NASA has successfully fired its new moon rocket’s 4 core engines – a key step towards a launch later this year

sls hot fire engines
The SLS core stage engines fire on the test stand, March 18, 2021.

NASA put the core stage of its new mega-rocket through its most grueling test yet on Thursday.

In what’s known as a “hot fire” test, the four RS-25 engines roared to life at 4:37 p.m. ET, producing about 2 million pounds of thrust. They continued roaring for more than eight minutes – the length of time required to deliver an upper-stage rocket and spaceship into orbit. A cloud of smoke churned out from the test stand, and when the engines finally burned through the fuel and cut off, test controllers applauded.

“There’s a lot of data now that’s going to have to be analyzed,” Bill Wrobel, the manager of the testing program, said during NASA’s live broadcast. “But I think the applause says a lot about how the team feels. They got through the test and it looks pretty good right now.”

At first glance, the only visible abnormality was a fire above the engines. It probably came from burning cork insulation, according to Wrobel. NASA will share more details about the test in a press conference Thursday evening.

As long as the data doesn’t reveal any hidden issues, Thursday’s success clears the way for NASA to integrate the core stage into the agency’s new moon rocket, called the Space Launch System (SLS). The system is a cornerstone of the agency’s Artemis program, which aims to put boots on the lunar surface for the first time since 1972 and lay the groundwork for a space station that would orbit the moon.

But first, SLS has to fly to the moon and back without a crew. With the hot fire done, NASA could launch that mission, called Artemis 1, before the end of the year.

The world’s most powerful rocket stage

sls hot fire 2 stennis space center
Smoke billows from the Stennis Space Center test stand as the SLS core stage fires its engines, March 18, 2021.

The rocket’s core stage is the biggest piece of SLS and its structural backbone. It’s also the world’s largest and most powerful rocket stage, according to NASA.

On Thursday, the 212-foot-tall stage stood vertical, strapped into a test stand at Stennis Space Center in Mississippi. Six barges carried 733,000 gallons of cryogenically chilled propellant to the stand and, over several hours, the fuel was pumped into the rocket stage’s tanks. The engines burned through all that fuel in the expected timeframe.

“They clearly got the full duration that they were after, which is really great news,” Wrobel said.

This final development test suggests that the stage’s engines can survive the journey from a launchpad to Earth’s orbit. If data from the test leads to the same conclusion, NASA will ship the core to Kennedy Space Center in Florida, where the rest of SLS waits.

The final product is designed to stand 365 feet tall, with twin rocket boosters strapped to the core stage and NASA’s Orion spacecraft secured on top of it.

space launch system
A NASA-provided rendering of the Space Launch System.

The system could launch to the moon as early as October. If that mission happens on schedule and goes smoothly, NASA would then be on track to realize its goal of ferrying astronauts to the moon sometime in the mid- to late-2020s.

Eventually, NASA has said, SLS could even carry humans to Mars.

orion spacecraft sls artemis 1 moon mission
An artist’s illustration shows the Orion spacecraft rocketing to the moon on the Artemis 1 mission.

NASA tried a hot-fire test in January, but it was cut short

NASA has spent about $18 billion developing SLS. Boeing built the core stage, and Aerojet Rocketdyne supplied the RS-25 engines, which were also used on NASA’s fleet of space shuttles. The hot fire is the eighth and final step in a program the agency designed to thoroughly test each part of the core stage before launch.

This was NASA’s second hot fire. The first was in January, but the engines suddenly shut down just one minute in.

NASA sls engine shutdown space launch system hot fire
An SLS engine burns propellant (left), then abruptly shuts down (right) during the hot fire test on January 16, 2021.

It turned out that a flight computer had automatically aborted the test because a system controlling the engines’ movements had exceeded the limits NASA set ahead of the hot fire. The limits were intentionally conservative, NASA said, because the agency doesn’t want to push the rocket so hard that it gets damaged during testing.

