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SpaceThe terminal count from T-10 minutes
The poll came back "go" and the final 10 minutes begin. The ground launch sequencer takes control and sends a precise series of automated commands: it pressurizes the tanks, activates the flight software, switches control from the ground to the onboard systems and runs the last health checks across thousands of sensors. You call each milestone of the Artemis II terminal count on time.
Free to startScenarios
- Artemis II: the terminal count starts at 6:25 p.m. for a T-0 of 6:35 p.m.
- The team holds at T-6 minutes and waits there for the rest of the launch window.
- A hold is needed between T-6 minutes and T-1 minute 30 seconds.
The steps
- T-10 minutes: the ground launch sequencer starts the terminal count.
- T-8 minutes: retract the crew access arm.
- T-6 minutes: go for core stage tank pressurization; Orion's ascent pyros armed and Orion on internal power.
- T-5 minutes 57 seconds: end core stage liquid hydrogen replenish.
- T-5 minutes 20 seconds: launch abort system capability available, and the commander is told.
- T-4 minutes 40 seconds: go for the liquid hydrogen high flow bleed check. T-4 minutes 30 seconds: flight termination system armed.
- T-4 minutes: go for core stage auxiliary power unit start; the unit starts and core stage liquid oxygen replenish ends. T-3 minutes 30 seconds: upper stage liquid oxygen replenish ends.
- T-3 minutes 10 seconds: go for purge sequence 4.
- T-2 minutes 2 seconds: upper stage on internal battery; T-2 minutes: boosters on internal battery; T-1 minute 30 seconds: core stage on internal power.
- T-1 minute 20 seconds: upper stage in terminal countdown mode. T-50 seconds: upper stage liquid hydrogen replenish ends.
Safety rules that stop the station
- Inside the terminal count the clock stops only by its hold rules: at T-6 minutes for the rest of the window, or up to 3 minutes between T-6 minutes and T-1 minute 30 seconds.
To pass
- Every milestone called in order and on time.
- Orion on internal power at T-6 minutes and every stage on internal power by T-1 minute 30 seconds.
- The flight termination system armed at T-4 minutes 30 seconds.
Official source
NASA · Artemis II launch day
Artemis II Launch Day Updates
NASA publishes its Artemis II launch day updates free: every milestone of the terminal count and the rules for holding inside it.
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