Created 16-Dec-25
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from spaceflightnow.com:
United Launch Alliance aced its final launch of 2025, a predawn flight of an Atlas 5 rocket carrying 27 satellites for Amazon’s recently re-branded Leo broadband internet service.
The on time liftoff from Space Launch Complex 41 at Cape Canaveral Space Force Station happened at 3:28 a.m. EST (0828 UTC), as the RD-180 engine on the booster roared to lift alongside five solid rocket boosters. The rocket flew on a north-easterly trajectory upon leaving the launch pad.
The mission, referred to by ULA as Amazon Leo 4 and dubbed Leo Atlas 4 (LA-04) by Amazon, was ULA’s fourth launch for the venture, previously known as Project Kuiper.
ULA opted to forego a launch opportunity Monday morning because of a high winds that caused forecasters to offer little hope for acceptable weather. The 45th Weather Squadron painted a much better picture for Tuesday morning, predicting a 95 percent chance for favorable conditions during the launch window.
On Saturday morning, ULA rolled its 205-foot-tall (62.5 m) rocket, designation AV-111, out of the Vertical Integration Facility to begin the journey of a third of a mile to the pad. It was lowered onto the launch pad piers and completed “hard down” at 11:51 a.m. EST (1651 UTC). Later that day 25,000 gallons of rocket-grade kerosene were loaded onto the first-stage booster.
ULA finished fueling its rocket with liquid oxygen and liquid hydrogen in the hours leading up to liftoff on Tuesday.
The Atlas 5 rocket flew in the 551 configuration, meaning the main RD-180 engine was supported by five solid rocket boosters around the base of the Atlas booster. Those SRBs jettisoned less than two minutes into the flight.
Roughly 4.5 minutes after leaving the pad, the Atlas booster separated and the RL10C-1-1 engine on the Centaur 3 upper stage began a burn lasting a little less than 13 minutes. A 15-minute-long deployment sequence for the Amazon Leo satellites will begin at about T+20 minutes.
Launch controllers will oversee a final burn of the Centaur’s engine to deorbit it.
Full story here:
United Launch Alliance aced its final launch of 2025, a predawn flight of an Atlas 5 rocket carrying 27 satellites for Amazon’s recently re-branded Leo broadband internet service.
The on time liftoff from Space Launch Complex 41 at Cape Canaveral Space Force Station happened at 3:28 a.m. EST (0828 UTC), as the RD-180 engine on the booster roared to lift alongside five solid rocket boosters. The rocket flew on a north-easterly trajectory upon leaving the launch pad.
The mission, referred to by ULA as Amazon Leo 4 and dubbed Leo Atlas 4 (LA-04) by Amazon, was ULA’s fourth launch for the venture, previously known as Project Kuiper.
ULA opted to forego a launch opportunity Monday morning because of a high winds that caused forecasters to offer little hope for acceptable weather. The 45th Weather Squadron painted a much better picture for Tuesday morning, predicting a 95 percent chance for favorable conditions during the launch window.
On Saturday morning, ULA rolled its 205-foot-tall (62.5 m) rocket, designation AV-111, out of the Vertical Integration Facility to begin the journey of a third of a mile to the pad. It was lowered onto the launch pad piers and completed “hard down” at 11:51 a.m. EST (1651 UTC). Later that day 25,000 gallons of rocket-grade kerosene were loaded onto the first-stage booster.
ULA finished fueling its rocket with liquid oxygen and liquid hydrogen in the hours leading up to liftoff on Tuesday.
The Atlas 5 rocket flew in the 551 configuration, meaning the main RD-180 engine was supported by five solid rocket boosters around the base of the Atlas booster. Those SRBs jettisoned less than two minutes into the flight.
Roughly 4.5 minutes after leaving the pad, the Atlas booster separated and the RL10C-1-1 engine on the Centaur 3 upper stage began a burn lasting a little less than 13 minutes. A 15-minute-long deployment sequence for the Amazon Leo satellites will begin at about T+20 minutes.
Launch controllers will oversee a final burn of the Centaur’s engine to deorbit it.
Full story here:
© Dennis Huff
