Testing Time for the SLS Engine Section
In schools across the country, many students just finished final exams. Now, part of the world’s most powerful rocket, the Space Launch System (SLS), is about to feel the pressure of testing time. The first SLS engine section has been moving slowly upriver from Michoud Assembly Facility near New Orleans, but once the barge Pegasus docks at our Marshall Space Flight Center in Huntsville, Alabama, the real strength test for the engine section will get started.
The engine section is the first of four of the major parts of the core stage that are being tested to make sure SLS is ready for the challenges of spaceflight.
The engine section is located at the bottom of the rocket. It has a couple of important jobs. It holds the four RS-25 liquid propellant engines, and it serves as one of two attach points for each of the twin solid propellant boosters. This first engine section will be used only for ground testing.
Of all the major parts of the rocket, the engine section gets perhaps the roughest workout during launch. Millions of pounds of core stage are pushing down, while the engines are pushing up with millions of pounds of thrust, and the boosters are tugging at it from both sides. That’s a lot of stress. Maybe that’s why there’s a saying in the rocket business: “Test like you fly, and fly like you test.”
After it was welded at Michoud, technicians installed the thrust structure, engine supports and other internal equipment and loaded it aboard the Pegasus for shipment to Marshall.
Once used to transport space shuttle external tanks, Pegasus was modified for the longer SLS core stage by removing 115 feet out of the middle of the barge and added a new 165-foot section with a reinforced main deck. Now as long as a football field, Pegasus – with the help of two tugboats – will transport core stage test articles to Marshall Space Flight Center as well as completed core stages to Stennis Space Center in Mississippi for test firing and then to Kennedy Space Center for launch.
The test article has no engines, cabling, or computers, but it will replicate all the structures that will undergo the extreme physical forces of launch. The test article is more than 30 feet tall, and weighs about 70,000 pounds. About 3,200 sensors attached to the test article will measure the stress during 59 separate tests. Flight-like physical forces will be applied through simulators and adaptors standing in for the liquid hydrogen tank and RS-25 engines.
The test fixture that will surround and secure the engine section weighs about 1.5 million pounds and is taller than a 5-story building. Fifty-five big pistons called “load lines” will impart more than 4.5 million pounds of force vertically and more than 428,000 pounds from the side.
The engineers and their computer design tools say the engine section can handle the stress. It’s the test team’s job prove that it can.
For more information about the powerful SLS rocket, check out: http://nasa.gov/SLS.
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