# Small oxygen tanks

Does anyone know of any type of small, refillable oxygen tank.

I'm trying to build a rocket and the smallest cylinder I could find is BernzOmatic's 1.4 oz. cylinder. A big cylinder isn't really safe for my purpose and I really need it to be refillable.

Also, is there any DIY solutions? Safety is very important for me, and putting a big tank on a rocket ain't really a good idea.

FYI, the tank has to be around 2" - 2.5" in diameter, and it's very important that it is REFILLABLE!!!

• I'd like to invite you to space.stackexchange.com - amateur rocketry is on-topic there, and you're likely to find more enthusiasts of it there.
– SF.
Feb 27 '17 at 13:10

First, if you plan to use the same tank for flight and storage, that's not a good approach, because the tank to last without leaking, corroding, or being at risk of damage, needs to be quite thick. Use a dedicated oxygen storage tank (like a gas welding tank), and a small 'flight' tank for the rocket, filled right before launch. It doesn't need to be up to quite high standards, as both the amount and duration of exposure to oxygen won't cause a significant risk.

You should be able to adapt a tanks used for Airsoft gas pistols - there's a wide range of sizes, they are refillable, can hold a respectable pressure, and you can get all the "plumbing" as spare parts for ASG pistols.

Although, if I were you, I'd go for nitrous oxide. The cartridges "whippets", while not refillable, are cheap enough to treat them as disposables, safe, light, and you can get all the "plumbing" from a whipped cream dispenser, for which these cartridges are made. Never mind they hold 8 grams of nitrous oxide for 22g of dry mass. You'll never get this weight ratio out of $O_2$ unless you go with liquid oxygen.

Why are you trying to use O2 stored as a gas in a rocket?

To get any real quantity of the stuff you would need enormous pressures which argues directly against a light weight tank, the tank structure would weigh more then the gas it contains.

The oxygen using rockets all start with liquid oxygen, which has all sorts of fun issues of its own in a small rocket (Just don't go there!).

What is wrong with Nitrous oxide instead? It liquifies at reasonable pressures at room temperature, so it is much easier to get a sane propellant mass fraction in a small rocket, it is MUCH safer to handle then pure O2 (or heaven forbid, liquid oxygen).

Norco, Airgas, or your local oxygen supplier is only going to refill cylinder with a DOT stamp and a current inspection date. Oxygen may also have NFPA requirements because it is an oxidizer. So for purchasing oxygen or storing it you need to use a purchased cylinder that is rated and consequently has a large safety factor. The oxygen will not be liquid in this container. To get the energy density, you will probably be looking at a cryogenic system. With the proper arrangements you may be able to purchase liquid oxygen in a dewar at atmospheric pressure.

For amateur rocketry, a 1.5 safety factor may be sufficient. That is with small volumes, safety glasses, and filled at the pad minutes before launch. Selecting a volume, pressure rating, pressure relief valve, and interface plumbing with your storage will take a lot of engineering.

If you were not aware, liquid oxygen or any (liquid propellant system) is expert level amateur rocketry; it will require strong engineering skills or access to those skills. Pre-manufactured solid fuel is the best to start with then work up to a non-cryogenic or cryogenic liquid fuel system