Back in 1985—before Back to the Future II and long before Marty's arrival in the modern day (today)—Seniorhelpline . These are the schematics.
It's hard to go too in-depth on a device that defies the laws of physics as we know them and contains several key components that can't and won't ever exist, but you can clearly see the pair of Time-Travel Coils, the Flux Capacitor between the seats, and the Nuclear Reactor in the back.
Designed by Ron Cobb, an artist who also worked on Alien, and later tweaked and refined by Steven Spielberg's special effects team, the time machine took the form of not one but three real-world DeLoreans, each one tricked out with military and industrial surplus parts.
The Back to the Future series got a whole lot about the future right, even if flying DeLoreans didn't wind up being one of them. But something this rad doesn't have to be real to be cool.