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  SLS: Core stage 'Green Run' test series

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Author Topic:   SLS: Core stage 'Green Run' test series
Robert Pearlman
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NASA release
NASA Artemis Program and Stennis Space Center Set the Stage for Testing in 2020

All eyes are on south Mississippi with this month's delivery and installation of NASA's Space Launch System (SLS) rocket's first core stage to Stennis Space Center for a milestone Green Run test series prior to its Artemis I flight.

The Green Run testing will be the first top-to-bottom integrated testing of the stage's systems prior to its maiden flight. The testing will be conducted on the B-2 Test Stand at Stennis, located near Bay St. Louis, Mississippi, and the nation's largest rocket propulsion test site. Green Run testing will take place over several months and culminates with an eight-minute, full-duration hot fire of the stage's four RS-25 engines to generate 2 million pounds of thrust, as during an actual launch.

"This critical test series will demonstrate the rocket's core stage propulsion system is ready for launch on missions to deep space," Stennis Director Rick Gilbrech said. "The countdown to this nation's next great era of space exploration is moving ahead."

NASA is building SLS as the world's most-powerful rocket to return humans to deep space, to such destinations as the Moon and Mars. Through the Artemis program, NASA will send the first woman and next man to the Moon by 2024. Artemis I will be a test flight without crew of the rocket and its Orion spacecraft. Artemis II will carry astronauts into lunar orbit. Artemis III will send astronauts to the surface of the Moon.

The SLS core stage, the largest rocket stage ever built by NASA, stands 212 feet tall and measures 27.6 feet in diameter. It is equipped with state-of-the-art avionics, miles of cables, propulsion systems and propellant tanks that hold a total of 733,000 gallons of liquid oxygen and liquid hydrogen to fuel the four RS-25 engines during launch. The core stage was designed by NASA and Boeing in Huntsville, Alabama, then manufactured at NASA's Michoud Assembly Facility in New Orleans by lead contractor Boeing, with input and contributions from more than 1,100 large and small businesses in 44 states.

"Delivering the Space Launch System rocket core stage to Stennis for testing is an epic historical milestone," said Julie Bassler, the SLS stages manager. "My team looks forward to bringing this flight hardware to life and conducting this vital test that will demonstrate the ability to provide 2 million pounds of thrust to send the Artemis I mission to space."

The stage was transported from Michoud to Stennis aboard the specially outfitted Pegasus barge. It arrived at the B-2 dock on Jan. 12 and was rolled out onto the test stand tarmac that night. Crews then began installing ground equipment needed for lifting the stage into a vertical position and onto the stand.

The lift was performed Jan. 21-22, which provided optimal weather and wind conditions. Crews now will fully secure the stage in place and to stand systems for testing.

NASA completed extensive modifications to prepare the B-2 stand for the test series. The stand has a notable history, having been used to test Saturn V stages that helped launch astronauts to the Moon as part of the Apollo Program and the three-engine propulsion system of the space shuttle prior to its first flight.

Preparing the stand for SLS core stage testing required upgrades of every major system on the stand, as well as the high pressure system that provides hundreds of thousands of gallons of water needed during a test. It also involved adding 1 million pounds of fabricated steel to the Main Propulsion Test Article framework that will hold the mounted core stage and extending the large derrick crane atop the stand that will be used to lift the SLS stage into place.

Once installed on the stand, operators will begin testing each of the stage's sophisticated systems. Among other things, they will power up avionics; conduct main propulsion system and engine leak checks; and check out the hydraulics system and the thrust vector control unit that allows for rotating the engines to direct thrust and "steer" the rocket's trajectory.

They also will conduct a simulated countdown, as well as a "wet dress rehearsal," in which propellants are loaded and flow throughout the stage system. The rehearsal exercise will end just prior to engine ignition, with the full four-engine hot fire to come in subsequent days.

After the hot fire test, crews plan to perform refurbishment work on the stage and inspect and configure it for shipment to Kennedy Space Center. The stage will be removed from the stand, lowered to its horizontal position on the tarmac and reloaded into Pegasus for the trip to Florida.

At Kennedy, the stage will be joined with other SLS elements and prepared for launch. The next time its four RS-25 engines fire, Artemis I will be taking flight.

Robert Pearlman
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NASA release
NASA Takes Preliminary Steps to Resume SLS Core Stage Testing Work

NASA resumed Green Run testing activities this week on the first flight stage of its Space Launch System (SLS) rocket, with the return of limited crews to perform work at the agency's Stennis Space Center in Bay St. Louis, Mississippi.

"This is an important step toward resuming the critical work to support NASA's Artemis program that will land the first woman and the next man on the south pole of the Moon by 2024," Stennis Center Director Rick Gilbrech said. "Though Stennis remains in Stage 4 of NASA's COVID-19 Response Framework, we assessed state and local conditions and worked with agency leadership to develop a plan to safely and methodically increase critical on-site work toward the launch of the next great era of space exploration."

