imp Posted May 21, 2007 Share Posted May 21, 2007 Some gases, such as oxygen, helium, and nitrous oxide, for example, are stored, transported, and used from high-strength cylinders having very high internal pressure, perhaps several thousand pounds per square inch (psi). The witches' tale about such cylinders is that if one is tipped over and the valve broken off, the "jet propulsion" action of the released gas will drive the tank forward at dangerous speed. Can anyone confirm/deny the truth in this old tale? Imp. Link to comment Share on other sites More sharing options...
insane_alien Posted May 21, 2007 Share Posted May 21, 2007 yeah this happens. its more like a rocket than a jet though. if you could get it to go in a straight line then there is the potential for a kilometer or two of flight with some of the bigger cylinders. typical pressures are around 300Barg (rougly 300 atmospheres). most cylinders have a big plastic bit to prevent the neck being smashed off. Link to comment Share on other sites More sharing options...
Rocket Man Posted May 21, 2007 Share Posted May 21, 2007 iirc, "myth busters" did a take on this one. they managed to completely remove the valve almost instantly with the cylinder lying horisontal facing a cavity brick wall. the cylinder went dead straight with no modifications, put a neat hole through the test wall and nearly made it through the next wall (also cavity brick... yay for foresight) i personally am a fan of pneumatic propulsion. but it works so much better when the propellant has more mass. like water for example. Link to comment Share on other sites More sharing options...
insane_alien Posted May 21, 2007 Share Posted May 21, 2007 how about a Xe cylinder. one atom of that has more mass than a couple of water molecules Link to comment Share on other sites More sharing options...
Rocket Man Posted May 21, 2007 Share Posted May 21, 2007 true, but as a whole, water liquid is more dense than xenon gas. so i'd expect you'd get more propellant mass in a cylinder using the cheap stuff. Link to comment Share on other sites More sharing options...
YT2095 Posted May 21, 2007 Share Posted May 21, 2007 typical pressures are around 300Barg (rougly 300 atmospheres). most cylinders have a big plastic bit to prevent the neck being smashed off. agreed, I have a 2L medical O2 bottle here and that`s 315Bar (when full). although there`s no plastic other than the regulator knob and the pressure meter. 27 Bar on the He bottle, no marking on my CO2 bottle, and I can`t read my propane tank but it`s 18.6Kg. Link to comment Share on other sites More sharing options...
Rocket Man Posted May 21, 2007 Share Posted May 21, 2007 the plastic is normally only there for transport, it's a big round thing that encompasses the entire valve set. purely protective. Link to comment Share on other sites More sharing options...
imp Posted May 21, 2007 Author Share Posted May 21, 2007 true, but as a whole, water liquid is more dense than xenon gas. so i'd expect you'd get more propellant mass in a cylinder using the cheap stuff. Hey, maybe I'm more dense than water, but it's incompressible. So, if you fill a tank with it under pressure, suddenly release that pressure (like break off the valve), a little bitty squirt of liquid will be evident, and the pressure will then be zero,. and nothing further will happen. This is why pressure vessels like boilers are proof-tested for containment strength and leakage by using liquid, generally water, as the medium, instead of gas. Am I all wet here? Imp. Link to comment Share on other sites More sharing options...
YT2095 Posted May 21, 2007 Share Posted May 21, 2007 it`s well known that you Only fill water rockets 2/3s the rest is for compressed gas. so IMP, your argument doesn`t hold water LOL Link to comment Share on other sites More sharing options...
grifter Posted May 21, 2007 Share Posted May 21, 2007 lol too much H20 for my liking! and word to the wise, IMP the pressure wont be zero, It'll be 1 bar Link to comment Share on other sites More sharing options...
swansont Posted May 21, 2007 Share Posted May 21, 2007 it`s well known that you Only fill water rockets 2/3s the rest is for compressed gas. I thought the optimal fill was ~1/3 water and ~2/3 compressed gas. Of course, that might depend on pressure. edit: 40% fill from this data: http://www.geocities.com/wrgarage/perform1.htm Link to comment Share on other sites More sharing options...
insane_alien Posted May 21, 2007 Share Posted May 21, 2007 water IS compressible. not by much but you can squash it to the point where it will form a type of ice. Link to comment Share on other sites More sharing options...
YT2095 Posted May 21, 2007 Share Posted May 21, 2007 I thought the optimal fill was ~1/3 water and ~2/3 compressed gas. Of course, that might depend on pressure. edit: 40% fill from this data: http://www.geocities.com/wrgarage/perform1.htm is it? I dunno, I know it had Something to do with 2/3`s (trust me to get it right but backwards) LOL Link to comment Share on other sites More sharing options...
insane_alien Posted May 21, 2007 Share Posted May 21, 2007 In soviet russia, backwards gets you! Link to comment Share on other sites More sharing options...
imp Posted May 22, 2007 Author Share Posted May 22, 2007 it`s well known that you Only fill water rockets 2/3s the rest is for compressed gas. so IMP, your argument doesn`t hold water LOL I believe the argument implied FILLING the tank full of water. Yes, liquids are slightly compressible, most less than 1% at 3,000 psi. Forgive use of antiquated units, it's the way I learned things in the Frozen Water Age. Thought we were talking about storage tanks for gas products, not rockets. But thinking things through is what we're all here for, right? Imp. Link to comment Share on other sites More sharing options...
Rocket Man Posted May 22, 2007 Share Posted May 22, 2007 Thought we were talking about storage tanks for gas products, not rockets. true, but we were also talking about the propulsive behaviour of compressed gasses so i thought the simple water rocket was appropriate. as for proportions, it really depends on the nossle diameter. a fine nossle will use a different water level to a wide nossle. compressing water into ice; was it 15 or 40 different types of ice that form under different conditions? Link to comment Share on other sites More sharing options...
grifter Posted May 22, 2007 Share Posted May 22, 2007 compressing water into ice; was it 15 or 40 different types of ice that form under different conditions? neither, there are 14 phases of ice they are: amorphous ice (three forms low, high and very high density) Ih Ic I 2-12 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now