But in the two months since, NASA has adjusted the test parameters to be less conservative. If the system had exceeded the prior limits during an actual launch, the agency later said, the rocket would have continued to fly.

nasa space launch system sls core stage green run stennis january 2021
Crews at Stennis Space Center lift the core stage of NASA’s Space Launch System into place on January 22, 2020.

The January test’s abrupt ending meant that the SLS team only had enough data to verify three of 10 design requirements. That’s why they redid the hot fire on Thursday.

In preparation for the second hot fire, the team also repaired a valve for the engines’ liquid-oxygen tank that was not opening properly.

The next moon flight could launch as early as October

None of the prior issues seemed to arise during Thursday’s hot fire, which burned for eight minutes and 19 seconds. SLS program managers had previously said they would need at least four minutes of data in order to verify the rest of their design requirements.

space launch system sls nasa rocket boosters kennedy space center
The Space Launch System’s twin rocket boosters inside the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida on March 3, 2021.

Now, the SLS team will comb through data from the test and finish the necessary verifications to certify the core stage for flight.

NASA has tentatively set the Artemis 1 launch date for November, but SLS program managers have said the rocket could lift off as early as October.

“We’re still on path to have an opportunity to launch this year, but we recognize also that there are things that can come up, like weather and COVID and some first-time operations,” Tom Whitmeyer, who leads the NASA program that develops new systems like SLS, said ahead of the second hot fire. “So the plan is to launch this year, but we’ll continue to provide progress as we go through the year and we’ll certainly let you know how we’re doing.”

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Watch NASA test-fire the world’s most powerful rocket stage on Thursday – a critical step towards the next moon mission

space launch system sls hot fire nasa green run
The core stage of NASA’s Space Launch System fires its engines for a hot fire test on January 16, 2021, at the Stennis Space Center in Mississippi.

NASA is building the world’s most powerful rocket stage in order to bring a new generation of astronauts to the moon. On Thursday, the agency plans to fire the engines.

The rocket, called Space Launch System (SLS), is designed to eventually stand 365 feet (111 meters) tall. The system is a piece of NASA’s larger Artemis program, a roughly $30 billion effort to put people on the lunar surface for the first time since 1972. NASA has spent about $18 billion developing the rocket.

The 212-foot-tall core stage – the system’s biggest piece and its structural backbone – is the world’s largest and most powerful rocket stage, according to NASA. It’s currently clamped into a test stand at the Stennis Space Center in Mississippi, ready for what’s known as a “hot fire” test on Thursday afternoon.

That means NASA will fire the engines continuously for about eight minutes – the length of time required to deliver an upper-stage rocket and spaceship into orbit. If the engines pass this test, the core stage will be ready to join the rest of the rocket at the Kennedy Space Center in Florida.

nasa space launch system sls core stage green run stennis january 2021
Crews at Stennis Space Center lift the core stage of NASA’s Space Launch System into place on January 22, 2020.

This hot fire is the eighth and final step in NASA’s Green Run program, which is designed to thoroughly test each part of the core stage ahead of SLS’s first launch – an uncrewed test flight around the moon called Artemis 1. If the hot fire goes as planned, SLS could launch in November.

The eventual goal is to ferry astronauts to the moon sometime in the mid- to late-2020s.

sls space launch system nasa
An artist’s rendering of the Space Launch System rocket lifting off from NASA’s Kennedy Space Center in Florida.

“Our core-stage Green Run is the most comprehensive test that we’re undertaking to make sure that SLS can safely launch the Artemis missions to the moon,” John Honeycutt, the SLS program manager, said in a February press conference. “This is a generational opportunity to learn as much as we can about the rocket while we’ve got it in this test configuration before we get to fly.”

