The last ever 'single stick' Delta IV scheduled to launch; here's what that means
Emre Kelly
UPDATE: United Launch Alliance successfully launches its last "single-stick" Delta IV rocket at 9:06 a.m. Thursday from Cape Canaveral Air Force Station.
In the mid-1990s, the Air Force spearheaded a new goal: ensure U.S. access to space through reliable, more affordable launch vehicles for national security spacecraft.
Enter United Launch Alliance’s Delta IV and Atlas V rockets.
Both have helped ULA launch more than 130 times on missions ranging from reconnaissance to the Global Positioning System constellation to deep-space robotic exploration. But after liftoff from Cape Canaveral Thursday, Delta IV will have fulfilled the mission – its 9 a.m. flight from Launch Complex 37 will be its last.
It will enter the history books, remembered as a towering orange-and-white vehicle that helped solidify U.S. access to space with an American-made engine, all while paving the way for its successor.
"Delta IV was an awesome beast that put a lot of heavy, extremely important payloads into space," said Dale Ketcham, chief of strategic alliances at Space Florida. "For quite some time, it was the only rocket flying with an American engine."
The Evolved Expendable Launch Vehicle program, renamed this year to National Security Space Launch, also fostered development of Atlas V, which flies with a Russian-made RD-180 engine. But combined, both Delta IV and Atlas V provided a diversified solution, reducing downtime if one system were to see a failure.
"There will always be people that have a close connection and emotional connection to the Delta IV system as we fly it out," said Tony Taliancich, director and general manager of ULA launch operations. "I was there for the first medium Delta IV launch and every one of them has been an emotional event for me. This last one will continue to be an emotional event.”
But the death of Delta IV’s “single stick” configuration – the three-core Delta IV Heavy will continue to fly well into the 2020s along with Atlas V – means life for ULA’s next rocket: Vulcan Centaur.
The origins of Delta IV
Both Delta IV and Atlas V launched on their premiere flights in 2002, the former of which has seen 29 in its “medium” single core configuration.
Having two launch systems on tap provided the military a way to spread risk, but Delta IV wasn't just a backup that operated exactly like Atlas V – it used liquid hydrogen instead of kerosene as its primary fuel. To do that meant using a different engine from the Russian RD-180 flying on Atlas V. Instead, Delta IV’s primary thrust came from the American-built RS-68 developed by Aerojet Rocketdyne.
"From a national security space market standpoint, they wanted to allocate appropriately even if it cost a little bit more to maintain two systems to make sure they had that capability," Taliancich said. "Up until 2018, ULA was chartered with maintaining two systems fully capable of launching all of those missions."
Since its introduction, the roughly 200-foot-tall medium configuration has flown 29 times on a mix of national security, science and GPS spacecraft, making up a respectable portion of the company's 135 total launches to date. Delta IV's retirement also comes within a year of the last Delta II launch, a smaller vehicle that last flew from Vandenberg Air Force Base in California in September 2018.
"Delta IV served well, but business moves on," Ketcham said.
That business is Vulcan Centaur.
Delta IV paves the way for Vulcan
Like most technological advances, lessons learned from Delta IV will carry over into Vulcan Centaur, ULA's next rocket slated for liftoff from Cape Canaveral no earlier than 2021.
Designed to streamline the company's processes and hardware by eventually replacing both Delta and Atlas, Vulcan is expected to become its workhorse for national security, commercial and science payloads. It also ditches the Atlas V's Russian engine in favor of an American one: BE-4, which is built by Blue Origin.
Most of Vulcan's components, such as its solid rocket motors, are interchangeable with existing ULA hardware and will fly before the fully stacked vehicle. Other elements like avionics will be moved over to Vulcan from Delta IV, effectively giving the rocket life beyond its final flight on Thursday.
"When we get to Vulcan's first flight in 2021, very little of that rocket will not have flown before," ULA CEO Tory Bruno said in Colorado Springs in April. "We are feathering it in."
ULA's streamlining of its services comes at a critical time for the company – a joint venture between Boeing and Lockheed Martin – and for the spaceflight industry as a whole. Entrants like SpaceX and Blue Origin have been putting pressure on the market and obtaining valuable commercial and government contracts, forcing competition to drive efficiencies. This means Launch Complex 37, the pad used by Delta IV and Delta IV Heavy, will eventually be retired. Vulcan will only fly from the Cape's Launch Complex 41 and Vandenberg.
"In order to provide a competitive offering for the future, we have to consolidate infrastructure as much as we can," Taliancich said. "Pads cost quite a bit to maintain."
Contact Emre Kelly at aekelly@floridatoday.com or 321-242-3715. Follow him on Twitter, Facebook and Instagram at @EmreKelly.
Launch Thursday
- Rocket: ULA Delta IV
- Mission: Air Force GPS satellite
- Launch Time: 9 a.m.
- Launch Window: Until 9:27 a.m.
- Launch Complex: 37 at Cape Canaveral Air Force Station
- Weather: Forecast expected Monday
Join FloridaToday.com/Space at 7 a.m. Thursday for countdown chat and updates, including streaming of ULA's launch webcast.