End of an era: Delta 4 Heavy soars one last time

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COLORADO SPRINGS — In a historic sendoff, United Launch Alliance on April 9 launched a classified National Reconnaissance Office spy satellite on the final flight of the Delta 4 Heavy rocket.

The Delta 4 Heavy, with three common core boosters strapped together, thundered off the pad at 12:53 p.m. Eastern from Space Launch Complex-37 at Cape Canaveral Space Force Station, Florida, marking the end of an era for the rocket that launched 16 missions since its debut in December 2004. 

NROL-70 was originally set to launch March 28 but ULA ran into trouble with the nitrogen distribution system at Cape Canaveral and scrubbed the launch minutes before the scheduled liftoff time. 

The initial phase of NROL-70 was completed in under seven minutes. The  outer boosters of the Delta 4 Heavy separated about four minutes after liftoff and the second stage separated about two minutes later. 

At the request of the NRO, ULA ended the webcast nearly seven minutes into the flight after the nose fairing was jettisoned. 

The launch of NROL-70 was ULA’s 160th mission overall and its 35th for the NRO. In its near 20-year history, the Delta 4 Heavy has performed mostly classified missions for the U.S. government. The NRO is the U.S. intelligence agency responsible for designing, building, launching, and maintaining the nation’s spy satellites. 

ULA years ago started planning a transition away from its legacy vehicles, the Atlas 5 and the Delta 4 Heavy, to its next-generation Vulcan Centaur rocket, powered by Blue Origin’s BE-4 engines. 

Vulcan flew its debut mission in January and is expected to fly for the second time later this year.

Tory Bruno, ULA’s president and chief executive officer, described the Delta 4 Heavy’s final flight as a “bittersweet moment.” 

The Delta family of launch vehicles dates back to the early days of the space age. The first Delta rocket launched in 1960. 

It is still unclear what the future holds for the SLC-37 launch pad after the retirement of the Delta 4 Heavy. The head of the U.S. Space Force’s national security launch program office, Brig. Gen. Kristin Panzenhagen, said the pad is still under lease to ULA and after it’s vacated the government will conduct an environmental review. 

“We’ll return it to the Space Force for whoever needs it,” Bruno said March 27 at a news conference.