Stennis moved to Stage 4 on March 20, with only personnel needed to perform mission-essential activities related to the safety and security of the center allowed on site. NASA's Marshall Space Flight Center in Huntsville, Alabama, and its Michoud Assembly Facility in New Orleans, which are building SLS, also are in Stage 4.

"The test facility has been in standby mode, so we allotted two days to reestablish some facility support of mechanical and electrical systems that will also assist the vehicle contractors in performing their operations," said Barry Robinson, project manager for the B-2 Test Stand SLS core stage Green Run testing at Stennis.

Reestablishing, or "waking up," the Stennis B-2 Test Stand systems in the days ahead includes restoring facility power and controls, as well as ensuring pressurized gas systems are at proper levels for SLS operators to proceed with testing activities.

"Michoud has been cleaning and preparing the rocket manufacturing facility for critical production restart of the SLS core stage and the Orion capsule," said Michoud Director Robert Champion.

According to Julie Bassler, SLS stages project manager responsible for the core stage work at Stennis, Michoud and Marshall, Marshall also is resuming critical flight software and hardware testing.

Returning workers were trained on general safety procedures, personal protective equipment requirements, and self-monitoring. Site personnel also installed signs and markings to indicate where employees should stand and sit during upcoming activities.

"We want to make sure employees are armed with the appropriate information to be effective on the job and return safely to their families," Robinson said.

All sites are closely following CDC guidance to safely operate and protect the health and welfare of all employees. Michoud plans to transition to Stage 3 and operate in that stage for 30 days, in coordination with local government plans. Marshall remains at Stage 4.

Stennis plans for 30 days of limited crew activity on site in anticipation of the center's transition from Stage 4 to Stage 3. Once that transition occurs, increases to on-site work will continue slowly and methodically. The focus then will shift to preparing for the avionics power-up test – the next in a series of core stage Green Run testing milestones. According to Robinson, it's too early to calculate a precise schedule for the various test milestones.

"Like so many others, in so many places, we're operating under a new normal. We're working now to determine exactly what that looks like," he explained. "The virus, and our knowledge of safety as it relates to the virus, will dictate any changes we consider and implement. We will adjust tasks based on the most current information and guidance."

Green Run represents the first top-to-bottom integrated test of all flight core stage systems prior to its maiden Artemis I flight. All testing will be conducted on the B-2 Test Stand in the coming months and will culminate with an eight-minute, full-duration hot fire of the core stage with its four RS-25 engines, as during an actual launch.

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NASA release
NASA's SLS Core Stage Green Run Tests Critical Systems For Artemis I

NASA is resuming work on a series of tests to bring the Space Launch System (SLS) rocket core stage to life for the first time, allowing engineers to evaluate the new complex stage that will launch the Artemis I lunar mission.

In January, engineers began activating the stage's components one by one over several months through a series of initial tests and functional checks designed to identify any issues. Those tests and checks collectively called Green Run will culminate in a test fire replicating the stage's first flight.

"Green Run is the step-by-step testing and analysis of the new SLS rocket core stage that will send astronauts to the Moon," said Richard Sheppard, the SLS Stages Green Run Test Lead from NASA's Marshall Space Flight Center in Huntsville, Alabama. "This testing will reduce risks for, not only the first flight, but also for the Artemis mission that will land astronauts on the Moon in 2024."

Above: Teams at NASA's Stennis Space Center near Bay St. Louis, Mississippi, completed the first test of the eight-part core stage Green Run test series for NASA's Space Launch System (SLS) rocket on Jan. 30, 2020. (NASA)

The Green Run test series, conducted in the historic B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi, is a collaborative effort between the SLS program, the Stennis test team, core stage manufacturer Boeing and engine manufacturer Aerojet Rocketdyne. On March 18, work was temporarily suspended on Green Run when Stennis Space Center went to Stage 4 on the Agency Response Framework in response to a rise in COVID-19 cases in the area near Stennis.

Prior to pausing test operations, engineers completed the modal test, the first of the eight tests in the Green Run series, to understand the vibration charateristics of the core stage. Now, work is slowly and methodically starting back, as workers return to prepare the facility and resume testing.

"The team connected the facility with the rocket earlier this year, both electrically and mechanically," said Ryan McKibben, Green Run test conductor at Stennis. "We are now preparing for the second test, which will power on the vehicle's avionics and the three computers that control the rocket's flight as it soars into space."

The avionics are distributed throughout the stage. Engineers at Marshall designed software similar to the flight software for Green Run. A special stage controller will be used to simulate the Launch Control Center operations that will control the actual launch at Kennedy Space Center in Florida.

