Interstellar features three spacecraft— the Endurance, a ranger, and a lander. The Endurance, the crew's mother ship, is a circular structure consisting of 12 capsules, laid flat to mimic a clock: Four capsules with planetary settling equipment, four with engines, and four with the permanent functions of cockpit, medical labs, and habitation. Production designer Nathan Crowley said the Endurance was based on the International Space Station : "It's a real mish-mash of different kinds of technology. You need analogue stuff, as well as digital stuff, you need backup systems and tangible switches. It's really like a submarine in space. Every inch of space is used, everything has a purpose." The ranger's function is similar to the Space Shuttle 's, being able to enter and exit planetary atmospheres. Lastly, the lander transports the capsules with settling equipment to planetary surfaces. Crowley compared it to "a heavy Russian helicopter."