Space Shuttle Engines Had 39 Locomotives' Power

When NASA needed to explain just how powerful the Space Shuttle's engines were, they turned to a comparison that would blow people's minds: each main engine weighed about 7,000 pounds—roughly one-seventh the weight of a typical train locomotive—yet delivered the horsepower equivalent of 39 locomotives combined.

This wasn't marketing hype. It came straight from NASA's official documentation during the shuttle era.

The Math Behind the Muscle

The Space Shuttle Main Engine (SSME) achieved this incredible power-to-weight ratio through two high-performance turbopumps. The high-pressure fuel turbopump alone generated 77,310 horsepower—the equivalent of 28 locomotives. Add the liquid oxygen turbopump's 29,430 horsepower (11 more locomotives), and you hit that magical number: 39.

For context, a typical freight locomotive weighs over 400,000 pounds and produces around 4,000-4,500 horsepower. The SSME packed more than 100,000 horsepower into a package that weighed just 3.5 tons.

Engineering at the Extreme

These weren't just powerful—they were precisely powerful. Each engine could throttle between 67% and 109% of rated power, allowing astronauts to fine-tune thrust during ascent. The fuel pump alone spun at 37,000 RPM, moving enough liquid hydrogen to drain an average swimming pool in 25 seconds.

• Total thrust per engine: 418,000 pounds at liftoff
• Operating temperature: up to 6,000°F in the combustion chamber
• Fuel efficiency: 452 seconds specific impulse in vacuum
• Service life: designed for 55 missions, 27,000 seconds of operation

The Shuttle's Retirement and Legacy

The Space Shuttle program flew its last mission in 2011, making this comparison a snapshot of historical achievement rather than current technology. But the RS-25 engines aren't museum pieces yet—NASA is refurbishing them for the Space Launch System, which will power future missions to the Moon and Mars.

The original comparison came from a 1977 Rocketdyne brochure titled "Incredible Facts: Space Shuttle Main Engines," designed to help the public grasp just how revolutionary this technology was. Forty-plus years later, it still does the job.