Live coverage: ULA prepares for final Atlas 5 launch supporting a national security payload

United Launch Alliance rolled its Atlas 5 551 rocket to the launchpad at Space Launch Complex 41 (SLC-41) on Saturday, July 27, 2024, ahead of the USSF-51 launch on Tuesday, July 30. Image: Will Robinson-Smith/Spaceflight Now

United Launch Alliance is preparing for a seminole moment for its Atlas 5 rocket. The launch vehicle is preparing to launch its 58th and final national security mission on Tuesday. The United States Space Force-51 (USSF-51) mission will also be the 100th national security mission launch for ULA.

Following the completion of a launch readiness review on Friday, ULA rolled the rocket to the launch pad at Space Launch Complex 41 (SLC-41) at Cape Canaveral Space Force Station. First motion came shortly after noon on Saturday with the journey wrapping up after 12:30 p.m. EDT.

Liftoff is targeting Tuesday, July 30, during a three-hour window that opens at 6:45 a.m. EDT (1045 UTC).

“This is a bittersweet moment for us. I’ve had the privilege of sitting console for the very first national security Atlas launch in 2007, STP-1 (Space Test Program 1) in March of that year and here we are with our last national security Atlas,” said Col. Jim Horne, Senior Materiel Leader of the Launch Execution Delta. “I do want to say thank you to the entire team, the government and ULA. It’s been a strong partnership over these last almost 20 years on this program and this has been our workhorse vehicle.”

Because of the nature of the launch, Horne declined to go into detail about the mission or if the flight was carrying a single payload or more than one.

“I can’t say much about that his is a very important mission for national security in this time of great power competition, but that’s really all we can say at this time,” Horne said.

The Atlas 5 launching the USSF-51 payload will fly in a 551 configuration, meaning it will be supported by five solid rocket boosters and a 17-foot (5 meter) diameter short payload fairing. The full stack stands about 196 feet (59.7 meters) tall.

Gary Wentz, ULA’s vice president of Government and Commercial Programs, said following this mission, out of the remaining 15 Atlas 5 rockets remaining, nine will fly in the 551 configuration in support of Amazon’s Project Kuiper constellation.

“Every time you fly you learn a lot. And we’re flying five GEM 63’s on this mission,” Wentz said. “So, we’ll learn from that, continue to get data and going forward, we’ll apply that to the subsequent Atlas missions.”

Passing the baton

This final mission as part of the National Security Space Launch (NSSL) for the Atlas 5 rocket marks a pivot point for ULA. Following the USSF-51 launch, ULA will turn its full attention to its second certification flight of its Vulcan rocket following a successful debut in January.

“What we’ll do after this mission flies is we’ll do some checkout of the ground system with the [mobile launch platform], the Atlas MLP, verify all of that’s good, then we’ll bring in the Vulcan launch platform, do checkout of it and immediately go into erection of the booster and prepping for the Cert-2 mission,” Wentz said.

“We won’t waste any time. It’ll be within a week and a half to two weeks we’ll have the hardware in process for the Cert. flight.”

As ground teams at the Cape were preparing to roll out the Atlas 5 rocket, ULA teams in Decatur watched as the barge named ‘RocketShip’ set sail with the third Vulcan booster on board. It will be used for the first NSSL mission a Vulcan rocket launches: USSF-87.

A Vulcan booster sits inside United Launch
Alliance’s Horizontal Integration Facility at Cape Canaveral Space Force Station. It will support the second certification flight of the rocket prior to launching national security payloads. Image: Will Robinson-Smith/Spaceflight Now

Dr. Walt Lauderdale, the mission director for the USSF-51 mission, said the close working relationship between the U.S. Space Force and ULA during the development of Vulcan. He said that the dozens of missions flown on Atlas are also helping to inform him and his teams as they work through the certification process.

“When we look at working with ULA, that partnership, it’s really having that intimate knowledge and understanding of the vehicle systems, the ground systems, how they interface,” Lauderdale said. “You can do all the modeling in the world, but there’s no replacement for actual, real live data, real data from the vehicle and the system.”

“Cert-1 was a terrific flight. It allowed us to validate a lot of things that we’ve worked with them up to that point and looking to Cert-2 as Col. Horne just said, its gives us an opportunity to take all that we know from the models, all the qualifications, all the testing that we’ve done, and make sure that there’s no surprises,” Lauderdale added. “That’s really what we’re looking for for Cert-2 is to make sure that there’s no surprises and that it’s well bounded by our experience and our qualification knowledge.

“And that really does set the stage for us as we move forward into those Vulcan launches to go forward with confidence. Everything is looking good at this point and we’re not done til we’re done.”