A United Launch Atlas 5 rocket is about to launch the US Army 's fourth high – frequency evolved communications satellite from Cape Canaveral. This timeline shows the main mission events scheduled on a flight of three and a half hours to an optimized geostationary transfer orbit.
The 60 meter (197 feet) high rocket, powered by a main engine of the RD-180 and five powerful thrusters, is expected to take off Wednesday in a two-hour launch window Wednesday at 12:15 pm (New York time). ).
The AEHF 4 mission will be the 79th flight of an Atlas 5 rocket and the fifth launch of Atlas 5 in 2018.
Built by Lockheed Martin, the AEHF 4 satellite joins the three previous satellites of the AEHF constellation launched by Atlas 5 in 2010, 2012 and 2013. With four AEHF satellites in orbit, the new generation of secure and enhanced voice communications from the Air Force , and the data relay satellite will provide global coverage.
Below you will find an overview of the launch sequence of the Atlas 5 / AEHF 4 and a ground trajectory map showing the trajectory of the rocket after take-off.
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Credit: United Launch Alliance
T + 0: 00: 01.1: Take off
After firing the main engine of the RD-180 in less than 2.7 seconds, Atlas 5 fires its five full-body thrusters and departs from Complex 41 at Cape Canaveral Air Force Base in Florida. with a push of about 2.6 million pounds.
T + 0: 00: 34.6: Mach 1
The Atlas 5 rocket exceeds the speed of sound, flying east from the Cape Canaveral Air Base.
T + 0: 00: 48.4: Max-Q
The Atlas rocket 5 crosses the region of maximum dynamic pressure during its ascent into the lower atmosphere.
T + 0: 01: 50.7: SRB Jettison
After burning the propeller about 20 seconds earlier, the five solid rocket propellers built by Aerojet Rocketdyne were dropped once dynamic pressure conditions were met.
T + 0: 03: 28.6: Payload fairing
The payload fairing of the Atlas 5 rocket, manufactured in Switzerland by Ruag Space, is dropped as a shell when the outdoor heating levels fall below the predetermined limits after passing through the dense lower atmosphere. The direct charge reactor bridge that connects the payload fairing structure to the Centaur's upper stage is released five seconds after the sail is dropped.
T + 0: 04: 27.4: Main engine shutdown
The main engine of the RD-180 completes its ignition after consuming its supply of kerosene and liquid oxygen in the first floor of the Atlas.
T + 0: 04: 33.4: Separation of floor
The first stage of the Common Core Booster of the Atlas 5 rocket separates from the upper floor of the Centaur. Over the next few seconds, Centaur's liquid hydrogen and oxygen systems are ready to ignite.
T + 0: 04: 43.4: Centaur ignition 1
The Centaur RL10C-1 engine turns on for the first of three top-floor reliefs. This engraving will inject the Centaur Platinum and the AEHF 4 satellite into an initial parking orbit.
T + 0: 11: 51.3: Centaur Break 1
The Centaur engine stops after arriving on a planned low ground parking orbit. The vehicle enters a coastal period of 10 minutes before arriving at the required location in the space for the second fire.
T + 0: 22: 25.2: Centaur 2 ignition
Producing 22,900 pounds of thrust, the Centaur reignites to accelerate the payload into a highly elliptical transfer orbit from the parking altitude reached earlier in the launch sequence. This burn lasts nearly six minutes.
T + 0: 28: 19.1: Cut Centaurus 2
The second Centaur shot puts the AEHF 4 satellite into an elliptical transfer orbit extending over 30,000 km above the Earth, marking the beginning of a three-hour coastal period for the last maneuver. orbital adjustment of the mission.
T + 3: 28: 20.4: Centaur Lighting 3
After three hours of coasting, the Centaur's RL10 engine fires for about 40 minutes to set the AEHF 4 satellite in the proper orbit for separation of the spacecraft.
T + 3: 30: 00.1: Centaur Break 3
The powered flight phase is complete when the Centaur reaches the predicted geostationary elliptical transfer orbit with an apogee or tilt point of 12.8 degrees.
T + 3: 32: 49.1: Separation AEHF 4
The AEHF 4 spacecraft deploys from the upper floor of the Centaur.
