NASAs Space Launch System (SLS) rocket with the Orion spacecraft aboard is seen atop the mobile launcher at Launch 39B at NASAs Kennedy Space Center in Florida. Credit: NASA/Steve Seipel
As the countdown continued on Tuesday toward the cryogenic demonstration test, NASA teams conducted last closeouts at the pad and carried out other preparations for the test. Work will continue through the night, and all non-essential personnel will leave Launch Pad 39B by 3:40 a.m. EDT (12:40 a.m. PDT) on Wednesday early morning. At approximately 7 a.m., the launch director is anticipated to offer a “go” to begin loading cryogenic propellants into the rocket.
The countdown clock is ticking down to a simulated liftoff time of 3:40 p.m., the test is prepared to conclude around 3 p.m. after the groups have fulfilled the goals. They will not proceed into the terminal count phase of the launch countdown. Teams might extend the duration of the test need to situations warrant it.
The Moon serves as a background for the Artemis I SLS and Orion spacecraft at Launch Complex 39B at NASAs Kennedy Space Center in Florida on March 21, 2022. Credit: NASA/Ben Smegelsky
“T minus” time refers to the time remaining on the official countdown clock and is a series of events that are developed into the launch countdown. Pauses in the countdown, or “holds,” are constructed into the countdown to enable the launch group to target a precise launch window, and to provide a cushion of time for particular jobs and treatments without impacting the overall schedule. Throughout prepared holds in the countdown procedure, the countdown clock is purposefully stopped and the T- time likewise stops.
By NASA
September 21, 2022
Below are some of the essential occasions that happen at each turning point after the countdown starts.
L-9 hours, 40 minutes, and counting
6 a.m.: Built-in countdown hold begins (L-9H40M– L-7H10M).
6 a.m.: Launch group carries out a weather and tanking briefing (L-9H40M– L-8H50M).
7 a.m.: Launch group decides if they are “go” or “no-go” to begin tanking the rocket (L-8H40M).
7:25 a.m. Core Stage LOX transfer line chilldown (L-8H15M– L-8H).
L-8 hours and counting.
7:40 a.m.: Core phase LOX main propulsion system (MPS) chilldown (L-8H– L-7H20M).
8:20 a.m.: Core stage LOX slow fill (L-7H20M– L-7H5M).
8:20 a.m.: Core Stage LH2 transfer line chilldown (L-7H20M– L-7H10M).
8:30 a.m.: Core Stage LH2 slow fill start (L-7H10M– L-6H10M).
8:40 a.m.: Core Stage LOX quick fill (L-7H5M– L-4H15M).
9:30 a.m.: Core Stage LH2 fast fill (L-6H10M– L-5H5M).
9:40 a.m.: Engine bleed begin (L-6H).
10:20 a.m.: ICPS LH2 ground support equipment (GSE) and tank chilldown (L-5H20M– L-5H).
10:35 a.m.: Core Stage LH2 topping (L-5H5M– L-5H).
L-5 hours and counting.
10:40 a.m.: Core Stage LH2 renew (L-5H– Launch).
10:40 a.m.: Core phase 90-minute bleed valve timer start (L-5H).
10:40 a.m.: ICPS LH2 quick fill start (L-5H– L-4H).
11:25 a.m.: Core phase LOX topping (L-4H15M– L-4H).
11:40 a.m.: Core Stage LOX replenish (L-4H– cutoff).
11:40 a.m.: ICPS LOX MPS chilldown (L-4H– L-3H45M).
11:55 a.m. ICPS LOX quick fill (L-3H45M– L-3H).
11:55 a.m. ICPS LH2 tank topping start (L-3H45M– L-2H55M).
L-3 hours and counting.
12:15 p.m.: ICPS LH2 replenish (L-3H25M– cutoff).
12:50 p.m.: Core stage LH2 Pre-press test– ~( L-2H50M)– around one hour.
1:10 p.m.: ICPS LOX topping (L-2H30M– L-2H10M).
1:30 p.m.: ICPS LOX replenish (L-2H10M– cutoff).
3 p.m.: Cutoff and important safing (L-40M).
Work will continue through the night, and all non-essential workers will leave Launch Pad 39B by 3:40 a.m. EDT (12:40 a.m. PDT) on Wednesday early morning. At around 7 a.m., the launch director is anticipated to give a “go” to begin filling cryogenic propellants into the rocket.
“T minus” time refers to the time staying on the official countdown clock and is a sequence of events that are built into the launch countdown. Pauses in the countdown, or “holds,” are constructed into the countdown to allow the launch group to target an accurate launch window, and to offer a cushion of time for specific jobs and procedures without impacting the general schedule. Throughout prepared holds in the countdown procedure, the countdown clock is deliberately stopped and the T- time also stops.