NASA tests the 'Ferrari of rocket engines' for mission to Mars

The RS-25 engine for NASA's new Space Launch System rocket makes current jet engines look like "a wind-up toy."

Michelle Starr Science editor
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
3 min read

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Billowing smoke as the RS-25 undergoes testing on August 13. NASA

If we're going to get humans to Mars, we're going to need a bigger rocket with a much more powerful engine.

This is the RS-25, the engine designed for NASA's Space Launch System rocket, intended to launch the Orion spacecraft and, eventually, see humanity on its way to Mars: the next big leap in physically exploring the solar system, our equivalent of putting astronauts on the moon in the 1960s.

At 4:30 p.m. EDT on August 13, 2015, NASA conducted a developmental test firing of the rocket's engines at its Stennis Space Center in Mississippi, the sixth in a series of seven tests for the rocket's main engine. Four RS-25 engines and two solid rocket boosters of five segments each will power the 70-metric-ton rocket configuration into deep space.

"It is the most complicated rocket engine out there on the market, but that's because it's the Ferrari of rocket engines," said Kathryn Crowe, RS-25 propulsion engineer.

"When you're looking at designing a rocket engine, there are several different ways you can optimise it. You can optimise 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 maximised all three."

The resulting engine, according to Martin Burkey of the SLS strategic communications team, blows everything we currently have out of the water.

"The RS-25 makes a modern race car or jet engine look like a wind-up toy," he said in a post on NASA's Rocketology blog.

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An earlier test of the RS-25, which took place on January 9 at NASA's Stennis Space Center in Mississippi. NASA

"It has to handle temperatures as low as minus 400 degrees where the propellants enter the engine and as high as 6,000 degrees as the exhaust exits the combustion chamber where the propellants are burned. It has to move a lot of propellants to generate a lot of energy. At the rate the four SLS core stage engines consume propellants, they could drain a family swimming pool in 1 minute."

The RS-25 produces 512,000 pounds of thrust, which is over 12 million horsepower. It's powered by four turbopumps that each generate 100 horsepower for each pound of weight, with a main shaft that rotates at a rate of 37,000 rpm, compared with 3,000 rpm for a car engine traveling at 60mph (96.5km/h).

"The RS-25 is about the same weight and size as two F-15 jet fighter engines, yet it produces eight times more thrust. A single turbine blade the size of a quarter -- and the exact number and configuration inside the pump is now considered sensitive -- produces more equivalent horsepower than a Corvette ZR1 engine," Burkey wrote.

At such high speeds, even the smallest hitch in the process can cause massive problems, which is why the engines need to be tested extensively in a controlled situation before even thinking about leaving the ground.

The test lasted nearly 9 minutes while NASA engineers collected performance data on the engine. The final test will involve firing all 4 RS-25 engines simultaneously, just as they would be fired during an actual launch of the SLS, Orion spacecraft included.