What Takes 55,000Hp Just to Run the Fuel Pump?

The mighty F-1 engine of the Saturn V rocket – recently reverse-engineered.


Interesting excerpts from an engineering perspective:

Each F-1 engine was uniquely built by hand, and each has its own undocumented quirks. In addition, the design process used in the 1960s was necessarily iterative: engineers would design a component, fabricate it, test it, and see how it performed. Then they would modify the design, build the new version, and test it again. This would continue until the design was “good enough.”

“Because they didn’t have the analytical tools we have today for minimizing weight, everything was very robust,” noted Betts, when I asked what they found as they tore down the engine. “That’s apparent in really every aspect of the engine. The welds—”

“Oh, the welds!” interrupted Case. “The welds on this engine are just a work of art, and everything on here was welded.” The admiration in his voice was obvious. “Today, we look at ways of reducing that, but that was something I picked up on from this engine: just how many welds there were, and how great they looked.”

“You look at a weld that takes a day,” he continued, “and there are thousands of them. And these guys were pumping engines out every two months. It’s amazing what they could do back then and all the touch labor it took.”

An engine like the F-1 is sort of like two separate rocket engines: one small, one large. The smaller one consumes the same fuel as the larger, but its rocket exhaust is not used to lift the vehicle; instead, it drives the enormous turbopump that draws fuel and oxidizer from the tanks and forces them through the injector plate into the main thrust chamber to be burned.

As with everything else about the F-1, even the gas generator boasts impressive specs. It churns out about 31,000 pounds of thrust (138 kilonewtons), more than an F-16 fighter’s engine running at full afterburner, and it was used to drive a turbine that produced 55,000 shaft horsepower. (That’s 55,000 horsepower just to run the F-1’s fuel and oxidizer pumps—the F-1 itself produced the equivalent of something like 32 million horsepower, though accurately measuring a rocket’s thrust at that scale is complicated.)

Fascinating article.

As I’ve noted previously, my father worked for IBM on the Saturn V Instrument Unit – the rocket guidance system. I got to see all of the Saturn launches as a child growing up on Florida’s Space Coast. I don’t think I’ll ever see anything that impressive again in my lifetime.

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