Watch NASA’s rocket test-fire live

NASA TV will begin a live broadcast of the test at 3 p.m. ET on Thursday. That’s the beginning of the two-hour window NASA has carved out for the hot fire. Watch the livestream here:

To prepare for the test, six barges will transport 733,000 gallons of cryogenically chilled propellant to the test site early on Thursday. Three of the barges will carry liquid hydrogen, while the other three carry liquid oxygen. The core stage has one fuel tank for each. Once NASA gives the “go,” the barges will load the propellant into those tanks, preparing the rocket stage for fire.

The last hot fire attempt cut itself short

Boeing is NASA’s lead contractor for the core stage, and Aerojet Rocketdyne is responsible for its four RS-25 engines, which were also used on NASA’s fleet of space shuttles.

NASA previously attempted this same hot-fire test in January, but the engines suddenly shut down just one minute in.

NASA sls engine shutdown space launch system hot fire
An SLS engine burns propellant (left), then abruptly shuts down (right) during a hot fire test on January 16, 2021.

It turned out that a flight computer had automatically aborted the test because a system controlling the engines’ movements had exceeded limits that NASA set ahead of the hot fire. The limits were intentionally conservative, NASA said, because the agency doesn’t want to push the rocket so hard that it gets damaged during testing.

But in the two months since, NASA has adjusted the test parameters to be less conservative. The SLS team determined that it can expand the limits without much additional risk to the hardware, Honeycutt said. If the system had exceeded the prior limits during an actual launch, NASA said, the rocket would have continued to fly.

The team has also repaired a liquid-oxygen valve that was not opening properly, an issue they discovered while preparing for the upcoming hot fire.

This time, SLS program managers are hoping the engines will fire for at least four minutes. Though the full test should be eight minutes, four would give NASA enough data to verify that the core stage is safe for flight.

If anything goes wrong, NASA will have to redo the hot fire a third time, which could delay the first mission and throw a wrench into the ambitious timeline of the Artemis program overall. The program aims to land the first woman and the next man on the moon in 2024.

“We’re still on path to have an opportunity to launch this year, but we recognize also that there are things that can come up, like weather and COVID and some first-time operations,” Tom Whitmeyer, who leads the NASA program that develops new exploration systems like SLS and Orion, said in the press conference. “So the plan is to launch this year, but we’ll continue to provide progress as we go through the year and we’ll certainly let you know how we’re doing.”

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Experts say the plane and engine used by United have a safe track record – and the scary landing in Colorado should have minimal impact on the airline

United Airlines Boeing 777-222
The United Airlines Boeing 777-222 that experienced an in-flight engine failure.

  • A United Airlines jet made an emergency landing after an engine failure on Saturday.
  • Three aviation regulators have effectively grounded Boeing 777s with PW4000-112 engines pending an investigation. 
  • Experts say the issue isn’t likely systemic with the plane or engine, given the track record of both. 
  • Only 69 aircraft in the world are affected, and United is the only US carrier with the model. 
  • Visit the Business section of Insider for more stories.

Regulators in the US, UK, and Japan have moved to effectively ground Boeing 777 aircraft powered by the Pratt & Whitney PW4000-112 engine pending an investigation into the United Airlines flight that made an emergency landing shortly after takeoff over the weekend. 

Flight 328 from Denver, Colorado to Honolulu safely returned to the airport after an uncontained engine failure occurred shortly after takeoff. The incident resulted in debris falling to the ground in Denver suburbs, but caused no death or injury to passengers or bystanders as the engine failure did not affect other critical aspects of the aircraft. 

The grounding affects 69 aircraft currently flying for carriers including United, All Nippon Airways, and Japan Airlines, and is supported by Boeing, the aircraft’s manufacturer. Impact to United, the only US carrier affecting by the grounding, should be minimal, experts told Insider. 

“We’re very lucky that the fan blades didn’t shatter the cabin, they didn’t puncture the wing, they didn’t puncture a fuel tank,” Henry Harteveldt, founder of travel research company Atmosphere Research Group, said in an interview. “As accidents go, this was as good as you can hope in that there was no injury, no death, and the airplane returned safely to the ground.” 

