What kind of power supply do TARS and CASE and other such automatons use? How do they recharge? Radioisotope Thermoelectric Generator? Solar power? Eating small rodents?

It appears they can operate for decades (TARS on the ship with Romilly), and they could probably spend years helping the astronauts build the new colony. Do they consume anything? Do they ever need to rest? (these are all variations of "where do they get their energy?")

I suspect this isn't explained at all, since Interstellar wasn't that kind of sci-fi, but perhaps it was discussed in BTS interviews or the novelization. It's also possible that they are shown recharging on the ship, so if the ship's power source was ever explained that would count. The actual screenplay has the following allusions:

TARS powers up a second articulated machine, CASE.


TARS: What’s wrong with him?

DR MANN: Degeneration. He misidentified the first organics we found as ammonia crystals. We struggled on for a time, but ultimately, I decommissioned him and used his power source to keep the mission going.

Romilly watches Tars crouch down beside Kipp and connect Kipp to his own power. Kipp shows signs of life ...

Cooper looks over the kitchen. Cooper sees a familiar-looking articulated machine

COOPER: Is that ...?

ADMINISTRATOR: The machine we found out near Saturn when we found you, yes. Its power source was shot, but we could get you another if you want to try and get it up and running again.


I don't believe it's ever mentioned explicitly (I half expect to be proven wrong), but what we do know is:

  • after Coop wakes up, he's told TARS has been found but "the power source is shot"
  • it seems they work in a vacuum, since it worked while "in" the black hole
  • they appear able to work under water (during the whole "tidal wave" incident), although we don't actually see them submerged
  • as you mention, they appear to work for decades though they could have been "recharging"

The only limitation I can see those imposing is that it's unlikely to be any kind of chemical battery or generator¹. Beyond that, it's really a toss-up between some kind of giant super-capacitor and the radioisotopes.

The radioisotopes sound cool (it's proper space-age technology after all), and NASA are hard at work coming up with new more durable and powerful versions — but the locomotion displayed on screen is going to need a lot of torque, thus rather a lot of current. Exercise for the reader: ask the Mythbusters guys whether “the next generation of nuclear power plants for future space missions” would be enough …

On the down side, those things are far from cool (see the space-age link above):

This complete module is placed inside a case with large radiator fins to help dissipate excess temperatures as high as 1,000 °C. This massive heat can also be used to keep the spacecraft warm despite outside temperatures being near absolute zero.

Ultimately it's down to whether that research bore enough fruit (in Nolan's vision of the timeline) to be suitably puissant to power the robots through all that running around, digging, and rescuing people from big waves — without burning them alive afterwards.

Sadly, this probably means the correct answer is a battery made from thin slices of lightly toasted handwavium electrode in an unobtainium and parsley sauce².

¹ Hamsters (with wheels) are a very complex, chemically-powered generator.

² [citation needed]

  • plus one for parsley sauce, absolutely essential in a handwavium and unobtanium power source – Megha Mar 15 '18 at 19:08
  • Humans can last for weeks without food but can only do so many push-ups. It's not certain that the robots can maintain high powered motion for long. Theoretically a slower source could charge a secondary storage that can be depleted rapidly for emergencies. I claim they run on electrolytes. It's got what your robot craves. – Haunt_House Mar 18 '18 at 5:25
  • Obey the thirst? Good point. To be fair, either radiation- or electrolyte-powered batteries are feasible, I just don't think they'd put radionucleotides that close to people ... which on reflection is naïve in the extreme. Nuclear-powered pacemakers, anyone? – Will Crawford Mar 18 '18 at 17:46

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