NASA's RS-25 rocket is roughly the same height and weight of two F-15 fighter jets, but with eight times the thrust.

NASA is testing the rocket engine that the space agency hopes will someday propel manned missions to Mars. The RS-25 engine relies on 12-million horsepower and a wider temperature range than any before. NASA says it makes a modern jet engine “look like a wind-up toy.”

Observers looked on outside the Stennis Space Center in Hancock County, Mississippi Thursday as NASA carried out the sixth of seven tests for the main engine of the 70-ton Space Launch System. It was a static fire start test mimicking an actual launch, firing 512,000 pounds of thrust for 535 seconds.

“It is the most complicated rocket engine out there on the market, but that's because it's the Ferrari of rocket engines,” Kathryn Crowe, NASA propulsion engineer, told CNET. “When you're looking at desgining a rocket engine, there are several different ways you can optimize it. You can optimize it through increasing its thrust, increasing the weight-to-thrust ratio, or increasing its overall efficiency and how it consumes your propellant. With this engine, they maximized all three.”

Another NASA engineer explained in a statement that the RS-25, including four turbopumps, is roughly the same height and weight of two F-15 fighter jets. But it produces eight times more thrust, and a single quarter-sized turbine blade produces more horspower than a Corvette ZR1 engine.