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+--- Thread: Years after shuttle, NASA rediscovers the perils of liquid hydrogen (space politics) (/thread-12812.html)
Years after shuttle, NASA rediscovers the perils of liquid hydrogen (space politics) - C C - Sep 5, 2022
https://arstechnica.com/science/2022/09/years-after-shuttle-nasa-rediscovers-the-perils-of-liquid-hydrogen/
EXCERPTS: America's space agency on Saturday sought to launch a rocket largely cobbled together from the space shuttle, which itself was designed and built more than four decades ago.
As the space shuttle often was delayed due to technical problems, it therefore comes as scant surprise that the debut launch of NASA's Space Launch System rocket scrubbed a few hours before its launch window opened. The showstopper was an 8-inch diameter line carrying liquid hydrogen into the rocket. It sprang a persistent leak at the inlet, known as a quick-disconnect, leading on board the vehicle.
[...] So why does NASA use liquid hydrogen as a fuel for its rockets, if it is so difficult to work with, and there are easier to handle alternatives such as methane or kerosene? [...] the real answer is that Congress mandated that NASA continue to use space shuttle main engines as part of the SLS rocket program.
In 2010, when Congress wrote the authorization bill for NASA that led to creation of the Space Launch System, it directed the agency to "utilize existing contracts, investments, workforce, industrial base, and capabilities from the Space Shuttle and Orion and Ares 1 projects, including ... existing United States propulsion systems, including liquid fuel engines, external tank or tank related capability, and solid rocket motor engines."
[...] Ars asked NASA Administrator Bill Nelson whether it was the right decision for NASA to continue working with hydrogen after the agency's experience with the space shuttle. ... "We deferred to the experts," Nelson said.
By this Nelson meant that the Senate worked alongside some officials at NASA, and within industry, to design the SLS rocket. These industry officials, who would continue to win lucrative contracts from NASA for their work on shuttle-related hardware, were only too happy to support the new rocket design.
Among the idea's opponents was Lori Garver, who served as NASA's deputy administrator at the time. She said the decision to use space shuttle components for the agency's next generation rocket seemed like a terrible idea, given the challenges of working with hydrogen demonstrated over the previous three decades.
"They took finicky, expensive programs that couldn't fly very often, stacked them together differently, and said now, all of a sudden, it's going to be cheap and easy," she told Ars in August. "Yeah, we've flown them before, but they've proven to be problematic and challenging. This is one of the things that boggled my mind. What about it was going to change? I attribute it to this sort of group think, the contractors and the self-licking ice cream cone."
Now, NASA faces the challenge of managing this finicky hardware through more inspections and tests after so many already... (MORE - missing details)
RE: Years after shuttle, NASA rediscovers the perils of liquid hydrogen (space politics) - C C - Sep 7, 2022
What To Make of the Artemis Launch Delays
https://theness.com/neurologicablog/index.php/what-to-make-of-the-artemis-launch-delays/
EXCERPTS: . . . Are these launch delays routine and expected or are they evidence that the SLS is a boondoggle, as its harshest critics maintain? I think it’s a little of both.
If we look at it from the perspective of the Artemis program, the original plan was to return to the Moon using the SLS and Orion by 2028. Trump decided he wanted to move this up to 2024, but this was never realistic. NASA has since pushed the date back to 2025, but are keeping the accelerated schedule.
These recent delays, therefore, are only relative to a significant acceleration of the program. Heavy lift launch vehicles are complex, and this is a new design. Attempting a launch is part of the process of testing the system and making sure everything works. A single faulty sensor can scrub a launch. As we learned from the Shuttle program, a loose bit of foam can doom a shuttle. Caution is appropriate, and this is what caution looks like.
However, the life of the SLS started well before Artemis was envisioned. In 2011 the Obama administration cancelled the Constellation program, which was NASA’s next heavy lift rocket. The Shuttle program also ended that year. NASA, and perhaps more importantly all of its contractors, were left without a heavy lift rocket program.
So a deal was struck, the Obama administration would fund a new heavy lift rocket program using as many existing components from Constellation and the Shuttle program as possible, and NASA would start outsourcing low Earth orbit (LEO) launches to private industry. The latter half of this deal has worked out spectacularly, with Space X being the prime example.
But the success of the private rocket industry also served to highlight the extreme cost and inefficiency of the SLS program...
These are genuine criticisms, although there’s not much we can do about it now. [...] the SLS is the only game in town...
Perhaps the best pathway forward from here is to use the SLS as developed for the Artemis program. We’ll get one launch per year out of the SLS, and hopefully there have been some lessons learned by the industry. At the same time, NASA needs to come up with a plan for what will replace the SLS as a heavy lift deep space launch system. Probably the best way to do this is in collaboration with private industry... (MORE - missing details)