AEHF-6 – Atlas V 551 (AV-086) – Canaveral SLC-41 – 26.03.2020 20:18 UTC

[tnt22]

Mar 26 19:23

The hazard area around the launch site has been cleared of all personnel for fueling and liftoff.

[tnt22]

Плановый

Mar 26 19:27
Countdown Holding

This is Atlas Launch Control at T-minus 2 hours (L-2 hours, 30 minutes) and holding. The countdown has entered the first of two planned, built-in holds that are scheduled in today's timeline. This first block of time gives the countdown some margin to resolve issues or catch up work that could be running late, and the hold provides an opportunity to ensure all is ready before fueling operations begin.

The final hold occurs at T-minus 4 minutes.

At the present time, all activities are on schedule and no problems are being addressed by the launch team.

[tnt22]

Mar 26 19:39
Go for Fueling

A readiness poll of the launch team by Launch Conductor Scott Barney, with concurrence of ULA Launch Director Tom Heter III, has approved cryogenic tanking operations to begin once the countdown resumes.

[tnt22]

Mar 26 19:42
Countdown Resumes

This is Atlas Launch Control at T-minus 2 hours (L-2 hours, 15 minutes) and counting. The next phase of today's launch countdown has started on schedule as we continue to target 2:57 p.m. EDT (1857 UTC) for liftoff of the United Launch Alliance Atlas V rocket carrying the AEHF-6 communications spacecraft for the U.S. Space Force's Space and Missile Systems Center.

Preparatory steps for fueling are being kicked off, including ground chilldown of the Atlas first liquid oxygen system and chilldown of the transfer lines to the Centaur upper stage liquid oxygen system.

[tnt22]

Mar 26 19:50
Centaur LO2 Loading Begins

With the thermal conditioning, or chilldown, now complete, liquid oxygen has started to flow into the Centaur upper stage for today's launch. About 4,150 gallons of liquid oxygen will be loaded into Centaur.

[tnt22]

Thomas Burghardt @TGMetsFan98 7:49 PM - Mar 26, 2020

Let's watch a rocket launch, shall we? #AtlasV #AEHF6

Article by @w_d_graham: https://www.nasaspaceflight.com/2020/03/atlas-v-launch-space-forces-aehf-6/ ...

NSF webcast: https://www.youtube.com/watch?v=Eaa3lADTlTQ&feature=emb_title ...

ULA webcast: https://www.youtube.com/watch?v=YBkB1BbblN0 ...

[tnt22]

Mar 26 20:14
Atlas LO2 loading begins

Filling of the Atlas V rocket's largest tank has begun. About 48,800 gallons of super-cold oxidizer for the main engine is flowing into the liquid oxygen tank on common core booster first stage.

[tnt22]

Mar 26 20:19

The Centaur liquid oxygen tank is topping to flight level.

[tnt22]

Mar 26 20:27

The first stage liquid oxygen tank has reached the 20 percent mark. And Centaur liquid oxygen is at flight level.

[tnt22]

03/26/2020 20:33 Stephen Clark

The chilldown sequence to thermally condition the Centaur stage's Aerojet Rocketdyne RL10C-1 engine has started.

[tnt22]

Mar 26 20:38
Centaur LH2 Loading Begins

The launch team has received the "go" to begin filling the Centaur upper stage with the super-cold liquid hydrogen fuel following chilldown of the system. The Centaur holds about 12,300 gallons of the cryogenic propellant for this three-burn mission to a geosynchronous transfer orbit.

[tnt22]

Mar 26 20:42

The countdown is passing T-minus 1 hour. We will be taking the clocks down to T-minus 4 minutes where they will hold for 15 minutes while managers perform the final readiness polls. Liftoff remains targeted for 2:57 p.m. EDT (1857 UTC).

[tnt22]

03/26/2020 20:44 Stephen Clark

There are no major weather concerns being monitored in the countdown, with partly cloudy skies over Cape Canaveral and no rain showers in the vicinity of the launch pad.

[tnt22]

[tnt22]

Mar 26 20:50

Flight control final preps are getting underway. This is the steering test pattern run on the Atlas V engine nozzles to ensure proper gimbaling during the ascent.

[tnt22]

Mar 26 20:52

The high-pressure helium bottles for first stage main engine pneumatics have been charged for flight.

[tnt22]

Mar 26 20:57

The liquid hydrogen tank in the Centaur upper stage just reached the 96 percent level. Topping is beginning.

[tnt22]

[tnt22]

Mar 26 21:00

Fast-filling of the first stage liquid oxygen tank has been completed. Topping mode is now underway. The cryogenics will be replenished throughout the countdown until the final minutes before launch to replace the liquid oxygen and liquid hydrogen that naturally boils away.

[tnt22]