spring to the firer - but over 0.5 sec instead of 0.05 sec... (which means much less acceleration - and thus the elasticity can dissipate it with much less risk of harm.) The muzzle brake helps reduce the direct recoil from the rocket equation applied to the barrel as rocket. (All gas powered projectile weapons, whether explosive generated, pressurized tank generated, or thermal expansion generated, have some rocket-into-the-firer effect.) One cannot have a reasonable projectile path which doesn't also produce rocket effect on the launcher when using gas propulsion.

Generating the force within the projectile and using a dual-open-end barrel produces a forward recoil from friction. A choke can actually (1) prevent the round from going backwards and (2) provide enough backforce to counter the friction pull; (3) it also has a slight improvement on forward motion, as well, thanks to increasing the pressure.

A muzzle brake isn't going to generate an equal an opposite force. It will reduce felt force and transmitted moment a bit.

 

[Blue Ghost]

Kind of a cool vid. Here's a couple of links to two previous threads on the subject;



http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=37695&highlight=accelerator+rifle

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=5590&highlight=accelerator+rifle

 

[Barrel]

Nice to see the carbine get fired. Here's another video of a gyrojet pistol being fired, as well as an attempt to fire a dardick. https://www.youtube.com/watch?v=VdW8Trh_MGg

What's a dardick, you ask? https://en.wikipedia.org/wiki/Dardick_tround

 

[Condottiere]

Sounds like something the Darrians should have.

 

[Redcap]

Hmm. I've looked at the various videos on the Gyrojet, and the weak link seems to me to be the hand construction of the ammunition - literally, they were all made and put together by hand. It occurred to me that the process in the Traveller Universe could be automated by CNC or the Traveller equivalent machinery, thus regularising the production of the components of the ammunition, and the final assembly of it as well; this would lead to a consistency of the discharge of the ammunition when fired, as the rounds would have a tighter tolerance of velocities and evenness of the exhaust/spin ports at the rear, which would combine to provide a more even burn and spin rate, thus allowing for a more consistent accuracy to be achieved.

Thoughts?

 

[JimMarn]

Hmm. I've looked at the various videos on the Gyrojet, and the weak link seems to me to be the hand construction of the ammunition - literally, they were all made and put together by hand. It occurred to me that the process in the Traveller Universe could be automated by CNC or the Traveller equivalent machinery, thus regularising the production of the components of the ammunition, and the final assembly of it as well; this would lead to a consistency of the discharge of the ammunition when fired, as the rounds would have a tighter tolerance of velocities and evenness of the exhaust/spin ports at the rear, which would combine to provide a more even burn and spin rate, thus allowing for a more consistent accuracy to be achieved.

Thoughts?

I think if they were made the way you suggest the results would be more satisfactory as to reliability.

But they have a slow acceleration. Maybe a newer solid rocket fuel would accelerate faster, some I have heard are very dangerous due to watching MythBusters, but may not be safe to be used in a Gyro Jet pistol.

 

[Enoki]

I think if they were made the way you suggest the results would be more satisfactory as to reliability.

But they have a slow acceleration. Maybe a newer solid rocket fuel would accelerate faster, some I have heard are very dangerous due to watching MythBusters, but may not be safe to be used in a Gyro Jet pistol.

The more energetic the fuel, the more it is likely to be unstable.

Aside from that, there are already zero-recoil muzzle brakes and other devices on the market that eliminate gun recoil as close to completely as possible. This means that something like the Gyro Jet isn't necessary to obtain a ZG usable weapon, particularly given several millennia of a additional development.