Powerlet Propelled Grenades

[nbk2000]

I got the idea for this while reading about the COMBLOC GP-25 40mm grenade launcher at <a href="http://club.guns.ru/eng/gp25.html" target="_blank">this site</a>.

Unlike a conventional 40mm grenade launcher that uses casings to contain the burning propellant charge, the propellant charge for the VOG-25 grenades are contained within the grenade itself, thus there is NO casing to eject, simplifying weapon design and enabling a high rate of fire.

<img src="http://www.volny.cz/ak-47/gp_30/vog-25p.jpg" alt=" - " />

in the picture, the propellant chamber is the "nipple" on the left end of the VOG-25P (Frog) grenade body

So, while doing further research on the VOG-25P airbursting grenade used by this weapon, I did a google search that came up with <a href="http://www.airburstrockets.com/index.html" target="_blank">this site</a>. It got me to thinking about using a compressed gas instead of the pyro propellant I'd originally thought of.

Knowing how easily CO₂ powerlets are to obtain, I thought that these would make good propelling charges since they contain 12 grams of CO₂ at more than 800PSI, which is way more power than the meager 120PSI used by these rockets which go more than 300 yards straight up.

The grenades, as I envision them, have a powerlet cast centrally within the grenade body (made of a NIPOLIT type explosive) with the impact fuse cast in the nose, and the BB frags on the circumference. The entire body of the grenade is explosive, maximizing effectiveness, unlike military grenades where the fuse mechanism takes up most of the volume.

<img src="http://nbk2000.freeyellow.com/Grenade_Powerlet_Side.jpg" alt=" - " />

The launcher would be a simple plastic pipe with a ball or spring detent to hold the grenade in place so it doesn't fall out. A spring loaded hammer is cocked back and released to strike the firing pin, which is simply a sharp nail, which pierces the powerlet seal, releasing the gas, and expelling the grenade.

For rifling, you could cast in a small plastic dowel that runs straight through to both sides of the grenade body. The small protusions of the dowel would engage 2 bars that would cause the grenade to spin in the same manner as the MLRS.

The nipple of the powerlet is slightly recessed within the body of the grenade to protect it from accidental puncture.

<img src="http://nbk2000.freeyellow.com/Grenade_Powerlet_Rear.jpg" alt=" - " />

Because of the simplicity of the design, and the low pressures involved, no sophisticated metal machining would be required. Also, because of the lack of pyro propellant, the device would emit no smoke or flash to give away your position.

<img src="http://www.37mm.com/lotw/images/sf-298.jpg" alt=" - " />

While I don't think you'd get anywhere near the same range as the VOG-25 (400 meters), you would be able to get the grenade further up, and there faster, than if you had thrown it. Even just 60 yards range puts you about 20 yards out of the range of an enemies hand-thrown grenades.

Also, being a projectile, it allows you to fire through narrow openings with precision to engage targets you'd otherwise not be able to engage with hand thrown grenades.

If half a "superball" was used as the nose, the grenade would bounce back into the air after impacting a hard surface (like a street) from a steep angle, where it would then airburst. A 1/10th second IC delay, using an impact detector like that found in those annoying blinking ball toys, would be the trigger.

You might even be able to hit an enemy hiding behind a corner if you can bounce the grenade off a wall behind them. :D

<small>[ January 20, 2003, 08:30 PM: Message edited by: nbk2000 ]</small>

[heaton3805]

I just watched the movie Ballistic: Ecks vs. Sever and saw this thing for the first time. Anyway, I got to dreaming last night about how easy it would be to make one of these, and dreampt just about the same idea as you did...Though mine ignites on impact since I haven't much of a clue on how to work with electrical delays...Anyhow, I just just dreampt of having an ingnition that used a small cone tip that was connected to a normal everyday rocket ignter and a few little watch batteries. Maybe tonight I might dream up a nice easy made explosive to use with these :rolleyes:

[Al Koholic]

We can develop this idea to be quite good I believe. Right now I see the surely uneven hole a nail will make in the end of the CO2 cartridge as a flaw (possibly dangerous to you or "your side").

The uneven hole which could be unbalanced could potentially turn the loose projectile on one of your own valued interests, or if anything, cause a lower range and poorer reliabilty.

By simply fashioning a metal jacket consisting of a section of pipe around the CO2 cartridge we can possibly increase the effectiveness of such a device. After the metal jacket (which must fit nice and snug over the cartridge) is in place, make a metal cap for it that has a hole drilled in it, directly in the center, without any gross imperfections like an angle or small metal frays.

Now when the nail is engaged, it will push through the hole and still rupture the CO2 cartridge but the gass will now enter a secondary chamber so to speak and from here it will exit straight and without any variation from shot to shot.

