DeLorean time machine


In the Back to the Future franchise, the DeLorean time machine is a time travel vehicle constructed from a retrofitted DMC DeLorean. Its time travel ability is derived from the "flux capacitor", a component that allows the car to travel to the past or future. This occurs when the car accelerates to 88 miles per hour and requires 1.21 [|gigawatts] of electricity.
In 2021, the time machine was added to the Library of Congress's National Historic Vehicle Register.

Operation

The control of the time machine is the same in all three films. The operator is seated inside the DeLorean, and turns on the time circuits by turning a handle near the gear lever, activating a unit containing multiple fourteen- and seven-segment displays that show the destination, present, and last departed dates and times. After entering a target date with the keypad inside the DeLorean, the operator accelerates the car to 88 mph, which activates the flux capacitor. As it accelerates, several coils around the body glow blue/white while a burst of light appears in front of it. Surrounded by an electric current similar to a Tesla coil, the whole car vanishes in a flash of white/blue light seconds later, leaving a pair of fiery tire tracks. A digital speedometer is attached to the dashboard so that the operator can accurately gauge the car's speed.
Various proposals have been brought forth in the past by fans of the movie franchise for why the car has to be moving at 88 mph to achieve temporal displacement, but actually the production crew chose the velocity simply because they liked how it looked on the speedometer, modified for the movie. The actual speedometer on the production DeLorean's dashboard only goes up to 85 mph, and the car itself was criticized for being underpowered.
Observers outside the vehicle see an implosion of plasma as the vehicle disappears, leaving behind a trail of fire aligned with the DeLorean's tires, while occupants within the vehicle see a quick flash of light and instantaneously arrive at the target time in the same spatial location as when it departed. In the destination time, immediately before the car's arrival, three large and loud flashes occur at the point from which the car emerges from its time travel. After the trip, the exterior of the DeLorean is extremely cold, and frost forms from atmospheric moisture all over the car's body. Vents on the back heat the vehicle after time travel.
The DeLorean suffers assorted malfunctions and damage over the course of the trilogy. In the first film, the car has starter problems and has a hard time restarting once stopped, much to Marty's repeated frustration. In the second film, the destination time display malfunctions and begins to show a series of random dates, causing Doc to be sent back to 1885 when the DeLorean is struck by lightning with him inside. In the third film, a note left by Doc's 1885 self reveals that the DeLorean's flying circuits were destroyed by the strike. After Marty travels back to 1885, the fuel line and fuel injection manifold both suffer damage, leaving the car unable to move under its own power.
The time machine is electric and requires a power input of to operate, originally provided by a plutonium-fueled nuclear reactor. In the first film, following Marty's accidental trip from 1985 to 1955, Doc has no access to plutonium in 1955, so he outfits the car with a large pole and hook to channel the power of a lightning bolt into the flux capacitor and send Marty back to 1985. During Doc's first visit to 2015, he has the machine refitted to fly in addition to standard road driving, and he replaces the nuclear reactor with a Mr. Fusion generator that uses garbage as fuel.
Although the Mr. Fusion unit provides the required power for the time machine, the DeLorean is still powered by an internal combustion engine for propulsion. The fuel line is damaged during Marty's trip to 1885 in Back to the Future Part III. After he and Doc patch it, they attempt to use whiskey as a replacement fuel since commercial gasoline is not yet available. The test fails, damaging the car's fuel injection manifold and leaving it unable to travel under its own power.
Doc and Marty consider options to reach the required 88 mph and ultimately settle on pushing the car with a steam locomotive. They replace the DeLorean's standard wheels with a set designed to mate with train rails. For the extra power needed to push it up to speed, Doc adds his own version of "Presto Logs" to the locomotive's boiler and chooses a location with a straight section of track long enough to achieve 88 mph.

"Jigowatts"

The power required is pronounced in the film as "one point twenty-one jigowatts", with a "jigowatt" referring to "one billion watts". The spelling of "jigowatts" is used in the script and was also the spelling used in the closed-captioning in earlier home video versions of the film. However, the correct spelling is "gigawatts". Although rarely used, the "j" sound at the beginning of the SI prefix "giga-" is an acceptable pronunciation. Later versions of closed captioning, such as in the 2020 DVD Trilogy release have corrected the spelling to "gigawatts". In the DVD commentary for Back to the Future, Bob Gale states that he had thought it was pronounced this way because it was how a scientific adviser for the film pronounced it. The "jigowatts" spelling is used by Alan Dean Foster in the novelizations of the second and third films.

