The launch director gave the “go” to start tanking operations. The countdown will resume at 9:20 a.m. EDT at T-6 hours, 40 minutes.
Tanking begins with chilling down, or cooling, the liquid oxygen propellant lines for the core stage. In sequential fashion, liquid oxygen (LOX) and liquid hydrogen (LH2) will flow into the rocket’s core stage and interim cryogenic propulsion stage tanks and be topped off and replenished as some of cryogenic propellant boils off. The team also will conduct leak checks to ensure propellant loading is proceeding as expected.
The core stage’s liquid oxygen tank holds 196,000 gallons of the propellant, cooled to minus 297 degrees Fahrenheit. Teams will fill the tank slowly at first and then will begin filling it more quickly. The liquid hydrogen tank holds 537,000 gallons. As the super cold liquid oxygen fills the core stage tank, some venting may be visible.