SpaceX also plans to mount Mars missions every 26 months after Red Dragon takes off, regardless of when ITS comes online, to establish a regular cargo route that takes scientific experiments to the Red Planet. (Earth and Mars align favorably, allowing interplanetary missions, just once every 26 months.)
1,000: The minimum number of ships SpaceX aims to send to Mars at every opportunity, once the ITS is fully up and running.
400: The height of the stacked ITS duo, in feet (equivalent to 122 meters). The Saturn V topped out at 365 feet (111 m). Separately, the ITS booster and the interplanetary ship that launches atop it will be 254 feet (77 m) and 162 feet (50 m) tall, respectively.
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300: The amount, in tons, that the reusable ITS booster will be able to launch to low Earth orbit (LEO). The Saturn V could loft 135 tons to LEO, Musk said. (An expendable version of the ITS would have a 550-ton LEO capacity, he added, but SpaceX's Mars-colonization architecture calls for repeated reuse of the ITS booster and spaceship.)
115: The initial average length, in days, of the trip from Earth to Mars aboard the ITS ship. These ships would be launched to Earth orbit atop the ITS booster and then zoom to Mars under their power when the time was right. The trip could be as short as 80 days depending on exactly where Earth and Mars were at the time of departure, said Musk, who added that he envisions eventually slashing the trip time to just 30 days or so.
100: The minimum number of passengers carried aboard each ITS ship, meaning it could take 10,000 flights to get 1 million people to Mars. But the ships may end up transporting about 200 people apiece, Musk said.
51: The total number of Raptor engines used by each ITS stack. The rocket will carry 42 Raptors, while nine will power the ship. (Raptor, the next-generation engine SpaceX is developing, is about the same size as the company's workhorse Merlin engine but three times more powerful, Musk said.)
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20: The maximum amount of time, in minutes, between the launch and landing of each ITS booster. These rockets will touch down softly at their launchpad - currently envisioned to be Launch Pad 39A at NASA's Kennedy Space Center in Florida - and will be quickly readied for another liftoff.
12: Number of people who have set foot on a world beyond Earth to date. All 12, of course, were Apollo astronauts who walked on the moon between 1969 and 1972.
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