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 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.

Green Run 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.

SLS core stage
This infographic explains more about the core stage and its massive liquid hydrogen and liquid oxygen tanks that hold more than 700,000 gallons of propellant.

For more updates, images and videos, check back at this blog or the Green Run web site: https://www.nasa.gov/artemisprogram/greenrun

NASA conducted a media briefing with several experts who support the Green Run team on Jan. 19, and a replay will be available for 30 days by dialing 888-566-0617.

Green Run Update: 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.

SLS ocket core stage comes alive during the Green Run hot fire test
The Space Launch System rocket core stage comes alive during the Green Run hot fire test on Jan. 16 at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. Image Credit: NASA

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.

Watch the Green Run hot fire video as the Space Launch System (SLS) rocket comes to life with all four engines firing together for the very first time.

Check back at this blog for updates.

 

Green Run Update: Hot Fire Conducted on Jan. 16

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.

Green Run Update: Engines Igniting as Hot Fire Gets Underway 

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.

Green Run Update: Terminal Countdown Sequence Started

The test conductor polled the team and has approved the decision to proceed with the terminal countdown that includes the final 10 minutes before the hot fire. During the terminal countdown, the team is executing the autonomous launch sequence that simulates the countdown for the Artemis I launch. The test transitions from ground control to on-board software control of the core stage and so the test is fully automated starting at T-30 seconds. 

Key milestones during the final count include starting the core stage auxiliary power units (CAPUs) for each engine to help operate and steer the engines during the test, purging the engines with nitrogen gas to ensure they are completely clean before flowing propellant, moving the engines into position for engine start, and switching the core stage from external test stand power to internal battery power. 

Below are the key milestones in the terminal countdown: 

  • T-4 minutes: Core Stage Auxiliary Power Unit CAPU Start 
  • T-3 minutes: Engine Purge Sequence Start 
  • T-2 minutes, 30 seconds: Pre-Ignition Gimbal Sequence Started 
  • T-1 minute, 30 seconds: Core Stage to Internal Power 
  • T-33 seconds: Automated Launch Sequence (ALS) Start 
  • T-6 seconds: Engine Start Commands 

The B-2 test stand flame deflector cooling water also will begin flowing to protect the deflector from superheated engine exhaust about a minute and a half before firing up the engines, and test stand acoustic suppression water flow will begin about 65 seconds before hot fire. 

Hear the test conductor in the final minutes before the countdown during live coverage underway on NASA Television and the agency’s website. 

Learn more about Green Runand check back at this blog for updates on the SLS core stage hot fire test. 

Green Run Update: Hot Fire Test Targeted for within an Hour

The teams are now targeting a hot fire test for NASA’s Space Launch System (SLS) rocket core stage within an hour. The team has completed a successful pressurization demonstration and is evaluating the data to ensure they are ready to proceed.

Live coverage is underway on NASA Television and the agency’s website.

Teams began the countdown for the hot fire test earlier today. This is the eighth and final test in the Green Run testing series for the rocket’s core stage that will launch NASA’s Artemis I mission around the Moon. Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: NASA TV Coverage Underway for Hot Fire Test 

Countdown is continuing for the hot fire test of the core stage for NASA’s Space Launch System (SLS) rocket. The test is targeted for as early as 4 p.m. EST and is expected to last about 8 minutes to simulate launch and ascent of the SLS to orbit.

NASA Television coverage has begun. Watch live: http://www.nasa.gov/live

Teams powered up the core stage’s avionics systems Thursday, Jan. 14, and began the countdown for the hot fire test earlier today. The team is continuing to closely monitor core stage and facility performance before proceeding into the final phase of the test: the terminal countdown leading to the hot fire.

During this test, the team has repeated many of the major milestones marked during the first wet dress rehearsal including chilling the main propulsion system and completely filling both propellant tanks. Coming up at 10 minutes before the test, the test conductor will poll the team who will give the final “go/no go” to proceed with the hot fire test.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: Teams Running Ahead of Schedule, NASA TV begins at 3:20 p.m. EST

Teams are progressing through the countdown and running approximately an hour ahead of schedule. The test is targeted for as early as 4 p.m. EST. Live coverage will begin earlier at 3:20 p.m. on NASA Television and the agency’s website.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: Tanking Complete for Hot Fire Test

Engineers have completed tanking for the hot fire test of NASA’s Space Launch System (SLS) rocket core stage at NASA’s Stennis Space Center, and the countdown is proceeding normally.

The liquid hydrogen tank holds 537,000 gallons of liquid hydrogen, cooled to minus 423 degrees Fahrenheit. The liquid oxygen tank holds 196,000 gallons of liquid oxygen, cooled to minus 297 degrees Fahrenheit. The cryogenic fuel and oxidizer in the tanks will be replenished, or “topped off,” as needed, because some of the fuel boils off due to temperature fluctuations as the propellant is loaded. The tanks were filled during an earlier wet dress rehearsal on Dec. 20. Today is only the second time that they have been completely loaded with propellant.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

This infographic explains more about the Green Run tests that have already occurred before this final hot fire test.This infographic explains more about the Green Run tests that have already occurred before this final hot fire test.