NASA's Marshall Space Flight Center is the location of an ongoing initiative to make access to space easier and more affordable. The center conducts extensive space propulsion research; four focus areas include advanced chemical propulsion, plasma propulsion, high-powered electrical propulsion, and propellantless propulsion. There is also a lot of information about the Integrated Space Transportation System and the Space Launch Initiative, which mainly deal with reusable launch vehicles (RLV). The space shuttle is the first generation RLV; second and third generation RLVs aim to increase safety while dramatically lowering launch costs.