"The core stage avionics along with Green Run software have successfully completed tests in our test laboratories at Marshall, said Lisa Espy, the core stage avionics lead at Marshall. "I am excited to see the flight systems come to life that will control the rocket as it sends the first Artemis mission to the Moon."

Above: The massive core stage for NASA's Space Launch System (SLS) rocket is in the B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi, for the core stage Green Run test series. (NASA)

Green Run tests minimize risk to the core stage and ensure the stage satisfies design objectives and validates design models:

  • Test 1- Modal Test: The first test in the Green Run series, a modal test was conducted in January. This test used shakers to impart dynamic forces on the suspended stage to identify primary bending modes of the stage. Information from the modal test will help engineers verify vehicle models needed for the operation of the rocket's guidance, navigation and control systems.

  • Test 2- Avionics: The rocket's avionics, which are distributed throughout the stage, will be turned on and checkout out. This includes not only flight computers and electronics that control the rocket but also those that collect flight data and monitor the overall health of the core stage.

  • Test 3- Fail-Safes: Engineers will check out all the safety systems that shut down operations during testing. To do this, they will simulate potential issues.

  • Test 4- Propulsion: This will be the first test of each of the main propulsion system components that connect to the engines. Command and control operations will be verified, and the core stage will be checked for leaks in fluid or gas.

  • Test 5- Thrust Vector Controls: Engineers will ensure that the thrust vector control system can move the four engines and check all the related hydraulic systems.

  • Test 6- Countdown: This test simulates the launch countdown, including step-by-step fueling procedures. Core stage avionics are powered on, and propellant loading and pressurization are simulated. The test team will exercise and validate the countdown timeline and sequence of events.

  • Test Case 7- "Wet" Dress Rehearsal: Engineers will demonstrate loading, controlling and draining more than 700,000 gallons of cryogenic propellants into the two test stand run tanks and then returning the stage to a safe condition.

  • Test Case 8- Hot Fire: The core stage's four RS-25 engines will operated for up to 8 minutes, generating 1.6 million pounds of thrust, the amount of thrust the engines produce at sea level on the launch pad at liftoff.
After the hot fire test, engineers will refurbish the core stage and configure it for its journey to Kennedy for launch preparations. The next time the RS-25 engines fire, the SLS will launch in an epic debut of Artemis I — the first in a series of increasingly complex missions that will enable human exploration to the Moon and Mars.

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NASA release
Four Down, Four to Go: Artemis I Rocket Moves Closer to Hot Fire Test

The Space Launch System (SLS) rocket core stage for the Artemis I lunar mission has successfully completed its first four Green Run tests and is building on those tests for the next phase of checkout as engineers require more capability of the hardware before hot-firing the stage and its four powerful engines.

Green Run is a demanding series of eight tests and nearly 30 firsts: first loading of the propellant tanks, first flow through the propellant feed systems, first firing of all four engines, and first exposure of the stage to the vibrations and temperatures of launch.

"We are methodically bringing several complex systems to life and checking them out during the first seven tests," explained SLS Stages Manager Julie Bassler. "Then it is show time for the eighth test when we put it all together and fire up the rocket's core stage, just like we'll fire it up for the Artemis I launch to the Moon."

On Aug. 5, engineers at NASA's Stennis Space Center near Bay St Louis, Mississippi, where the stage is loaded into the B-2 Test Stand, completed the fourth of eight planned tests of the 212-foot-tall core stage. For Test 4, engineers performed the initial functional checkout of the main propulsion system components to verify command and control operability (valve response, timing, etc.) and performed leak checks on the core stage-to-facility umbilical fluid and gas connections.

"With test gases flowing through this many parts of a complex rocket stage, we expected the test team to encounter some issues," said Jonathan Looser, who manages the SLS core stage main propulsion system. "Historically, there's never been a NASA human-rated launch vehicle flown without one or more full-up tests before flight, and they have all encountered first-time issues. As expected, we found a few with valves and seals and addressed them, and now we're ready to complete the next four Green Run tests."

The Green Run testing series formally started in January with modal testing to verify computer models and support guidance and navigation control systems. In March, the test series was interrupted by a shutdown related to COVID-19 cases in Mississippi. When testing resumed in May with appropriate safety measures in place, the team completed Test 2, activation of computers, data collection health monitoring and other "avionics" that make up the brains and nervous system of the core stage. Test 3 was a check of the fail-safe systems that shut down the stage in a contingency situation. Each test builds on the prior test and is longer than the previous one, adding new hardware activations to those already completed.

For Test 4, functional and leak checks of the stage main propulsion systems and engines lasted three weeks. Engineers were able to conduct the test with gaseous nitrogen and helium, which is more efficient than using liquid hydrogen and oxygen propellants, which are only needed for the actual hot-fire test. As these gases flowed through systems, special instrumentation monitored for any leaks or poor connections.

