section_path: Design/Tanks
section_name: Tanks
paragraph_text: Tanks
  
  The propellant tank walls and domes are made from an aluminum–lithium alloy. SpaceX uses an all friction-stir welded tank, for its strength and reliability. The second stage tank is a shorter version of the first stage tank. It uses most of the same tooling, material, and manufacturing techniques.
  
  The F9 interstage, which connects the upper and lower stages, is a carbon-fibre aluminium-core composite structure that holds reusable separation collets and a pneumatic pusher system. The original stage separation system had twelve attachment points, reduced to three for v1.1.