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I'm making an 'Iron Man' inspired type of repulser, but I want it to do stuff besides lighting up. I made a hydrogen generator a few days ago, and I want to implement thrusters into the glove. My plan is to put EMG sensors on my arms, and the more I flex, the more thrust is added. The only problem is that I have no idea what to use to control the throttle. It's dealing with gas, so it needs to be air tight. It can't be 2-position only, so it needs to be able to be controlled by PWM. Preferably by using an Arduino board. Any ideas? Maybe a servo attached to a ball valve or something of the sort?
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Why hydrogen? Why not propane? Variable-position propane valves are commonplace. I'm sure you could find one that would suit your needs. But, given that you're thinking of using a "ball valve and servo" to handle a flammable gas, maybe it'd be better to leave this one be. This may be one of those projects where, if you have to ask, you shouldn't do it.
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Why hydrogen? Why not propane? Variable-position propane valves are commonplace. I'm sure you could find one that would suit your needs. But, given that you're thinking of using a "ball valve and servo" to handle a flammable gas, maybe it'd be better to leave this one be. This may be one of those projects where, if you have to ask, you shouldn't do it.

I'm using hydrogen because I can produce it on-board and it has more thrust. This project is all about thrust. And if I knew how to throttle it, I wouldn't be making the question. I just threw a ball valve and a servo out there as a crap shoot.
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I see. You're actually looking to make a working thruster, not just a simulated thruster that shoots fire. Sorry--over my pay grade. Best of luck.
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Okay, so I think I know how I'm going to do throttle, but I need to use it in a liquid fuel system anyway. So, does anyone here know how to cool stuff below -500 degrees Fahrenheit?
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Okay, so I think I know how I'm going to do throttle, but I need to use it in a liquid fuel system anyway. So, does anyone here know how to cool stuff below -500 degrees Fahrenheit?

no.
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Okay, so I think I know how I'm going to do throttle, but I need to use it in a liquid fuel system anyway. So, does anyone here know how to cool stuff below -500 degrees Fahrenheit?

no.

There's obviously a way, I just need to find out how.
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http://en.wikipedia.org/wiki/Absolute_zero
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Well, i don't need it to be that cold. Just cold enough so i can create and store liquid hydrogen.
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The phrase, "ambitious, but rubbish," comes to mind. You, sir, are out of your depth. And the depth that you are in involves flammable gasses being strapped to a person's body. Turn back.
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But, what the heck: if you really want liquid H2, just go down to your local Praxair and buy a container of it. You don't have to compress it yourself.
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Well, i don't need it to be that cold. Just cold enough so i can create and store liquid hydrogen.

Absolute zero is: −459.67°F
Boiling point of hydrogen is: -423.17 °F

So, yeah....you've got a little wiggle room.

It will be cheaper to buy liquid hydrogen than to liquefy your own.

But...if you want to try, here ya go -

The critical temperature for hydrogen as 33 Kelvin. This is the maximum temperature at which hydrogen can be a liquid, no matter how great the pressure is. The process of liquefying hydrogen must therefore get it below 33 Kelvin.
The critical pressure for hydrogen is about 13 atmospheres (atm). This is the minimum pressure needed to keep hydrogen a liquid at its critical temperature. These critical points provide the parameters for keeping hydrogen a liquid.
The regenerative cooling process. This method pressurizes gas and allows it to expand. This allows the gas to exchange heat with its environment, thus cooling it. The gas is then passed through a heat exchanger, which cools the gas, thereby compressing it. This process is repeated until the gas cools enough to liquefy.

Step 1)
Apply the regenerative cooling process to liquefy hydrogen as first performed by James Dewar in 1898. Pressurize the hydrogen to 180 atm and pre-cool it with liquid nitrogen. Allow the hydrogen to expand through a valve that is also cooled by liquid nitrogen.

Step 2)
Repeat Step 1 until the hydrogen liquefies. Dewar's experiment yielded about 20 cubic centimeters (CCs) of liquid hydrogen, which was about 1 percent of the hydrogen in the experiment.

Good luck!
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But, what the heck: if you really want liquid H2, just go down to your local Praxair and buy a container of it. You don't have to compress it yourself.

I'd rather try and fail than not try at all. And I don't have a Praxair anywhere near me. And I'm sure if I could get to one, it would be extremely expensive.
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Don't forget to put a camera at at least 200m when you do your experiments. or better one that uploads the video stream directly.
I'd love to see the results.
best regards
Jantje
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Well, i don't need it to be that cold. Just cold enough so i can create and store liquid hydrogen.

Absolute zero is: −459.67°F
Boiling point of hydrogen is: -423.17 °F

So, yeah....you've got a little wiggle room.

It will be cheaper to buy liquid hydrogen than to liquefy your own.

But...if you want to try, here ya go -

The critical temperature for hydrogen as 33 Kelvin. This is the maximum temperature at which hydrogen can be a liquid, no matter how great the pressure is. The process of liquefying hydrogen must therefore get it below 33 Kelvin.
The critical pressure for hydrogen is about 13 atmospheres (atm). This is the minimum pressure needed to keep hydrogen a liquid at its critical temperature. These critical points provide the parameters for keeping hydrogen a liquid.
The regenerative cooling process. This method pressurizes gas and allows it to expand. This allows the gas to exchange heat with its environment, thus cooling it. The gas is then passed through a heat exchanger, which cools the gas, thereby compressing it. This process is repeated until the gas cools enough to liquefy.

Step 1)
Apply the regenerative cooling process to liquefy hydrogen as first performed by James Dewar in 1898. Pressurize the hydrogen to 180 atm and pre-cool it with liquid nitrogen. Allow the hydrogen to expand through a valve that is also cooled by liquid nitrogen.

Step 2)
Repeat Step 1 until the hydrogen liquefies. Dewar's experiment yielded about 20 cubic centimeters (CCs) of liquid hydrogen, which was about 1 percent of the hydrogen in the experiment.

Good luck!

I'd rather make the liquid hydrogen myself just because I plan on using it a lot and it would be less expensive in the long run most likely. I'm hoping the university I've contacted will be willing to help me. if anything, I can do tests using gas instead.
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