- Doc: "Unfortunately it requires something with a little more kick: plutonium."
- Marty: "Oh, plutonium. Whoa Doc, do you mean to tell me this sucker is nuclear?!"
- Doc: "No, no, no, no. This sucker's electrical, but I need a nuclear reaction to- to generate the 1.21 gigawatts of electricity I need."
- — Doc and Marty, Twin Pines Mall
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94.
The chemical element plutonium was used in the first version of the DeLorean time machine to fuel an onboard nuclear reactor which could generate the 1.21 gigawatts of momentary power required for temporal displacement of the vehicle while traveling at 88 miles per hour. A vial of plutonium could only power a single jump through time; A round trip would require at least two vials.
Dr. Emmett Brown, unable to obtain the plutonium on his own, made a deal with Libyan terrorists who had raided a nuclear power plant earlier that month. Doc assured them that he would build a bomb with it in return, but sent them an empty bomb casing full of old pinball machine parts instead. This drove the Libyans to track Doc down to Twin Pines Mall and kill him on sight.
Dispensing the plutonium into the DeLorean required use of a full radiation suit. After twisting and removing the reactor cap, a container could be inserted and then rotated into place, causing the vial to drop into the fuel slot. Once the vial was dropped into the reactor, the cap could be replaced, the radiation suit removed, and the empty container discarded. The containers appear to surround the vials with water, likely to contain at least some of the harmful radiation, but little enough to still require a radiation suit to ensure safety.
After refueling the DeLorean with plutonium, Doc prepared to travel twenty-five years into the future, but quickly realized that he had forgotten the case of plutonium in his truck, exclaiming "How did I ever expect to get back? One pellet, one trip. I must be out of my mind!". As he was about to pack up the case, the Libyans arrived for revenge, killing Doc. Marty McFly, seeing Doc dead on the ground, quickly jumped into the DeLorean and drove off without the extra plutonium before the Libyans could kill him too. Marty accidentally enabled the time circuits while escaping the Libyans, causing him to travel through time. Moments after arriving at Lyon Estates in 1955, the roentgen meter fell to empty, flashing a an illuminated warning light and sounding an alarm. Marty was forced to disable the time circuits and hide the DeLorean so he could search for the help of Doc's past self.
Unfortunately, plutonium was not readily available in 1955 or 1985, leaving Marty stranded. In 1985, he remarked to Doc that "You don't just walk into a store and buy plutonium!", while in 1955, young Doc ironically noted that while he's certain that it will be for sale "in every corner drugstore" in 1985, "Here in 1955, it's a little hard to come by." Doc and Marty instead settled on an alternate plan to channel a bolt of lightning into the flux capacitor.
Soon after Marty returned home, present day Doc traveled to the year 2015. While there, he upgraded the time machine. One of these upgrades allowed it to make use of the Mr. Fusion home energy reactor. This reactor relied on nuclear fusion rather than fission, and could make use of everyday garbage as fuel.
Behind the scenes
- The idea of using nuclear energy came as early as the first draft screenplay of Back to the Future, where Marty, stuck in 1952, would have to drive through a nuclear test site to make use of a nuclear explosion to fuel his trip.
- The appearance of a vial of red liquid in a container of clear liquid as plutonium was likely chosen because it sold the idea of some sort of exotic fuel. However, actual plutonium is a solid, grey metal, and is formed into pellets to be used as nuclear fuel.
- Back to the Future
- Back to the Future: The Card Game
- Back to the Future: The Game