Non-pyro CO2 Ejection System

[DaveHein]

There have been a couple of threads recently on non-pyro ejections systems, so I thought I would start investigating a non-pyro CO2 system.

I ran some tests to determine how much force is needed to puncture a CO2 cartridge. It took about 42 pounds to pierce the cartridge with the point of a #10 metal screw. I used a 16 gram threaded cartridge made by Genuine Innovations. It seems that it would be difficult to produce 42 pounds of force with a non-pyro device. A strong spring would be required, or possibly an electric motor with reduction gears. This would add additional weight. The 16 gram cartridge weighs about 60 grams when full, and 44 grams when empty.

When I get a chance I'm going to sharpen the tip of the screw to see if this reduces the puncturing force. One thing I noticed when I ran my tests was that the tip of the screw would partially seal the opening until I reduced the force on the screw. So the piercing mechanism must puncture the cartridge and then back off so that the CO2 can be released quickly. The Rouse-Tech device was designed to do this.

One solution for using a CO2 cartridge without BP would be to puncture the CO2 cartridge on the ground during flight prep. A rubber seal around the puncturing pin would keep the CO2 from leaking out. At ejection time, the puncturing pin could be released by an actuator allowing the CO2 to come out.

 

[heada]

https://www.aeroconsystems.com/motors/Screamer_folder/screamer.htm

Check out the method of bursting the N2O canister and releasing the gas.

-Aaron

 

[DaveHein]

https://www.aeroconsystems.com/motors/Screamer_folder/screamer.htm

Check out the method of bursting the N2O canister and releasing the gas.

-Aaron

This is interesting, but it uses a pyro method to release the gas. A pyrodex starter grain burns up the burst disk, which allows the gas to flow.

The Genuine Innovations website shows various CO2 valves, but they are all mechanical. They are first attached to the CO2 cartridge, which breaks the seal. The CO2 is made to flow by twisting the valve. I need to figure out how to electrically actuate this instead.

Dave

 

[WillMarchant]

This is interesting, but it uses a pyro method to release the gas. A pyrodex starter grain burns up the burst disk, which allows the gas to flow.

https://www.aeroconsystems.com/motors/Screamer_folder/ObCol_whip-it_hybrid.pdf

 

[DaveHein]

https://www.aeroconsystems.com/motors/Screamer_folder/ObCol_whip-it_hybrid.pdf

This method is a possibility. It uses a piercing needle of 0.016 inches in diameter, which should take less force than the screw tip I used. I measured the screw tip with some calipers, and the tip is close to 0.01 inches, but it very quickly widens to 0.03 inches. 0.03 inches would require about 4 times the force as compared to 0.016 inches.

I am still leaning toward piercing the cartridge during rocket prep, and then using some electrical method to release the CO2 at ejection.

 

[ghost]

Maybe someone sells an attachment that runs from something like a 12gram CO2 threaded tank to pneumatic tubing. Then, a standard, high pressure (what's the OC2's pressure?) solenoid could be used. The altimeter could directly activate the solenoid or even use a relay if needed...

 

[WillMarchant]

I looked around for solenoid valves that will run at 900 psi and didn't find any that seemed small enough.

One could imagine using one of the bicycle filling mechanisms to pierce the cylinder pre-flight. Instead of that being hooked up to a tire you could put a short stump of sealed plastic tube on it. Put a wrap of Nichrome around that and maybe when it heats up it would cause the plastic tube to rupture.

 

[shockwaveriderz]

Perhaps somebody needs to open up a paintball gun or daisy Co2 powered bb pistol to see what simple mechanical means they use and then modify it to be released electronically?

or use a spring that is nitinol?


spring calculator/designer:

https://www.efunda.com/DesignStandards/springs/spring_calculators.cfm

terry dean
nar 16158

 

[shockwaveriderz]

Ok how about this:

A latching solenoid holds a compressed spring...the top of the spring has a pin in it... when the altimeter senses the altitude, it sends its electrical output that releases the latched solenoid, thus releasing the compressed spring... the pin punctures the CO2 cartridge, and teh then it acts like a rocket piston to push out the receovery system...

terry dean
nar 16158

 

[heada]

Everyone seems to hate solenoids for some reason (moving parts, fail under high G loads) and so that would be an up-hill battle. I was looking over another site looking for a particular resistor and saw a solenoid that worked off of 12VDC and would move it's arm 0.6 inches with 3.7 pounds of force. Problem is it pulled 0.4A to do so and it wasn't small at all (1.5in x 2in x 2in)

What about using a very small solenoid to fire a real igniter connected to a MMX motor? Maybe even use a solid state solenoid. Doesn't require anything special as far as ematch or BP but still produces lots of gases at good pressures and shouldn't increase weight all that much.

-Aaron

 

[DaveHein]

I sketched up the idea I have for a non-pyro CO2 ejection system. The ejection mechanism consists of a piercing pin surrounded by a small O-ring. A couple of small levers are used to hold the piercing pin in place. This is shown in the following image.

The CO2 cartridge is screwed into the ejection mechanism until it seals tightly against the O-ring. There will be a small amount of CO2 released as the cartridge's seal is pierced. The Genuine Innovations valve works in the same way. The following image illustrates the compression of the O-ring, which keeps the CO2 from releasing.

In the third image, the upper lever is pulled up by an actuator. This releases the piercing pin from the CO2 catridge and allows the CO2 to quickly flow out.

I think this scheme should work, and it shouldn't weight too much. I hope to build a prototype in the next few weeks.

