Homemade Liquid Nitrogen


As far as DIY cryogenics are concerned, dry ice is easy mode. You can get frozen carbon dioxide at WalMart, or from a nozzle that screws onto a CO2 tank. It’s all very ordinary, and not really special at all. Want to know what’s cool? Making liquid nitrogen at home.

[imsmooth] is getting his nitrogen from a standard tank, sending the gas through a CO2 and H2O scrubber, compressing it, putting the compressed gas in an ice bath, and slowly diffusing the compressed, cooled gas into a vacuum reservoir. When the cold compressed gas is released into the reservoir, Boyle’s law happens and liquid nitrogen condenses in a flask.

As far as materials and equipment are concerned, [imsmooth] is using a PVC tower filled with zeolite to filter out the CO2 and H2O, a SCUBA compressor (no oil), and an almost absurd amount of stainless steel tubing for the precooler and regenerative cooling tower. Except for a few expensive valves, dewar, and the SCUBA compressor, it’s all stuff you could easily scrounge up from the usual home improvement stores.

[imsmooth] is producing about 350cc/hr of liquid nitrogen,  or more than enough for anyone who isn’t running an industrial process in their garage. Check out the video of the build below.

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Attitude control for a really big rocket

If this is meant for a model rocket it must be the biggest we’ve ever seen. [Scott] and [Trevor] took on the task of building a rocket attitude control system after reading about some research on the topic. But that researcher only tested the theories using simulations so they set out to build their own. The prototype above has a tank of compressed Nitrogen which can hold up to 3000 PSI. You can begin to understand why this needs to be used with a big rocket. The pressurized gas is connected through a regulator to four valves which feed nozzles around the circumference of the fuselage. An Arduino takes readings from a gyroscope and actuates the gas valves via a relay board.

You can check out the test rig in the video after the break. The prototype is suspended horizontally from a wire and its orientation held at one position by the system. There’s also a paper (PDF) if you’re interested in the equations that went into the stabilization control. This system would have been right at home on that huge sugar rocket we saw back in October.

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Making liquid nitrogen at home

If you’ve got some time to scour eBay and $500 sitting around you can build your own liquid nitrogen plant. [Ben Krasnow] figured it all out for you and estimates he can produce a liter of the stuff for around $1.15. The process depends on a membrane to separate nitrogen from the other materials in the air around us and a cryocooler to get the gas cold enough to condense into a liquid. Other than atmospheric air, you need to pump in electricity. About 9.6 kWh per liter… yikes! Is your human hair solar panel up to that?

Anyway, once you’re up and running you can make yourself some ice cream or possibly save the world from oily destruction.

[Thanks Chris]