NASA learns the hard way about liquid hydrogen years after the shuttle programme

NASA learns the hard way about liquid hydrogen years after the shuttle programme

On Saturday, the American space agency attempted to launch a rocket constructed mostly out of parts from the space shuttle, which was developed and constructed almost four decades ago.

The inaugural flight of NASA’s Space Launch System rocket was scrubbed a few hours before its launch window opened, which came as little surprise given the frequency with which technical issues delayed the space shuttle. A line of 8-inch diameter that fed liquid hydrogen into the rocket was the main attraction. The inlet, also called a quick-disconnect, which leads inside the car began leaking continuously.

The Kennedy Space Center launch crew tried valiantly on three separate occasions to stop the leak, but to no effect. Hours after their scheduled launch time, at 11:17 a.m. ET, launch director Charlie Blackwell-Thompson requested a halt to the rocket’s fueling process.

 

What happens next will be determined by the results of Monday’s inspection of the vehicle at the launch pad by engineers and technicians. If the launch team is certain that it can replace the quick-disconnect gear on the pad, a partial fuelling test could be conducted to verify the effectiveness of the repair. In preparation for the next launch, NASA may be able to retain the vehicle on the pad if this happens. The engineers could also determine that the Vehicle Assembly Building is the ideal place to make the necessary repairs, in which case the rocket would be rolled back inside.

 

To accommodate the orbital dynamics of the Artemis I mission, which will send an unmanned Orion spacecraft to the Moon, NASA’s next launch window will be September 19–October 4. To get back into that window, though, the rocket would need to be repaired at the launch pad and permission to launch would have to be granted by the US Space Force, which controls the Florida coast launch range.

 

The concern revolves around the flight termination system, which is powered by batteries separate from the rocket and has a 25-day endurance. For NASA’s purposes, that battery life must be increased to around 40 days. Those talks between the space agency and the range authorities are imminent.

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NASA has another Artemis I launch option between October 17 and October 31 if the rocket is brought back to the Vehicle Assembly Building to service the flight termination system or do more extensive work at the launch pad.

 

Something extremely minute

Combining solid-rocket boosters (which are like very, very powerful firecrackers) with precisely designed main engines fueled by the combustion of liquid hydrogen propellant and liquid oxygen to serve as an oxidizer, the space shuttle was an exceedingly complicated spacecraft.

 

Because of this complexity, the shuttle had to abort approximately one out of every two launches over its career. Some shuttle flights were delayed as many as five times before they finally took off. Managing the space shuttle’s intricate fuelling procedure was never simple for launch controllers, and hydrogen was often to blame.

 

Hydrogen is not just the lightest element but also the most common. 600 sextillion hydrogen atoms are needed to equal one gramme of mass. Hydrogen may easily pass through a 0.025-millimeter opening because of its little size. At room temperature and pressure, this is not a major issue, but at extremely low temperatures and high pressures, hydrogen readily escapes via any cracks or crevices.

 

Rockets require propellant lines going from ground-based equipment to be linked to the booster until just before liftoff. These lines’ “quick-disconnects” disconnect from the rocket at the last possible moment. The problem is that it’s very difficult to seal these connections at high pressure and low temperatures, so even fail-safes for detaching from the rocket can’t be made from equipment that’s bolted together firmly enough to prevent the flow of hydrogen atoms.

 

Therefore, NASA can tolerate some hydrogen leaking. The hydrogen concentration in the purge area near the quick disconnect must not exceed 4%, however, or it poses a fire risk. Mike Sarafin, NASA’s Artemis I Mission Manager, said on Saturday, “We were seeing in excess of that by two or three times that.” “It was obvious that we would be unable to find a way around this obstacle. When we saw a leak, it always got quite flammable, pretty fast.”

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Launch controllers cut off hydrogen to the vehicle twice, hoping the quick-disconnect would warm up. Quick-disconnect was hoping to discover a tighter connection with the booster after they resumed the sluggish flow of cryogenic hydrogen on board. That did not happen. Once again, they attempted to reseat the quick disconnect by exerting force.

 

Officials at NASA are still trying to determine what caused the leak, but they suspect a faulty valve. While cooling the rocket down for liquid hydrogen loading, something happened. Among a series of around a dozen commands transmitted to the rocket, a directive was sent to open the incorrect valve. According to Sarafin, this was fixed in just a minute. Unfortunately, it was during this time that the hydrogen line that would later develop a troublesome quick-disconnect was briefly over-pressurized.

 

Taking advice from professionals

NASA uses liquid hydrogen as a rocket fuel despite the fact that other, more manageable fuels, like as methane or kerosene, are available. Because hydrogen is so fuel-efficient, it allows rockets to travel farther on each tank of fuel. But the truth is that the main engines from the space shuttle must be used for the SLS rocket development.

“utilise existing contracts, investments, workforce, industrial base, and capabilities from the Space Shuttle and Orion and Ares 1 projects,” Congress wrote in the 2010 NASA authorization bill that led to the development of the Space Launch System. This included “existing United States propulsion systems, including liquid fuel engines, external tank or tank related capability, and solid rocket motor engines.”

 

On Saturday, Ars questioned NASA Administrator Bill Nelson if the agency made the correct choice by continuing to work with hydrogen in the wake of the space shuttle disaster. Along with Texas’s Kay Bailey Hutchison, Nelson was a key player in the 2010 effort to authorise space travel by the United States government. Nelson remarked, “We trusted the professionals.”

 

Nelson sought to convey that the Senate collaborated with NASA and industry on the SLS rocket’s design. Those in the business world were eager to back the new rocket design since it would mean more money for them from NASA for their work on shuttle-related components.

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Lori Garver, the current and former deputy administrator of NASA, was one of several who opposed the plan. To her, it seemed like a poor idea to recycle parts from the space shuttle into the government’s next-generation rocket, especially in light of the difficulties that have been shown to arise when working with hydrogen during the past three decades.

 

In an August interview with Ars, she explained that the company had taken “finicky, expensive programmes that couldn’t fly very often, piled them up differently,” and claimed that the result would be “cheap and easy.” “We have flown them previously, and it was a difficult and frustrating experience. One of the things that has baffled me is this. Exactly what was going to alter was unknown. Those contractors and their self-licking ice cream cones are to blame, as is this kind of groupthink.”

 

NASA must now deal with the difficulty of overseeing this fragile hardware through additional inspections and tests. Boeing delivered the rocket’s core stage out of its plant in Louisiana over two and a half years ago. From April of 2021 until then, it was put through nearly a year of testing in Mississippi before making its way to Kennedy Space Center. NASA and its contractors have been putting the finishing touches on the rocket and conducting launch pad tests since then.

 

Saturday’s “launch” attempt was actually NASA’s sixth effort to fully fuel the first and second stages of the rocket and then enter the late stages of the countdown. These fueling tests, sometimes known as wet dress rehearsals, have not been successful thus far. This past Saturday, the scrub was called after the enormous liquid hydrogen tank for the core stage, which can hold over 500,000 gallons, was just 11% filled.