# Does the BttF time travel require fuel/power?

After seeing this question about the time-travelling range of the DeLorean, the consensus was that it was merely restricted by the controls (a 4 digit number, giving it a range of 0-9999).

However, the goal of Back to the Future 1 was to give the Flux Capacitor enough (electrical) power to function correctly; at the end of BttF 2, when Doc Brown arrives and tells him he needs to go to the future, he starts rooting through the trash for fuel; and then in BttF 3, the gas tank gets punctured, (effectively) stranding them in the past.

So my question is - does the time travel require "fuel"? Or is it just for the driving around town?

• The car's engine (needed to get to the requisite 88mph) requires gasoline. The time travel engine is powered by "Mr Fusion", which converts garbage to electrical power (presumably by atomic fusion). Hence in BttF the train was able to push the DeLorean to speed without any gasoline in its tank. Jul 17, 2015 at 4:46
• Jul 17, 2015 at 4:51
• If the DeLorean time machine wasn't tied to the gravity well (it doesn't physically move in relation to the Earth while time traveling), it could simply fall straight down to achieve 88 mph.
– user16696
Jul 17, 2015 at 5:16
• @janeS no, it didn't fly, it was gliding from enough momentum to temporarily overpower gravity. At the end of the movie it rolls to a stop on the present train tracks before it got smashed by the train. The Doc's future train or the flying DeLorean parts most likely did require nuclear levels of energy to operate, unlike the regular combustion engine of the non flying DeLorean. That would make a good question tho
– user16696
Jul 17, 2015 at 5:32
• @cde problem with falling to achieve 88 mph is, that after they travel in time, they will land with the same momentum. Jul 17, 2015 at 6:04

From what I'm seeing in this article: http://backtothefuture.wikia.com/wiki/Mr._Fusion yes fuel is needed for time travel. As the article states

the Mr. Fusion Home Energy Reactor converted household waste to power the time machine's flux capacitor and time circuits using nuclear fusion. (It is thought that this is cold fusion.) Mr. Fusion allowed the DeLorean time machine to generate the required 1.21 gigawatts to travel through the space-time continuum. The energy produced by Mr. Fusion replaced plutonium as the primary power source of the DeLorean's time travel and flight capabilities.

But if you recall in the first movie, the flux capacitor was powered by plutonium, not the petroleum fuel of the DeLorean. But technically the car's gas tank would also be required for time travel in that it would need to give the De Lorean enough momentum to reach 88mph and thus travel through time.

This is why in the 3rd movie Doc comes up with an alternate method of accelerating the vehicle fast enough to reach that speed. Internal combustion engines powered by petroleum fuel were still a few decades away in the Wild West.

• Unless you use something, say a train, to push it to 88mph :) Jul 17, 2015 at 4:48
• I explained that as you posted that Jane :) "This is why in the 3rd movie Doc comes up with an alternate method of accelerating the vehicle fast enough to reach that speed. " Thx though! Jul 17, 2015 at 4:49
• Just to nit-pick, coal is a fossil fuel. Jul 17, 2015 at 12:22
• It was almost bedtime when I posted this, leave me alone :P. Jul 17, 2015 at 16:13
• Once the car was hover-converted, it could also reach 88 mph by flying--and the movies never really make clear whether the flying circuits were powered by Mr. Fusion or the engine that powered the wheels when it was driving. There is reason to think at least some flying cars only needed fusion power to fly, since the Texaco service station offered "fusion gold" and "super fusion plus+" as fueling options. Oct 13, 2015 at 2:03