WASHINGTON – As United Launch Alliance prepares for the final launch of its Delta 4 Medium rocket on Thursday, the company is also reporting on its last five missions with the Delta 4 Heavy.
Gary Wentz, Vice President of Government and Commercial Programs at ULA, stated that Delta 4's last heavy mission is currently scheduled for the second half of 2023.
"We have two planned burdens currently targeting June and September next year, "Wentz said during a Aug. 20 teleconference on the planned launch of GPS-3 on Thursday. "Then we have two planned in the last part of  22, and the final is aimed at launching in 2023."
A ULA spokesman said all future Delta 4 heavy missions should "support our US Air Force / National Intelligence Office Client. "
The two Delta 4 heavy launches planned for 2020 are the NRL-44 mission of the National Intelligence Service in Cape Canaveral, Florida, and NROL-82 of the Wadenberg Air Force Base, California, according to Spaceflightnow. [1
Additional contract awards are expected in the coming months to cover actual launches of NROL-70 and NROL-91 in 2022 and NROL-68 in 2023.
ULA terminated Delta 4 Heavy in favor of Vulcan, its next-generation rocket ich Wentz said it was the first it will fly in April 2021. The Delta 4 Heavy is an expensive rocket that costs upwards of $ 350 million to launch, limiting its use to government customers, while ULA's Delta 4 Heavy is reported to have fallen below $ 300 million, it is still considered too expensive to be commercially viable.
For certain government payloads, such as large-ticket espionage satellites, Delta 4 Heavy remains attractive.
"We continue to take off Delta 4 Heavy during the last part of 2023 for specific payloads that require this capability and guarantee the success of the mission we provide," he said. "We will continue to fly these until the customer meets the need and plan to work for Centaur Volcano to provide us with an overlap for this capability to give our customers an additional cut."
Delta 4 Heavy uses three rocket boosters with liquid fuel in its first phase to eject 14,200 kilograms into geostationary transfer orbit. The capacity of the missile lift is unrivaled until the launch of SpaceX last year on the Falcon Heavy, which can lift 26,700 kilograms in this orbit, also using three liquid-fueled rocket cores.
Delta 4 Heavy launches 11 times since 2004 Introduction. Apart from lower-than-expected performance on its debut mission, the heavy-lift missile – like the rest of the current ULA fleet – has failed.
The ULA Delta 4 Medium, which uses a first-stage liquid engine supplemented by smaller solid fuel boosters, has been launched 28 times. Its 29th and final mission will carry the Air Force's second satellite on 22 August.