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National Aeronautics and Space Administration

Space Launch SystemRS-25 Core Stage EnginesPowerful Proven Propulsion for America’s Exploration of Deep Space: The SLS RS-25 Engine

The RS-25 is half of the powerful, proven SLS propulsion systems designed to launch humans and large exploration payloads to the Moon and ultimately to Mars and beyond. Four RS-25 engines, along with two 5-segment solid rocket boosters, will give SLS approximately 8.8 million pounds of thrust during launch – more lift than any current launch vehicle and 15 percent more than the Saturn V rockets that launched astronauts on journeys to the moon. With unmatched payload mass and volume capability, the advanced, super heavy-lift SLS is the only rocket that can send the Orion spacecraft, astronauts, and a large cargo to the Moon on a single mission. This reduces the number and complexity of in-space operations and increases the chances of mission success.

Designed and built by Aerojet Rocketdyne of Sacramento, California, RS-25 engines helped power the space shuttle over three decades through 135 missions, accumulating more than 3,000 starts and one million seconds of ground test and flight operation time. The SLS Program has an inventory of 16 RS-25 flight engines from the Space Shuttle Program to support the first four SLS missions. While each shuttle used three RS-25 engines, each SLS mission requires four. While shuttle engines operated at 104.5 percent of rated thrust, each SLS engine will operate at 109 percent thrust – approximately 512,000 pounds of vacuum thrust. Originally developed for the Space Shuttle Program, the RS-25 was updated five times during the shuttle program to improve service life, durability, safety,

RS-25 Rocket Engine Call-outs: 1-4 - Turbo Pumps, 5 - Main Combustion Chamber, 6 - Nozzle, 7 - Engine Controller

RS-25 Engine Facts

Thrust............................... 512,000 pounds

Size/Weight ..................... 14 feet x 8 feet, 7,775 lbs.

Operational Thrust .......... 109%

Operational Time ............ 8 minutes

Operating Temp. Range... - 423 to + 6000 degrees F

FS-2015-11-105-MSFC NASA Facts

National Aeronautics and Space Administration

George C. Marshall Space Flight CenterHuntsville, AL 35812www.nasa.gov/marshall

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and performance. SLS takes advantage of that technology investment and experience. Fourteen flown engines and two new engines from the shuttle program will be adapted for use on the first four SLS missions. For SLS, the engines will experience increased propellant inlet pressures and temperatures. In addition, the existing inventory is receiving new engine controllers with contemporary avionics, and new exhaust nozzle insulation for the higher heating environment. Two existing development engines are being used at NASA’s Stennis Space Center to hot-fire test updates to the engine, adapt it to SLS performance requirements and operating environments, certify new controllers, and support development of future engine components. Powered by liquid oxygen and liquid hydrogen and employing high performance fuel and oxidizer turbopumps, the RS-25 has the power and efficiency to carry larger payloads without increasing launch vehicle size – ideal for missions more ambitious and challenging than any NASA has ever attempted in the past. The engines for the first SLS launch – Exploration Mission 1 (EM-1) – have completed all modifications, test and checkouts and are ready for installation in the EM-1 core stage. SLS is designed to evolve to greater capability as the nation’s exploration goals become more ambitious. The initial Block 1 configuration can take more than 26 metric tons (57,320 pounds) of crew and cargo to the Moon. Future configurations can send more than 45 metric tons (99,208 pounds) to the Moon. All will be powered by the RS-25. Anticipating the need for new engines after the current inventory is expended, NASA and Aerojet Rocketdyne have restarted production of RS-25s that will cost at least 30 percent less than

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previous RS-25 engines while providing more thrust than the current RS-25 – 521,000 pounds, or 111% of rated thrust. The new variant will be simplified, eliminating the shuttle engine’s reusable features and employing state-of-the-art manufacturing processes, materials, technologies, and inspection techniques that will reduce labor, hardware defects, and production time. One of the most promising manufacturing technologies is selective laser melting. This technology, a form of 3-D printing, uses a high-energy laser and metal powder to produce parts more quickly and at lower cost than possible with conventional manufacturing methods. Because they are not welded, these printed parts are structurally stronger and more reliable, resulting in a safer vehicle. The first part has already been hotfire tested and more are planned for the future. With greater performance and lower cost, the RS-25 will be powering human exploration for years to come.