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Atlas 5 launch timeline for the AEHF 6 mission – Spaceflight Now

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A United Launch Atlas 5 rocket is ready to launch the U.S. Air Power’s sixth and last Superior Extraordinarily Excessive Frequency communications satellite tv for pc from Cape Canaveral. This timeline reveals the foremost mission occasions deliberate over an almost six-hour flight to an optimized geostationary switch orbit.

The 197-foot-tall (60-meter) rocket, propelled by an RD-180 fundamental engine and 5 strong rocket boosters, is ready for liftoff throughout a two-hour launch window Thursday, March 26, that opens at 2:57 p.m. EDT (1857 GMT).

The AEHF 5 mission would be the 83rd flight of an Atlas 5 rocket, and the second Atlas 5 launch of 2020.

Constructed by Lockheed Martin, the AEHF 6 satellite tv for pc joins 5 earlier satellites within the AEHF constellation launched by Atlas 5 rockets in 2010, 2012, 2013, 2018 and 2019. The primary 4 AEHF satellites in orbit allowed the Air Power’s new era of safe, nuclear-hardened voice, video and information relay spacecraft to span the globe, and the addition of two extra AEHF geostationary relay satellite tv for pc will develop the community’s capability and resiliency.

The Atlas 5 launch sequence will final 5 hours, 40 minutes, from liftoff till deployment of the AEHF 6 spacecraft. On this mission, ULA added further hardware and maneuvering gasoline to the Centaur higher stage, enabling the launcher to ship the AEHF 6 satellite tv for pc nearer to its last orbit greater than 22,000 miles (practically 36,000 kilometers) above the equator.

The GSO package was added to the Atlas 5 rocket on the fifth AEHF launch final August, after the primary 4 AEHF missions didn’t make use of the extra functionality.

The additional efficiency offered by the GSO package will permit the Centaur higher stage to coast a further two hours earlier than its third firing. Spacecraft separation is scheduled for T+plus 5 hours, 40 minutes.

Due to the mission profile change, the AEHF 6 satellite tv for pc will separate in an orbit with a perigee, or low level, a number of thousand miles greater than can be attainable with out the GSO package. Meaning AEHF 6 — like AEHF 5 final 12 months — might want to devour much less of its personal finite propellant provide to circularize its orbit, resulting in an extended working lifetime for the mission.

In keeping with an Atlas 5 consumer’s information revealed by ULA, the GSO package consists of further battery energy, a full load of hydrazine to manage the higher stage’s orientation in area, and extra shielding over delicate parts, together with the Centaur’ hydrogen and oxygen tanks.

An outline of the Atlas 5/AEHF 6 launch sequence and a floor monitor map illustrating the rocket’s path after liftoff are are posted beneath.

Credit score: United Launch Alliance

T+zero:00:01.1: Liftoff

After igniting its RD-180 fundamental engine at T-minus 2.7 seconds, the Atlas 5 rocket fires its 5 strong rocket boosters and rises away from Advanced 41 at Cape Canaveral Air Power Station, Florida, with roughly 2.6 million kilos of thrust.

T+zero:00:34.four: Mach 1

The Atlas 5 rocket exceeds the velocity of sound, flying east from Cape Canaveral Air Power Station.

T+zero:00:46.2: Max-Q

The Atlas 5 rocket passes by means of the area of most dynamic strain throughout ascent by means of the decrease ambiance.

T+zero:01:46.7: Jettison SRBs

Having burned out of propellant roughly 15 seconds earlier, the 5 spent Aerojet Rocketdyne-built strong rocket boosters are jettisoned as soon as dynamic strain situations are glad. The primary pair of boosters will jettison, adopted a second-and-a-half later by the remaining three.

T+zero:03:24.9: Payload Fairing Jettison

The Atlas 5 rocket’s payload fairing, made in Switzerland by RUAG Area, is jettisoned in a clamshell-like style as soon as exterior heating ranges drop beneath predetermined limits after climbing by means of the dense decrease ambiance. The Ahead Load Reactor deck that linked the payload fairing’s construction to the Centaur higher stage is launched 5 seconds after the shroud’s jettison.

T+zero:04:26.three: Fundamental Engine Cutoff

The RD-180 fundamental engine completes its firing after consuming its kerosene and liquid oxygen gasoline provide within the Atlas first stage.

T+zero:04:32.three: Stage Separation

The Widespread Core Booster first stage of the Atlas 5 rocket separates from the Centaur higher stage. Over the following few seconds, the Centaur engine liquid hydrogen and liquid oxygen programs are readied for ignition.

T+zero:04:42.three: Centaur Ignition 1

The Centaur RL10C-1 engine ignites for the primary of three higher stage firings. This burn will inject the Centaur stage and the AEHF 6 satellite tv for pc into an preliminary parking orbit.

T+zero:11:46.9: Centaur Cutoff 1

The Centaur engine shuts down after arriving in a deliberate low-Earth parking orbit. The automobile enters an 11-minute coast interval earlier than arriving on the required location in area for the second burn.

T+zero:22:44.three: Centaur Ignition 2

Producing 22,900 kilos of thrust, the Centaur re-ignites to speed up the AEHF 6 payload right into a extremely elliptical switch orbit from the parking altitude achieved earlier within the launch sequence. This burn lasts greater than six minutes.

T+zero:28:52.7: Centaur Cutoff 2

The second Centaur firing locations the AEHF 6 satellite tv for pc into an elliptical switch orbit stretching greater than 20,000 miles above Earth, starting a five-hour coast interval for the mission’s last orbital adjustment maneuver. A secondary U.S. Air Power smallsat payload named TDO 2 will separate from the Centaur higher stage’s aft bulkhead round 30 seconds after the RL10 engine shuts down. The TDO 2 mission assist area area consciousness by means of optical calibration and satellite tv for pc laser ranging.

T+5:36:39.1: Centaur Ignition three

After a five-hour coast, the Centaur’s RL10 engine reignites for a roughly one-minute, 28-second firing to position the AEHF 6 satellite tv for pc within the correct orbit for spacecraft separation.

T+5:38:07.eight: Centaur Cutoff three

The powered part of flight is concluded because the Centaur reaches the deliberate elliptical geostationary switch orbit with an anticipated perigee, or low level, of 6,758 miles (10,876 kilometers), an apogee, or excessive level, of 21,933 miles (35,298 kilometers), and an inclination of 13.9 levels. The ultimate RL10 engine burn will hearth till depletion of the Centaur higher stage’s propellant, giving the AEHF 6 satellite tv for pc essentially the most favorable orbit attainable earlier than spacecraft separation.

T+5:40:56.9: AEHF 6 Separation

The AEHF 6 spacecraft deploys from the Centaur higher stage.

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Observe Stephen Clark on Twitter: @StephenClark1.




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