NASA’s preparations for the launch of its Space Launch System (SLS) rocket today, Saturday, September 3, have been interrupted by a hydrogen leak issue. The issue occurred during tanking, in which the rocket is filled with fuel ahead of the launch, and is currently ongoing.
The launch today is the culmination of years of work on the SLS, but there have been many problems along the way including a previous liquid hydrogen leak during the various wet dress rehearsals which the rocket went through earlier in the year. The rocket uses a mixture of liquid oxygen and liquid hydrogen as its fuel, and these liquids have to be sent through a line and into the rocket. As the ratio of liquid oxygen to liquid hydrogen needs to be maintained, the flow of liquid oxygen also had to be mediated while the liquid hydrogen leak was dealt with.
The liquid hydrogen leak occurred just before 7:30 a.m. ET on September 3, with hydrogen leaking from a quick disconnect cavity. The flow of the hydrogen was halted so that engineers could work on the quick disconnect to get it to seal correctly, in an operation that lasted around half an hour.
The fix seemed to work at first, and the liquid hydrogen began flowing again after 8 a.m. ET. “Launch controllers have resumed flow of liquid hydrogen to the core stage after warming up a quick disconnect in the engine section where a hydrogen leak was detected in the cavity between the ground and flight side plates of the quick disconnect,” NASA wrote in an update. “Teams warmed up the quick disconnect to attempt to reseat it and set a proper seal.”
However, once propellant was flowing again and back up to pressure, the problem reappeared. When the tanks of liquid oxygen were 56% full and the liquid hydrogen tank was 8% full, the connection to the rocket core stage was leaking again. According to NASA TV, engineers will now attempt to use helium to bring up pressure in the line to try to reseat the quick disconnect.
For live updates on the tanking process, you can watch NASA’s livestream on YouTube, and for details on how to watch the launch itself, with coverage scheduled to begin today at 12:15 p.m. ET, you can check out our guide.
