NASA to Discuss Second Hot Fire Test of Rocket for Artemis Moon Missions

NASA will host a media teleconference at 9 a.m. EST Friday, Feb.19, to discuss 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.

The team is targeting Thursday, Feb. 25, for the test, known as the hot fire, to take place at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The target date will be confirmed following a test readiness review later this week.

Audio of the teleconference will stream live on the agency’s website.

For 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 to simulate the rocket’s core stage operation during launch.

On Jan. 16, NASA conducted the first hot fire of the Artemis I core stage. All four RS-25 engines ignited successfully, but the test experienced an early shutdown after about 67 seconds due to conservative test parameters. After evaluating data from the first hot fire and the seven prior Green Run tests, NASA and core stage lead contractor Boeing determined that a second, longer hot fire test would provide valuable data to help certify the core stage for flight and pose minimal risk to the Artemis I core stage.

Participating in the briefing are:

• Tom Whitmeyer, deputy associate administrator for exploration systems development, NASA Headquarters
• John Honeycutt, SLS program manager, NASA’s Marshall Space Flight Center
• Julie Bassler, SLS stages manager, Marshall
• Ryan McKibben, Green Run test conductor, Stennis
• Johnny Helfin, SLS liquid engines manager, Marshall
• John Shannon, vice president and SLS program manager, Boeing
• Jeff Zotti, RS-25 program director, Aerojet Rocketdyne

To participate in the teleconference, media must contact Kathryn Hambleton at kathryn.hambleton@nasa.gov by 5 p.m. Thursday, Feb. 18, for dial-in information. 

The Green Run test series is a comprehensive assessment of the rocket’s core stage prior to SLS launching Artemis missions to the Moon. The core stage includes the liquid hydrogen tank and liquid oxygen tank, four RS-25 engines, plumbing, and the computers, electronics, and avionics that serve as the “brains” of the rocket.

The first in a series of increasingly complex missions, Artemis I will test the SLS rocket and Orion spacecraft as an integrated system ahead of crewed flights to the Moon. Under the Artemis program, NASA is working to land the first woman and the next man on the Moon to pave the way for sustainable exploration at the Moon and future missions to Mars.

Quelle: NASA

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Update: 26.02.2021

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Stuck propulsion valve delays second SLS test-firing

A troublesome liquid oxygen valve on the Space Launch System’s first flight-rated core stage will keep NASA from performing a second test-firing of the rocket’s four main engines this week.

NASA hoped to conduct the second hotfire test on SLS core stage Thursday, but the agency announced Monday that the engine firing will be postponed to evaluate a misbehaving valve in the rocket’s propulsion system.

The space agency said Monday that engineers identified the problem over the weekend. One of eight “prevalves” in the core stage propulsion system was not working properly, NASA said.

The prevalve supplies liquid oxygen to one of the rocket’s four RS-25 main engines. The engines are left over from the space shuttle program, and consume liquid hydrogen fuel in combination with super-cold liquid oxygen. All eight prevalves functioned properly during the first SLS core stage hotfire test Jan. 16, officials said.

“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,” NASA said Monday.

The Jan. 16 hotfire test was supposed to last more than eight minutes, but the four RS-25 engines shut down a little more than a minute after ignition. Engineers traced the cause of the premature shutdown to a hydraulic system parameter that tripped an overly-conservative setting for the test, the last phase of a “Green Run” test and checkout campaign for the SLS core stage at NASA’s Stennis Space Center in Mississippi.

The core stage hydraulics drive actuators that pivot, or gimbal, the four RS-25 engines to steer the rocket after liftoff. The Space Launch System will fly with two solid rocket boosters mounted on each side of the 212-foot-tall (64.6-meter) core stage. An upper stage and Orion crew capsule on top of the core stage will bring the total launcher height to 322 feet (98 meters) tall.

