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I am trying to work out costs and order parts for a small liquid fuelled rocket I have designed. My oxidiser is liquid oxygen but I can’t seem to find anywhere to purchase it on the internet. Does anyone know where to buy liquid oxygen?

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  • $\begingroup$ A company that sells gases... Oxygen., Acetylene etc etc $\endgroup$ – Solar Mike Nov 12 '19 at 19:27
  • $\begingroup$ If you don't understand why you can't buy LOX in an "uncontrolled" way, you probably shouldn't be allowed anywhere near the stuff, because you don't realize the hazards involved. It is available for "home use" for medical reasons for example, but only with the appropriate professional risk assessments and safety training. $\endgroup$ – alephzero Nov 13 '19 at 0:09
  • $\begingroup$ Also, liquid-fueled rockets in general -- these are VERY tricky to get right compared to solid fuel rockets. There definitely are amateurs who have done them, but it's an advanced (and expensive!) project. $\endgroup$ – ikrase Nov 13 '19 at 7:00
  • $\begingroup$ I am pretty sure that medical applications use pressurized gaseous oxygen, which is vastly less dangerous than liquid oxygen. Liquid oxygen can do some nasty stuff -- it will make materials which are moderately combustible such as cloth, leather, grease, asphalt roads, etc into shock or friction sensitive explosives. I will note that liquid nitrogen will condense liquid oxygen out of the air, but that's really only useful for a few drops worth -- usually this is an unwanted and dangerous side effect of liquid nitrogen. $\endgroup$ – ikrase Nov 13 '19 at 7:04
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    $\begingroup$ @ikrase Oxygen is stored as liquid for medical use, not only for high volume users like hospitals but also for home use in some situations. Ref: bochealthcare.co.uk/en/images/… $\endgroup$ – alephzero Nov 13 '19 at 12:15
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In general, you can't buy cryogens on the internet because they're both hazardous, and perishable (as they boil off). This goes double for LOX, which does things like turn leather gaskets and asphalt road surfaces into a shock-sensitive explosive. This caused the Bell X-1 Rocket Plane to mysteriously explode at least once.

The vendors would be those such as Airgas, Linde, and Praxair, which also sell various compressed industrial gases and liquid nitrogen. However, you can expect to need a lot more credentials and restrictions than you would for the everyday gaseous oxygen, acetylene, argon, CO2, or even liquid nitrogen.

It is likely that they will require a DOT-certified dewar to put it in, or that they will want to deliver one of those big ~50 gallon dewars with all the valves and hose fittings on the top. It is likely that they will impose other restrictions or want to see the kind of paperwork, training, etc that a business regulated under OSHA would be required to have. They may be flatly unwilling to deliver it anywhere that is not a business address -- and it is probably both illegal and unwise to carry any quantity of liquid oxygen in a passenger automobile.

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  • $\begingroup$ Last paragraph you mention delivering liquid nitrogen, did you mean liquid oxygen? $\endgroup$ – Solar Mike Nov 13 '19 at 8:53
  • $\begingroup$ Carrying LOX in a vehicle is not illegal per se, but it definitely requires special procedures. For example, remove all possible sources of ignition/explosion in a high-oxygen atmosphere (that may include plastic trim, standard-issue seats, etc). Modify the vehicle body to provide adequate ventilation in case of leaks. Install sensors to check atmospheric O2 levels in the engine compartment before engine start. Etc, etc... $\endgroup$ – alephzero Nov 13 '19 at 12:04

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