Dave

 

[ghost]

I sketched up the idea I have for a non-pyro CO2 ejection system. The ejection mechanism consists of a piercing pin surrounded by a small O-ring. A couple of small levers are used to hold the piercing pin in place. This is shown in the following image.

The CO2 cartridge is screwed into the ejection mechanism until it seals tightly against the O-ring. There will be a small amount of CO2 released as the cartridge's seal is pierced. The Genuine Innovations valve works in the same way. The following image illustrates the compression of the O-ring, which keeps the CO2 from releasing.

In the third image, the upper lever is pulled up by an actuator. This releases the piercing pin from the CO2 catridge and allows the CO2 to quickly flow out.

I think this scheme should work, and it shouldn't weight too much. I hope to build a prototype in the next few weeks.

Dave

I really like this concept. Are there any commercial valves like this? Or any BB guns one can take apart for this setup?

 

[DaveHein]

Are there any commercial valves like this? Or any BB guns one can take apart for this setup?

I think most commercial devices release the CO2 at a fairly low rate. The bicycle tire inflators take a few seconds to empty the cartridge. I haven't looked at the design for BB guns, but I assume there is a small chamber that holds enough CO2 for each shot. It is worth looking into the BB gun mechanism to see if it can be altered to dump the CO2 cartridge quickly.

Dave

 

[that_guy]

Hi Dave!


I know this is an old post but you mentioned how you were trying to make a Non-Pyro CO2 Ejection System and i have the same idea and some of the same problems you encountered and so I was hoping you could give me some help.

In my design i have a CO2 cartridge that will be perforated by a pointy bit (much like in the eagle pyro system). This pointy bit will get its momentum from a spring that will be released by removing a pin at a certain altitude. In order to determine how strong the spring will be i need to know how much force it will take to perforate the CO2 cartridge. Because you have done some experiments in the past i was hoping you could maybe still have some reference values for the tests.

In that same post you also posted some pictures of the system that you were designing (which are now not available). Do you still remember how your system was designed?


Thanks in advance, any help you could provide would be greatly appreciated!

 

[rocket_troy]

In order to determine how strong the spring will be i need to know how much force it will take to perforate the CO2 cartridge. B

https://www.rocketryforum.com/threads/co2-vs-black-powder.136983/post-1634770
If that's any help.

TP

 

[jderimig]

Having just been involved in co2 design project you don't want to depend on spring at the point of plunger contact to puncture the CO2 cartridge because you need the plunger to be able to retract far enough so as to not 'throttle' your CO2 flow. How to you plan to let the piercer get out of the way after you puncture the seal?

 

[Hobie1dog]

Hi Dave!


I know this is an old post but you mentioned how you were trying to make a Non-Pyro CO2 Ejection System and i have the same idea and some of the same problems you encountered and so I was hoping you could give me some help.

Welcome to the forum, but Dave hasn't been on here for the last year. When you scroll over his name, it will tell you when the person was last seen.

 

[that_guy]

Having just been involved in co2 design project you don't want to depend on spring at the point of plunger contact to puncture the CO2 cartridge because you need the plunger to be able to retract far enough so as to not 'throttle' your CO2 flow. How to you plan to let the piercer get out of the way after you puncture the seal?

Thank very much for the suggestion and sorry for the delay in my replay. My ideia was to use another weaker spring to push the sharp piece back just enough so it doesn´t interfere the out flow of CO2. This would mean that the first spring would have to be much stronger in order to compress the weaker one. Do you think this is feasible?

 

[jderimig]

Thank very much for the suggestion and sorry for the delay in my replay. My ideia was to use another weaker spring to push the sharp piece back just enough so it doesn´t interfere the out flow of CO2. This would mean that the first spring would have to be much stronger in order to compress the weaker one. Do you think this is feasible?

I would suggest using the principle of designing the piercer as a projectile with the spring giving it the velocity to pierce the cartridge. Size it so there is no spring force or even a gap on the piercer when the cartridge is punctured.

 

[rocket_troy]

Another option is to use a hollow piercer that punches out a complete internal disc. Obviously this would require very careful attention to the construction of the piercer as the wall will need to be very thin. It would need to be hardened steel but with reasonable toughness or even better, some hypodermic stainless steel tubing if you can find it. It comes in very small diameters and is of a special grade unannealed stainless that's probably in the 50-60HRC ball park typically.

TP

 

[OverTheTop]

What about a pointy thing driven by a RC servo with a cam?

Also, if your pointy thing is a bit bulbous on the end it could open a hole and then let the gas past a skinnier rod behind the tip.

Alternatively a groove or two on the piercing part?

 

[jderimig]

What about a pointy thing driven by a RC servo with a cam?

Also, if your pointy thing is a bit bulbous on the end it could open a hole and then let the gas past a skinnier rod behind the tip.

Alternatively a groove or two on the piercing part?

In our design we use a stepper driving a jack screw. Pierce then retreat. Flutes on the pierce is something we considered but we found you need a hole venting area equivalent to at least a 1mm hole to be able to discharge the CO2 quickly enough to be useful. Then the piercer grows in diameter and the force needed to puncture the seal goes up rapidly.

We did look at the cam idea because it would easily provide the ability to retreat quickly. But that design required more volume for the mechanism.

 

[rocket_troy]

Another possible way you could do it with just a spring (with a solid piercer) is to utilise the pneumatic power from the CO2 to push the piercer back via piston action. The piston (as part of the piercer) would be a close fit to cylinder but with no o-ring sealing. The cylinder would have all its vent ports (as many as you like) far enough back to only allow high gas flow once the piston has retracted enough to enable "unrestricted" flow out from the pierced orifice. The retracted distance should only need 3ish mm or 1/8" I imagine.

TP