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SLS Green Run test-firing to verify Core Stage design, analysis before first launch - NASASpaceflight.com
Aug 11, 2020 4 mins, 27 secs

August 6, 2020.

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May 30, 2020.

The Green Run test campaign for NASA’s first Space Launch System (SLS) Core Stage will culminate in two critical tests that will demonstrate the real-world performance of the large, complicated vehicle.

The last two of the eight test cases of the campaign at the Stennis Space Center in Mississippi will finally load the stage with cryogenic propellant for the first time and then fire its four RS-25 engines, running the stage propulsion systems through a full mission cycle.

NASA and Core Stage prime contractor Boeing have several experiments planned during the terminal count and test firing to help validate and calibrate their analytical models on how the stage design behaves

Boeing is conducting the Green Run campaign with the stage bolted into the B-2 Test Stand at Stennis

Overall, the Core Stage is undergoing an eight test case series of diagnostics at Stennis.  Test cases one through three were complete prior to August

The WDR is the first critical test because it is the first time a working Core Stage article has ever been subjected to its designed cryogenic conditions

The Green Run test campaign represents both a first and last chance for the SLS Program; the goal is to demonstrate that the rocket stage behaves as designed

The campaign is the first opportunity for the SLS Program to see the real interactions between the complicated stage systems in a test environment before committing the foundation of the vehicle to a first launch

“This Green Run and this Green Run only is for us to learn everything that we can about the Core Stage while we’ve got it here on the ground with us.”

“It’s not a development test series, where you bring a new stage [or] a new test article out there and run it on all the corners of the boxes and see what it’ll do and see what it won’t do and then go make changes,” Marc Neely, Core Stage Green Run Test Operations and Execution Manager for NASA, said last year

“I look at the team’s product as providing the data necessary to clear the test article, in this case the stage, for shipment to KSC for flight,” Neely said

The first-ever test campaign for the SLS Core Stage is also a last chance; at the same time that NASA decided last year to keep one Green Run for the first working article, it also decided that this first working stage article would be the only one to ever visit Stennis, cancelling plans for any subsequent Core Stage acceptance tests in the B-2 Stand

(Photo Caption: The B Test Stand on July 14, with Core Stage-1 installed in the B-2 position on the left. The stage’s four RS-25 engines will fire in the refurbished flame bucket below it on the left. The right-hand B-1 position of the stand supports single-engine RS-68 testing for Aerojet Rocketdyne.)

The B-2 position of the B Test Stand at Stennis was rebuilt and refurbished to support SLS Core Stage test firings

The test stand also provides the sound suppression water to protect the stage from the acoustics of an eight-minute long static firing and a water deluge to protect the flame bucket while the stage is firing its engines into it

Boeing provides the ground control computer system to orchestrate the test, called the Stage Controller

As the test team monitors from the test control center, the Stage Controller will command vehicle purges, load the propellants from barges docked at the test stand into the Core Stage, manage heaters in the vehicle, manage the terminal countdown sequence, safe all the elements after engine shutdown, and capture many continuous data streams from start to finish of the test results

The terminal sequence requires the ground control and test stand infrastructure to support preparing the Core Stage to fire its engines under launch conditions, pressurizing the fully-loaded fuel tanks, and timing thermal conditioning of the engines so they reach their start box temperatures and pressures at the right time

The B-2 Stand isn’t exactly the same as KSC and naturally when they do their launch they have to worry about ICPS (Interim Cryogenic Propulsion Stage), Orion, Boosters, which fortunately we don’t,” he added.  “But the basic Core Stage sequence is exactly why we partnered with EGS, so we will be a really good proof of pudding for them if you will,” he added

(Photo Caption: Core Stage avionics are mounted to a semicircular ring in the Avionics & Software System Integration Lab at Marshall Space Flight Center. The avionics like the flight computers and the flight software for SLS are new and the Green Run tests are verifying that the computer systems are ready to fly for the first time on Artemis 1.)

The Core Stage flight computers running the Green Run Application Software take over primary control of the vehicle for the final half minute of the countdown and throughout the firing

The flight computers take over enforcing the large set of vehicle criteria needed to continue the countdown through ignition, but the Stage Controller also continues to monitor those and remains in charge of the health of critical test stand systems

The terminal sequence of events begins at T-10 minutes, with the Stage Controller in command until T-30 seconds when it hands off to the Core Stage flight computers to fire the stage

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