{"id":12182,"date":"2020-10-09T21:14:32","date_gmt":"2020-10-09T13:14:32","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/crucial-first-fueling-test-on-tap-for-sls-core-stage-later-this-month\/"},"modified":"2020-10-09T21:14:32","modified_gmt":"2020-10-09T13:14:32","slug":"crucial-first-fueling-test-on-tap-for-sls-core-stage-later-this-month","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/crucial-first-fueling-test-on-tap-for-sls-core-stage-later-this-month\/","title":{"rendered":"Crucial first fueling test on tap for SLS core stage later this month"},"content":{"rendered":"
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The first Space Launch System core stage on the B-2 test stand at NASA\u2019s Stennis Space Center in Mississippi. Credit: NASA<\/figcaption><\/figure>\n

If all goes according to plan, engineers in southern Mississippi later this month will load cryogenic propellants into the core stage of a rocket NASA says will launch astronauts back to the moon, exposing its tankage and internal plumbing to extreme operating conditions hundreds of degrees below zero for the first time.<\/p>\n

The fueling test \u2014 a major milestone in its own right \u2014 is a precursor to a high-stakes eight-minute test-firing of the Space Launch System\u2019s four shuttle-era main engines planned as soon as November.<\/p>\n

Covered in orange foam insulation, the huge Boeing-built rocket stage has been fastened in the B-2 test stand at NASA\u2019s Stennis Space Center since January, when it arrived by barge from a manufacturing plant at NASA\u2019s Michoud Assembly Facility in New Orleans.<\/p>\n

Since January, work to ready the rocket stage for its first test-firing has been suspended several times, first by the coronavirus pandemic, and then by several close calls with hurricanes approaching the Gulf Coast.<\/p>\n

With Hurricane Delta on track to make landfall in Louisiana Friday, hands-on work on the SLS core stage has again been paused on the B-2 test stand, according to Valerie Buckingham, a NASA spokesperson at the Stennis Space Center.<\/p>\n

But Stennis is expected to receive limited impacts from Hurricane Delta, and assuming the forecast holds up, operations on the test stand could quickly resume.<\/p>\n

The next step in the SLS test campaign at Stennis, known as the \u201cGreen Run,\u201d will be to load 733,000 gallons of super-cold liquid hydrogen and liquid oxygen into the core stage. NASA expects that major step to occur later this month, according to Tracy McMahan, a spokesperson at the Marshall Space Flight Center, which manages the Space Launch System program.<\/p>\n

Numerous sensors will measure how the core stage and its intricate plumbing respond to the loading of cryogenic propellants.<\/p>\n

The liquid hydrogen is stored at minus 423 degrees (minus 253 degrees Celsius) in the case of liquid hydrogen, and liquid oxygen is kept at minus 298 degrees Fahrenheit (minus 183 degrees Celsius).<\/p>\n

The fueling test, known as a wet dress rehearsal, is the penultimate test in the Green Run. If everything checks out in the wet dress rehearsal, engineers will load cryogenic propellants into the core stage again in November and ignite the rocket\u2019s four RS-25 main engines for more than eight minutes, the duration of their burn during a real launch.<\/p>\n

The hotfire test is a final exam in the development of the core stage, the tallest rocket stage ever built. The SLS core is derived from the space shuttle external tank, and its four RS-25 engines \u2014 built by Aerojet Rocketdyne \u2014 are leftovers from the shuttle program.<\/p>\n

The 212-foot-long (64.6-meter), 27.6-foot-wide (8.4-meter) SLS core stage has the same diameter as the shuttle\u2019s fuel tank. It weighs about 188,000 pounds (85 metric tons) empty, and will weigh around 2.3 million pounds (more than 1,000 metric tons) fully fueled.<\/p>\n

After the core stage arrived at Stennis in January, ground teams lifted the rocket by crane and lowered it onto the B-2 test stand, a facility once used for test-firings of the powerful first stage of NASA\u2019s Apollo-era Saturn 5 moon rocket.<\/p>\n

