 The time machine has been through several variations. In the first  draft of the screenplay the time machine was a laser device that was  housed in a room. At the end of the first draft the device was  attached to a refrigerator and taken to an atomic bomb test. In the  third draft of the film the time machine was a DeLorean, but in  order to send Marty back to the future the vehicle had to drive the  DeLorean into an atomic bomb test.