الثلاثاء، 19 يناير 2021

NEWS TECHNOLOGIE

NASA retired the Space Shuttle in 2011 and embarked on two projects that would eventually restore its access to space. There’s the Commercial Crew Program, which recently led to the SpaceX Dragon successfully transporting astronauts to and from the International Space Station. The Space Launch System (SLS), which is NASA’s upcoming heavy-lift rocket, has been slower to take shape. In its first major engine test over the weekend, the SLS had to shut down after just one minute of a planned eight-minute test. NASA doesn’t want to call it a failure, but plenty of others are. 

The SLS is a heavy-lift rocket similar to the Saturn V or SpaceX Falcon Heavy. In the last decade, NASA has spent over $17 billion on the SLS. When complete, it will have enough power to send humans to the moon again and launch large payloads to the outer solar system. The vessel will have a pair of solid rocket boosters, the design of which has already been tested, but there’s less that can go wrong with solid boosters. The test over the weekend focused on the core stage’s four RS-25 engines (above), the same model used on the Space Shuttle. 

In the hot test, the core stage was docked to a test rig on the ground to keep it from flying off. NASA intended to fire the engines for eight minutes, just like a real launch. However, the flight control center called an “MCF” on engine four after one minute — that stands for major component failure, which sounds pretty bad. The test ended after 67 seconds. Outgoing NASA administrator Jim Bridenstine said of the test, “It’s not everything we hoped it would be.”

We don’t know exactly what happened yet, but the timing of the failure could offer some clues. At one minute in the SLS launch protocol, the engines are supposed to throttle down from 109 percent nominal thrust to 95 percent while also adjusting their axis of thrust, known as gimbaling. Engineers spotted a small flash on the thermal protection sheath surrounding engine four, followed by the error that led to the shutdown. If there’s a problem with engine four, NASA can swap it with a spare RS-25 that it has left over from the Shuttle program, but that won’t do the trick if there’s a problem with the way the engines are integrated with the rocket itself. 

NASA, Boeing (the primary SLS contractor), and Aerojet Rocketdyne (builder of the RS-25 engines) are investigating the problem. If the solution is as simple as swapping the engine, that could happen in as little as a week or 10 days. However, NASA’s plan to launch the uncrewed Artemis 1 mission in 2024 is looking increasingly unworkable.

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