Spaceflight Insider

NASA fires up mini rockets for SLS base heating tests

SLS model as seen on Spaceflight Insider

A 2-percent scale model of the Space Launch System core stage RS-25 engines, in the pictures at left, and a model of the SLS without the twin boosters is used for nominal, core-stage-only testing at CUBRC Inc. Photo Credit: NASA/MSFC

Engineers from NASA’s Marshall Space Center in Huntsville, Alabama are collaborating with  the Buffalo, New York based company CUBRC Inc. to conduct a series of tests that will provide important information about the heating conditions at the base of the space agency’s Space Launch System (SLS) rocket. As NASA works to get this new heavy-lift booster off the ground and into the skies – these latest tests should assist in the agency’s efforts.

The NASA engineers have been working with CUBRC to design and build 2 percent scale models of SLS propulsion system. The tests will use models of the SLS’s two five-segment solid rocket boosters and four core-stage RS-25 engines and a 6.5 foot tall scale model of the entire rocket. The models are fired for brief durations of about 50-150 milliseconds per test.

“There’s a lot of complex work that goes in to such a short-duration test,” said Manish Mehta, lead engineer for the SLS Base Heating Test Program at Marshall, where the SLS Program is managed for the agency. “The timing of the propulsion systems and shock tunnel have to be precise. Although this test program has been technically challenging, there’s no heritage data that we can fall back on to predict SLS base environments because this vehicle has never been flown before”

“There are four engines and two booster rocket plumes that are firing into the base,” Mehta added. “This results in highly complex flow physics, which is not something you can develop analytically and predict very accurately.”

Two-percent scale models of the SLS solid rocket boosters and core stage RS-25 engines.  Photo Credit: NASA/MSFC

Two-percent scale models of the SLS solid rocket boosters and core stage RS-25 engines. Photo Credit: NASA/MSFC

Testing of the scale models will provide information on the heating conditions that the base of the SLS will experience during both planned and unplanned flight events.  Data from the series of tests will be used to verify flight hardware design environments and set specifications for the thermal protection system of the rocket’s base. The system will protect the rocket’s  systems and crew from the extreme heat created by the engines during liftoff and ascent.

Testing of the core stage in normal launch scenarios was  conducted first, followed by testing of the entire SLS model in early January. The full-stack configuration had 200 heat flux and pressure sensors inside the aft section of the rocket for data collection. Over 30 test cases out of a planned total of 85 have been performed. The test series, which began in August 2014, is scheduled to conclude early this summer.

The test program takes advantage of new technologies that weren’t available during the development of previous human space flight programs, such as high-speed visible light and infrared cameras, laser diagnostics and new designs of model propulsion systems to more accurately simulate full scale rocket engines.

It’s great to be working on hardware and stretching our engineering skills on coming up with solutions to technical issues we’ve experienced along the way,” said Mehta. “I think we’ve done well.”

SLS boosters as seen on Spaceflight Insider

Artist rendering of the RS-25 engines and boosters powering the liftoff of the SLS from the pad. Image Credit: NASA

It took about a year and a half to design and build the models to flight specifications. For the test series the models are loaded with propellant, pressurized with oxygen and hydrogen lines and ignited inside of one of CUBRC’s  shock tunnels. The shock tunnels replicate both supersonic and hypersonic flight conditions, simulating environmental conditions  that the rocket will experience during ascent including temperature, pressure and velocity.

“We like to say we’re duplicating a flight test on the ground,” said Aaron Dufrene, technical lead at CUBRC. “What’s great about the design of these models is we can run them dozens, even hundreds, of times and reuse most all of the hardware every single time.”

“That’s why NASA historically started doing this short-duration testing technique,” added Mark Seaford, a Marshall engineer who works on the test project. “Since you are testing at a much smaller scale, in this case 2 percent, the heating goes up at the throat of the nozzles. We can’t run it for a substantial length of time or the hardware would be compromised under the heat. We really had to challenge ourselves in the design process to get the right materials to minimize that risk.”

The first flight test of the SLS will launch an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system. The flight test, which will use the 70 metric ton (77 ton) lift capacity configuration  of the SLS, is scheduled for 2018.


Video courtesy of NASA


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Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.

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