This is a very simple method which with a little effort and time, could be even more optimal in that you could figure out what the optimum nozzle diameter is, you could fashion a real nozzle with the correct angulature and form so as to maximize exit gas velocity, etc etc...

This could even be adapted to larger (higher pressure) tanks to make small, high power improvised rockets. Imagine a 30 litre 3600psi N2 tank afixed inside a pipe with a fashioned nozzle. Figure out a way to rupture the tank in a controlled way...

[nbk2000]

If the propellant is expended before the projectile leaves the barrel, than it will follow a ballistic trajectory.

If the projectile is still venting propellant once it's left the barrel, than that will act as a rockets thrust, causing the grenade to veer off course.

So, the main thing to ensure is that all propellant is expended while the grenade is still contained within the barrel.

One variable I'm worried about is the effect of temperature on pressure. Grenades fires in hot weather would travel further than those in extremely cold weather. This variable would effect accuracy unless you could compensate with a temperature adjustable sight. :(

If the powerlets were custom made (I wish) to have a frangible glass disk, then there'd be no worries about uneven puncture, since the disk would instantly shatter to dust. :) A high pressure gas like helium would greatly reduce the hot/cold variable. Though at the ranges this would be useful for, I doubt a foot or two will matter much.

This might be a good idea (more developed, of course) for MOUT because of the near total stealth of this launch method, compared to the usual 40mm grenades. The popping of a powerlet with a spring-loaded centerpunch isn't much louder than the popping of a ballon.

In the extremely close and personal range of MOUT, being able to fire your weapon without giving yourself away would be a huge advantage. Especially at night since any little bit of flash would be hugely magnified in the enemies NVD.

[Agent Blak]

After a great deal of testing would be able to Range preformance via Temperature. Have a launch tube set at a given angle. I don't believe that you would be able to achieve acurrate distances without the use of a PSI(Kpa)guage; this is always an option.

I am always Sketchy about operating improvised/Commercially produce device with moving parts in extreme Temp.

Your Whole device would be able to be made of ABS enforced with Fiberglass resin. This is due to there being no Pyrotechnic charge which after repeat firings will degrade the materials. This is not true with CO2 Powerlets.

The only concern I have is the cost of practice rounds($1 per can add up).

[nbk2000]

Well, the practice round could be made of body putty plastic resin (properly weighted), with the powerlet being removable for replacement. Then, buying powerlets in bulk would reduce practice shots to about 20 cents per shot. That's a hell of a lot cheaper than the $15/shot for the 40mm! :)

[Mr Cool]

I don't think uneven rupture of the powerlet's seal would be a problem, if you used a firing pin with a perfecly round cross section all the way down the point, and a good deal of force behind it.
One potential problem that I forsee is that the CO2 would rapidly drop in temperature, so that after a short time the pressure would be absolutely negligable. It might already be going fast enough, or it might not. Experimentation is needed...

[Marcus]

I had a similar idea to this a while ago so i made a prototype launcher. Pictures of this can be found here:
<a href="http://www.geocities.com/marcuschurch2000" target="_blank">http://www.geocities.com/marcuschurch2000</a>
(i know everyone hates geocities but hey never mind)

The barrel is made from a piece of 22mm copper pipe (id 20mm) so the powerlet is wraped in masking tape to make a snug fit. The powerlet seal is punctured by a sharpened screw mounted in the bolt face. The major problem is that (as has already been discussed) although the barrel is 420mm long the powerlet is still venting gas as it leaves the muzzle causing an erratic flight.
In the pyrotechnics section ther was a disscussion about spin stabilized rockets. The gyrojet rifle was mentioned which used small spinnig rockets.A similar effect could maybe be achieved if the powerlet was fixed inside a metal tube and the end was sealed with a plug that 3 holes in it. The centre hole would hold a nail which would puncture the seal and two outer hole could be angled to impart spin. I know im rambling but its difficult to write what i mean.

What does anybody think?

[A-BOMB]

I was thinking of something like this a bit more complex but you dont need to worry about temp or if all the propellent is spent before it leaves the barrel.

<img src="ftp://ewf:sd332gf@209.195.155.80/Hosted%20Images/New%20Folder/imp%20launching%20grenade.jpg" alt=" - " />

[Anthony]

If NO2, N2 etc, basically non-liquified gas cartridges are available at a reasonable price, I'm sure they'd vent much faster. Due to them not having to take the time to abosrb the energy required for the liquid CO2 to change state. Non-liquified carts would contain less gas though so thrust might be reduced, even though the gas is likely held at higher pressure than the CO2.

The mention of NV brought up a small thought - when fired, the operator would be washed in cold CO2. So if they enemy immediately swept the area with a thermal imaging device, the cold cloud of gas *might* help conceal the operator.

[nbk2000]

IIRC, the CO2 in the powerlets is a liquid under great pressure. Once that pressure is released, the liquid instantly changes into gas or "dry" ice, being violently expelled out of the powerlet.

