KENNEDY SPACE CENTER, Fla. — America’s space agency on Saturday attempted to launch a rocket largely assembled from the space shuttle, which was designed and built more than four decades ago. With the space shuttle often delayed by technical issues, it’s no surprise that the first launch of NASA’s Space Launch System rocket was cleared just hours before the launch window opened. The demonstration plug was an 8-inch-diameter line that carried liquid hydrogen to the rocket. It caused a persistent leak at the inlet, known as a quick disconnect, leading to the vehicle. Bravely, the launch team at the Kennedy Space Center tried three different times to stop the leak, all to no avail. Finally at 11:17 am. ET, hours behind schedule to fuel the rocket, launch manager Charlie Blackwell-Thompson called a halt. What comes next depends on what engineers and technicians find Monday when they inspect the vehicle at the launch site. If the launch team decides they can replace the quick disconnect material on the pad, it may be an option to perform a partial fuel test to determine the integrity of the repair. This may allow NASA to keep the vehicle on the pad before the next launch. Alternatively, the engineers may decide that repairs are best done inside the Vehicle Assembly Building and bring the rocket back inside. Due to the orbital dynamics of the Artemis I mission to fly an unmanned Orion spacecraft to the Moon, NASA will then have the opportunity to launch from September 19th to October 4th. However, creating that window would require securing the rocket to the pad and then getting a waiver from the US Space Force, which operates the launch site along the Florida coast. At issue is the flight termination system, which is independently powered by the rocket, with batteries rated for 25 days. NASA will need to extend this battery evaluation to about 40 days. The space agency is expected to have those discussions with range officials soon. If the rocket returns to the Vehicle Assembly Building, which would be necessary to repair the flight termination system or perform more than rough work on the launch pad, NASA has another chance to launch Artemis I from Oct. 17 to Oct. 31 .

A tiny element

The space shuttle was an extremely complex vehicle, combining the use of solid rocket boosters—which are akin to very, very powerful firecrackers—along with highly engineered main engines fueled by burning liquid hydrogen propellant and liquid oxygen to act as an oxidizer. . Advertising
During its lifetime, because of this complexity, the shuttle on average scraped almost once per launch attempt. Some bus flights cleared up to five times before finally taking off. For launch controllers, managing the complex process of fueling the space shuttle has never been much easier, and hydrogen has often been a culprit. Hydrogen is the most abundant element in the universe, but it is also the lightest. It takes 600 billion hydrogen atoms to reach the mass of a single gram. Because it is so tiny, hydrogen can squeeze through the smallest of gaps. This is not so much of a problem at ambient temperatures and pressures, but at very low temperatures and high pressures, hydrogen readily leaks through any available opening. To keep a rocket’s fuel tanks full, propellant lines leading from ground systems must remain attached to the booster until the moment of launch. At the last second, the “quick disconnects” at the end of these lines are detached from the rocket. The difficulty is that, to be safe during disconnection from the rocket, this equipment cannot be screwed down tightly enough to completely block the passage of hydrogen atoms – it is extremely difficult to seal these connections under high pressure and low temperatures. NASA, therefore, has a tolerance for a small amount of hydrogen leakage. However, anything above a 4 percent hydrogen concentration in the purge area near the quick disconnect is considered a flammability hazard. “We were seeing two or three times more than that,” said Mike Sarafin, the director of NASA’s Artemis I mission. “It was pretty clear that we weren’t going to be able to deal with it. Every time we saw a leak, it exceeded our flammability limits very quickly.” Twice, launch controllers stopped the flow of hydrogen to the vehicle, hoping the quick disconnect would warm it up a bit. They hoped that when they started slowly flowing cryogenic hydrogen into the rocket again, the quick disconnect would find a tighter fit with the booster. He did not do it. Another time they tried to apply significant pressure to reinstate the quick disconnect. NASA officials are still evaluating the cause of the leak, but believe it may have been due to a faulty valve opening. This happened during the rocket’s cooling process before loading liquid hydrogen propellant. In the middle of a sequence of about a dozen commands sent to the rocket, a command was sent to the wrong valve to open. That was fixed within 3 or 4 seconds, Sarafin said. However, during this time, the hydrogen line that would have created a problematic quick disconnect was briefly over-pressurized.

Outsourcing to the experts

So why does NASA use liquid hydrogen as fuel for its rockets if it is so difficult to work with and there are easier alternatives like methane or kerosene? One reason is that hydrogen is a very efficient fuel, meaning it provides better “gas mileage” when used in rocket engines. However, the real answer is that Congress mandated NASA to continue using the main engines of the space shuttles as part of the SLS rocket program. Advertising
In 2010, when Congress wrote the authorization bill for NASA that led to the creation of the Space Launch System, it instructed the agency to “use existing contracts, investments, manpower, industrial base and capabilities from the Space Shuttle and Orion and Ares projects 1 , including … existing United States propulsion systems, including liquid propellant engines, external tank or tank-related capability, and solid rocket engines.” During a press conference Saturday, Ars asked NASA Administrator Bill Nelson if it was the right decision for NASA to continue working with hydrogen after the experience of the space shuttle service. In 2010, Nelson was a US Senator from Florida and co-sponsored the space authorization bill with US Senator Kay Bailey Hutchison, from Texas. “We put off the experts,” Nelson said. By this Nelson meant that the Senate worked with some NASA officials, and within industry, to design the SLS rocket. These industry officials, who would go on to win lucrative contracts from NASA working on shuttle-related hardware, were only too happy to support the new rocket design. Among the opponents of the idea was Lori Garver, who was serving as NASA’s deputy administrator at the time. He 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 presented over the past three decades. “They took difficult, expensive programs that couldn’t fly very often, stacked them differently and said now, all of a sudden, it’s going to be cheap and easy,” he said. “Yes, we’ve thrown them in the past, but they’ve proven to be problematic and challenging. That’s one of the things that boggles my mind. What would change? I attribute it to that kind of groupthink, the contractors and the ice cream cone that licks itself of”. Now, NASA faces the challenge of managing this complex material through more inspections and tests after so much already. The rocket’s main stage, built by Boeing, was shipped from its Louisiana factory two and a half years ago. It underwent nearly a year of testing in Mississippi before arriving at the Kennedy Space Center in April 2021. Since then, NASA and its contractors have been assembling the complete rocket and testing it on the launch pad. Essentially, Saturday’s “launch” attempt was the sixth time NASA has attempted to fully fuel the rocket’s first and second stages and then go deep into the countdown. To date, none of these feeding tests, known as wet dressing trials, have succeeded. On Saturday, the center stage’s massive liquid hydrogen tank, with a capacity of more than 500,000 gallons, was only 11 percent full when the scrub was called. Maybe the seventh time is a charm.