Equipment

Flux capacitor

The flux capacitor, which consists of a rectangular-shaped compartment with three flashing Geissler-style tubes arranged in a "Y" configuration, is described by Doc as "what makes time travel possible". The device is the core component of the time machine.
As the time machine nears 88 mph, light coming from the flux capacitor begins pulsing more rapidly until it becomes a steady stream. Doctor Emmet Brown originally conceived the idea for the flux capacitor on November 5, 1955, when he slipped on the edge of his toilet while hanging a clock in his bathroom and hit his head on the sink. In 1955, Doc had named the flux capacitor the "Flux Compresser" as shown on 1955 Doc's diagram. A similar flux capacitor is also seen in the chimney headlamp of Doc's second time machine, the Time Machine Locomotive, at the end of Back to the Future Part III.
Although the films do not describe exactly how the flux capacitor works, Doc mentions at one point that the stainless steel body of the DeLorean has a direct and influential effect on the "flux dispersal", but he is interrupted before he can finish the explanation. The explanation is finished in BTTF's "Delorean Time Machine; Doc Brown's Owners' Workshop Manual", which says "However, the stainless-steel construction of the DeLorean would serve to make the Flux Dispersal uniform across the entire surface area of the vehicle."
The instruction manual for the AMT/ERTL DeLorean model kit also states: "Because the car's stainless steel body improves the flux dispersal generated by the flux capacitor, and this in turn allows the vehicle smooth passage through the space-time continuum".

Time circuits

The time circuits are an integral part of the DeLorean time machine. They were built with an input device and a display. The display was divided into three sections: destination time, present time, and last time departed, all annotated with Dymo labels. Each display includes a month, a day, a year, and the hour and minutes in that point in time. The years on the time circuits were limited to four digits and there were no possible negative years that could be reached, i.e. years before "0 A.D.". This means the DeLorean could travel to any time from 12:00 am on January 1, 1 B.C. to 11:59 pm on December 31, A.D. 9999.
The destination time display shows the date that the operator wants the DeLorean to go to, the present time display shows the DeLorean's current location in time, and the last time departed display shows what point in time the DeLorean originally was after making a journey through time. Doc demonstrated its capabilities to Marty after its first test, giving two well-known but erroneous dates as examples: the signing of the Declaration of Independence, July 4, 1776; and the birth of Christ, December 25, 0000. He also displayed the day that he first conceived of the flux capacitor, by which he marks the day he invented time travel, November 5, 1955, as he explains to Marty in the beginning of the first film.
During the second film, because of Biff Tannen's tampering following his theft of the DeLorean, the time circuits began malfunctioning, displaying January 1, 1885, in the destination time display. A bolt of lightning triggers the malfunction to send the DeLorean from 1955 to 1885. Though the vehicle was in mid-air, the spin created by the lightning bolt allowed it to reach 88 mph. Doc is trapped in 1885 and repairs were impossible because the time circuit control microchip, which governed the time circuits, was destroyed by the lightning bolt, and suitable replacement parts would not be invented until at least 1947. Doc places repair instructions and a schematic diagram in the time machine to enable his 1955 counterpart to repair it using components from that era – which included vacuum tubes — before boarding it up within a silver mine. He then writes Marty a letter explaining the situation and places it in the custody of Western Union, with instructions to deliver it to Marty in 1955.

Mr. Fusion

The Mr. Fusion Home Energy Reactor is the name of a power source used by the DeLorean time machine in the Back to the Future trilogy. It can be seen for the first time at the end of Back to the Future when Doc pulls into the McFly's driveway after a trip to the year 2015. It was a piece of technology he was only able to obtain due to his journey to 2015, which in the movie existed by then. It is a parody of Mr. Coffee machines, which were very popular at the time of filming. The appliance from which the prop was made was actually a Krups "Coffina" model coffee grinder.
The Mr. Fusion Home Energy Reactor converts household waste to power for the time machine's flux capacitor and time circuits using nuclear fusion, presumably cold fusion. In the film, Mr. Fusion allows the DeLorean time machine to generate the required 1.21 gigawatts needed to travel to any point in time. The energy produced by Mr. Fusion replaces plutonium as the primary power source of the DeLorean's time travel, allowing the characters to bypass the arduous power-generation requirements upon which the plot of the first film hinges. The plutonium fission reactor was most likely left installed underneath Mr. Fusion as a backup power source.
The Mr. Fusion can provide enough power to the flux capacitor and the time circuits, but is not used to power up the DeLorean itself, which makes use of an ordinary gasoline combustion engine to reach the 88 mph speed necessary for it to time travel. This limitation proved crucial in the third movie when Doc and Marty find themselves stuck in 1885 and unable to drive the DeLorean due to a punctured fuel line. The vehicle's hover system is powered by Mr. Fusion and is capable of bringing the DeLorean up to the required 88 mph. However, the flight systems are destroyed as a result of the lightning strike that occurs at the end of the second film, leaving Marty to rely on the original combustion engine, which is also disabled.