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NASA tests shuttle-era rocket engine for Mars mission

NASA tests shuttle-era rocket engine for Mars mission - A RS-25 engine, an improved version of NASA's space shuttle main engine, was test fired at Stennis Space Center in Mississippi on Thursday, burning for 9 minutes to collect data required to clear the power plants for use in the Space Launch System -- SLS -- super rocket NASA is building for deep space exploration missions.

The 535 second long test firing of RS-25 development engine was conducted on A-1 test stand and ran for the planned full duration of nine 9 minutes, matching the time they will fire during an actual SLS launch.

With the propellants burning at 6,000 degrees Fahrenheit, the Aerojet Rocketdyne engine's exhaust plums shot out its liquid hydrogen-cooled nozzle at 13 times the speed of sound, blasting a rising cloud of white steam high into the sky above the test stand.

6 seconds after ignition, the RS-25 engine's new flight computer was programmed to command valve settings that increased the thrust level to 109 percent of the power originally meant for shuttle launchings. The test plan called for the thrust level to reduce to 80 percent before finally throttling back up above 90 percent.

Once called the space shuttle main engine, or SSME, the compact powerplants flew three at a time aboard NASA's winged orbiters, along with a pair of four-segment solid-fuel boosters that provided the lion's share of the initial push out of the deep lower atmosphere.

For NASA's massive 322-foot-tall SLS booster, required for eventual piloted flights into deep space, two more powerful five-segment boosters will be utilized, along with 4 renamed RS-25 engines.

Initially, the SLS first stage will develop around 8.4 million pounds of thrust - 10 percent more than NASA's Saturn 5 moon rockets - with about 2 million pounds of push coming from a quartet of RS-25s.

The initial version of the rocket will lift 70 metric tons to space, while a later version with a more powerful second stage engine will lift 130 metric tons.

First flight of the SLS is planned for 2018 when the rocket will boost an uncrewed Orion capsule around the moon and back to an ocean splashdown and the second test flight, Exploration Mission No. 2, or EM-2, is planned for launch around 2021.

The U.S. space agency's projected budget covers one SLS flight every other year or so, but managers hope to improve processing and efficiency to improve that rate to one mission per year with an ability to launch up to 3 flights in 12 months if warranted.

The SLS engines will be set up in a square pattern at the base of booster, putting them closer to the nozzles of the solid-fuel boosters than they were in the shuttle program when 3 engines were arranged in an offset triangular pattern.

The SLS constellation will subject the engines to higher radiated temperatures and new insulation was tested during Thursday test firing to assist in protecting the nozzles during launch.

The engines usually operated at 104.5 percent the thrust level they were initially designed for and were certified to run at up to 109 percent in certain abort scenarios.

The SLS RS-25s will run at 109 percent as a baseline throttle setting, generating up to 512,000 pounds of thrust each. Engineers are studying ways to improve performance to 111 percent and possibly to 113 percent.