Same as in the title: how many years did Cooper experience away from Earth? In the end they waste 23+ years on the water planet and 51+ years when the Endurance gets almost destroyed, but while for people on Earth 70+ years pass, I would like to know how many years they felt they spent on their mission, not including the time he spent in hypersleep.
Did they say something like that in the movie? Is it even possible to tell?
Not including hypersleep, Coop only experienced Months at best. They did not have extended supplies and even a few extra days awake in the beginning would have taxed their supplies. This is seen in the scene prior to their I believe 1 Month wakeup, Followed by the 2 years to reach the Saturn-adjacent wormhole/gravitational anomaly. When they made it to the solar system (black hole system?) with the three planets surrounding Gargantua, they spend most of the trip to orbit asleep as well.
Planetary distances with their technology would take months to years as seen in our solar system. They would have to sleep, to conserve oxygen; let alone food or water. First from before their nap:
Amelia: Don't stay up.
Cooper: I'll be in a minute.
Amelia: Just remember Coop, you're literally wasting your breath.
Then from the discussion on which planet to go to first:
Amelia: We have to think about time as a resource just like...
...oxygen and food.
Going down there [To Miller's] is gonna cost us [time, due to gravitational time dilation].Doyle: Okay look, Dr. Mann's data is promising, alright, but it's gonna take us months to get there, and Edmunds', it's even further.
So Cooper literally sees his kids lives pass him by. Years to months, as he sleeps through most of his time, and gravitational effects dilate the rest of it.
The five major events seen on screen amount to hours, maybe a day. Travel through the wormhole, landing on the water planet, spending time to save private Ryan, slingshot around and falling into Gargantua are shown to be hours at best. The down time between these events is not shown much.
This is in contrast to how much time passed on Earth, which is roughly 75~90 years depending on his age when he left. Also contrasting to how much linear time he experience including sleep, which is 3~4 years. 2 years From Earth to Saturn's wormhole, let's say a year and a half between reaching Miller's and then Mann's planet. Only a day or two for the slingshot around Gargantua, Falling into Gargantua, Tesseract, and rescue. Of course, cryogenic hyper sleep would mean he didn't physically age this much, so he's only a few months older biologically speaking.
