Launch Managers Give “Go” to Proceed with Terminal Count, Launch Set for 1:47 a.m.

The mission management team has polled “go” to proceed with the terminal count sequence. The launch director is also “go” and teams have set a new target launch time of 1:47 a.m. EST and the countdown clock  resumed at 1:37 a.m.

With approval from the launch director and managers, a series of countdown milestones for the Artemis I terminal count to launch will be initiated by the Ground Launch Sequencer at T-10 minutes:

  • Ground Launch Sequencer (GLS) initiates terminal count (T-10M)
  • GLS go for core stage tank pressurization (T-6M)
  • Orion ascent pyros are armed (T-6M)
  • Orion set to internal power (T-6M)
  • Core Stage LH2 terminate replenish (T-5M57S)
  • GLS is go for flight termination system (FTS) arm (T-5M)
  • GLS is go for LH2 high flow bleed check (T-4M40S)
  • GLS is go for core stage auxiliary power unit (APU) start (T-4M)
  • Core Stage auxiliary power unit starts (T-4M)
  • Core stage L0X terminate replenish (T-4M)
  • ICPS LOX terminate replenish (T-3M30S)
  • GLS is go for purge sequence 4 (T-3M10S)
  • ICPS switches to internal battery power (T-1M56S)
  • Core stage switches to internal power (T-1M30S)
  • ICPS enters terminal countdown mode (T-1M20S)
  • ICPS LH2 terminate replenish (T-50S)
  • GLS sends “Go for automated launch sequencer” command (T-33S)
  • Core stage flight computer to automated launching sequencer (T-30S)
  • Hydrogen burn off igniters initiated (T-12S)
  • GLS sends the command for core stage engine start (T-10S)
  • RS-25 engines startup (T-6.36S)

Liftoff (T-0)

  • Solid rocket booster separation (Mission Elapsed Time 00:02:12)
  • Service module fairing jettison (MET 00:03:11)
  • Launch abort system jettison (MET 00:03:16)
  • Core stage main engine cutoff commanded (MET 00:08:03)
  • Core stage/ICPS separation (MET 00:08:15)
  • Orion solar array wing deploy begins (MET 00:18:09) – approx. 12 min duration
  • Perigee raise maneuver (MET 00:52:56)
  • Trans-lunar injection (MET 01:29:27)
  • Orion/ICPS separation (MET 01:57:36)

The timing of events after liftoff may vary by a few seconds.

Teams to Target New Launch Time

Teams have extended their planned 30-minute hold, and mission managers are expected to target a new time for launch. The Eastern Range and launch teams have since resolved an issue that caused a loss of signal from a radar site and are currently in the process of conducting required tests to ensure communication and tracking of the rocket and spacecraft.

Core Stage Liquid Hydrogen Back in Replenish, Upper Stage in Fast Fill

Teams are replenishing liquid hydrogen into the core stage and report seeing good data where a red crew tightened connections in the area of a leaky valve on the mobile launcher. The leak is not reoccurring. Engineers are back into liquid hydrogen fast fill operations on the interim cryogenic propulsion stage.

Engineers also are tracking the loss of signal from a radar site required for launch. The Range is in the process of troubleshooting it while launch operations continue.

Red Crew Departs Pad

The red crew has departed the launch pad and is now outside the designated danger area surrounding the pad. The technicians entered the zero deck, or base, of the mobile launcher and tightened several bolts to troubleshoot a valve used to replenish the core stage with liquid hydrogen which showed a leak with readings above limits. The launch team will check the valves to determine if the leak has been fixed and resume launch countdown operations.

Red Crew Arrives at Pad

Technicians who are part of the “red crew” of personnel specially trained to conduct operations at the launch pad during cryogenic loading operations have arrived at the launch pad. They will enter the zero deck or base of the mobile launcher to tighten connections to ensure a hydrogen valve used to replenish the core stage remains tight.

NASA has historically sent teams to the pad to conduct inspections during active launch operations as needed.

Core Stage Liquid Hydrogen Flow Paused, Red Crew Being Assembled

Engineers have paused flowing liquid hydrogen into the core stage because of a small leak on a hydrogen valve inside of the mobile launcher. A team of personnel called a red crew is being assembled to go to the pad to make sure all of the connections and valves remain tight. The valve is located within the base of the mobile launcher.

Upper Stage Liquid Hydrogen and Liquid Oxygen in Fast Fill

Teams are in fast fill operations for the interim cryogenic propulsion stage’s (ICPS) liquid hydrogen and liquid oxygen tanks. The ICPS is the upper stage of the Space Launch System rocket responsible for giving the Orion spacecraft the big push it needs in space to head toward the Moon.

Teams continue to work toward a two-hour launch window that opens at 1:04 a.m. EST, from Launch Pad 39B at NASA’s Kennedy Space Center in Florida.

Coverage of tanking operations continues on NASA TV and the agency’s website and the NASA app. A full launch broadcast will begin at 10:30 p.m. EST in English and at midnight, Spanish coverage begins on the NASA en español YouTube page.

Core Stage Liquid Hydrogen in Replenish

Engineers have completed filling the core stage liquid hydrogen tank, and have moved into the replenish phase. Core stage liquid oxygen fast fill is still underway. Although the LH2 tank is larger than the LOX tank, LOX is denser than LH2 and takes longer to load.

Teams continue to work toward a two-hour launch window that opens at 1:04 a.m. EST, from Launch Pad 39B at NASA’s Kennedy Space Center in Florida.