The Sundarban
Lauren E. Low
Mar 26, 2026
Earlier than NASA sends its astronauts Reid Wiseman, Victor Glover, Christina Koch, and CSA (Canadian Field Company) astronaut Jeremy Hansen on their Artemis II mission across the Moon, the inaugurate group at NASA’s Kennedy Field Center in Florida and groups across the country will originate up counting down about two days ahead of liftoff.
A inaugurate countdown incorporates “L Minus” and “T Minus” times. The “L minus” signifies how a long way away liftoff is in hours and minutes. The “T minus” time is a chain of events constructed into the inaugurate countdown. Pauses in the countdown, or “holds,” are constructed in to allow the inaugurate group to concentrate on a true inaugurate window, and to manufacture a cushion of time for definite duties and procedures with out impacting the general schedule. All the plan in which via deliberate holds in the countdown course of, the countdown clock is deliberately stopped and the T- time also stops. The L- time, on the opposite hand, continues to reach.
Below are most likely the most important events that seize issue at every milestone after the countdown begins.
All times are approximate for when these milestones occur.
L-49 hours 50 minutes and counting
- L-49H50M – Starting up group arrives to stations
- L-49H40M – Countdown clock begins
- L-49H40M – L-42H30M: Liquid oxygen (LOX)/Liquid hydrogen (LH2) system
preparations for vehicle loading - L-45H30M – L-44H: Orion spacecraft powered up
- L-42H20M – L-41H: Core stage powered up
- L-42H10M – L-40H30M: Period in-between cryogenic propulsion stage (ICPS) powered up
- L-39H45M – L-35H30M: Final preparations of the four RS-25 engines
L-35 hours and counting
- L-34H45M – L-34H10M: ICPS is powered down
- L-33H30M – L-29H30M: Price Orion flight batteries to 100%
- L-31H30M – L-24H30M: Price core stage flight batteries
- L-20H15M – L-18H45M: ICPS is powered up for inaugurate
L-16 hours and counting
- L-15H30M – L-14H: All non-mandatory personnel leave Starting up Complex 39B
- L-14H15M – L-12H05M: Air-to-gaseous nitrogen (GN2) changeover and rocket
cavity inerting - L-13H15M – L-11H45M: Floor inaugurate sequencer (GLS) activation
L-13 hours and counting
- L-12H35M – L-9H50M: 2-hour Forty five-minute constructed in countdown merit begins
- L-10H50M – Starting up group decides “scurry” or “no-scurry” to originate up tanking
- L-10H50M – L-9H35M: Orion cold soak
- L-10H40M – L-10H35M: Core stage LOX transfer line chilldown
- L-10H40M – L-9H55M: Core stage LH2 chilldown
- L-10H25M – L-9H40M: Core stage LOX predominant propulsion system chilldown
L-10 hours and counting
- L-9H55M – L-9H25M: Core stage LH2 listless occupy originate up
- L-9H50M – Resume T-Clock from T-8H10M
- L-9H40M – L-9H30M: Core stage LOX listless occupy
- L-9H30M – L-6H40M: Core stage LOX like a flash occupy
- L-9H25M – L-8H: Core stage LH2 like a flash occupy
- L-9H05M – L-8H30M: ICPS LH2 chilldown
- L-8H30M – L-7H45M: ICPS LH2 like a flash occupy originate up
- L-8H – L-7H55M: Core stage LH2 topping
- L-7H55M – terminal count: Core stage LH2 stock up
- L-7H45M – L-7H20M: ICPS LH2 vent and reduction take a look at
- L-7H20M – L-7H10M: ICPS LH2 tank topping originate up
- L-7H05M – terminal count: ICPS LH2 stock up
- L-6H40M – L-6H10M: Orion communications system activated (radio frequency to mission control)
- L-6H40M – L-6H05M: Core stage LOX topping
- L-6H40M – L-6H30M: ICPS LOX predominant propulsion system chilldown
- L-6H30M – L-5H45M: ICPS LOX like a flash occupy
- L-6H10M – Stage pad rescue
- L-6H10M: – Closeout crew assemble
- L-6H05M – terminal count: Core stage LOX stock up
L-6 hours and counting
- L-6H – Flight crew climate short
- L-5H45M – L-5H30M: ICPS LOX vent and reduction take a look at
- L-5H30M – L-5H10M: ICPS LOX topping
- L-5H10M – terminal count: ICPS LOX stock up
- L-5H10M – All stages stock up
- L-5H10M – Open 1-hour 10-minute constructed in merit
- L-5H10M – L-4H55M: Closeout crew to white room
- L-4H40M – L-4H10M: Flight crew deployment to pad
- L-4H: Flight crew board Orion
- L-3H40M – L-3H10M: Crew module hatch preps and closure
- L-3H10M – L-2H45M: Counterbalance mechanism hatch sealpress decay
assessments - L-2H20M – L-1H40M: Crew module hatch provider panel install/closeouts
- L-1H40M – L1H30M: Starting up abort system (LAS) hatch closure for flight
- L-1H10M – Starting up director short – rocket & thermal protection system scan outcomes with the imagery console
- L-50M – L-40M: Closeout crew departs Starting up Complex 39B
- L-50M – Final NASA take a look at director briefing is held
L-40 minutes and maintaining
- L-40M – Built in 30-minute countdown merit begins
L-25 minutes and maintaining
- L-25M – Transition group to Orion to Earth communication loop following closing NTD briefing
- L-17M – Starting up director polls group to guarantee that they are “scurry” for inaugurate
- L-15M – Flight crew visors down
- L-14M – Flight crew rapid purge verification
T-10 minutes and counting
- T-10M – GLS initiates terminal count
- T-8M – Crew Access Arm retract
- T-6M – GLS scurry for core stage tank pressurization
- T-6M – Orion ascent pyros are armed
- T-6M – Orion plan to internal energy
- T-5M57S – Core stage LH2 discontinuance stock up
- T-5M20S – LAS functionality is equipped
- T-5M20S – NTD lets commander knows LAS functionality is equipped
- T-4M40S – GLS scurry for LH2 excessive scurry with the circulate bleed take a look at
- T-4M30S – Flight termination system armed
- T-4M – GLS is scurry for core stage auxiliary energy unit (APU) originate up
- T-4M – Core Stage APU starts
- T-4M – Core stage LOX discontinuance stock up
- T-3M30S – ICPS LOX discontinuance stock up