Next up for the Green Run team is Test 5. It will ensure the stage thrust vector control system works correctly, which includes huge components that steer the four RS-25 engines, called actuators, and provides hydraulics to the engine valves.

Test 6 simulates the launch countdown to validate the countdown timeline and sequence of events. This includes the step-by-step fueling procedures in addition to the previous test steps of powering on the avionics and simulated propellant loading and pressurization.

As one final checkout before the full firing test, Test 7 is called the "wet dress rehearsal," meaning it builds on the simulations in Test 6 and includes fueling the rocket. After once again powering on the avionics, hydraulic systems, fail-safe systems, and other related systems that have been checked out in the prior six tests, the team will load, control, and drain more than 700,000 gallons of cryogenic, or super cold, propellants.

Only after passing these seven tests will it be time for Test 8, a full countdown and hot fire test for up to eight minutes. During the test, all four RS-25 engines will be firing at a full, combined 1.6 million pounds of thrust just as they will on the launch pad. Test 8 will be the final checkout to verify the stage is ready for launch. Afterward, engineers will prepare the stage for its trip to Kennedy Space Center in Florida.

"We want to find any issues here on the ground at Stennis, where we've added hundreds of special ground test sensors to the stage for Green Run," said Ryan McKibben, one of the Stennis Green Run test conductors. "We have great access to the stage on the B-2 Test Stand and have engineers and technicians on hand who are familiar with this stage."

By the time all eight Green Run tests are complete, Boeing, the prime contractor for the core stage, estimates it will collect 75-100 terabytes of data, not including voice and video data collected. And that's a lot of homework considering that all the data in the Library of Congress amounts to just 15 terabytes.

Robert Pearlman
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NASA release
Engineers Complete 5th Green Run Test of Space Launch System Core Stage

Engineers have completed the fifth of eight Green Run tests on the core stage of NASA's new Space Launch System (SLS) rocket, continuing progress toward a milestone hot fire test this fall.

Operators concluded a test of the stage's thrust vector control system on the historic B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Miss., on Sept. 13. The test provided critical verification of the control system and its related hydraulics as operators gimbaled the stage's four RS-25 engines just as they must move during flight to steer the rocket and maintain a proper trajectory.

The stage now is set for two more tests – a simulated countdown demonstration and wet dress rehearsal – directly leading to the hot fire of all four RS-25 engines, just as during an actual flight. In the countdown demonstration, engineers will simulate the launch countdown and procedures to validate the established timeline and sequence of events. In the wet dress rehearsal, engineers will conduct another countdown exercise and actually load, control and drain more than 700,000 gallons of cryogenic propellants to ensure all is set for the final test of the Green Run series.

The concluding test will activate all stage systems and fire the four RS-25 engines to generate the same combined 1.6 million pounds of thrust that will help launch the SLS rocket when it flies on its maiden Artemis I mission.

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NASA release
NASA Moon Rocket Stage Passes Simulated Countdown Test

Engineers at NASA's Stennis Space Center near Bay St. Louis, Mississippi, completed a simulated launch countdown sequence on Oct. 5 for the sixth test of the eight-part core stage Green Run test series for NASA's Space Launch System (SLS) rocket.

During the simulated countdown, NASA engineers and technicians, along with prime contractors Boeing, and Aerojet Rocketdyne, monitored the stage to validate the timeline and sequence of events leading up to the test, which is similar to the countdown for the Artemis I launch.

The countdown sequence for an actual Artemis launch begins roughly two days prior to liftoff. In addition to all the procedures leading up to the ignition of the four RS-25 engines, the SLS core stage requires about six hours to fully load fuel into the two liquid propellant tanks.

The simulated countdown sequence test at Stennis began at the 48-hour mark as if the stage was first powered up before liftoff. Engineers then skipped ahead in the sequence to monitor the stage and procedures of the stage 10 minutes before the hot fire.

The simulated countdown sequence is one of the final tests of the SLS Green Run campaign. The series of tests is designed to gradually bring the rocket stage and all its systems to life for the first time.

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NASA update
NASA 'Go' for Green Run Wet Dress Rehearsal

In a test readiness review on Friday, Dec. 4, NASA gave the "go" to start the next Green Run test, wet dress rehearsal, for NASA's Artemis I Space Launch System (SLS) rocket core stage. The wet dress rehearsal is the first time the stage will be fully loaded with propellants and is planned to last approximately 48 hours.

The test will begin on Saturday, Dec. 5 by powering up the core stage avionics, and engineers plan to load more than 700,000 gallons of cryogenic, or supercooled, propellant on Monday, Dec. 7.

This is the seventh of eight Green Run tests for the Artemis I core stage built by Boeing and the four RS-25 engines manufactured by Aerojet Rocketdyne. For this test, the team will focus on the core stage's first exposure to cryogenic propellants. Six barges filled with liquid hydrogen and oxygen are supplying the propellant to the B-2 test stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi where the Green Run tests are taking place.

