What is Composite overwrapped pressure vessel (COPV)?

A Composite overwrapped pressure vessel or COPV is a special tank that holds gas tightly using layers of strong plastic fibers wrapped around a metal skin.

Imagine a soda can. It is made entirely of metal, which is sturdy but heavy. Now imagine wrapping that can in thick yarn until it becomes super tough and light. That is what a COPV does for things like rockets or airplanes. The metal inside acts like a soft inner tube to keep the gas from leaking out through tiny holes. The plastic fibers wrapped around it act like muscle fibers, holding the pressure with incredible strength without adding much weight.

Think about a basketball. The rubber bladder inside holds all the air. Now picture wrapping that basketball in many layers of strong string. The string stops the ball from bursting when you squeeze it hard, while the rubber keeps the air from sneaking out. In a COPV, the metal liner is the rubber bladder, and the composite layer is the string. This combination makes the tank much lighter than an all-metal one, which helps rockets fly higher because they do not have to carry as much dead weight.

Scientists use these tanks in spaceships and even in hydrogen fuel cell cars. By using lightweight plastic instead of heavy steel for the main structure, engineers can carry more fuel or passengers without making the vehicle too heavy to move easily through the sky.