The incident mirrored a similar issue with the same airline, aircraft, and engine, per Aviation Safety Network data, as a 2018 United flight from San Francisco to Honolulu similarly experienced an engine issue and was able to land safely with no injuries or loss of life. But experts don’t believe that there’s a systemic problem with the engine or the aircraft itself, noting the track record of safety for both.

“This was the launch engine for the plane back a quarter-century ago,” Richard Aboulafia, vice president of analysis at Teal Group, told Insider, as the Boeing 777 has been in commercial service since 1995. If there was an inherent problem with this specific combination of engine and airframe, Aboulafia says we would’ve known about it already.

The first fatal Boeing 737 Max crash, for example, occurred just over one year into its commercial life. The Boeing 777, on the other hand, has over 25 years of service under its belt with no hint of such troubles. The full investigation will reveal whether the incident was an unforeseen problem with the engine or the aircraft, or whether it was a mechanical issue on United’s end. 

What experts don’t agree on, however, is why that particular engine and airframe combination was grounded by regulators around the world. Harteveldt told Insider that the grounding and inspection requirements set by the Federal Aviation Administration and others may be due to the heightened safety environment that exists in aviation following the 737 Max grounding of March 2019. 

“I think the FAA wants to err very much on the side of caution in the wake of what happened with the 737 Max to understand what this problem is,” Harteveldt said.

The FAA was criticized in the wake of the 737 Max crashes for a lack of oversight and was one of the last regulators to ground the now-notorious aircraft. Now, the agency is taking an “extremely cautious” approach to this incident, according to Harteveldt.

“This is definitely an extraordinary step that’s being taken, but it’s being taken out of intelligent prudence,” Harteveldt said. “What United, the FAA, and Pratt & Whitney want to do is understand what caused these fan blades to come apart.”

Aboulafia called the move “par for the course” as there are so few Boeing 777 aircraft with this type of engine currently flying. 

“This is what you would do given this incident,” Aboulafia said.

What happens to United

It remains to be seen how long the grounding will last and how long it will take the airline to perform the required inspections, which will determine the overall impact.. 

In the interim, flights that were scheduled to be flown by the Pratt & Whitney-powered Boeing 777s in the next few days will be swapped for other aircraft like the Boeing 787 Dreamliner or Boeing 777-300ER, depending on factors like passenger demand, and distance for a particular route. 

“The grounding of these 24 planes to United will definitely affect the airline’s operation,” Harteveldt said. “But if there is a time for something like this to happen, it is now, when United is operating far fewer flights than it normally does because of COVID.”

This type of aircraft typically spends its life flying overseas routes, but the pandemic has grounded most of those flights. That takes some of pressure off United since the aircraft aren’t needed as much as they would be if air travel were at 2019 levels. 

“I don’t think it’s going to be more than an operational headache,” Aboulafia said. 

United’s analysts are likely troubleshooting the mid to long-term effects of the grounding, according to Harteveldt, and how it will affect operations as the airline heads into the spring and summer season. 

Cargo is also an important factor that will determine United’s next move as airlines have been relying on freight revenues to make up for the loss of passengers. The loss of 24 Boeing 777-200s, as one of the airline’s largest aircraft, will reduce United’s cargo-carrying ability in the short-term. 

The Chicago-based airline, however, still has a fleet of active Boeing 777-200 aircraft currently flying passengers and cargo, the difference is that they’re equipped with General Electric engines and not the PW4000-112 used on Saturday’s aircraft. Airlines typically choose one engine to fly a particular fleet but United acquired the General Electric-powered aircraft as a result of a merger with Continental Airlines. 

United also may consider pulling planes out of storage if the grounding lasts more than a few weeks. The airline has 28 Boeing 777s currently sitting in storage that could be brought back up to the majors; though, it might take around one to two weeks per plane to get them back into flying condition. 

Regardless of the path United takes, Aboulafia says the grounding should have “zero impact whatsoever” on the airline’s overall recovery from the COVID-19 pandemic. 

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