Engineers will monitor the core stage's giant propellant tanks and complex propulsion systems for potential leaks or other issues that stages have historically experienced the first time cryogenic propellants are loaded.

To prepare for Artemis launches, engineers also will put the stage through scenarios it might experience on the pad before lift-off. They plan to conduct two different holds in the countdown timeline while the stage is in a launch-ready state. This provides an opportunity to observe how the stage would respond if the countdown was paused during the upcoming hot fire test or a future Artemis launch.

At the end of the test, all the propellant will be drained following similar procedures that would be used during a launch scrub on the pad. After draining the tanks, the team will review the test data before proceeding with plans for the hot fire test.

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NASA release
Green Run Wet Dress Rehearsal Update

NASA successfully powered up the core stage at the agency's Stennis Space Center near Bay St. Louis, Mississippi on Dec. 5 and started the process to load propellant for the first time into the Space Launch System (SLS) rocket core stage Dec. 7.

To complete this wet dress rehearsal exercise, cryogenic propellants are transferred from facility barge systems to the core stage. To test propellant loading procedures, engineers successfully loaded a small amount of liquid hydrogen into the core stage without any issues. Then, they paused propellant loading to review data and adjust procedures before loading additional propellant.

Operations are continuing, and the team will refine the procedures and resume the wet dress rehearsal test in the coming days. The core stage performed well, and there are no issues with the stage, the B-2 test stand, or other facilities at Stennis.

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NASA release
SLS Green Run Team Powers Up Core Stage for Wet Dress Rehearsal

NASA and Boeing engineers have powered up the Space Launch System rocket core stage to continue with the seventh test, wet dress rehearsal at the agency’s Stennis Space Center near Bay St. Louis, Mississippi. The NASA and Boeing team plan to fully load the stage’s liquid hydrogen and liquid oxygen tanks this week. This test demonstrates the ability to load the core stage with cryogenic propellant.

Following a partial loading of the tanks earlier this month, the team is now resuming the seventh of the eight tests in the Green Run series being completed with the Artemis I core stage. Upon completion of the wet dress rehearsal, the team will spend a few days analyzing data to determine if NASA is ready to proceed with the final Green Run test: the hot fire when all four engines will ignite simulating the countdown and launch of the Artemis I mission.

NASA will set a date for the hot fire after the wet dress rehearsal is complete.

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NASA release
SLS Team Completes Propellant Loading of Core Stage During Green Run Test

NASA and Boeing engineers successfully completed propellant loading during the seventh core stage Green Run test, wet dress rehearsal Sunday, Dec. 20. The massive Space Launch System (SLS) rocket's tanks were loaded with more than 700,000 gallons of liquid hydrogen and liquid oxygen.

Engineers working in the Test Control Center monitored all core stage systems during the test as propellant flowed from six barges into the core stage in the B-2 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi. First looks at the data indicate the stage performed well during the propellant loading and replenish process. Part of the test was to simulate the countdown with the tanks loaded, leading up to 33 seconds prior to the engines firing. However, the test ended a few minutes short of the planned countdown duration.

The core stage and the B-2 test stand are in excellent condition, and it does not appear to be an issue with the hardware. The team is evaluating data to pinpoint the exact cause of the early shutdown. Then they will decide if they are ready to move forward with the final test, a hot fire when all four engines will be fired simultaneously.

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NASA release
NASA Space Launch System Proceeding with Green Run Hot Fire

NASA is targeting the final test in the Green Run series, the hot fire, for as early as Jan.17. The hot fire is the culmination of the Green Run test series, an eight-part test campaign that gradually brings the core stage of the Space Launch System (SLS) — the deep space rocket that will power the agency's next-generation Moon missions — to life for the first time.

NASA conducted the seventh test of the SLS core stage Green Run test series – the wet dress rehearsal – on Dec. 20 at NASA's Stennis Space Center near Bay St. Louis, Mississippi and marked the first time cryogenic, or super cold, liquid propellant was fully loaded into, and drained from, the SLS core stage's two immense tanks. The wet dress rehearsal provided structural and environmental data, verified the stage's cryogenic storage capabilities, demonstrated software with the stage's flight computers and avionics, and conducted functional checks of all the stage's systems. The end of the test was automatically stopped a few minutes early due to timing on a valve closure. Subsequent analysis of the data determined the valve's predicted closure was off by a fraction of a second, and the hardware, software, and stage controller all performed properly to stop the test. The team has corrected the timing and is ready to proceed with the final test of the Green Run series.

"During our wet dress rehearsal Green Run test, the core stage, the stage controller, and the Green Run software all performed flawlessly, and there were no leaks when the tanks were fully loaded and replenished for approximately two hours," said Julie Bassler, SLS Stages manager at NASA's Marshall Space Flight Center in Huntsville, Alabama. "Data from all the tests to date has given us the confidence to proceed with the hot fire."

