ULA successfully launched the first mission for Amazon’s Project Kuiper, “KA-01”. The batch of satellites lifted off aboard an Atlas V 551 rocket on April 28th, 2025, at 23:01 UTC from Space Launch Complex-41 at Cape Canaveral Space Force Station, Florida. The launcher carried a group of 27 satellites for Amazon’s new satellite broadband network at an altitude of 450 kilometers above Earth. A previous launch attempt had taken place on April 9th, but it was ultimately scrubbed due to poor weather.
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Flight Profile
At 23:01 UTC, the two RD-180 main engines and the five side solid boosters ignited, lifting the rocket off the pad at Cape Canaveral and initiating its climb through Earth’s atmosphere. Within the first minute of the flight, the vehicle broke the sound barrier and soon passed through max-Q, the point of maximum aerodynamic stress.
Shortly after, the solid rocket boosters were jettisoned, having completed their role in the early boost phase. As the rocket continued its ascent, the payload fairing detached, exposing the spacecraft to space for the first time.
Just over four minutes into flight, the first stage shut down and separated, giving way to the Centaur upper stage, which ignited its engine to begin orbital insertion. The Centaur continued firing for several minutes before shutting down at T+00:18, completing the first phase of the mission and placing the payload on a trajectory toward its final orbit.
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Project Kuiper
Project Kuiper is Amazon’s low Earth orbit satellite network aiming to deliver fast, reliable internet to underserved and unserved communities worldwide. It will offer affordable customer terminals, a global network of ground stations, and resilient communications infrastructure powered by Amazon Web Services.
Amazon began research and development on Project Kuiper in 2018. In July 2020, the U.S. Federal Communications Commission (FCC) granted Amazon a license to deploy and operate Project Kuiper satellites.
To deploy over 3,200 satellites, Amazon has partnered with ULA in the largest commercial launch agreement, using eight Atlas V and 38 Vulcan rockets. Additionally, 18 Arianespace’s Ariane 6 launches are scheduled, and another twelve launches (with options for 15 more launches) are scheduled with Blue Origin’s New Glenn rocket, currently under testing. Going against many predictions, Amazon has also acquired three Falcon 9 rocket launches from SpaceX.
On October 6th, 2023, United Launch Alliance successfully delivered two prototype satellites for Amazon’s Kuiper constellation into orbit.
Within 30 days of sending two prototype satellites into space, Project Kuiper has achieved a 100% success rate for its Protoflight mission, validating key technologies that underpin the network and moving the program another step closer toward today’s launch.
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Launch vehicle configuration
Atlas V is an expendable launch system capable of delivering up to 18.9 tons of payload to LEO. It is America’s longest-serving active rocket. For this mission, it comes in the 551 configuration, where the first digit represents the payload fairing size, the second is the number of solid rocket boosters, and the third is the number of Centaur engines.
A 5.4 m diameter medium payload fairing encapsulates the spacecraft. The PLF encapsulates both the Centaur and the satellites. The vehicle’s height with the PLF is approximately 62.5 m.
Centaur is a cryogenic stage, fueled with liquid hydrogen and liquid oxygen, powered by an RL10A-4-2 engine producing 100.5 kN of thrust.
Booster propulsion is provided by the RD-180 engine system (a single engine with two thrust chambers). The RD-180 burns RP-1 (Rocket Propellant-1 or highly purified kerosene) and liquid oxygen and delivers 3.83 MN of thrust at sea level.
Five solid rocket boosters (SRBs) generate the additional thrust required at liftoff, with each providing 1.6 MN of thrust.
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Vulcan Certification
As the last eight Atlas launches run out, Vulcan has completed certification and is preparing for its first launches for the Space Force and the 38 launches agreed upon for Amazon’s Kuiper constellation project.
On March 26, the Space Force’s Space Systems Command announced it had completed the long-awaited certification of the Vulcan rocket, following analysis of its two certification launches in January and October 2024, along with additional development reviews.
The certification was delayed by an incident on the second Vulcan launch. The Vulcan Cert-2 launch encountered an anomaly just over 30 seconds after liftoff on October 4th, when the nozzle of one of its two solid rocket strap-on boosters from Northrop Grumman detached. Despite the loss of thrust, the rocket adjusted and successfully completed its mission.
“We’re all staged up and ready, and as spacecraft show up, we’ll be able to fly them,” stated ULA’s president and CEO, Tory Bruno.
Today’s launch will be followed by the first two Vulcan national security launches, missions designated USSF-106 and USSF-87, which have not been scheduled yet.
*Cover image credits: ULA and Amazon
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