Ending an era in American rocketry, United Launch Alliance fired its 16th and final triple-core Delta 4 Heavy Tuesday, launching a secret spy satellite in the last hurray of a legendary rocket family dating back to the beginning of the space age.
The Heavy's three hydrogen-powered RS-68A first stage engines ignited with a stream of bright orange flames at 12:53 p.m. EDT, pushing the 230-foot-tall rocket smoothly away from pad 37 at the Cape Canaveral Space Force Station in Florida .
The launch was 12 days late, mainly due to work to replace a pump in a system that supplies nitrogen gas to multiple launch pads from a pipeline that runs through the Kennedy Space Center and the Cape Canaveral Space Force Station. There were no problems on Tuesday.
Mounted atop the rocket was a secret satellite provided by the National Reconnaissance Office, the secret government agency that manages the nation's fleet of advanced optical and radar imaging satellites and electronic eavesdropping stations.
In accordance with standard NRO-US Space Force policy for such missions, no details about the NROL-70's payload have been released. But about six hours after launch, the National Reconnaissance Office declared the launch a success, indicating that the satellite had reached its intended orbit.
"All of our missions are very important, and this one is right up there," NRO Director Chris Scolese told reporters before the rocket's first launch attempt. "But it is even more special because it will be the last flight of the Delta 4 Heavy.
"Like all of our missions, they are focused on national security and provide, we believe, the best information in the world for our policymakers, the warfighters and the civilian community."
Based on the Heavy's easterly trajectory, safety announcements and other factors, independent analysts concluded that the payload was most likely an advanced signal intelligence satellite bound for a geosynchronous orbit 22,000 miles (36,000 kilometers) above the equator.
Satellites at that altitude appear stationary in the sky as they orbit the Earth, allowing continuous observations of specific regions.
Such signals intelligence satellites are believed to feature giant mesh antennas that deploy in space and act as "huge... 'ears' in the sky, monitoring large areas for radio emissions, especially military ( communication)," says Marco Langbroek. independent analyst based in the Netherlands.
When asked specifically about the nature of the NROL-70 satellite, Scolese told reporters: "There's really not much I can say other than it's a national security payload that will provide outstanding capabilities that many people and organizations need." clearly to the policymakers, the warfighter and others, so that they can know what is going on."
In any case, as is customary on classified missions, ULA ended launch coverage with confirmation of the second stage engine ignition and payload fairing separation seven minutes after launch. The rest of the ascent was carried out in secret.
The final appearance of a Delta rocket, 63 years after the first flight of the first variant, was an emotional milestone for the managers, engineers and technicians who assembled and launched the last member of the family.
"The launch of the final Delta 4 is bittersweet for me," Col. Eric Zarybnisky, director of NRO's Office of Space Launch, said in a statement. "I was part of the team that launched the first Delta 4 for NRO. Since that time, Delta 4 has brought amazing capabilities into orbit for this country."
Tory Bruno, president and CEO of United Launch Alliance, also called the flight a "bittersweet" moment as the company continues the transition to the next generation of Vulcan rockets and phases out the more expensive Delta and Atlas families.
"Soon, Vulcan will pick up that mantle and we will retire this venerable rocket that has done so much important work for our country," he said in a pre-recorded video after the launch.
"I would like to thank everyone involved with the Delta 4 Heavy. We have many employees who were here for the very first Delta 4 launch and who are still here for the final Delta 4 launch to bring this amazing vehicle to its well to send -earned pension."
He previously told reporters that closing the Delta line "is clearly the future, moving to Vulcan, a cheaper rocket with higher performance. But still sad."
The single-core Delta 4 and triple-core Heavy were expensive, with some versions of the Heavy reportedly selling for over $300 million each. While the program was capable of delivering high-priority military payloads into complex, difficult-to-reach orbits, it was not considered sustainable in an era of smaller, more numerous satellites and cheaper boosters from SpaceX.
The Delta family of stages and rockets had its origins in the early space program, first serving in the national fleet of medium-range ballistic missiles and evolving through multiple versions used to deliver military, NASA and civilian payloads into orbit to bring to the earth.
The now retired Delta 2 debuted in 1990, placing the first Global Positioning System satellites into orbit and sending multiple planetary probes into deep space, including Messenger to Mercury, multiple Mars orbiters, the Pathfinder, Spirit and Opportunity Mars rovers, the Spitzer Space Telescope and much more.
The single-core Delta 4 first flew in 2002 and the first Heavy followed two years later. The single-core version flew the final flight of the program in 2019. Tuesday's launch marked the 45th flight of a Delta 4 and the 16th and final Delta 4 Heavy.
"We're very excited to get started with Vulcan and fly these missions, but at the same time we love this rocket," Bruno said of the Delta family.
"Delta has been around in one form or another for 60 years," he added. "It just has a storied legacy and it's done great things for our nation. We're very proud to have been a part of that, and even though Vulcan is the future, I'm personally sad to see it go."
NASA will launch rockets into the path of the total solar eclipse
The largest dam removal project in U.S. history aims to revive America's salmon population
A total solar eclipse cuts the path across the US
