NASA today began its test of the Space Launch System core tank and upper stage at Kennedy Space Center that could pave the way for the launch of Artemis I to the moon next week, but a new leak in a line of fuel again caused NASA headaches.
The test that began at 7:30 a.m. on Launch Pad 39-B seeks to ensure that fuel lines have been repaired since a cleaning on September 1. 3 can support the more than 730,000 gallons of cryogenic liquid hydrogen and liquid oxygen that need to flow into the core stage, as well as the SLS interim cryogenic propulsion upper stage.
But a new leak was detected in the same line that caused that thicket when NASA stopped the supply of liquid hydrogen fuel shortly before 10 a.m.
“They had a detection of a hydrogen leak in the umbilical of the tail service mast,” commenter Derrol Nail of NASA Communications said. It’s at the bottom of the rocket. They’ve got a 7% hydrogen reading in a cavity where that quick disconnect line is. This is the one that was repaired.”
A quick disconnect is designed to fall off and away from the rocket when launched.
The 7% leak is above the 4% threshold set by NASA for cryogenic fuel limits. NASA had been loading liquid oxygen without problems since before 9 a.m., but once again, liquid hydrogen, which also gave NASA problems during the first launch attempt in August, as well as during dress rehearsals at the spring, stopped the charging process.
NASA then moved on to troubleshooting using the same warm-up procedure it had tried multiple times in previous leak detections. That process brings the lines’ temperatures back up from their super-cold fill temperatures: minus 423 degrees Fahrenheit for liquid hydrogen and minus 294 degrees Fahrenheit for liquid oxygen.
The lines are then recooled in the hope that pressure and temperature changes can close off any places that may have been the source of the leak.
The liquid hydrogen loading retry began after 11:30 a.m., but with a slight change in operation.
“It’s different from previous plans during the second launch attempt in that they’re going to reduce the pressure in the storage tank to less than 5% psi, which is very low pressure for this operation,” Nail said. “And then as they get the flow back into the tank, into the cryosphere, they’re going to build up the pressure very slowly, as gently and as gently as possible.”
The solution worked to some extent with operations on both cryogenic fuels running, so that by noon, the liquid oxygen was approaching 100% of its 196,000-gallon capacity and the liquid hydrogen, flowing not very fast, was about above 25%. , of its capacity of 538,263 gallons.
NASA officials stated that after the restart, the leak peaked at just 3.4%, and the teams were able to complete another planned test called startup bleed, during which liquid hydrogen is used to cool all four engines. RS-25 under the core. scenery. That process was one of the problems that led to the debugging of the first launch attempt in August due to a faulty sensor that said one of the engines wasn’t as cold as it should be, a requirement that NASA has to thermally condition the engines to that they can resist. super cold fuel as it flows to the engines.
At 12:45 pm, the liquid hydrogen fill process was at 68%, but was still under the normal fast-fill pressure flow normally used for refueling on launch day.
“The team discussed with the launch director the plan to go forward from here and this is where they settled,” Nail said. “They want to gradually increase the pressure in the storage tank, which will also increase the pressure in this quick disconnect. It also increases the flow, hopefully bringing it to the fast-fill flow that would be nominal for a launch attempt. That is the ultimate goal.”
At 1 p.m., the liquid hydrogen was above 90%, and shortly thereafter it filled up, so the teams were in replenishment mode, during which only enough liquid hydrogen is pumped in to make up for the amount that evaporates into the tank. center stage.
“Some interesting data to pass along that we just learned is that during the flash fill operation, where the storage tank was at full pressure to load the liquid hydrogen, the leak rate was less than half a percent,” Nail said. “Very manageable for the team here, but also at the moment there are a lot of people scratching their heads over this.”
Today’s test also uncovered a faulty sensor that would have caused the liquid hydrogen to switch from slow to fast filling. NASA teams stopped loading liquid hydrogen while looking to switch to a backup sensor, and that’s when the leak detection happened.
“We are getting good news from the liquid hydrogen team regarding the leak,” Nail said. “That is, it reversed its trend where previously, when pressure increased, leakage increased, but now they are seeing a trend for this particular seal that when pressure increases, it decreases. That’s how the engineers say, the way it’s designed and meant to work. …So now, both core stage tanks are resupplied and stable.”
Now that the core stage is full, the plan is to open supply lines into the ICPS upper stage, which is the hardware with its own engine that will be used once SLS sends the Orion spacecraft out of Earth’s atmosphere.
The teams set out to tank the ICPS shortly before 2 pm. Its smaller tanks hold 19,250 gallons of liquid hydrogen and 5,700 gallons of liquid oxygen.
ICPS will push Orion into what is known as translunar injection, sending it on its way for a several-week mission in which the uncrewed spacecraft will travel beyond the moon and bring it back to Earth faster than any previous one. human-rated spacecraft to ensure it is safe for astronauts on future Artemis missions.
After the ICPS depot, NASA plans to do what’s called a pre-pressurization test, which will bring the core-stage liquid hydrogen tank up to the pressure level that would be needed just before launch, allowing engineers to calibrate the engine conditioning that would be needed to what would be a higher propellant flow rate, something that would be done during the terminal count on launch day.
Tank operations were originally expected to be complete by 3 p.m., but delays due to the leak have extended that deadline.
After the most recent cleanup, NASA made repairs to the launch pad, so if today’s test works, a potential launch attempt could happen next Tuesday.
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The core stage engines, combined with two solid rocket boosters not being tested today, will combine to provide 8.8 million pounds of thrust at liftoff, which would make the SLS the most powerful rocket ever launched since Earth, outperforming the Saturn V rockets used in Apollo. Program.
The test was already incorporating what NASA managers called a kinder, gentler form of charging to avoid any temperature and pressure shocks that might have been the reason behind the Sept. 1 accident. 3 leaks.
“This is part of the new operation where they are taking it very slowly with the liquid hydrogen, allowing the lines to cool down very slowly and then the slow fill has gone a little bit slower than normal in the tank,” Nail said.
NASA still needs the go-ahead from the US Space Force, which controls the Eastern Ridge over which the rocket would launch. NASA is seeking an exemption to a rule on checking batteries in rocket flight termination systems, which currently requires NASA to ensure batteries are charged within 25 days, a process that would have required the massive 5.75-million-pound, 322-foot-tall combination of rocket, launcher and spacecraft to return to the Vehicle Assembly Building.
The last time the self-destruct mechanism was checked was before August 1. 16 when Artemis I rolled to the launch pad for the last time from the VAB.
If NASA gets the waiver, it will look at two possible launch dates. The first is Tuesday, September 10. On November 27, a 70-minute window opening at 11:37 a.m. he would fly on a nearly 40-day mission landing back on Earth on November 2. 5. The second is on Sunday, October 1. 2, a 109-minute window that opens at 2:52 p.m. and flies for a roughly 41-day mission, landing on November 2. eleven.
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