After a delay, the Delta IV Heavy lifts last

The storied life of the Delta family of rockets had to wait a little longer than planned to turn the page on its final chapter, but its last type was lifted off the Space Coast on April 9.

A United Launch Alliance Delta IV Heavy, the largest and most powerful version of the Delta rockets, lifted off from Space Launch Complex 37 at the Cape Canaveral Space Force Station at 12:53 p.m. ET. The classified payload, called the NROL-70 mission, was for the National Reconnaissance Office.

The rocket arrived within four minutes of the countdown clock hitting zero on March 28, but crews discovered a problem with the pipeline of gaseous nitrogen used to supply the inert gas needed for safe operations of liftoff, which took several days to resolve before ULA and ULA. Its customers can try again.

The first Delta rocket attempted to launch in May 1960 when Dwight Eisenhower was president. They have been responsible for launching Mars rovers, space telescopes, solar probes, weather satellites and more during their 63-year run.

This final launch made 389 launch attempts through rocket design changes. Delta II The last medium-lift version of the Delta IV flew in 2019 and was retired in 2018. The Delta IV Heavy, which flew 15 times before this launch since its debut in 2004, is the surviving rocket of the Delta family. They make their way to ULA's Vulcan Centaur rocket, which debuted in January, along with the final 17 Atlas V rockets.

„This is a bittersweet moment for us. This is an amazing technology,” said ULA President and CEO Tory Bruno. „It's metal that ignites itself in rockets before they go into space.”

The Delta IV Heavy has three main boosters powered by cryogenic liquid hydrogen and liquid oxygen that generate more than 2.1 million pounds of thrust upon liftoff.

The flow of propellant ahead of liftoff creates a large flare on the launch pad.

It also marks the final ULA launch for SLC 37, which is envisioned as the future home for SpaceX starship and superheavy launches.

„Retiring this is the future of low-cost, high-performance rockets. It's still sad, but it's an honor for us to serve these missions,” Bruno said.

The first Delta launch attempt was on May 13, 1960, from Canaveral's Space Launch Complex 17. Its design was born from the Thor intermediate-range ballistic missile and could send a 400-pound payload into low-Earth orbit. It was then 90 feet tall and weighed 112,000 pounds.

Among its payloads over the years, Delta rockets have launched NASA's Pioneer and Explorer spacecraft, the first Mars rover Sojourner on the Pathfinder mission and the twin rovers Spirit and Opportunity, the Dawn mission to Ceres and Vesta, and the Deep Impactor that crashed into a comet. Temple 1.

They have launched the Spitzer and Kepler space telescopes, the Parker Solar Probe, NOAA's GOES satellites, and dozens of GPS satellites.

While many Delta IV Heavy flights are classified as missions for the military, it was the rocket that sent the Orion spacecraft back on its test mission in 2014 on the EFT-1 mission, which is now the precursor to the Artemis missions to Orion. Flies.

The last Delta IV heavy mission was reclassified as an NRO satellite „strengthening NRO's ability to provide support to national decision makers, warfighters, and intelligence analysts to protect the nation's vital interests and support global humanitarian efforts. .”

2024 will be the 25th launch from the Space Coast, but the second for ULA since the Vulcan launch in January. The company has only flown three times by 2023, while rival SpaceX has amassed 98 orbital launches at its Florida and California launch sites.

The coming years promise to be exciting for ULA.

ULA still has 17 Atlas V rockets in its stable, including seven Boeing CST-100 Starliners assigned to bring crews to the International Space Station for missions. The first test flight with humans is scheduled as early as May 6, with operational missions that could fly once a year from 2025-2030.

Eight more Atlas V rockets are earmarked to launch satellites for Amazon's Project Kuiper Internet constellation. Two other Atlas V missions are slated for its final Space Force flight later this year and a private communications satellite in 2025.

Meanwhile, ULA is upgrading the Vulcan Centaur hardware with its next mission this summer to fly Sierra Space's Dream Chaser cargo spacecraft to the ISS. It also serves as the second certification flight for Vulcan, opening up space force missions on its plate.

„All the hardware I'm building right now in my supply chain and in a factory with four or five boosters … is good to go,” Bruno said.

He said the goal is to launch from the Cape once every two weeks.

„We're really moving forward, so we can build inventory and then come into that as the infrastructure comes online,” he said. Here at the Cape, the most important and visible thing is an entirely different vertical integration facility … integrating interceptor rockets. So now there will be two paths, so we will build two rockets at the same time.

Among them are dozens of launches for Project Kuiper, which is slated to fly before 2026.

„We feel really good about the ramp up,” Bruno said. „I'm not going to tell you, it's going to be tight in '24 and '25, but we're on track and we're confident we'll hit that tempo when we get late next year. .”