As the United Launch Alliance (ULA) prepares for the 16th and final launch of the Delta IV Heavy rocket, it marks the end of an era for one of the most powerful and reliable launch vehicles in the history of spaceflight. The Delta IV Heavy, a member of the Delta rocket family, has been a workhorse for the U.S. Air Force, National Reconnaissance Office (NRO), and NASA since its debut in 2004. Its upcoming mission, NROL-70, will be a fitting farewell to a rocket that has played a crucial role in advancing America’s space capabilities.
The Delta Legacy
The Delta IV Heavy is the culmination of over six decades of innovation and evolution in the Delta rocket family. The Delta program, initiated by NASA in the late 1950s, was derived from the Thor intermediate-range ballistic missile and incorporated components from the Vanguard rocket. The first Delta launch took place on May 13, 1960, from Cape Canaveral, marking the beginning of a remarkable journey.
Throughout the years, the Delta rockets have undergone numerous improvements to meet the growing demands of satellite launches. These enhancements included larger first-stage tanks, the addition of solid rocket boosters, increased propellant capacity, advanced engines, and the development of upper stages and payload systems. The Delta family has grown from the early 90-foot (27.4 m) tall, 112,000-pound (50,800 kg) rockets to the massive Delta IV Heavy, standing at 235 feet (71.6 m) tall and weighing 1.6 million pounds (733,000 kg) at liftoff.
The Birth of Delta IV
The Delta IV program was developed by Boeing in the late 1990s as part of the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) program. The goal was to create a family of rockets that could efficiently and reliably launch high-priority government payloads. The Delta IV family consists of five configurations: the Delta IV Medium, three variants of the Delta IV Medium-Plus, and the Delta IV Heavy.
The Delta IV introduced several new technologies, including the RS-68 engine, the largest hydrogen-burning engine in existence. Designed by Aerojet Rocketdyne, the RS-68 features a simplified design with fewer parts, resulting in lower risk and inherently reliable operation. The Delta IV also utilizes a 5-meter diameter payload fairing and an advanced avionics system.
The Rise of the Delta IV Heavy
The Delta IV Heavy, the most powerful variant of the Delta IV family, made its debut on December 21, 2004. Although the demonstration flight experienced an early shutdown of the boosters and core stage, leading to a lower-than-planned orbit, it still marked a significant milestone in the program’s history.
The Delta IV Heavy consists of three Common Booster Cores (CBCs) strapped together, each powered by an RS-68A engine. At liftoff, the three cores generate a combined thrust of 2.1 million pounds (9,420 kN), making it one of the most powerful rockets in operation. The rocket’s distinctive orange foam insulation and the fiery ignition of the hydrogen-rich exhaust have earned it the nickname “the most metal of rockets” from ULA.
Memorable Missions
Over its 15-year operational history, the Delta IV Heavy has launched numerous critical missions for the U.S. government and NASA. One of the most notable missions was the launch of NASA’s Parker Solar Probe in August 2018. The Delta IV Heavy successfully delivered the spacecraft, designed to study the Sun’s outer corona, on a trajectory that would take it closer to the Sun than any previous mission.
Another significant mission was the Orion EFT-1 (Exploration Flight Test-1) in December 2014. The Delta IV Heavy launched NASA’s Orion spacecraft on a two-orbit test flight, paving the way for future crewed missions to the Moon and beyond.
The Delta IV Heavy has also been a reliable workhorse for the NRO, launching classified payloads critical to national security. These missions have showcased the rocket’s ability to deliver heavy payloads to a variety of orbits with unparalleled precision.
The Final Launch
As ULA prepares for the final launch of the Delta IV Heavy, the NROL-70 mission, emotions are running high among the team members who have worked on this remarkable rocket. The launch, scheduled for March 28, 2024, from Space Launch Complex-37 at Cape Canaveral Space Force Station, will mark the end of an era for the Delta family.
The NROL-70 mission, like many of the Delta IV Heavy’s previous flights, will carry a classified payload for the NRO. As the rocket soars into the Florida sky one last time, it will be a bittersweet moment for all those who have been a part of its incredible journey.
The Legacy Lives On
While the Delta IV Heavy may be retiring, its legacy will live on through the next-generation Vulcan Centaur rocket. ULA has incorporated lessons learned and technologies developed during the Delta IV program into the design of the Vulcan, ensuring that the new rocket will build upon the success of its predecessor.
The Vulcan Centaur, which made its debut in 2023, will take over the heavy-lift duties from the Delta IV Heavy. With its more powerful engines, increased payload capacity, and innovative features like reusable engine sections, the Vulcan represents the future of ULA’s launch capabilities.
Conclusion
As we bid farewell to the Delta IV Heavy, it is essential to recognize the countless individuals who have contributed to its success over the years. From the engineers who designed and built the rocket to the launch teams who ensured each mission’s success, the Delta IV Heavy’s achievements are a testament to their dedication and expertise.
The Delta IV Heavy will forever hold a special place in the annals of spaceflight history. Its powerful launches, unmatched reliability, and ability to deliver critical payloads have made it an invaluable asset to the United States’ space program. As it takes to the skies one final time, we celebrate the Delta IV Heavy’s remarkable legacy and look forward to the exciting future of space exploration.