NASA officials decided to redo the Green Run test-firing after the early cutoff last month. Managers want to get at least four minutes of run time on the RS-25 engines on the second hotfire test to gather enough data to build confidence in the rocket’s performance before shipping the stage to the Kennedy Space Center in Florida for launch preparations.

But the goal for the second hotfire test is to burn the engines for more than eight minutes, the duration they will fire on a real SLS flight.

Kathy Lueders, associate administrator for NASA’s human spaceflight division, said Wednesday that engineers were having trouble getting the liquid oxygen prevalve to fully open during checkouts before the second Green Run hotfire test.

“It’s very frustrating,” Lueders said in a panel discussion at the 47th Spaceport Summit.

“On your LOX (liquid oxygen) system, if you’re trying to run your engines at the power level we’re trying to run our engines, you need to have that prevalve open,” she said.

The Green Run hotfire test has been delayed more than six months since the SLS core stage arrived at Stennis in January 2020. A temporary suspension of work caused by the COVID-19 pandemic initially delayed preparations for the test, and a series of hurricanes and tropical storms that impacted the Gulf Coast last year also slowed work at the Stennis Space Center.

Engineers aimed to perform the hotfire test before the end of the year, but a problem during a fueling test in December pushed the engine firing into January. With the most recent delay, the earliest the full-duration core stage test-firing is some time in March.

The first SLS test launch will carry an unpiloted Orion crew capsule into space on NASA’s Artemis 1 mission. The Orion spacecraft will fly into orbit around the moon on a multi-week test flight before returning to Earth for a splashdown in the Pacific Ocean. If successful, the mission will pave the way for Artemis 2, the first crewed SLS/Orion mission, to carry four astronauts around the moon and back to Earth as soon as 2023.

The Artemis program is NASA’s initiative to return astronauts to the moon. NASA was tasked by the Trump administration with landing a crew near the south pole of the moon by the end of 2024. The Biden administration has expressed support for the Artemis program, but has not set a timetable for a crewed lunar landing mission.

The 2024 schedule goal was already slipping away before the end of the Trump administration. Congress approved only a fraction of the funding NASA requested in fiscal year 2021 for the Artemis program’s human-rated lunar lander development.

Lueders, a former manager of NASA’s commercial crew program, said the SLS Green Run delays were “very, very tough.”

“This is the one last piece that we have waiting for us to get down to the Cape for us to go fly,” Lueders said.

She said NASA is still “hoping” to fly the first SLS rocket at the end of this year.

“Like I used to say with the commercial crew program, we’re going to fly when we’re ready,” Lueders said Wednesday.

Quelle: SN

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Update: 12.03.2021

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NASA Targets March 18 for Second Test Fire of SLS Moon Rocket

NASA and Boeing are targeting March 18 for a second test fire of the space agency’s mammoth Space Launch System (SLS) moon rocket core stage, following inspections, tests and checkouts over the past 2 weeks which discovered (and fixed) a liquid oxygen valve which was not working properly inside the rocket’s engine section.

There are a total of eight valves, called prevalves, and they are quite important because they are part of the vehicle’s main propulsion system that supplies liquid oxygen and liquid hydrogen to each of the four powerhouse RS-25 engines, and they must work properly for the test fire. If they do not allow fuel flow, then obviously the engines won’t work.

The upcoming second test fire comes following a much shorter than anticipated debut test fire of 212 foot tall core stage two months ago at Stennis Space Center in Bay St Louis, Mississippi. The planned 8-minute test fire barely made it past 1-minute, before an automatic shutdown was triggered by intentionally conservative test parameters, according to NASA. After all, the rocket is the actual flight vehicle for the first Artemis moon mission, not just simply a test article.

The team at Stennis now plans to power up the core stage later this week for a final check of all its systems, before powering it up again on March 16 to start the countdown for the second test fire on March 18.

