The timeline below covers major countdown activities planned during the NASA\u2019s wet dress rehearsal for the Artemis 1 mission. The wet dress rehearsal will include loading of more than 700,000 gallons of cryogenic liquid hydrogen and liquid oxygen into the Space Launch System moon rocket on launch pad 39B at the Kennedy Space Center in Florida.<\/p>\n
See our Mission Status Center for additional coverage and real-time mission updates.<\/p>\n
EDITOR\u2019S NOTE: <\/strong>The times below are listed using the \u201cT\u201d time on the countdown clock, which includes build-in holds. This timeline was updated to remove tanking milestones associated with the ICPS, or Interim Cryogenic Propulsion Stage.<\/p>\n \u2022 T-06:40:00: <\/strong>The countdown enters a 90-minute built-in hold; Mission management team meets to give \u201cgo\u201d for tanking<\/p>\n \u2022<\/strong> T-06:40:00: <\/strong>The countdown clock resumes after the build-in hold; Core stage liquid oxygen chilldown begins<\/p>\n \u2022<\/strong> T-05:55:00: <\/strong>Core stage liquid oxygen slow fill begins<\/p>\n \u2022 T-05:40:00: <\/strong>Core stage liquid oxygen fast fill begins<\/p>\n \u2022 T-05:35:00: <\/strong>Core stage liquid hydrogen chilldown begins<\/p>\n \u2022<\/strong> T-05:30:00: <\/strong>Core stage liquid hydrogen slow fill begins<\/p>\n \u2022<\/strong> T-05:10:00: <\/strong>Core stage liquid hydrogen fast fill begins<\/p>\n \u2022 T-04:00:00:<\/strong> Core stage liquid hydrogen topping begins<\/p>\n \u2022 T-03:55:00: <\/strong> \u2022 T-03:50:00: <\/strong>Orion communications system activation begins<\/p>\n \u2022 T-03:30:00: <\/strong> \u2022 T-02:55:00: <\/strong>Core stage liquid oxygen topping begins<\/p>\n \u2022 T-02:50:00: <\/strong>Core stage liquid oxygen in replenish mode; \u2022 T-02:45:00: <\/strong> \u2022 T-02:40:00: <\/strong> \u2022 T-02:30:00: <\/strong> \u2022 T-02:10:00: <\/strong> \u2022 T-01:50:00: <\/strong> \u2022 T-01:40:00: <\/strong> \u2022 T-01:30:00: <\/strong>Core stage liquid hydrogen\/liquid oxygen stop flow and recover test begins<\/p>\n \u2022 T-00:10:00: <\/strong>Final 30-minute built-in hold begins; Final NASA Test Director briefing; Final Launch Director poll<\/p>\n \u2022 T-00:10:00: <\/strong>Countdown resumes<\/p>\n \u2022 T-00:06:00: <\/strong>Orion ascent pyros armed; Orion transitions to internal battery power<\/p>\n \u2022 T-00:05:57: <\/strong>Core stage liquid hydrogen replenish terminates<\/p>\n \u2022 T-00:04:00: <\/strong>Core stage auxiliary power unit starts; Core stage liquid oxygen replenish terminates; Solid rocket boosters armed for ignition<\/p>\n \u2022 T-00:03:30: <\/strong> \u2022 T-00:03:07: <\/strong>RS-25 main engine purge sequence 4<\/p>\n \u2022 T-00:01:56: <\/strong>ICPS transitions to internal battery power<\/p>\n \u2022 T-00:01:30: <\/strong>Core stage transitions to internal battery power; Countdown pauses for approximately 3 minutes to demonstrate \u201claunch ready\u201d hold<\/p>\n \u2022 T-00:01:20: <\/strong>ICPS enters terminal countdown mode<\/p>\n \u2022 T-00:00:50: <\/strong> \u2022 T-00:00:33: <\/strong>Ground Launch Sequencer sends cutoff command; Countdown recycles back to T-minus 10 minutes<\/p>\n EDITOR\u2019S NOTE: <\/strong>The countdown will recycle back to T-minus 10 minutes to allow the launch team to rehearse their ability to hold the countdown and set up for a second launch attempt on the same day.