Audio problem: Murph's dialogue doesn't sync with her mouth at the lines "you hate farming, Dad." (00:17:43)
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)
Continuity mistake: When Cooper is driving to the coordinates the shot from inside the cab of his truck shows he using the interior light to follow his map, the next shot shows the truck driving away with the light off. (00:22:00 - 00:24:00)
Continuity mistake: When Cooper draws on the board and talks about landing on water, his drawing changes between shots. (01:04:25)
Continuity mistake: When Cooper is trying to console Murph before he leaves, he explains that time will slow down for him. In the first shot of the wrist watches side by side, the watches read at slightly after 9:00. Then Cooper says when he returns they can compare and the watches are shown again. This time they read around 8:20.
Audio problem: Tom's wife coughs into her sleeve as the shot changes; when it switches to Murph's boyfriend, you can see her reflection in the window and she is not coughing. "How long have you had that cough?" he asks, and although she replies "A while," you can see in the reflection that she was originally filmed coughing again as a reply. (01:49:20)
Continuity mistake: Cooper is saying goodbye to Murphy. Her necklace jumps in and out of her T-shirt throughout the scene. (00:38:25)
Revealing mistake: After returning from the ocean planet, the crew has a long discussion on board their ship. Directly behind Cooper, the grey control panels are the pneumatic and pressurization control panels from a Lockheed L1011 airliner. (01:26:30)
Character mistake: Shortly before the drone chase scene Cooper tells Murph to put the truck in second gear. She pushes the gear lever forward, however on the 6-speed manual in the Ram 3500 second gear is in the back row.
Continuity mistake: Cooper drops a coin onto the binary sequence in Murph's room. In the next shot, the coin has moved.
Other mistake: In the docking scene, CASE analyzes the Endurance's spin rate to be 68 revolutions per minute. When the Endurance is shown onscreen, it is not spinning that fast - it is spinning at maybe 20 RPM.
Continuity mistake: When Murphy pleads with Cooper to stay shortly before he leaves, as she shows him the message "STAY" on the notebook, in the first shot she looks down, but in the next one she looks at Cooper.
Continuity mistake: When Murphy asks Cooper to stay, a strand of hair on her right temple alternates from loose to brushed backwards depending on the shot.
Continuity mistake: After Mann says, "You have literally raised me from the dead," the shot changes to Cooper who says, "Lazarus." When the shot goes back to Mann, the reflective sheet he is wearing is propped open more, exposing more of his body. (01:38:10)
Continuity mistake: Coop is consoling Murph about his trip. His watch says 9:07. In the next shot, Coop pulls out another watch to give to Murph. But now both watches say 8:21.
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)
Continuity mistake: At the beginning of the movie when Cooper and the kids arrive to the lake after they took the control of the drone, Murph steps out of the truck and leaves the door open, but in the next shot the door is closed and it's sure that in the entire scene there's no sound of a car door getting closed.
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.
Continuity mistake: Midway through the movie, Cooper is said to be 124 years old while in the new galaxy, and at that time his daughter was still a young girl. Later, when he is back in our solar system and waiting for time to find an opening back to his daughter, who is now in her midlife years, he is awakened at the colony off Saturn, and he's told to take it easy because he's 124 years old but his daughter is a very elderly dying woman. Estimating her age at 90, Cooper should have aged a bit more.
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.