NASA Investigates Why NASA’s Lunar Rocket Launch Test End Early – Spaceflight Now

The four RS-25 engines of the Space Launch System launch during the abbreviated Green Run test on Saturday. Credit: NASA

A critical test of NASA’s Lunar Rocket Launch System ended in Mississippi just 67 seconds after its launch on Saturday, far short of the planned eight-minute burn that was supposed to pave the way for the space agency to finally charge the primary stage of the rocket to center Space Kennedy in Florida in preparation for launch.

The base stage of the SLS, built by Boeing, lit its four Aerojet Rocketdyne RS-25 engines for the first time at 5:27 PM EST (4:27 PM CST; 2227 GMT) on Saturday to burn that was expected to last longer. From eight minutes, the culmination of a series of exits over the course of a year at the Stennis Space Center in southern Mississippi.

Installed on the giant B-2 test platform in Stennis, the 212-foot (98 m) SLS base stage was throttled to its maximum capacity after the four main engines lit at 120 millisecond intervals.

The engines, left over from the Space Shuttle program, accumulated up to 1.6 million pounds of thrust, making Saturday’s hot fire the most powerful rocket launch at the Stennis Space Center since NASA tested an Apollo-era Saturn 5 moon rocket on the same platform in the 1960s.

But after life rattled and generating ground-shaking thunder for just over a minute, the RS-25 engines were cut off by order of the on-board computer system, which detected an unspecified malfunction at one of the power plants.

Engineers have been tracking the cause of the engine’s premature shutdown Saturday night, but NASA officials have few details about what might have led to the early end of the test.

„I know not everyone is as happy as we can because we wanted to have eight minutes of a hot fire, and we were just over a minute,“ said NASA Administrator Jim Bridenstine.

Before the test began on Saturday, NASA officials said preparations are on track for the first test flight of the Space Launch System at the end of 2021. It was not immediately clear how the premature shutdown of the SLS engines on Saturday could affect that schedule, although it will add Certainly more risks to it.

„We’ve got a lot of data that we’re going to go through, and we’ll be able to sort, get to a point where we can determine if a launch in 2021 is possible or not,“ Bridenstein said. . „While today wasn’t everything we hoped it would be, this was an important day.“

The outgoing NASA chief, who will leave office on Wednesday as the Trump administration ends, said engineers have gathered important data about the missile’s performance despite the engines outage. The Space Launch System is a major part of NASA’s Artemis program, which aims to return astronauts to the moon for the first time since 1972.

SLS will launch NASA’s Orion crew capsule to send astronauts to the vicinity of the moon, and NASA plans to build a small space station to serve as a research site and waypoint for crews traveling between Earth and the surface of the Moon. The Orion spacecraft will be linked to a lunar orbit lander, where the astronauts will float in the lander to head to the surface of the moon.

The first SLS test flight, known as Artemis 1, will launch the Orion spacecraft to orbit the moon without astronauts. A second SLS / Orion flight around the moon for the 2023 timeframe will feature three astronauts and one Canadian crew member.

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The Trump administration’s goal of a human landing on the south pole of the Moon by the end of 2024 is fading fast. The timeline has been strict from the moment Vice President Mike Pence announced the 2024 moon landing goal in 2019. But Congress has not allocated the money that NASA said it needs to develop human-coded lunar landers to meet the schedule, making it clear It raised more doubts about the deadline for 2024..

Space policy experts believe the Biden administration is unlikely to maintain the 2024 schedule target for a lunar landing, but it may make a slower effort to bring American astronauts back to the moon.

The Space Launch System has been delayed repeatedly since the program was announced in 2011, losing targets for the first time in 2017, 2018, 2019, and 2020. NASA spent more than $ 18 billion on the SLS program from 2011 through September 30, 2020.

„This is an important program for the United States of America,“ Bridenstein said on Saturday, „It is important for our leadership in the world, and it is important for us to go to the moon, and to go quickly,“ adding that the purpose of the Artemis program goes beyond science.

It is a diplomatic tool. It’s about American leadership. „It’s about exploration,“ he said.

Bridenstein said running all four of the RS-25 engines simultaneously was a „win in itself“. The engines flew three times at a time on the space shuttle.

While developing the Saturn 5 moon rocket and space shuttle, NASA launched test articles at Stennis to verify the propulsion system design. In order to save money, SLS first complete base stage serves as test article and flight unit. NASA officials said they are very keen on stage because it is ultimately aimed at flying.

