[hydrogen7800]

Yeah, the metal deforms. They are single use devices. Imagine a spherical metal tank, with a thin metal hemisphere welded inside. The hemisphere would invert as the propellant is expelled. Hard engineering and manufacturing problems here. I think there have been piston tanks (which would be reusable with sliding elastomer seals. Not many elastomers play well with hypergolics), but they would be very weight inefficient.