SLS Green Run Cuts Static Fire by “Intentionally Conservative” Testing Limits


Eastern updated at 7:45 pm with details of the briefing.

WASHINGTON – The space-launch system core stage’s static-fire test ended early on January 16 when a hydraulic system for one of the four engines hit a “deliberately conservative” range during testing.

In a January 19 statement, NASA said that the hydraulic system for Engine 2 at the core stage “exceeded the pre-set test limit that was installed for the Green Run test”. “Flight computers automatically finished testing as they were programmed to do.”

Later that same day, during a call with reporters, NASA officials said that the hydraulic reservoir level and hydraulic pressure at the core stage auxiliary power unit, or CAPU, for that engine “exceeded a range of more than a millisecond”. Fell, which triggered the flight. Computer to end the test. The CAPU drives a thrust vector control system used to speed the engines, and this problem occurred after one second when a gimble sequence began in a 60-second trial.

This also led to the closure of that CAPU. Talking on the phone with John Shannon, vice president and SLS program manager at the unit owner at Boeing, “Automated software on board turns off CAPU2 to secure the system”.

A hydraulic system problem was not associated with a major component failure (MCF) reported by test controllers about 45 seconds after ignition. NASA stated that the MCF actually occurred 1.5 seconds after ignition, and was caused by the loss of “one leg of redundancy” in engine 4 instrumentation. Test barriers for hot fires were installed to allow the test to proceed from this position. Because there is still enough redundancy in the engine control system to ensure safe engine operation during testing, ”the agency said.

NASA is still investigating what officials said soon after testing that a “flash” was seen in the vicinity of a thermal safety blanket around Engine 4. The blanket showed signs of scorching, but was expected by standard engine operation and temperature in the engine. The sections were common.

The agency said that the parameters used for the Green Run test were “intentionally conservative to ensure the safety of the core stage during the test.” NASA officials first asserted that they are taking a cautious stance to test the main stage as it is flight hardware intended to be used on the first SLS launch, the Artemis 1.

“We need to remember that the rocket we just tested is a rocket orbiting the Orion around the moon,” NASA Administrator Jim Bridenstein said in a briefing after the Jan. 16 test. “When we do this test, there is a risk that we cannot take because it is the same vehicle that will blow up the Orion.”

“Our test parameters reflect our safety-first approach and were reasonably conservative. This main platform is a high-value flight article that will return America to a deeper place, ”Shannon said in a company statement about the Green Run test. “Our redline limits were set to achieve data collection without unnecessarily putting the system at risk.”

But he acknowledged in the call that they could be too conservative. The hydraulic system was “a reading, a parameter that was probably set a little too conservatively,” Bridenstein said. “If it had been an actual launch, the parameters would not have been set so conservatively and the rocket would have continued.”

“Between ensuring that this is the first time that we use this hardware, that we have sufficient security to keep the platform in a secure configuration, but also to operate through a test regime, precisely between The line has to go on “Shannon said. “There’s a decision call out there about how you set those parameters to make sure the platform stays in a good configuration for a further test or launch.”

NASA has not yet decided whether it will conduct a second hotfire test. In observations prior to the first test, NASA and Boeing officials said that while the test was to last 485 seconds, they would collect most of the data they needed after 250 seconds. However, the incident occurred just 67.2 seconds after the engine stopped.

NASA said they wanted to review the data collected during the test, before deciding whether to perform a second hotfire test, or to stage ship at the Kennedy Space Center for final preparations for the Artemis 1 mission. “You have to understand the risk of exposing the flight core stage to another round of testing, and how to learn the risk that we have to do,” said NASA’s Human Administrator and NASA associate for operations.

One factor, Bridenstein said, is the rated lifetime of the main stage. He said the stage has been filled with liquid hydrogen and liquid oxygen propellants nine times. It has been done twice so far: in December for a wet dress rehearsal and static-fire test. A limited amount of propellant was loaded for the first attempt at a wet dress rehearsal in early December.

Performing another static-fire test means loading the stage with propellants at least once. “Every time we do something like this, it takes away one of our nine bars that we can tank,” he said. “There are reasons to do full-term hotfires, and there are reasons that we probably won’t do full-term hotfires.”

A former NASA official recommended the agency conduct a second hotfire test. “My advice would be to get ready again and get all the data – maybe a couple of weeks but the schedule is secondary,” Tweeted Wayne Hale, former shuttle program manager and current chairman of the Human Advisory and Steering Committee of the NASA Advisory Council.

NASA’s SLS program manager John Honeycutt said the cancellation hotfight test was in progress after the engines were re-cycled in the call, either to support a second hotfire test or to prepare the stage for shipment to KSC for. He previously stated that it would take 21 to 30 days to get the core stage ready, which would take time for NASA to review the data and decide if a second hotfire was needed.

“Data analysis is going to drive us and inform our decision whether we proceed to launch or we do an additional hotfire test,” he said. “We don’t have a date right now when we’re going to that decision point.”

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