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NASA conducts 13th test of Space Launch System RS-25 engine

An RS-25 rocket engines is tested at NASA's Stennis Space Center in Mississippi, the 13th such test for NASA's new Space Launch System. Photo Credit: NASA

An RS-25 rocket engine is tested at NASA’s Stennis Space Center in Mississippi, the 13th such test for NASA’s new Space Launch System. Photo Credit: NASA

The powerful RS-25 engine that will be used on NASA’s new super-heavy-lift Space Launch System (SLS) underwent its 13th test March 23, 2017, at NASA’s Stennis Space Center in Bay St. Louis, Mississippi.

An RS-25 being tested at NASA's John C. Stennis Space Center. Photo Credit: NASA / Aerojet Rocketdyne RS-25 rocket engine test firing at Stennis Space Center in Mississippi NASA photo posted on SpaceFlight Insider

An RS-25 being tested at NASA’s John C. Stennis Space Center. Photo Credit: NASA / Aerojet Rocketdyne

The RS-25 engine

Formerly known to many as the Space Shuttle Main Engine (SSME), an RS-25 burns liquid hydrogen (LH2) and liquid oxygen (LOX). During the shuttle era, each produced produce 491,000 pounds (2,184 kilonewtons) of vacuum thrust while running at 104.5 percent of the rated thrust.

Three at a time, these engines helped launch all 135 Space Shuttle missions into orbit.

SLS, however, will need a bit more power, and part of this testing is to evaluate its durability at its new power level, which is now 109 percent of rated thrust resulting in 512,000 pounds (2,277.5 kilonewtons) of vacuum thrust.

Additionally, the RS-25 will experience other conditions that will be more extreme than during a Space Shuttle flight.

“The engines for SLS will encounter colder liquid oxygen temperatures than shuttle, greater inlet pressure due to the taller core stage liquid oxygen tank and higher vehicle acceleration, and more nozzle heating due to the four-engine configuration and their position in-plane with the SLS booster exhaust nozzles,” said Steve Wofford, manager of the SLS Liquid Engines Office at NASA’s Marshall Space Flight Center, following the first test of the SLS engines in 2015.

Unlike during the Space Shuttle era, the SLS engines will not be reused since the booster will not be recovered. There are currently 16 former Space Shuttle engines at the Stennis facility for use on the first SLS launches. After that inventory is exhausted, however, new engines will be built using modern techniques and materials to lower the cost of producing an expendable version of the RS-25.

The March 23 engine test lasted for approximately 500 seconds which simulated the actual burn time the engines will operate during an SLS launch.

The engine controller

Aerojet Rocketdyne technicians inspect the new controller on the RS-25 development engine. Photo Credit: Aerojet Rocketdyne

Aerojet Rocketdyne technicians inspect the new controller on the RS-25 development engine. Photo Credit: Aerojet Rocketdyne

This firing also included a test of a new SLS engine controller that not only operates the engine, taking commands from the SLS flight computers and translating it to the engine, but also monitors the health and performance of the engine and communicates that back to the flight computers.

The new controller has 20 times more processing power than the Space Shuttle engine controllers it replaces. Increased reliability has been built into it and it weighs 50 pounds (22.7 kilograms) less than its shuttle counterpart.

“Just think about all the advances in computing technology and electronics that have occurred over the recent years, we’ve been able to include those advances into the controller,” said Dan Adamski, RS-25 program director at Aerojet Rocketdyne. “We’ve been able to increase the processing speed, add memory and greatly improve the reliability of the entire controller communication network.”

This particular controller, once the test data certifies its performance, will be installed on one of the four flight engines that will propel the SLS on its maiden flight.

Four RS-25 engines, providing over two million pounds of thrust, along with two five-segment solid rocket boosters will provide the power to lift the SLS off the pad and into orbit.

Currently, the maiden flight of the SLS is tentatively scheduled for late in 2018. That launch will send an uncrewed Orion spacecraft on a journey to orbit the Moon to test all of its systems.

However, following a directive from the Trump administration, NASA is investigating the requirements needed to put a crew on that first launch. If a crewed mission becomes a reality, the extra time needed to ready the flight will push it into 2019, if not later.

Video courtesy of NASA




Lloyd Campbell’s first interest in space began when he was a very young boy in the 1960s with NASA’s Gemini and Apollo programs. That passion continued in the early 1970s with our continued exploration of our Moon, and was renewed by the Shuttle Program. Having attended the launch of Space Shuttle Discovery on its final two missions, STS-131, and STS-133, he began to do more social networking on space and that developed into writing more in-depth articles. Since then he’s attended the launch of the Mars Science Laboratory Curiosity rover, the agency’s new crew-rated Orion spacecraft on Exploration Flight Test 1, and multiple other uncrewed launches. In addition to writing, Lloyd has also been doing more photography of launches and aviation. He enjoys all aspects of space exploration, both human, and robotic, but his primary passions lie with human exploration and the vehicles, rockets, and other technologies that allow humanity to explore space.

Reader Comments

It still saddens me that these pretty engines will eventually be thrown away

Favorites can be jetting outdoor thermal imaging footage gases and comparing them after testing

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