Moving forward with OHKLA | Project planning and misc | Forum

Thanks very much for doing this work!

I agree that with the oxidiser tank, aluminium makes more sense than steel, since there is no need to worry about melting point.

Perhaps a question we should consider first with the tank is whether we want to build our own (in which case things like weldability are a concern) or buy an industrial tank of appropriate size.  Obviously buying a tank is a lot easier, but I am concerned that:

1. It may be hard to find tanks with the capacity we want which are tall and thin enough to incorporate into a rocket.
2. The outlet nozzles (or whatever the word is) on commercial tanks may be too narrow for our purposes, i.e. we may not be able to move N2O into the combustion chamber at the rate that we want.  I don't know if this is likely to be true or not, it's just something that occurred to me.

If we were to build our own tank we could make sure we solved both of these problems.

I did try to do some research on the range of aluminium tanks out there, but I found it very hard – manufacturers advertise the size of these tanks in terms of how many litres of certain gases they can hold, which is completely illogical, since litres are a unit of volume and not a quantity of gas.  Presumably they mean "can contain as much of gas x as would be found in so many litres of space under such-and-such pressure and temperature conditions", but who knows what those conditions are?

I think a single tank would be a lot simpler, provide a better mass fraction and be much more reliable (fewer valves to need to open at the correct times, etc) than multiple small tanks in parallel, so unless some issues force us down the parallel route, it makes sense to stick with one.

My biggest concern with automotive NOS tanks is that, since they're designed to fit in cars – and probably cars on the small end of the size scale – they are going to be short and squat in shape, which is the exact opposite of what we need.  This probably applies for scuba tanks, too.  Long and thin is probably quite an odd shape for a tank outside of rocketry.