The upcoming hot fire test will fire all four of the stage's RS-25 engines simultaneously for up to eight minutes to simulate the core stage's performance during launch. After the firing at Stennis, the core stage for SLS will be refurbished and shipped to NASA's Kennedy Space Center in Florida. The stage will then be assembled with the other parts of the rocket and NASA's Orion spacecraft in preparation for Artemis I, the first integrated flight of SLS and Orion and the first mission of the agency's Artemis program.

"The next few days are critical in preparing the Artemis I rocket stage, the B-2 Test Stand at NASA's Stennis Space Center, and the test team for the finale of the Green Run test series," said Barry Robinson, project manager for SLS core stage Green Run testing at Stennis. "The upcoming Green Run hot fire test is the culmination of a lot of hard work by this team as we approach a key milestone event for NASA's Artemis missions."

Testing the SLS rocket's core stage is a combined effort for NASA and its industry partners. Boeing is the prime contractor for the core stage and Aerojet Rocketdyne is the lead contractor for the RS-25 engines. Prior tests in the Green Run test series evaluated the stage's avionics systems, propulsion systems, and hydraulic systems.

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NASA update
NASA accelerates SLS hot fire test

Following a test readiness review on Monday (Jan. 11), NASA is now targeting Saturday, Jan. 16, for the final test in the Green Run testing series for the core stage of the Space Launch System (SLS) rocket that will launch the agency's Artemis I mission.

During the test, engineers will power up all the core stage systems, load more than 700,000 gallons of cryogenic, or supercold, propellant into the tanks and fire all four engines at the same time.

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collectSPACE
NASA ignites first Space Launch System core stage, but test fire cuts off early

The world's largest rocket stage roared to life for the first time on Saturday (Jan. 16), but then shut down too soon for NASA to immediately know if it could move forward with launching the stage on a mission to the moon.

The abbreviated hot fire test of NASA's first Space Launch System (SLS) core stage was still the largest display of thrust seen from Stennis Space Center's B-2 test stand since NASA tested Apollo Saturn V rocket stages there more than 50 years ago. But one of the four space shuttle engines modified for use with the rocket reported a "major component failure" and then seconds later, the engines shut down, cutting short the 8-minute "Green Run" test at just over a minute long.

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NASA release
Data and Inspections Indicate Core Stage in Good Condition

The Space Launch System (SLS) rocket Green Run team has reviewed extensive data and completed preliminary inspections that show the rocket's hardware is in excellent condition after the Green Run test that ignited all the engines at 5:27 p.m. EST at NASA's Stennis Space Center near Bay St. Louis, Mississippi. After analyzing initial data, the team determined that the shutdown after firing the engines for 67.2-seconds on Jan.16 was triggered by test parameters that were intentionally conservative to ensure the safety of the core stage during the test.

These preprogrammed parameters are designed specifically for ground testing with the flight hardware that will fly NASA's Artemis I mission to ensure the core stage's thrust vector control system safely moves the engines. There is a thrust vector control (TVC) system that gimbals, or pivots, each engine, and there are two actuators that generate the forces to gimbal each engine. The actuators in the TVC system are powered by Core Stage Auxiliary Power Units (CAPU). As planned, the thrust vector control systems gimbaled the engines to simulate how they move to direct thrust during the rocket's ascent.

During gimballing, the hydraulic system associated with the core stage's power unit for Engine 2, also known as engine E2056, exceeded the pre-set test limits that had been established. As they were programmed to do, the flight computers automatically ended the test. The specific logic that stopped the test is unique to the ground test when the core stage is mounted in the B-2 test stand at Stennis. If this scenario occurred during a flight, the rocket would have continued to fly using the remaining CAPUs to power the thrust vector control systems for the engines.

During the test, the functionality of shutting down one CAPU and transferring the power to the remaining CAPUs was successfully demonstrated. This gimballing test event that resulted in shutting down the CAPU was an intentionally stressing case for the system that was intended to exercise the capabilities of the system. The data is being assessed as part of the process of finalizing the pre-set test limits prior to the next usage of the core stage.

Throughout the hot fire, all four engines performed as expected. While the test planned to fire the four engines for about 8 minutes, the team still achieved several objectives during the shorter firing. They repeated the wet dress rehearsal, once again filling the tanks with more than 700,000 gallons of propellant with some added modifications to procedures to ensure proper thermal conditioning of the engines. They successfully pressurized the propellant tanks, completed the countdown, and ignited the engines for the first time. The engines reached their full power of 109 percent producing 1.6 million pounds of thrust, just as they will during the Artemis I launch.

