The Delta IV Heavy, a rocket whose time has come and gone, will fly once more

You can watch the launch on ULA’s live broadcast, embedded below.

https://www.youtube.com/watch?v=HCoyHHhX3rw

This is also the final flight overall for the Delta rocket family—the 389th rocket with the Delta name—since 1960. But those earlier rockets share virtually nothing in common with the Delta IV, which debuted in 2002. The older generations of Delta rockets could trace at least some of their design lineage to the Thor program, a Cold War-era ballistic missile later converted into a satellite launcher.

The last of that older family of Delta rockets, the Delta II, launched for the final time in 2018. The Delta IV was a clean-sheet design, initially conceived by McDonnell Douglas, that won a contract from the Air Force in 1998, alongside Lockheed Martin’s Atlas V rocket, to become the new workhorse launch vehicles for the military’s fleet of satellites.

The Delta IV program became part of Boeing when that company merged with McDonnell Douglas in 1997. In 2006, Boeing merged its Delta rocket program with Lockheed Martin’s Atlas V program, creating United Launch Alliance in a 50-50 joint venture.

The launch this week will mark the 45th flight of a Delta IV rocket and the 16th to fly in the Delta IV Heavy configuration. The Delta IV Heavy, in particular, launched the kinds of heavy military and intelligence-gathering satellites that once flew on the Titan IV rocket, which retired in 2005. These payloads have primarily included NRO eavesdropping satellites and the massive bus-size Keyhole imaging platforms, essentially Hubble-class telescopes pointed at Earth.

The Delta IV boasts a nearly perfect success record. The only blemish was on the first flight of the Delta IV Heavy in 2004 when a dummy payload was deployed into a lower-than-planned orbit after the three booster engines shut down a few seconds early.

But the Delta IV Heavy is expensive. At one time, a single launch on this expendable rocket cost as much as much as $400 million, although the government secured a somewhat lower price from ULA for buying in bulk the the final three missions on Delta IV Heavy. The Delta IV launched a commercial satellite on its first flight in 2002, but no more commercial customers ever bought a Delta IV launch.

The Delta IV launch pads in Florida and California were particularly complex, requiring maintenance and sustainment even during years-long lulls in launch activity.

These high prices helped open a path for SpaceX, then a newcomer to the national security launch business, to petition the Pentagon for the right to compete for military launch contracts. With its partially reusable Falcon 9 rocket, SpaceX offered lower prices than ULA. “I don’t know how to build a $400 million rocket,” Gwynne Shotwell, SpaceX’s president and chief operating officer, told Congress in 2015.

The Falcon Heavy rocket debuted in 2018, giving SpaceX the capability to launch nearly all of the military’s space missions. There are a few exceptions, like the NRO payloads assigned to the final few Delta IV Heavy rockets. SpaceX is developing a longer payload fairing for the Falcon Heavy to accommodate these types of satellites.

Now, ULA has the less expensive Vulcan rocket, which flew on a problem-free test flight in January. Vulcan will replace the Delta IV and Atlas V rockets in ULA’s fleet. There are still 17 Atlas V rockets remaining in ULA’s inventory, primarily missions to launch Boeing’s Starliner crew capsule and Amazon’s Kuiper broadband network.

Under a contract the Pentagon awarded in 2020, ULA’s Vulcan rocket and SpaceX’s Falcon 9 and Falcon Heavy will launch all of the military’s most expensive and sensitive satellites over the next few years. In its heaviest configuration, the Vulcan will outlift the Delta IV Heavy without needing three first-stage boosters to do the job.

“Delta IV Heavy is three rockets bolted together,” Bruno said. “With a single core Vulcan, we’re able to collapse that cost (of Delta IV Heavy) by 70 percent and make that mission a lot more practical.”

SpaceX has an agreement with the Space Force to take over the former Delta IV launch pad at Vandenberg Space Force Base in California. Falcon 9 and Falcon Heavy rockets will launch from there. And SpaceX has its eye on Space Launch Complex-37 at Cape Canaveral, where the final Delta IV Heavy will take off this week, as a possible future home for the giant Starship rocket.