Mr. Fusion

Home Energy Reactor: Turning trash into time travel power since 1985.

Mr. Fusion is the compact, home-use nuclear fusion reactor first seen at the end of Back to the Future that replaced the plutonium requirement for the DeLorean time machine. Constructed by Michael Scheffe, who took over from art department liaison Michael Fink during production, this device was built specifically out of a Krups coffee grinder. It serves as the time machine's power supply, allowing Doc Brown and Marty McFly to generate the necessary 1.21 gigawatts of electricity without needing plutonium or a lightning strike. This invention enables the time machine to function independently in any era where waste is available.

Quick Facts

Primary function: Replacement power supply for the DeLorean
Power output target: 1.21 gigawatts
Builder: Michael Scheffe
Base component: Krups coffee grinder

Lore & Background

The creation of Mr. Fusion was driven by practical production needs as much as narrative ones. When Michael Fink departed the project, he selected Michael Scheffe to replace him as the lead on the build. Scheffe finished the construction of the Flux Capacitor and then designed the replacement power supply using a Krups coffee grinder. Bob Gale said that having an eccentric individual build the time machine in his garage, rather than a corporation, gave it a "slapdash, kind of cool look". The device operates by processing household waste directly into energy for the flux capacitor and the time circuits; the car itself still relies on its gasoline engine to reach 88 miles per hour. Unlike the earlier reliance on plutonium or the clock tower lightning, Mr. Fusion provides a consistent and accessible fuel source derived from common refuse.

Reader's Guide

For fans seeking to understand the physical origins of Mr. Fusion, the key detail lies in its construction material: a Krups coffee grinder. This specific brand and item were chosen by Michael Scheffe to fulfill his role after replacing Michael Fink. The device is not a complex machine built from rare parts but a repurposed household appliance, reflecting Doc Brown's 'slapdash' design philosophy mentioned by Bob Gale. This practical effect approach aligns with the broader production strategy where common objects were transformed into futuristic technology, such as using LMB boxes for time displays and Torr High-Voltage relays for the flux system.

Did You Know?

The time machine requires exactly 1.21 gigawatts of electricity to activate the flux capacitor and travel through time.
A custom speedometer was specifically built for the film because a 1979 law limited standard car speedometers to 85 mph, making 88 mph impossible to display on real gauges.
The DeLorean's time travel ability depends on accelerating to exactly 88 miles per hour (142 km/h).
Five real DeLoreans were used in the filming of the trilogy, plus one "process" car built for interior shots.