Bold claim: the truck-sized engines underneath NASA’s legendary behemoth aren’t just powerful—they’re historic marvels you can still see at work today. The largest self-propelled ground vehicle on Earth, officially recognized by Guinness, sits at NASA’s Kennedy Space Center in Florida. Known as Crawler-Transporter 2 (CT-2), this leviathan is roughly the size of a baseball diamond, more than five decades old, and still poised to support the United States’ space program for many years to come. NASA notes its top speed is a modest 2 miles per hour, and that pace drops further when the CT-2 carries a launch payload. Even at that crawl, the transporter has logged over 2,300 miles on its odometer, driven by two gigantic ALCO 251C V16 diesel engines with a combined output of 5,500 horsepower.
To accommodate heavier loads for the Space Launch System (SLS) rockets—the backbone of Artemis aimed at returning humans to the Moon—the CT-2 underwent a Super Crawler upgrade. This upgrade enables it to move the extra weight of the SLS, while budget pressures in Congress loom as a separate potential factor influencing future missions. All told, the machine itself weighs 6.6 million pounds, and the SLS rocket it moves adds another 5.8 million pounds of mass. The dual diesel engines work in tandem with 16 electric traction motors delivering a total of 6,000 horsepower and instantly variable torque. In 1965, CT-2 would have required the power of 20 high-performance V8 Mustangs to achieve the same mobility; by 2026, its horsepower footprint could be likened to the output of about four Lucid Air Sapphire electric sedans—an interesting contrast between heritage and modernity.
But were those ALCO engines built specifically for space work, or did they start life elsewhere? ALCO, short for American Locomotive Company, manufactured these engines in Schenectady, New York, long before NASA began using them to move rockets. The original purpose of the ALCO 251C was to power trains across North America, Mexico, and via other routes around the world.
Over time, the 251C persisted even after ALCO’s dissolution in 1969. Today it mainly serves as a stationary backup generator for industrial and municipal facilities. Its reliability for NASA’s needs—high uptime, long service life, and readiness in unpredictable Florida weather—speaks to why NASA trusts this engine to accompany its space vehicles.
This engine is genuinely enormous: each cylinder spans 9 inches in diameter with a 10.5-inch stroke, equating to roughly 10.95 liters per cylinder. With 16 cylinders per engine and two engines, the total displacement is staggering, underscoring just how much power it takes to relocate immense payloads. Fuel efficiency is not its strong suit—at around 32 feet per gallon, CT-2’s fuel economy is approximate 165 gallons per mile of movement, a reminder that this vehicle prioritizes capability over efficiency.
When footage of NASA’s upcoming manned lunar missions rolls, you’ll likely see CT-2 at work, performing the core task it was designed for six decades ago. It’s a reminder that, in aerospace, some engineering legacies endure long after their creators have passed into history—and perhaps that’s a kind of athleticism we should all admire, even if we’re not contemplating a Moon mission anytime soon.
