October 18, 2018

Launch timeline for Atlas 5’s AFSPC 11 mission


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A United Launch Atlas 5 rocket is set to loft three military satellites for the U.S. Air Force on a mission codenamed AFSPC 11. This timeline shows the major mission events planned over a six-hour flight to a near-geostationary orbit.

The 197-foot-tall (60-meter) rocket, propelled by an RD-180 main engine and five solid rocket boosters, is set for liftoff during a launch window Saturday that opens at 7:13 p.m. EDT (2313 GMT) and closes at 9:11 p.m. EDT (0111 GMT Sunday).

The AFSPC 11 mission will be the 77th flight of an Atlas 5 rocket, and the third Atlas 5 launch of 2018.

A military communications satellite named CBAS, or Continuous Broadcast Augmenting SATCOM, is the forward payload in the Atlas 5’s upper shroud. A spacecraft named EAGLE, which contains several military experiments including a separating subsatellite named Mycroft, is in the aft position inside the Atlas 5 payload fairing.

The artist’s concepts posted below show generic payload illustrations used on previous missions.

Read our mission preview story for details on the launch.

T+0:00:01.1: Liftoff

After igniting its RD-180 main engine at T-minus 2.7 seconds, the Atlas 5 rocket fires its five solid rocket boosters and rises away from Complex 41 at Cape Canaveral Air Force Station, Florida, with approximately 2.6 million pounds of thrust.

T+0:00:34.4: Mach 1

The Atlas 5 rocket exceeds the speed of sound, flying on a launch azimuth of 89.9 degrees.

T+0:00:45.9: Max-Q

The Atlas 5 rocket passes through the region of maximum dynamic pressure during ascent through the lower atmosphere.

T+0:01:47.0: Jettison SRBs

Having burned out of propellant approximately 20 seconds earlier, the five spent Aerojet Rocketdyne-built solid rocket boosters are jettisoned once dynamic pressure conditions are satisfied.

T+0:03:31.0: Payload Fairing Jettison

The Atlas 5 rocket’s payload fairing, made in Switzerland by Ruag Space, is jettisoned in a clamshell-like fashion once external heating levels drop below predetermined limits after climbing through the dense lower atmosphere. The Forward Load Reactor deck that connected the payload fairing’s structure to the Centaur upper stage is released five seconds after the shroud’s jettison.

T+0:04:33.5: Main Engine Cutoff

The RD-180 main engine completes its firing after consuming its kerosene and liquid oxygen fuel supply in the Atlas first stage.

T+0:04:39.5: Stage Separation

The Common Core Booster first stage of the Atlas 5 rocket separates from the Centaur upper stage. Over the next few seconds, the Centaur engine liquid hydrogen and liquid oxygen systems are readied for ignition.

T+0:04:49.5: Centaur Ignition 1

The Centaur RL10C-1 engine ignites for the first of three upper stage firings. This burn will inject the Centaur stage and the AFSPC 11 payloads into an initial parking orbit.

T+0:10:50.7: Centaur Cutoff 1

The Centaur engine shuts down after arriving in a planned low-Earth parking orbit. The vehicle enters a 12-minute coast period before arriving at the required location in space for the second burn.

T+0:22:57.4: Centaur Ignition 2

Producing 22,900 pounds of thrust, the Centaur re-ignites to accelerate the payload into a highly elliptical transfer orbit from the parking altitude achieved earlier in the launch sequence. This burn lasts nearly six minutes.

T+0:28:46.3: Centaur Cutoff 2

The second Centaur firing places the AFSPC 11 payloads into an elliptical transfer orbit stretching more than 20,000 miles above Earth, beginning a five-hour coast period for the mission’s final orbital adjustment maneuver.

T+5:34:46.2: Centaur Ignition 3

After a three-hour coast, the Centaur’s RL10 engine reignites for a roughly two-and-a-half minute firing to raise the AFSPC 11 payloads’ perigee, or orbital low point, and reduce its inclination to 0 degrees over the equator.

T+5:37:22.4: Centaur Cutoff 3

The powered phase of flight is concluded as the Centaur reaches the planned circular near-geostationary orbit at an altitude of approximately 24,233 miles (39,000 kilometers). The Centaur stage then begins re-orienting itself for deployment of the AFSPC 11 payloads.

T+6:57:24.3: Spacecraft Separation Window Closes

The window for deployment of the AFSPC 11 mission’s two main payloads — the Continuous Broadcast Augmenting SATCOM satellite and the EAGLE spacecraft — closes and the Atlas 5 mission ends.

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Follow Stephen Clark on Twitter: @StephenClark1.


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