SpaceX initially envisioned a 12-meter-diameter Interplanetary Transport System (ITS) concept in 2016 which was only planned for Mars travel and other interplanetary uses. In 2017, SpaceX designed a smaller 9-meter-diameter "Big Falcon Rocket" to replace all of SpaceX launch capabilities— Earth-orbit, lunar-orbit, interplanetary missions, and potentially, even earth transit—but do so on a fully reusable set of vehicles with a lower cost structure. A large portion of the components on Starship are made of 301 stainless steel. Private passenger Yusaku Maezawa has contracted to fly around the Moon in Starship in 2023.