Visible crew/equipment: Murph sneaks into Cooper's truck to get to NASA. Once Cooper closes the vehicle door after placing some blankets into it, a boom mic can be seen in the left wing mirror. (00:22:05)
Visible crew/equipment: When Cooper steps into his car, just before the flat tyre, the boom of a microphone is visible in the reflection of the rear window. Also, the top of head of the boom operator is seconds later and remains visible for quite some time. (00:04:57)
Visible crew/equipment: When Cooper gets on board his pickup with the kids to follow the drone at the beginning of the movie, at the precise moment when Cooper is getting on board a boom microphone is reflected on the door's window moving synchronously with the actor's movement.
Answer: I am not exactly sure what kind of propulsion system is used, however; you must consider that although in our galaxy even the closest planets to Earth take years to travel to, in this alternate universe, the planets may be arranged in a closer formation.