Pressurised aluminium body.

It looks like this thread, and construction option will never go anywhere because it is not allowed to fly. This is probably true on both sides of the pond.
Although it would defeat the whole object of the idea, which is reducing weight and lowering costs, it seems you can even TIG weld drinks cans together even though this will have probably annealed the very part of the structure helping to keep the strength up!

Once I have build some representative body tubes using both the adhesive and solder options, I will power them on a test rig, against a thrust stop, to see what kind of motor power these re-purposed tubes can withstand without getting crushed.

Before anyone has kittens about that, I was once lucky enough to be part of a team that statically tested Hydrazine thrusters at RAF Westcott, Buckinghamshire, which was then the home of PERME, (The Propellants, Explosives, and Rocket Motor Establishment) I was merely a minion, but that does make me a professional rocket thruster test technician minion, so I will be taking every care, telling the neighbours when to duck, and locking the dogs in the house first.

Beer cans are pretty thin, but they work much like the stainless steel balloon tanks of the early Atlas years (I think Centaur still uses them). The strength of the tank is imparted by the pressure. without being pressurized, balloon tanks will crumple under their own weight.

Working with aluminum, you need to weld it, though you can get some decent results from bonding it. 6061 is a waste of money unless you heat treat it. 5000 series is MUCH cheaper and doesn't require heat treating (IIRC 6061 un-heat treated is actually weaker than 5000, however, once heat treated, it become stronger)

shreadvector said:

A metal body tube does indeed violate the safety code.

If it comes in ballistic (arc over and streams in like a javelin with gravity or under power) and hits a human, the metal tube will slice into them and take a "core sample" of their head and brain (or whatever other body part you hit).

A cardboard tube will crumble if thin walled or it will be blunt if thicker walled.
Yes, generally a nose cone that is too hard or dense is a concern, but a metal tube is "primary structure". it is not a small part like a motor hook or screw eye.
This will violate National Fire Code and be illegal in most states.

Click to expand...

I see plenty of fiberglass and carbon fiber rocket kits. -Why are these allowed, but aluminum is not? Carbon is significantly stronger, and while it's lighter for the same strength, I'd still not want to be hit by it (or even 'glass, for that matter) if it's coming in ballistically.

Tigerstripe40,
I didn't want to depart from the beer cans to other grades of alloy because I cannot form it into the wafer thin tube required.
Our can sizes I Europe are 66mm (beer) and 53mm OD (Red bull) so I think I will concentrate on experimenting with the 53mm size? We don't get aluminium bottles like you do in the States. What size choices do you have?
Soft soldering looks to be a good option for joints, if a tad heavy. I have also successfully used acetone to thin down a standard automotive windshield mastic to a watery consistency, which if then left to evaporate shows no loss of adhesion, and forms into a hard rubber, so this could maybe be sparingly applied to each joint with a syringe. This will then wick into the joint surfaces to form cast in place o rings on the inside of each body joint.
I have a carbon tube sample with a .004" wall thickness and 1 1/2" diameter, made by a simple wrap and join method rather than wound. It is from a fishing pole. It is very strong for it's weight.
How about this as a safety feature that would put beer can thickness alloy tubes way ahead of carbon:- The strength and rigidity of the thin alloy is only there when the assembly is pressurised, so each end of the body tube could have a device in place that punctured and deflated the tube if it impacted a surface ballisticly, so it instantly reverted from rigid tube to safely deforming crumple zone!
With the advent of modern materials, someone in authority needs to re visit this area of the codes, and perhaps even do some ballistic gell testing to see how these modern tubes behave when coming in ballistic and hitting someone. I've a hunch that it won't look good as the rigid tubes are not going to absorb any of the in line forces, just transferr them.
It shouldn't be too hard to devise a drop test of some sort that has gell blocks land on representative tubes at representative speeds and weights to give some idea of dangers and benefits.
What about nose cones that absorb the energy in the same way as F1 race car nose cones do? During design, they have to be able to crash the car into a static block at about 30 mph, and the chassis must be in race condition with just a replacement nose cone, or they are not allowed to compete!! Bloody clever.
It is a shame that "myth busters" is on it's last series!!!

You can always shake a beer can, turn it upside down, then open it. Easy beer-can rocket.