Initial data indicate the sensor reading for a major component failure, or MCF, that occurred about 1.5 seconds after engine start was not related to the hot fire shutdown. It involved the loss of one leg of redundancy prior to T-0 in the instrumentation for Engine 4, also known as engine number E2060. Engine ignition begins 6 seconds prior to T-0, and they fire in sequence about 120 milliseconds apart. Test constraints for hot fire were set up to allow the test to proceed with this condition, because the engine control system still has sufficient redundancy to ensure safe engine operation during the test. The team plans to investigate and resolve the Engine 4 instrumentation issue before the next use of the core stage.

Engineers also continue to investigate reports of a "flash" around the engines. A visual inspection of the thermal blankets that protect the engine show signs of some exterior scorching, which was anticipated due to their proximity to engine and CAPU exhaust. Sensor data indicate temperatures in the core stage engine section were normal. Both observations are an early indication the blankets did their job and protected the rocket from the extreme heat generated by the engines and CAPU exhaust.

Data analysis is continuing to help the team determine if a second hot fire test is required. The team can make slight adjustments to the thrust vector control parameters and prevent an automatic shut down if they decide to conduct another test with the core stage mounted in the B-2 stand.

Robert Pearlman
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NASA update
Hot Fire Met Many Objectives, Test Assessment Underway

For the Green Run hot fire test on Jan. 16, NASA set out to acquire test data to support 23 detailed verification objectives. To satisfy the objectives, hot fire test data is used in combination with analysis and testing that has already been completed. These detailed verification objectives are used to certify the design of the Space Launch System rocket's core stage.

The preliminary assessment indicates that the data acquired met the goals for a number of the 23 objectives, such as those related to activities prior to engine ignition. The initial assessment also indicates that data acquired partially met the goals for several additional of the 23 objectives related to simultaneous operations of four RS-25 engines.

NASA and its industry partners, Boeing and Aerojet Rocketdyne, are continuing to assess the extensive data from the test. As part of the planned near-term activities, they will complete the final assessment determining which objectives were fully met and which ones were partially met. They also are evaluating the value of acquiring additional test data and a longer run time to augment the existing analyses and data.

Currently, the SLS core stage can still be loaded with propellant and pressurized 20 more times for a total of 22 cycles. Rocket stages like the core stage are designed to be loaded with cryogenic propellant and pressurized a specific number of times. These are called cryogenic loading cycles. Before Green Run testing began, SLS had allocated nine cryogenic cycles for testing at NASA's Stennis Space Center in Bay St. Louis, Mississippi and has used two of those during the hot fire and wet dress rehearsal, with seven cryogenic cycles remaining for additional testing. For the Artemis I Iaunch, NASA is preserving 13 of the remaining 20 cryogenic loading cycles. These can be used for multiple launch attempts, a wet dress rehearsal on the launch pad, and other activities that require propellant loading and tank pressurization.

One of the critical activities that must happen before either another hot fire test or launch is drying and refurbishment of the engines. That activity is underway. NASA is continuing to inspect the core stage and its RS-25 engines on the B-2 test stand, and initial inspections indicate the hardware is in excellent condition.

Hardware inspection and data assessment will continue and will inform NASA's decision on whether to conduct a second Green Run test or proceed with shipping the core stage to Kennedy for integration with other SLS hardware in the Vehicle Assembly Building.

Robert Pearlman
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posted 01-29-2021 04:23 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
Green Run Update: NASA Proceeds With Plans for Second Hot Fire Test

NASA plans to conduct a second Green Run hot fire test as early as the fourth week in February with the Space Launch System (SLS) rocket's core stage that will launch the Artemis I mission to the Moon. The Green Run is a comprehensive assessment of the rocket's core stage prior to launching Artemis missions.

While the first hot fire test marked a major milestone for the program with the firing of all four RS-25 engines together for the first time for about a minute, it ended earlier than planned. After evaluating data from the first hot fire and the prior seven Green Run tests, NASA and core stage lead contractor Boeing determined that a second, longer hot fire test should be conducted and would pose minimal risk to the Artemis I core stage while providing valuable data to help certify the core stage for flight.

Inspections showed the core stage hardware, including its engines, and the B-2 test stand are in excellent condition after the first hot fire test, and no major repairs are needed to prepare for a second hot fire test at NASA's Stennis Space Center in Bay St. Louis, Mississippi.

All SLS rockets use the same core stage design, so a second Green Run hot fire will reduce risk for not only Artemis I, but also for all future SLS missions. The Green Run series of tests is designed to certify the core stage design and verify that the new stage is ready for flight. The hot fire test is the final Green Run test and will provide valuable data that minimizes risk for American deep space exploration missions for years to come.

