Engineers have successfully repaired a liquid oxygen valve on the Space Launch System rocket’s core stage with subsequent checks confirming the valve to be operating properly. The team plans to power up the core stage for remaining functional checks later this week before moving forward with final preparations for a hot fire test in mid-March at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. NASA anticipates setting a target date for the hot fire next week.
Last week during checkouts for the second hot fire test, data indicated the valve (a type of valve called a pre-valve) was not working properly. The valve is part of the core stage’s main propulsion system and is opened at the beginning of the test and closed if necessary to stop the flow of liquid oxygen from the core stage propellant tank to the respective RS-25 engine during the hot fire.
While the valve was repaired over the weekend, the team continued to prepare the core stage, its four RS-25 engines, and the B-2 test stand for the second hot fire at Stennis. This hot fire test will be the last test before the Artemis I core stage is shipped to the agency’s Kennedy Space Center for assembly and integration with the rest of the rocket’s major elements and the Orion spacecraft.
The Space Launch System (SLS) rocket’s interim cryogenic propulsion stage (ICPS) moved into the Multi-Payload Processing Facility February 18, 2021, at NASA’s Kennedy Space Center in Florida alongside one of its flight partners for the Artemis I mission, the Orion spacecraft. Both pieces of hardware will undergo fueling and servicing in the facility ahead of launch by teams from NASA’s Exploration Ground Systems and their primary contractor, Jacobs Technology. The rocket stage and Orion will remain close during their journey to space.
Built by United Launch Alliance and Boeing, the ICPS will be positioned above the core stage and will provide the power needed to give Orion the big push it needs to break out of Earth orbit on a precise trajectory toward the Moon during Artemis I.
This is the first time since the shuttle program that two pieces of flight hardware have been processed inside this facility at the same time. Once final checkouts are complete, the ICPS and Orion will part ways on the ground and be reunited in the Vehicle Assembly Building for integration onto the SLS rocket.
Artemis I will be an integrated flight test of the SLS rocket and Orion spacecraft ahead of the crewed flights to the Moon. Under the Artemis program, NASA will land the first woman and the next man on the lunar surface and establish a sustainable presence at the Moon to prepare for human missions to Mars.
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.
NASA’s Artemis IOrion spacecraft is being outfitted with additional artwork as technicians began installing the logo for ESA (European Space Agency). ESA provided the European-built service module, which provides power and propulsion for the Orion spacecraft, and will also provide water and air for astronauts on future missions.
Artemis I extends NASA and ESA’s strong international partnership beyond low-Earth orbit to lunar exploration with Orion on Artemis missions. The ESA logo joins the historic NASA “meatball” insignia on the Artemis I spacecraft adapter jettison fairing panels that protect the service module during launch.
Orion is currently stationed at NASA’s Kennedy Space Center in the Multi-Payload Processing Facility, where it will undergo fueling and servicing by NASA’s Exploration Ground Systems and Jacobs Technology teams in preparation for the upcoming flight test with the Space Launch System rocket under the agency’s Artemis program.
The twin boosters will power the first flight of the agency’s new deep space rocket on its first Artemis Program mission. Artemis I will be an uncrewed flight to test the SLS rocket and Orion spacecraft as an integrated system ahead of crewed flights.
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 four minutes would provide significant data to help verify the core stage is ready for flight. A second hot fire test is planned for about eight minutes to simulate the amount of time it will take to send the rocket to space following launch. The Green Run wet dress rehearsal and first hot fire test 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.
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.
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.
Teams from NASA’s Space Launch System (SLS) Program conducted a hot fire of the Artemis I core stage on Jan. 16 at NASA’s Stennis Space Center.
All four RS-25 engines ignited successfully, but the test was stopped early after about a minute. At this point, the test was fully automated. During the firing, the onboard software acted appropriately and initiated a safe shutdown of the engines. During the test, the propellant tanks were pressurized, and this data will be valuable as the team plans the path forward. In coming days, engineers will continue to analyze data and will inspect the core stage and its four RS-25 engines to determine the next steps.
To learn more, tune in to NASA TV for a post-test briefing at 8:00 EST.
Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test. Watch a replay of the test on NASA Television or NASA’s YouTube channel.
The hot fire is underway for the Space Launch System (SLS) rocket core stage at NASA’s Stennis Space Center near Bay St. Louis, Mississippi.
Engine ignition began at approximately six tenths of a second before T-0, beginning with Engine 1, then Engines 3, 4, and 2 ignited in sequence a few hundredths of a second apart. The test is expected to last about 8 minutes and will include three different power levels for the engines, as well as two 30-second engine gimballing, or pivoting, movements to simulate flight steering commands. Depending on the rate propellant is burned the time is estimated to range from 485 to 493 seconds to simulate launch.
Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.