The leak of hydrogen casts doubt on the launch of NASA’s Artemis 1 test flight

The leak of hydrogen casts doubt on the launch of NASA’s Artemis 1 test flight

The leak of hydrogen casts doubt on the launch of NASA’s Artemis 1 test flight

After months of testing, troubleshooting, and repairs, engineers began powering the Space Launch System lunar rocket for takeoff Monday on NASA’s long-awaited Artemis 1 test flight, but a leak of hydrogen, similar to what has derailed a previous refueling test, interrupted the complex procedure.

The leak developed in a launch pad service facility where propellants are fed into the rocket’s central stage through umbilicals designed to ensure a tight seal until takeoff when they are retracted. The buildup was detected in the chamber around those umbilicals, known as the “bleed can.”

Leaks are potentially dangerous and sensors monitor concentrations to make sure safety limits are not violated. During the refueling procedure on Monday, higher than permitted hydrogen concentrations were observed as the flow went from “slow fill” to “fast fill” at 10 times the speed, subjecting the hydraulic system to higher pressures.

After returning to slow fill and evaluating the readings, the engineers decided to resume the quick fill to see if the hydrogen concentration in the tail service navel has risen. Concentrations above 4 percent violate safety criteria and prohibit launch.

The Space Launch System lunar rocket atop pad 39B early Monday, awaiting a possible take-off on a mission to send an unmanned Orion capsule on a 42-day flight over the moon and back.  / Credit: NASA

The Space Launch System lunar rocket atop pad 39B early Monday, awaiting a possible take-off on a mission to send an unmanned Orion capsule on a 42-day flight over the moon and back. / Credit: NASA

Takeoff was originally scheduled for 8:33 am EDT. It was not immediately clear what impact the weather-related refueling delay and hydrogen troubleshooting might have on the eventual launch time, assuming the issue can be resolved before the end of a two-hour launch window. .

The central stage of the SLS rocket must be loaded with 196,000 gallons of liquid oxygen and 537,000 gallons of hydrogen for takeoff. An additional 22,000 gallons of oxygen and hydrogen are required for the upper stage, for a total of 750,000 gallons of propellant.

All that propellant will power the four mid-stage shuttle-era engines. Combined with two solid fuel boosters, the rocket will generate 8.8 million-pound thrust at takeoff to propel the 5.7 million-pound rocket away from Pad 39B at Kennedy Space Center.

The initial test flight of Artemis 1 is intended to test the rocket’s ability to propel Orion’s capsules into Earth’s orbit and then onto the moon. The engineers will also test the crew ship’s myriad systems in deep space and make sure its heat shield can protect returning astronauts from the 5,000-degree heat of reentry.

NASA plans to follow the Artemis 1 mission unmanned by launching four astronauts on a flight around the moon in 2024, setting the stage for the first astronaut’s landing in nearly 50 years, when the first woman and the next man rise to the surface in the period 2025-26.

But first, NASA has to prove that the rocket and capsule will perform as planned and this begins with the launch of Artemis 1 on Monday.

NASA ran four countdowns for dress rehearsals and refueling tests earlier this year, and all four ran into problems. The hardest to fix were the hydrogen leaks in the tail service shaft umbilical system that derailed the initial test and into a 4-inch quick release fitting that surfaced during the most recent test on June 20.

Hydrogen leaks are notoriously difficult to find and repair because they tend to only show up when hardware is subjected to cryogenic temperatures. For hydrogen, that’s minus 423 degrees Fahrenheit.

The umbilical system leak during the rocket’s first refueling test was repaired at room temperature in the vehicle assembly building and operated normally during a subsequent refueling test at the pad.

It was not immediately clear whether the problem that developed on Monday was a repetition of the initial problem, but it was in the same area.

The 4-inch quick release was repaired on a subsequent return trip to the VAB, but the fitting had not yet been exposed to hydrogen when the umbilical system leak was detected, interrupting the refueling procedure.

NASA engineers were confident the rocket was finally ready for flight, but the latest leak raised concerns that another rollback to the VAB may be needed.

Due to the ever-changing positions of the Earth and the Moon, NASA can only launch the SLS rocket during limited launch periods.

The current launch period, no. 25, was opened on 23 August and will run until 6 September. Launch period 26 opens on September 19th and lasts until October 4th. The following period, n. 27, opens on 17 October and lasts until 31 October.

Due to the need to repair the batteries of the self-destruct system, which cannot be accessed from the launch pad, the SLS rocket must take off by September 6 or it will have to be returned to the Vehicle Assembly Building.

Repairing another hydrogen leak would also require a return trip to the VAB, which would almost certainly delay launch until late September or October at the earliest.

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