- #1
salamander
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Hi. I've been wondering about these disposable CO2 capsules for airguns:
Please share opinions on my reasoning, any hints or ideas of how to calculate this, what to look for and so on will be appriciated.
What if I punched a hole in the seal of one of these capsules, how much thrust would I get from the ejection of the gas?
I know the pressure in the capsule must be way above critical, thus I can assume that the CO2 is in liquid state inside the cylinder. The CO2 will vaporize on a constant pressure around 70-80 bar at around 20-30 deg. C, if I haven't got the concept all messed up. However the rapid vaporization of the CO2 will need energy which must be taken from the capsule shell, thus cooling the capsule dramaticly, and also, I believe from the co2, which will lower vapor pressure. A probable diameter of the hole is about 1 - 2.5 mm and a capsule contains 16 g of co2. I guess the volume of such a capsule is about 10 - 15 cm^3.
Now imagine I'd put an expansion chamber on this and let the gas accelerate through a de Lavall nozzle, what would happen? May it be possible to reach supersonic flow, or will the pressure drop to much due to temprature loss in flow acceleration? I guess such an engine could be designed in such manner to make it operate at roughly the same pressure as a [chemical] model rocket engine by using a proper chamber in/out flow ratio. However I guess the difference in temprature between model rockets and my cold CO2 flow will limit the nozzle expansion ratio, and maybe even make a standard nozzle counter productive. What do you think?
What I'm really interested in is wheter you, making a rough estimation, think that a capsule of CO2 will deliver enough impulse to make a useful rocket engine. I've heard of simple CO2 powered cars and rockets on strings, but i have no idea how effective they are. And yes, I'm going for the non chemical rocket altitude world record
Please share opinions on my reasoning, any hints or ideas of how to calculate this, what to look for and so on will be appriciated.
What if I punched a hole in the seal of one of these capsules, how much thrust would I get from the ejection of the gas?
I know the pressure in the capsule must be way above critical, thus I can assume that the CO2 is in liquid state inside the cylinder. The CO2 will vaporize on a constant pressure around 70-80 bar at around 20-30 deg. C, if I haven't got the concept all messed up. However the rapid vaporization of the CO2 will need energy which must be taken from the capsule shell, thus cooling the capsule dramaticly, and also, I believe from the co2, which will lower vapor pressure. A probable diameter of the hole is about 1 - 2.5 mm and a capsule contains 16 g of co2. I guess the volume of such a capsule is about 10 - 15 cm^3.
Now imagine I'd put an expansion chamber on this and let the gas accelerate through a de Lavall nozzle, what would happen? May it be possible to reach supersonic flow, or will the pressure drop to much due to temprature loss in flow acceleration? I guess such an engine could be designed in such manner to make it operate at roughly the same pressure as a [chemical] model rocket engine by using a proper chamber in/out flow ratio. However I guess the difference in temprature between model rockets and my cold CO2 flow will limit the nozzle expansion ratio, and maybe even make a standard nozzle counter productive. What do you think?
What I'm really interested in is wheter you, making a rough estimation, think that a capsule of CO2 will deliver enough impulse to make a useful rocket engine. I've heard of simple CO2 powered cars and rockets on strings, but i have no idea how effective they are. And yes, I'm going for the non chemical rocket altitude world record
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