The first major test on the core stage was a modal test on the core stage to measure the resonant frequency of the rocket.<\/p>\n

In March, NASA halted operations on the test stand for two months with the onset of the coronavirus pandemic. NASA and Boeing engineers resumed work on the core stage in May after introducing new guidelines for physical distancing and other measures to guard against COVID-19.<\/p>\n

Ground teams switched on the core stage\u2019s avionics in June and performed a thorough checkout of the rocket, then proceeded into safing checks, which verified controllers can send commands to shut down the rocket\u2019s engines and other major systems in the event of a problem.<\/p>\n

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This checklist shows the series of tests the SLS core stage is undergoing this year at the Stennis Space Center in Mississippi. Up next is a cryogenic fueling test. Credit: NASA<\/figcaption><\/figure>\n

Then engineers commenced testing of the core stage\u2019s main propulsion system, searching for any signs of leaks and verifying all connections between the engines and the rocket\u2019s tankage. That test, known as Test 4 in the Green Run, also included engine igniter checks and tests of the engine control valves.<\/p>\n

With that test passed successfully over the summer, teams moved on to a checkout of the core stage\u2019s hydraulic system, which drives thrust vector control actuators to swivel the four RS-25 engines and steer the rocket in flight.<\/p>\n

Teams activated the rocket\u2019s auxiliary power units, which drive the hydraulic loops for engine steering system. The engines then gimbaled individually to ensure they could be swiveled within an 8-degree cone, followed by gimbal test profiles to simulate how the engines will move together in flight.<\/p>\n

The hydraulic thrust vector control test concluded Sept. 13, wrapping up a series of functional checks on the rocket as engineers moved into final reviews and rehearsals for the wet dress rehearsal and hotfire.<\/p>\n

The next milestone, known as Test 6, was completed Oct. 5 after control teams at Stennis ran through a simulated 48-hour launch countdown to validate activation, fuel loading, and pressurization sequences.<\/p>\n

Engineers and technicians from NASA, Boeing, and engine-builder Aerojet Rocketdyne participated in the countdown simulation, which provided a \u201crefresher course\u201d for test controllers to ensure they are ready to load cryogenic propellants into the rocket for the first time, according to Mark Nappi, Boeing\u2019s Green Run test director.<\/p>\n

\u201cOnce we\u2019re done with that, we\u2019ll stop, we\u2019ll break, we\u2019ll review the data, and we\u2019ll go into the actual wet dress rehearsal,\u201d Nappi said in an interview before the countdown simulation test.<\/p>\n

NASA has not announced a target date for the cryogenic loading test, but it will mark a significant step for the SLS program, a milestone that comes with unknowns.<\/p>\n

\u201cFilling everything with cryo is huge because that\u2019s the first time you have your tanks moving the way they\u2019re going to move when they\u2019re filled with cryo fluid,\u201d said Alex Cagnola, a propulsion engineer at NASA\u2019s Marshall Space Flight Center.<\/p>\n

\u201cYou\u2019re testing all your joints. You\u2019re testing how everything basically acts under a cryogenic environment,\u201d Cagnola said in an interview earlier this year.<\/p>\n

John Shannon, SLS program manager at Boeing, said all of the testing on the rocket so far has been at ambient temperatures<\/p>\n

\u201cThings change when you get down at cryogenic temperatures, and as we saw after our experience with the shuttle, you can end up having systems perform differently,\u201d said Shannon, a former NASA flight director and space shuttle program manager.<\/p>\n

Teams will check for leaks, and ensure valves and other hardware still work at cryogenic temperatures. It takes about six hours to pump liquid hydrogen and liquid oxygen into the core stage.<\/p>\n

\u201cThe next big unknown as a program is when we put the cryogenic liquids in the oxygen tank and the hydrogen tank, and we look at the plumbing and all the systems and make sure that they remain tight, and that they perform as expected through our qualification test,\u201d Shannon told reporters earlier this year. \u201cWe have high confidence that they will, but until you see it in an integrated fashion, you don\u2019t really know.\u201d<\/p>\n