As outlined in detail previously on AmericaSpace by Ben Evans, the SLS Hot Fire Test is the eighth and final step in the “Green Run”, a year-long campaign to wring out the Core Stage’s myriad systems ahead of the rocket’s maiden voyage and the uncrewed Artemis-1 mission around the Moon, possibly as soon as early 2022.

Five “functional” tests to validate the rocket’s Guidance, Navigation and Control (GNC) systems, evaluate its avionics and safety systems and check out its Main Propulsion System (MPS), Thrust Vector Control (TVC) and hydraulics were completed between January and September 2020. Satisfactory completion of these steps allowed Stennis teams to press into three “operational” tests, beginning last fall, which saw the Core Stage put through a mock countdown, fueled with its full load of propellants in a so-called “Wet Dress Rehearsal” (WDR) and all four RS-25 engines hot-fired.

Original plans called for the four engines—all of which are refurbished Space Shuttle Main Engines (SSMEs), with over 1.1 million seconds’ worth of “burn-time” and a total of 25 shuttle missions to their credit—to be fired for up to 485 seconds, approximating as closely as possible the conditions that they will encounter during the raging, eight-minute climb to orbit on a real mission.

To mimic the passage through a period of maximum aerodynamic turbulence (“Max Q”), about a minute after liftoff, the RS-25s were to be throttled back from their maximum 109-percent thrust level to 95 percent for about 30 seconds, then returned to full power. It was also expected that the engines would be “gimbaled” under TVC control to demonstrate their steering capabilities.

As the first test fire got underway and all four engines came alive, the first minute of stable thrust proceeded without incident. Then at 60 seconds, the pre-planned gimbaling test of the engines under TVC control got underway. Responsibility for gimbaling each engine fell to the TVC actuators, each powered by a Core Stage Auxiliary Power Unit (CAPU).

At approximately 61 seconds, CAPU-2—serving the Core Stage’s No. 2 engine—detected low hydraulic fluid levels and after a series of verification checks over the next two or three milliseconds to validate this reading, it shut itself down. The other three CAPUs momentarily increased their hydraulic pressures to 105 percent to compensate for this evolving situation. CAPU-2 then commanded the Core Stage flight computer to shut down the other engines. This was executed safely over the next few seconds and the Hot Fire Test ended after 67.2 seconds, which represented less than 15 percent of a full-flight-duration burn.

Summing up the first test fire, NASA noted that—had it been a “real” flight—the CAPU margins would have been higher and CAPU-2 would have continued to function nominally. “The specific logic that stopped the test is unique to the ground test, where the Core Stage is mounted in the B-2 Test Stand at Stennis,” NASA explained. “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.”

Meanwhile, the teams at Kennedy Space Center (KSC) in Florida are wrapping up stacking of the giant rocket’s powerhouse solid rocket boosters (SRBs) atop a mobile launcher in NASA’s iconic Vehicle Assembly Building (VAB). Other parts and the spacecraft itself, Orion, are all at KSC awaiting arrival of the core stage following a successful test fire on March 18. In the meantime, KSC will finish installing electrical instrumentation and pyrotechnics, then test the systems on the SRBs.

“Seeing the Space Launch System solid rocket boosters stacked completely on the Mobile Launcher for the first time makes me proud of the entire team especially  the Exploration Ground Systems crew at Kennedy who are assembling them and also the teams at Marshall and Northrop Grumman who designed, tested and built them,” said Bruce Tiller, the SLS boosters manager at NASA’s Marshall Space Flight Center. “This team has created the tallest, most powerful boosters ever built for flight, boosters that will help launch the Artemis I mission to the Moon.”

Once the test fire is complete, the core stage will be shipped to KSC on the Pegasus barge, arriving at KSC’s Turn Basin for offload and transport straight into the VAB, where it will be lifted and placed between the two SRBs and attached at the core stage engine and intertank sections. It will be a sight to see, as was such operations with the Apollo Saturn V and space shuttle missions in the very same building.

Quelle: AS