photography concluded in December 2013. Production had a budget of , less than was allotted by Paramount, Warner Bros., and Legendary Pictures. Production design Interstellar features three spacecraft— a ranger, the Endurance, and a lander. The ranger's function is similar to the Space Shuttle's, being able to enter and exit planetary atmospheres. 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." Lastly, the lander transports the capsules with settling equipment to planetary surfaces. Crowley compared it to "a heavy Russian helicopter." The film also features two robots, CASE and TARS, as well as a dismantled third robot, KIPP. Nolan wanted to avoid making the robots anthropomorphic and chose a quadrilateral design. The director said: "It has a very complicated design philosophy. It's based on mathematics. You've got four main blocks and they can be joined in three ways. So, you have three combinations you follow. But then within that, it subdivides into a further three joints. And all the places we see lines—those can subdivide further. So you can unfold a finger, essentially, but it's all proportional." Actor Bill Irwin voiced and physically controlled both robots, but his image was digitally removed from the film, and actor Josh Stewart's voice replaced his voicing for CASE. The human space habitats resemble O'Neill cylinders, a theoretical space habitat model proposed by physicist Gerard K. O'Neill in 1976. Sound design and music Gregg Landaker and Gary Rizzo were the film's audio engineers tasked with audio mixing, while sound editor Richard King supervised the process. Christopher Nolan sought to mix the sound to take maximum advantage of theater equipment and paid close attention to designing the sound mix, like focusing on the sound of buttons being pressed with astronaut suit gloves. The studio's website stated that the film was "mixed to maximize the power of the low-end frequencies in the main channels, as well as in