KENNEDY SPACE CENTER, Fla.America’s space agency attempted Saturday to launch a rocket largely cobbled together with the space shuttle, which itself was designed and built more than four decades ago.
Since the space shuttle was often delayed due to technical problems, it’s no surprise, then, that the debut launch of NASA’s Space Launch System rocket was scrubbed a few hours before the launch window opened. The showstopper was an 8 inch diameter line that carried liquid hydrogen inside the rocket. It caused a persistent leak at the intake, known as a quick disconnect, that led aboard the vehicle.
The Kennedy Space Center launch team tried valiantly three times to plug the leak, but to no avail. Finally at 11:17 a.m. ET, hours behind their timeline to fuel the rocket, launch director Charlie Blackwell-Thompson called a halt.
What comes next depends on what engineers and technicians find Monday when they inspect the vehicle on the launch pad. If the launch team decides it can replace the shortcut hardware on the pad, it may be an option to perform a partial fuel test to determine the integrity of the solution. This will allow NASA to keep the vehicle on track for the next launch. Alternatively, the engineers may decide that repairs are best done in the Vehicle Assembly Building, and roll the rocket back in.
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 19 to October 4. To make that window, however, would require the rocket to be secured to the path, then get a waiver from the US Space Force, which operates the launch range along the Florida coast.
It concerns the flight termination system, which is powered independently of the rocket, with batteries that last 25 days. NASA should extend that battery rating to about 40 days. The space agency is expected to have those discussions with range officials soon.
If the rocket is rolled back to the Vehicle Assembly Building, which would be necessary to maintain the flight termination system or perform more than fleeting work on the launch pad, NASA has another Artemis I launch opportunity from Oct. 17 to Oct. 31.
A small, small element
The space shuttle was an extremely complex vehicle, mixing the use of solid rocket boosters – which are similar to very, very powerful firecrackers – along with beautifully built main engines powered by the combustion of liquid hydrogen propellant and liquid oxygen to serve as an oxidizer. .
Because of this complexity, the shuttle has scrubbed an average of nearly once per launch attempt during its lifetime. Some shuttle flights were scrubbed five times before finally taking off. It has never really gotten easier for launch controllers to manage the space shuttle’s complex fueling process, 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 six million hydrogen atoms to reach the mass of a single gram. Because it is so small, hydrogen can squeeze through the tiniest of gaps. This isn’t much of a problem at ambient temperatures and pressures, but at supercooled temperatures and high pressures, hydrogen seeps easily from any available orifice.
To maintain a rocket’s fuel tanks, the propellant lines leading from ground systems must remain attached to the booster until launch. In the last second, the “quick-disconnects” at the end of these lines break away from the missile. The difficulty is that, to be fail safe when disconnecting the missile, this equipment cannot be bolted together tightly enough to completely preclude the passage of hydrogen atoms – it is extremely difficult to seal these connections under high temperatures. 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 connector is considered a flammability hazard. “We we saw more than that with two or three times that,” said Mike Sarafin, NASA’s Artemis I Mission Manager, of Saturday’s hydrogen leak. “It was pretty clear that we weren’t going to be able to work our way through it. Every time we saw a leak, it exceeded our flammability limits pretty quickly.”
Twice, launch controllers stopped the hydrogen flow in the vehicle, hoping the shortcut would warm up a bit. They hoped that when they restarted slow-flowing cryogenic hydrogen aboard the rocket, the shortcut would better match the booster. It didn’t. Another time, they tried to apply a significant amount of pressure to reseat the shortcut.
NASA officials are still assessing the cause of the leak, but they believe it could be due to a faulty valve opening. This happened during the cooling of the rocket before liquid hydrogen was charged. Amid a series of about a dozen commands sent to the missile, one command was sent to a wrong valve to open. This was fixed in 3 or 4 seconds, Sarafin said. During this time, however, the hydrogen line that would develop a problematic shortcut was briefly overloaded.
Postpone to the experts
So why does NASA use liquid hydrogen as fuel for its rockets, when it’s so difficult to work with and there are easier-to-handle alternatives like methane or kerosene? One reason is that hydrogen is a very efficient fuel, meaning it provides better “gas consumption” when used in rocket engines. However, the real answer is that Congress required NASA to continue using the space shuttle’s main engines as part of the SLS rocket program.
In 2010, when Congress wrote the authorization law for NASA that led to the creation of the Space Launch System, it instructed the agency to “examine existing contracts, investments, personnel, industrial base, and capabilities of the Space Shuttle and Orion and Ares 1 projects. , including … existing propulsion systems in the United States, including liquid fuel engines, external tank or tank-related capabilities, and solid rocket motor engines.”
At a press conference on Saturday, 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. In 2010, Nelson was a US Senator from Florida and leader of the space authorization bill alongside US Senator Kay Bailey Hutchison of Texas. “We left it to the experts,” Nelson said.
By this, Nelson meant that the Senate worked with some NASA and industry officials 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.
One of those opposed to the idea was Lori Garver, who was 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 past three decades.
“They took finicky, expensive programs that didn’t fly very often, stacked them in a different way and now said it’s suddenly going to be cheap and easy,” she told Ars in August. “Yes, we’ve flown them before, but they’ve proved problematic and challenging. This is one of the things that puzzled me. What would change? I attribute it to this kind of groupthink, 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 much. The rocket’s core stage, manufactured by Boeing, was shipped from its Louisiana plant more than two and a half years ago. It underwent nearly a year of testing in Mississippi before arriving at Kennedy Space Center in April 2021. Since then, NASA and its contractors have assembled and tested the complete rocket on the launch pad.
In fact, Saturday’s “launch attempt” was the sixth time NASA has attempted to fully fuel the rocket’s first and second stages, then go deep into the countdown. To date, none of these fuel tests, known as wet dress rehearsals, have failed. On Saturday, the core phase’s massive liquid hydrogen tank, with a capacity of more than 500,000 gallons, was only 11 percent full when the scrub was mentioned.
Maybe the seventh time will be a charm.