„This is not a failure,“ said Bridenstein. „This is a test … we’ll make adjustments, and we’ll fly to the moon.“

Based on video and audio analysis broadcast on NASA TV, the first sign of a problem came during a brief SLS hot-fire test about 50 seconds after the engine ignition, when an engineer on the test team declared a „MCF“ or „pioneer of component failure“ in Engine # 4.

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„Copy that, but we’re still working, and we still have four good engines, right?“ Test conductor answered on network connections.

One member of the test team said, „Yes, copy that.“

Soon after calling the MCF, about 67 seconds after the engine had started, the video showed that the primary stage motors appeared to be in the shutdown sequence. Verbal confirmation to shut down the engine came a few seconds later from a member of the test team.

„There was some talk about ‚FID‘ on the engine 4, which is our term for identifying a failure, and then soon followed by the MCF, which is a major failure of a component,“ NASA’s SLS Program Manager John Honeycutt said at a press conference. A few hours after the test. „I don’t know much more about it than you do at this time. Any parameter that deflects in the engine can send a failure ID.“

Artist’s concept of launching the Space Launch System with NASA’s Orion spacecraft. Credit: NASA

The engines turned off about a minute after the test program began, around the same time the RS-25s were programmed to throttle again to 95% before restarting to full power at 109% of rated performance. At the same time, the motors were to rotate with hydraulic axes.

„So there’s a lot of dynamics going on at that time,“ Honeycutt said. “We saw a little flash coming from around the front of the thermal protection cover in the Engine 4 at the time we started the gimbal, (or) nearly so.

„At that time … the engine control device sent the data to the primary stage control unit to shut down the vehicle,“ Honeycutt said. „The team accomplished a lot today, we learned a lot about the car, we loaded the car, our pressure system malfunctioned, the engines had air conditioning, and we got about 60 seconds of time on the RS-25s.“

Before firing squads wanted to have at least 250 seconds of uptime in the base stage before moving on from hot fire, said John Shannon, SLS Program Manager at Boeing. By that stage of the test, the motors could have been slowed and run back to full thrust and had completed two coils, including a sweep in about T + plus 2 minutes and 30 seconds, to verify the structural response to the engine’s motions.

“We’ve said all the time that we’d like to hit at least 250 seconds, but I think we need to do our due diligence and look at the data we’ve gathered to make sure we have a good plan going forward,” Honeycutt said.

Bridenstine said Saturday it is too early to tell if engineers will need to run another hot fire test in the base stage, or whether an early engine shutdown is likely to delay the launch of the first SLS test, known as the Artemis 1 mission, to 2022.

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„It depends on what the anomaly is, and how difficult it is to fix it,“ Bridenstein said. „And we have a lot to learn to find out. So I think it’s very good that it’s something that can be easily fixed, and we can feel confident going down the head and then sticking to the schedule. It’s also true that we might find a challenge that will take more time.“

NASA could have shipped the base stage of the SLS to the Kennedy Space Center before the end of February if the Saturday shooting test went perfectly, and moved the stage into place for stacking with two solid rocket boosters, a top stage, and the Orion spacecraft. Assuming NASA officials decide to retest the hot fire, February is the closest another test might happen.

Honeycutt said it takes three to four weeks to dry the RS-25 engines, carry out inspections, and prepare the base stage for the second hot fire test, assuming managers decide to go for another test. This time taken does not take into account how long it would take to complete any repairs to fix the issue that caused the early end of the hot fire test on Saturday.

Each of the four RS-25 engines launched on Saturday flew over NASA’s Space Shuttle Fleet. The engines were launched on 21 shuttle missions dating back to 1998.

NASA has a reserve of RS-25s available should engineers need to replace one of the engines in the SLS’s Primary Stage 1. Officials said ground crews at the Stennis could switch engines to the missile mounted on the test platform.

„We have to fully understand the problem, and evaluate the primary stage as well as the engines to make sure we understand the problem and what needs to be fixed or fixed, if we need to,“ Honeycutt said Saturday night. .

The only damage to the missile after its test launch on Saturday was on the thermal blanket near the No. 4 engine, Honeycutt said, as the difference noticed a flash just before the engine was turned off.

Asked if any of the data analyzed so far indicated that engineers need to make any major changes to the base stage, Honeycutt said: “What have I seen so far about the performance of the devices during our rehearsals, during the hot fire today, and the quantity? Ltd. from the images that I have been able to see so far, I don’t think we are looking forward to a major design change. „

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