A typical communication satellite uses small rocket thrusters to maintain its position in orbit over its lifespan of more than 15 years. Providing fuel to these 'thrusters'throughout the life of the ...mission requires the marriage of clever design, and several manufacturing technologies and, welding is the make-or-break technology for the propellant tanks that carry the fuel. Propellant tanks look plain and unimpressive until one realizes their functional requirements. Unlike fuel tanks on earth where gravity separates liquid fuel from vapors and puts the liquid at the proper opening, in space the forces of gravity are exactly counteracted by centrifugal forces to create zero gravity (more accurately called microgravity).
