- 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 jigowatts 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. It was used in the first version of the DeLorean time machine to create the nuclear energy needed (1.21 gigawatts) to create temporal displacement. One pellet of plutonium covered one trip. Dr. Emmett Brown obtained the plutonium from Libyan nationalists that raided a power plant earlier that month, giving them the assurance that he would build them a bomb with it. However, he sent them an empty bombshell casing comprised of used pinball machine parts instead. This drove the Libyans to sent a team out to Twin Pines Mall to kill him.
Dispensing the plutonium into the DeLorean required donning a full radiation suit and rotating the container (which encased a pellet of the deadly element within a red liquid) over a slot. Once the pellet was sucked into the flux capacitor, the process was complete and it was safe to remove the radiation suit.
Doc was preparing to travel 25 years into the future when he realized that he had left the extra plutonium in his truck ("How did I ever expect to get back? One pellet, one trip, I must be out of my mind!") , and was preparing to get it when the Libyans arrived to exact their revenge. Thus, the extra plutonium was not taken with Marty McFly as he accidentally traveled to 1955 while escaping the Libyans. After arriving at Lyon Estates, the roentgen meter measured empty and Marty was forced to hide the DeLorean until he found Doc in 1955.
Plutonium was not readily available in 1955 or 1985. In 1985, Marty remarked to Doc that "You don't just walk into a store and buy plutonium!", while in 1955, young Doc 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 settled on an alternate plan, by channeling a bolt of lightning into the flux capacitor. After their plan succeeded and Marty saved Doc from being killed by the terrorists, Doc traveled to 2015 where he upgraded the time machine from plutonium to a Mr. Fusion which only required garbage to produce nuclear fusion rather than fission.
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 a refrigerator into a nuclear test site and wait for the explosion.
- Back to the Future
- Back to the Future: The Game