SpudFiles

Ive been thinking about building a steam rocket for the past while and I want to use aluminum, its a lot cheaper than stainless steel and much much much lighter which will help a lot with performance. The pipe I want to use is often the type used by amature rocketry people for the rocket casing which often have to withstand over 1500PSI so it can handle pressure in the right wall thickness (6061-T6 Aluminum). The big problem that I am having is the fact that the pipe does not fair well with heat. Does any body know of some kind of insulation that I could wrap around the inside to handle around 400 degrees fahrenheit for around 10 minutes without to much heat transfer to the metal? I plan on heating the water to boiling point before adding to the rocket to keep the time down before pressure can build and it to super heat.

Any help would be really apreciated.

Thanks.

400*F isn't really hot for metal, is it?
My gut says that it should be fine with that pressure at that temperature, but my gut isn't exactly a PHD.

Its just that Im pretty sure that the welding temperature for this aluminum is 750 kind of really close to 400.

Is welding temperature the same as melting point if it is aluminum melts at around 1,200 F. This should be for all aluminum unless you have some sort of alloy.

The only thing I can think of for insulation is fire clay but you would have to make sure there were no cracks in the curing process.

I don't really think that fire clay could handle the G forces involved during takeoff, it would most likely crack and break.

Ya i just looked up some of the properties of 6061-T6 Aluminum it definetly shouldn't have any problem with 400 degrees fahrenheit. Here is the link:
http://www.matweb.com/search/SpecificMa ... num=MA6016

How much do you think the pipe would weaken when heated to 200 Celsius? At 1500PSI I have a 2.5X safety factor but that's not taking into account degradation from the heat.

I have the formula but i need some info first. I entered it in the formula with just an initial pressure of 14.7 (atmospheric) and i got a wrong answer. Maybe you can just do the formula your self. Its Charles law. It finds the pressure if you have a constant volume and raise the temperature.
Forumula:
P2=(P1*T2)/T1

P2=final pressure
P1= initial pressure of rocket
T2= final temp
T1= initial temp.
Note(BEFORE ANYTHING) : you have to add 460 to the temperatures. And 14.7 to pressures. I did everything in Fahrenheit

Reason: this formula is done from absolute zero and that is -460

Charles law doesn't help here.

Anyway, I looked up the temperature derating factor of aluminum; at 400*F, it's .4 according to <a href="http://www.parker.com/ICD/cat/english/4 ... F">this</a>.

Now, they didn't tell me what alloy that was for, so you may want to try and find some better data.

I think I will just buy a few feet and weld a cap on both ends of 3 1' pieces and do several tests at around 1000PSI at 400 degrees fahrenheit for several hours multiple times and see how it holds up. I don't plan on standing beside the rocket to begin with and Im still hoping to find a good thermal insulator.

Ok i look up some possible insulators and kept coming back to the old asbestos but its not really safe much so i found out they have ceramic blankets. They are flexible and depending on the style can be heat resistent to 3000 F. I don't know how much you are willing to spend because they are kind of costly for rolls but if you get them custom cut it might be cheaper. Any way here is one link. There are plenty more.

lol asbestos? isnt that poisonous?

Not if it is new. Ony when it gets old and particles start to float in the air. thats when it gets in your lungs . Bad bad bad. Thats why i recomended the ceramic blanket.

Man there is a product out for auto use, mainly older chevys with aftermarket headers, cause these type headers burn up chevy starters, it's a wrap, like a roll of tape, i think it's called thermal wrap, it works good, also for protecting spark plug wires. You can get it cheap from ebay/jc whitney.