The last time NASA fired an F-1 in anger was in 1972, with the launch of Skylab. Since then, the F-1 program has been largely dormant, passed over in favor of the Space Shuttle and its solid fuel booster rockets. But NASA still has a bunch of old F-1s kicking around (17 of them at last count), and last week, the agency got one out of storage at the Smithsonian where it had been sitting for like 40 years and fired up a little piece of it:
This firing was not of the entire F-1 engine, which would have been stupendously more firey. No, what you're looking at is what's called a gas generator, which is an auxiliary rocket engine used to power components of the actual rocket engine. In this case, the gas generator is what powers the turbine that pumps liquid fuel into the combustion chamber on the engine itself: the generator burns liquid oxygen and kerosene, just like a normal rocket engine, but all of that power is fed to a turbine instead of used as thrust.
On the F-1, that turbine spins at 5,500 RPM and produces 55,000 horsepower (!), while driving over 40,000 gallons of fuel into the F-1 combustion chamber every minute. So yeah, the fact that this rocket engine doesn't even count as a real rocket engine when it's attached to the F-1 should give you a good sense of how ridiculously powerful the whole thing was.
The F-1s worked incredibly well, both in terms of power and reliability, and NASA is hoping to learn from the design of the F-1 as it develops booster rockets to power the Space Launch System. Last year, NASA awarded three contracts aimed at improving the affordability, reliability and performance of the SLS boosters, and one of these contracts is focused entirely on the F-1: the engine could soon be back, and better than ever.