NASA Test Fires SLS Flight Engine Destined to Launch Astronauts Back to the Moon

NASA engineers conduct a successful test firing of RS-25 rocket engine No. 2059 on the A-1 Test Stand at NASA’s Stennis Space Center in Bay St. Louis, Mississippi. The hot fire marks the first test of an RS-25 flight engine for NASA’s new Space Launch System vehicle. Credits: NASA/SSC

NASA engineers have successfully test fired the first flight engine destined to power the agency’s mammoth new SLS rocket that will launch American astronauts back to the Moon and deep space for the first time in nearly five decades.

The flight proven RS-25 powerplant engine previously flew as one of three main engines that successfully rocketed NASA’s space shuttle orbiters to space during the three decade long Space Shuttle era that ended in 2011.

On March 10, NASA engineers conducted a successful 500 second long test firing of RS-25 rocket engine No. 2059 on the A-1 Test Stand at NASA’s Stennis Space Center in Bay St. Louis, Mississippi.

The hot fire marks the first test of an RS-25 flight engine for NASA’s new Space Launch System (SLS) vehicle. It also simultaneously marks a major milestone towards implementing the agency’s vision of sending humans on future deep-space missions to destinations including the Moon, an asteroid and a ‘Journey to Mars.’

“What a great moment for NASA and Stennis,” said Rick Gilbrech, director of NASA’s Stennis Space Center in Bay St. Louis, Mississippi, in a statement.

“We have exciting days ahead with a return to deep space and a journey to Mars, and this test is a very big step in that direction.”

This NASA video shows the full duration hot-fire test:

Video caption: NASA engineers at Stennis Space Center tested RS-25 engine No. 2059 on the A-1 Test Stand on March 10, 2016. This was the first flight engine for NASA’s new rocket, the Space Launch System (SLS), to be tested at Stennis. Credit: NASA

The SLS is the most powerful rocket the world has ever seen and will loft astronauts in the Orion capsule on missions back to the Moon by around 2021, to an asteroid around 2025 and then beyond on a ‘Journey to Mars’ in the 2030s – NASA’s overriding and agency wide goal. The first unmanned SLS test flight is slated for late 2018.

Thursdays hot fire test follows a lengthy series of engine tests with development versions of the RS-25 at Stennis last year that were used to begin proving out the modifications enabling NASA to upgrade the engines for use in the SLS.

The primary goal of the development tests was “to validate the capabilities of a new controller – or, “brain” – for the engine and to verify the different operating conditions needed for the SLS vehicle,” according to NASA officials.

Aerojet Rocketdyne is the prime contractor for the RS-25 engine work and originally built them during the shuttle era.

The remaining cache of 16 heritage RS-25 engines are being recycled from their previous use as reusable space shuttle main engines (SSMEs). They are now being refurbished, upgraded and tested by NASA and Aerojet Rocketdyne to power the core stage of the Space Launch System rocket now under full development.

A cluster of four RS-25 engines will power the SLS core stage. They will fire at 109 percent thrust level for some eight and a half minutes while generating a combined two million pounds of thrust.

Each of the RS-25’s engines generates some 500,000 pounds of thrust. They are fueled by cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX). For SLS they will be operating at 109% of power, compared to a routine usage of 104.5% during the shuttle era. They measure 14 feet tall and 8 feet in diameter.

They have to withstand and survive temperature extremes ranging from -423 degrees F to more than 6000 degrees F.

The workhorse engines are among the most proven in the world, says NASA, having powered 135 space shuttle missions from 1981 to 2011.

“Not only does this test mark an important step towards proving our existing design for SLS’s first flight,” said Steve Wofford, engines manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama, where the SLS Program is managed for the agency, “but it’s also a great feeling that this engine that has carried so many astronauts into space before is being prepared to take astronauts to space once again on SLS’s first crewed flight.”

The next step is to continue hot fire development tests with all the upgrades and qualify all the RS-25 flight engines for SLS launches.

Last November, NASA announced the long awaited decision to formally restart production of the venerable RS-25 engine by awarding a manufacturing contract to Aerojet Rocketdyne.

The existing RS-25 inventory of 16 heritage engines is only sufficient for the first 4 SLS flights.

The maiden test flight of the SLS is targeted for no later than November 2018 and will be configured in its initial 70-metric-ton (77-ton) version with a liftoff thrust of 8.4 million pounds.

SLS-1 will boost the unmanned Orion EM-1 capsule on an approximately three week long test flight beyond the Moon and back.

I was on hand when the welded skeleton of Orion EM-1 recently arrived at the Kennedy Space Center on Feb. 1 for outfitting with all the systems and subsystems necessary for flight.

Orion crew module pressure vessel for NASA’s Exploration Mission-1 (EM-1) is unveiled for the first time on Feb. 3, 2016 after arrival at the agency’s Kennedy Space Center (KSC) in Florida. It is secured for processing in a test stand called the birdcage in the high bay inside the Neil Armstrong Operations and Checkout (O&C) Building at KSC. Launch to the Moon is slated in 2018 atop the SLS rocket. Credit: Ken Kremer/

NASA plans to gradually upgrade the SLS to achieve an unprecedented lift capability of 130 metric tons (143 tons), enabling the more distant missions even farther into our solar system.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Dr. Ken Kremer is a speaker, research scientist, freelance science journalist (KSC area,FL) and photographer whose articles, space exploration images and Mars mosaics have appeared in magazines, books, websites and calendars including Astronomy Picture of the Day, NBC, FOX, BBC,, Spaceflight Now, Science and the covers of Aviation Week & Space Technology, Spaceflight and the Explorers Club magazines. Ken has presented at numerous educational institutions, civic & religious organizations, museums and astronomy clubs. Ken has reported first hand from the Kennedy Space Center, Cape Canaveral, NASA Wallops, NASA Michoud/Stennis/Langley and on over 80 launches including 8 shuttle launches. He lectures on both Human and Robotic spaceflight - Follow Ken on Facebook and Twitter

View Comments

  • Ken, I like your work a lot, but here's my issue: Charles Bolden has already come out publicly and stated that this SLS system is NOT going to land astronauts on the Moon again. So why are you continuing the angle that it will? Has there been an update on Bolden's stance?

    • there is no mention in the article about landing on the Moon. the plan is to orbit around and beyond the Moon

  • It is too bad that we do not have a spacecraft - or even PLANS for a spacecraft - that could take us to Mars, even for a no-landing, orbit-only, "Mars Lite" mission.

  • Where is the innovation, BOEING? Where is the increase in efficiency? Where is the cost reduction?
    It seems, that only SpaceX is innovative enough not to be ignored by lobbyist-infested D.C.
    SLS to go to the moon, what for? all the photos of the rock have already been made by Russians, Japanese, Europeans and so on.
    The SLS is another foul compromise only politicians and lobbyists can produce...

  • Not sure why this program is running, unless there is a good reason for the guys to go on deep space rides. China?

  • Question. How is the "rated" power determined? As opposed to say, absolute power? Absolute may be wrong word. The question stems from the use of 109% of power for launch, as they did with the 104.5% for the shuttle?

    Or is there a technique that forces the engines to produce more power, for example with a car. It has a a maximum (100%) that it will produce, but slotting in some nos, for example, squeezes out an extra percentage.

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