Yesterday at the Stennis Space Center in Mississippi, NASA tested a rocket engine that will one day send astronauts to Mars. The RS-25 engine powers the Space Launch System (SLS), a giant rocket in development that's able to lift more, faster, than any rocket to come before.
The test involved convincing the engine that the test stand structure to which it was mounted is an actual rocket. Conditions were then fed to the engine to see how it reacted. At yesterday's test (the sixth so far in a series), the RS-25 was run through a complete launch, blasting 512,000 pounds of thrust over a period of 535 seconds — the precise amount of time it would take to send a spacecraft into space. This firing's central objective involved testing a new controller — €”the engine's "brain."
It was magnificent. The engine was like an inverted volcano. White clouds billowed forth at 13 times the speed of sound, blasting so forcefully that even its component water vapor seemed confused and alarmed. The sound was like a sustained, rolling thunder that you could feel in your teeth, and its timbre dominated even your pulse. The experience was truly awesome in force and effect. The power and fury of the test was terrifying — and yet the RS-25 is perhaps the most peaceful product of the space age thus far. It's not a weapon of war. It powers no ballistic missiles, nuclear or otherwise. It exists only for exploration and the betterment of humankind.
THE FERRARI OF ROCKET ENGINES
The RS-25 has been around for decades now. Described as "the Ferrari of rocket engines," it was originally used as the main engine of the space shuttle. (The engine tested yesterday has already been to space and back.) Though it was designed for reusability, its use on the SLS will be a one-shot deal. As part of the rocket's core stage, it will be jettisoned after launch, falling back to Earth and into the ocean. Using a powerful, reusable engine in single-use conditions allows engineers to push the RS-25 much harder on the SLS than they might otherwise have done on the space shuttle.
Reusable engines are much more expensive than expendable ones. But NASA already has 16 RS-25s that were pulled from the shuttle fleet and are just lying around in warehouses. Because the SLS uses four RS-25 engines per launch, that's enough for four launches. No matter what budget crunches NASA might face in the years ahead, those engines are ready to fly. The first SLS launch is slated for 2018.
Meanwhile, the agency is working with Aerojet Rocketdyne, the company that designed and built the RS-25, to restart manufacturing the engine. Because of new technology and a single-use objective, the next batch will be designed with a goal of reducing costs by 30 percent.
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