<\/p>\n \u2022 T-00:10:00: <\/strong>Final NASA Test Director briefing; Final Launch Director poll<\/p>\n \u2022 T-00:10:00: <\/strong>Countdown resumes<\/p>\n \u2022 T-00:06:00: <\/strong>Orion ascent pyros armed; Orion transitions to internal battery power<\/p>\n \u2022 T-00:05:57: <\/strong>Core stage liquid hydrogen replenish terminates<\/p>\n \u2022 T-00:04:00: <\/strong>Core stage auxiliary power unit starts; Core stage liquid oxygen replenish terminates; Solid rocket boosters armed for ignition<\/p>\n \u2022 T-00:03:30: <\/strong> \u2022 T-00:01:56: <\/strong>ICPS transitions to internal battery power<\/p>\n \u2022 T-00:01:30: <\/strong>Core stage transitions to internal battery power; Countdown pauses for approximately 3 minutes to demonstrate \u201claunch ready\u201d hold<\/p>\n \u2022 T-00:01:20: <\/strong>ICPS enters terminal countdown mode<\/p>\n \u2022 T-00:00:50: <\/strong> \u2022 T-00:00:33: <\/strong>Ground launch sequencer sends \u201cgo for automated launch sequencer\u201d command<\/p>\n \u2022 T-00:00:30: <\/strong>Core stage flight computer transitions to automated launch sequencer<\/p>\n \u2022 T-00:00:28:<\/strong> Solid rocket booster hydraulic power unit starts<\/p>\n \u2022 T-00:00:19:<\/strong> Solid rocket booster thrust vector control gimbal profile<\/p>\n \u2022 T-00:00:10:<\/strong> Ground launch sequencer sends \u201cgo for core stage engine start\u201d command<\/p>\n \u2022 T-00:00:09.34: <\/strong>Ground launch sequencer sends cutoff command<\/p>\n The countdown will stop at T-minus 9.34 seconds, just before ignition of the SLS core stage\u2019s RS-25 main engines. Pre-programmed software settings in the Ground Launch Sequencer computer will ensure the countdown holds at this point, and an engineer in the Launch Control Center will be ready to send a manual cutoff command if necessary.<\/p>\n Once the countdown is stopped, the launch team will begin draining liquid hydrogen and liquid oxygen from the rocket and secure the launch vehicle.<\/p>\n Email the author.<\/i><\/b><\/p>\n Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":" The timeline below covers major countdown activities planned during the NASA\u2019s wet dress rehearsal for the Artemis 1 mission. The wet dress rehearsal will include loading of more than 700,000 gallons of cryogenic liquid hydrogen and liquid oxygen into the Space Launch System moon rocket on launch pad 39B at the Kennedy Space Center in […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-10599","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/10599"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=10599"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/10599\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=10599"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=10599"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=10599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}ICPS liquid hydrogen chilldown begins;<\/del> Core stage liquid hydrogen in replenish mode<\/p>\nICPS liquid hydrogen fast fill begins<\/del><\/p>\nICPS liquid oxygen chilldown begins<\/del><\/p>\nICPS liquid hydrogen validation and leak test begins<\/del><\/p>\nICPS liquid oxygen fill begins<\/del><\/p>\nICPS liquid hydrogen topping begins<\/del>; ICPS\/SLS telemetry data verified with MCC and SLS support center<\/p>\nICPS liquid hydrogen in replenish mode; ICPS liquid oxygen validation and leak test begins<\/del><\/p>\nICPS liquid oxygen topping begins<\/del><\/p>\nICPS liquid oxygen in replenish mode<\/del><\/p>\nICPS liquid oxygen replenish terminates<\/del><\/p>\nICPS liquid hydrogen replenish terminates<\/del><\/p>\nICPS liquid oxygen replenish terminates<\/del><\/p>\nICPS liquid hydrogen replenish terminates<\/del><\/p>\n