The Green Run team scrutinized data from the first hot fire test and determined that a second hot fire lasting approximately at least 4 minutes would provide significant data to help verify the core stage is ready for flight. The Green Run wet dress rehearsal and hot fire operations completed several operations:

  • transitioning to the automated launch sequence operated by the core stage flight computer and Green Run software,

  • completing the terminal countdown sequence that is like the launch countdown

  • pressuring the tanks and delivering propellant to the engines and demonstrating performance of the core stage's main propulsion system,

  • firing the engines at 109 percent power level, and

  • operating the thrust vector control system that steers the engines.
Conducting a second hot fire test will allow the team to repeat operations from the first hot fire test and obtain data on how the core stage and the engines perform over a longer period that simulates more activities during the rocket's launch and ascent.

To prepare for the second hot fire test, the team is continuing to analyze data from the first test, drying and refurbishing the engines, and making minor thermal protection system repairs. They are also updating conservative control logic parameters that resulted in the flight computer ending the first hot fire test earlier than planned.

The team has already repaired the faulty electrical harness which resulted in a notification of a Major Component Failure on Engine 4. This instrumentation issue did not affect the engine's performance and did not contribute to ending the first test early.

After the second hot fire test, it will take about a month to refurbish the core stage and its engines. Then, the Pegasus barge will transport the core stage to NASA's Kennedy Space Center in Florida where it will be assembled with the other parts of the SLS rocket and the Orion spacecraft being prepared for the Artemis I launch later this year.

Robert Pearlman
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posted 02-12-2021 06:38 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
SLS Team Prepares Core Stage for Second Hot Fire Test

The core stage Green Run test team has completed refurbishment activities and is preparing the Space Launch System (SLS) rocket’s core stage and its four RS-25 engines for a second hot fire test.

After the first SLS core stage hot fire test on Jan. 16 at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, the team put the stand and core stage in a configuration so that the stage and stand could be refurbished. This involved installing platforms on the test stand so that technicians could inspect, access, and perform procedures on the hardware.

The team has now completed this refurbishment work and conducted a review referred to as “the break of configuration review” to transition the core stage hardware to the test configuration for the second hot fire test. During refurbishment, the team thoroughly inspected the stage, dried the four RS-25 engines, and made minor repairs to the engines and thermal protection system.

The team is also modifying and testing the Green Run software for the flight computers based on data from the first hot fire. The team adjusted parameters used by the software logic, which operating on the flight computers automatically monitors a variety of parameters and controls the test during the terminal countdown and after engine ignition. The updated Green Run software was tested in the systems integration test facility at NASA’s Marshall Space Flight Center in Huntsville, Alabama, which has avionics and flight computers identical to the ones in the core stage.

Now, the team is preparing the core stage, the B-2 Test Stand, and the Stennis Test Control Centers for the upcoming hot fire test targeted for the week of Feb. 21. A target date for the test will be announced next week. The core stage is flight hardware that will be used for the Artemis I mission.

Robert Pearlman
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posted 02-22-2021 03:22 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
NASA Investigating Valve Performance Before Second Hot Fire

NASA is reviewing the performance of a valve on the core stage of the Space Launch System rocket before proceeding with a second hot fire test at the agency's Stennis Space Center near Bay St. Louis, Mississippi.

During checkout preparations over the weekend, engineers determined that one of eight valves (a type of valve called a prevalve) was not working properly. This valve is part of the core stage main propulsion system that supplies liquid oxygen to an RS-25 engine. During the first hot fire, all four liquid oxygen valves performed as expected as did the four liquid hydrogen valves.

NASA and the core stage lead contractor Boeing will identify a path forward in the days ahead and reschedule the hot fire test that was originally scheduled for Feb. 25.

Robert Pearlman
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From: Houston, TX
Registered: Nov 1999

posted 02-26-2021 11:19 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
NASA Inspecting Valve, Continuing Hot Fire Preparations

NASA and Space Launch System (SLS) core stage prime contractor Boeing are thoroughly examining a liquid oxygen valve inside the stage's engine section in order to identify repairs needed before a second hot fire with the Artemis I stage.

During preparations for the second hot fire, data indicated the valve was not opening correctly. Technicians installed platforms that allow engineers to access the valve inside the core stage engine section while the stage remains in the B-2 stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi. After completion of troubleshooting, which will continue over the weekend, NASA will be in a better position to identify a potential date for the second hot fire test.

This valve, called a pre-valve, must be fully operational during hot fire testing. The valve is part of the core stage main propulsion system, and it helps deliver liquid oxygen propellant flowing from the liquid oxygen tank to an RS-25 engine. For the first hot fire on Jan. 16, all four liquid oxygen pre-valves performed as expected as did all four liquid hydrogen pre-valves.

The Green Run is a comprehensive series of tests for the SLS core stage before it launches the Artemis missions to the Moon, and the hot fire is the final and most intensive test. The Green Run tests have provided invaluable information on how the new rocket stage operates before it is used to launch the Artemis I mission.

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