The time I used a centerpunch to vent one, it was all vented (except for wisps) the instant I punched it, and the hole was perfectly round.

What about the nitrous oxide ones? Better?

The problem is how to hold the grenade still while whacking it with a punch. If you hit it fast enough, the inertia of the grenade would be enough, I'd think.

A-bomb, you wouldn't want to use any kind of pyro propellant with a NIPOLIT grenade body because NIPOLIT is made of NC, hence very flammable. <img border="0" title="" alt="[Eek!]" src="eek.gif" />

[heaton3805]

The best that I've been able to come up with so far is using the NO's (some of my burnt out buddies call them whippits...) since they can be purchased at 25 a box for around $8-$12, and also don't freeze up like the CO2 does, ingaged by a steel rod (sharpened of course) centered inside of a small cylinder to keep the firing pin (the rod) constently aligned inside the firing mech.

As far as holding the grenade in place to be punctured, just use the ball & spring detent that was mentioned in the beginning. If two of these are used opposite each other in the barrel and a little bit of rifling put into the outter casing of the grenade that lines up correctly with the detents, it should create the desired spin while leaving the barrel. This therefore solves the problem with spin, puncturing, and holding (so that it doesn't fall out while on the move).

The barrel shouldn't be very long, since the gas is expelled nearly immediatly and would loose propelling power unless the inner barrel was air tight. One would, of course, have to experiment with this to get their desired effect...But hey, isn't that always the case? :p

[mark]

Do you think with like a 4 foot launch tube the rockets could just be dropped down the barrel to fire? This would make it like a mini morar round, and would let you launch a lit m80 tipped round. Im very interested in this project, but does anone know if these things have enough power to launchthemselves out the barrel?

[nbk2000]

There used to be a handle that would grip the neck of a powerlet, then punch the seal, only allowing the gas to vent once the handle was released. It was for some kind of model "rocket" back in the 50's that would fly on a string. As for distance...I don't know.

[Agent Blak]

I would advice Creating a dye or mold to manufactor the rounds. This would allow the rounds to be all Pretty much the Same Size. It would also allow for the Powlet to be centered aswell.

Your best bet would be to use a cast Polyester Resin as this would have slight mount of flex; Assists in the sealing action.

The Ideal way would be to have slightly tighter fit at the Breach. This allows for the build up a Gas(PSI/KPA). This will cause the round to act more as if it were shot opposed to being thrown; Plus giving you greater range. Aswell it will help to hold the round in place when the firing pin strikes.

NIP. is not a primary... you know that right? It is different that AP Putty; both are castable though

[nbk2000]

Hmmm...use a tight fitting neoprene gasket cast into the grenade to grip a nipple that goes into the hole at the base of the grenade, aligning and holding the powerlet seal with the striker. :)

[vulture]

How about surrounding the CO2 powerlet with a little bit of pyrotechnic composition that is ignited just before or even at the moment of rupturing the vent hole, so the liquid/gas is heated up very fast. Given the high burning temperature of most pyrotechnic compositions this would make the effect of ambient temperature on range insignificant. Add to that the added gas production by the pyro comp.

Ofcourse this would rule out nipolit as the explosive charge.

<small>[ January 23, 2003, 02:40 PM: Message edited by: vulture ]</small>

[Anthony]

The carts do hold liquid CO2 under high pressure. Once the pressure in the container drops i.e. you puncture it, the liquid boils off and changes state into gaseous CO2. The energy required to change state is taken from the immediate surroundings. If it can't draw the energy fast enough then you get solid CO2 (no thrust) and also the temp drops, droping pressure with it (reduced thrust).

I don't think a small pyro charge will make an signicant difference, firstly because of the very short contact time and also because it takes a lot of heat to warm up CO2.

Butane is similar. It takes a lot more pyro comp to burn a hole in a full plastic lighter than an empty one.

The pyro charge would also negate the advantages of a non-combusting propellant.

I think ambient temp is going to make more of a difference in range than a few yards. For example:

"a full CO2 cylinder at 80 degrees F will have 969 PSI in it. The same full cylinder at 40 degrees F will have only 567 PSI in it"

There's a full graph here: <a href="http://www.airsmith.com/co2n2/co2graph.htm" target="_blank">http://www.airsmith.com/co2n2/co2graph.htm</a>

A possible explanation for a CO2 cart emptying instantly in open air, but still venting when exiting Marcus' launcher's barrel is the pressure in the barrel is keeping the CO2 in liquid state for longer.

[nbk2000]

Well, after punching my powerlets, I'd see wisps of vapor coming out, but that was just residual vapors with no pressure remaining in the powerlet.

I knew temperature is going to affect the pressure, so this'd have to be compensated with a temperature adjusted sight. This is assuming that the powerlet concept has sufficient range to make it worth bothering with.