The weather might not have been perfect, but that didn’t prevent United Launch Alliance (ULA) from successfully delivering the EchoStar XIX satellite to orbit atop their Atlas V rocket. The launch marked ULA’s 12th of 2016 and 115th overall since the company’s founding more than 10 years ago.
Amidst broken clouds from an approaching cold front, the Atlas V 431 lifted off on Dec. 18 from Cape Canaveral Air Force Station’s (CCAFS) Space Launch Complex 41 (SLC-41) at 2:13 p.m. EST (19:13 GMT), after a 42-minute hold at T-minus 4 minutes from the initial opening of the two-hour launch window due to a technical glitch.
“Congratulations to ULA and the entire integrated team who ensured the success of our last launch capping off what has been a very busy year,” Col. Walt Jackim, 45th Space Wing vice commander and mission Launch Decision Authority, said in a news release. “This mission once again clearly demonstrates the successful collaboration we have with our mission partners as we continue to shape the future of America’s space operations and showcase why the 45th Space Wing is the ‘World’s Premiere Gateway to Space.'”
Nearly three seconds before liftoff, the Atlas V’s Russian-built RD-180 main engine roared to life, burning a mixture of liquid oxygen (LOX) and RP-1 – a highly refined version of kerosene – in a build-up to producing its 860,200 pounds (3,827 kilonewtons) of sea-level thrust.
Once the flight computer determined the RD-180 had passed all health checks, it signaled the three supplemental solid rocket motors (SRMs) – the largest single-segment carbon composite motors currently produced – to ignite, with each providing an additional 348,500 pounds (1,550 kilonewtons) of thrust at liftoff.
The vehicle quickly cleared the tower and began its pitch, roll, and yaw maneuver as it accelerated on its ascent to orbit, passing Mach 1 (the speed of sound) after 45 seconds into its flight.
Less than 15 seconds later, the rocket encountered the area of greatest aerodynamic stress on the vehicle, also known as “max Q”. Though the air thins as the vehicle rises, the increasing acceleration – combined with what little atmosphere remains – reaches a point where the loads imparted on the structure are greatest.
The three SRMs continued to burn for another 30 seconds and were jettisoned more than two minutes after liftoff. The RD-180 main engine fired for nearly two-and-a-half minutes more before booster engine cutoff (BECO) occurred nearly four-and-a-half minutes after ignition.
Empty, and with its job complete, the first stage separated from the Centaur stage six seconds later and ultimately splashed-down in the Atlantic Ocean.
The Centaur’s RL10C-1 came to life 10 seconds after separation, with its 22,900 pounds (101.86 kilonewtons) of vacuum thrust taking over the job of delivering the EchoStar XIX satellite to orbit.
Shortly after ignition of the RL10C-1, the 4-meter payload fairing was jettisoned, exposing the payload to the near-vacuum of space. Though providing needed protection from the stresses of launch, the payload fairing also burdened the vehicle with considerable mass – 5,483 pounds (2,487 kilograms), in the case of the XEPF variant used for this mission.
The RL10C-1 continued to fire, operating for approximately 9 minutes in this phase of the mission, with its first shut-down coming nearly 14 minutes after liftoff.
The Centaur and EchoStar XIX satellite then entered a 10-minute coast phase, after which the RL10C-1 was restarted for nearly 6 minutes.
After coasting for an additional 3 minutes, the approximately 13,890-pound (6,300-kilogram) EchoStar XIX satellite separated from the Centaur over the southern half of Africa.
Flying freely, it is the job of the satellite’s main propulsion system to circularize the spacecraft’s orbit, approximately 22,300 miles (35,800 kilometers) above the equator. EchoStar XIX will eventually settle into its orbital slot at 97.1 degrees West longitude.
The launch of EchoStar closes out ULA’s manifest for 2016. It marked a pace of launch that few have been able to keep up with.
“As we celebrate 10 years, ULA continues to be the nation’s premier launch provider because of our unmatched reliability and mission success,” said Gary Wentz, ULA vice president of Human and Commercial Systems. “The Atlas V continues to provide the optimum performance to precisely deliver a range of missions. As we move into our second decade, we will maintain our ongoing focus on mission success, one launch at a time even as we transform the space industry, making space more accessible, affordable and commercialized.”
Written by: Curt Godwin
Original source: spaceflightinsider.com