After delay, Delta IV Heavy lifts off for the last time

ORLANDO, Fla. — The storied career of the Delta family of rockets had to wait a little longer than planned to turn the page on its final chapter, but the last of its kind lifted off on the Space Coast on Tuesday.

A United Launch Alliance Delta IV Heavy, the largest and most powerful version of Delta rockets, launched from Cape Canaveral Space Force Station’s Space Launch Complex 37 at 12:53 p.m. Eastern time. Dubbed the NROL-70 mission, the classified payload is for the National Reconnaissance Office.

The rocket had come within four minutes of the countdown clock hitting zero back on March 28, but teams discovered an issue with a pipeline of gaseous nitrogen used to supply the inert gas needed for safe operations on liftoff that took several days to remedy before ULA and its customer were OK to try again.

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

This final launch makes 389 launch attempts through a series of rocket design changes. The Delta II retired in 2018 with the last medium-lift version of the Delta IV flying in 2019. The Delta IV Heavy, which had flown 15 times before this launch since its debut in 2004, was the lone remaining rocket of the Delta family. They are making way, along with the final 17 Atlas V rockets, for ULA’s Vulcan Centaur rocket that debuted in January.

“It’s a bittersweet moment for us. This is such an amazing piece of technology,” said ULA President and CEO Tory Bruno. “It’s the most metal of rockets setting itself on fire before it goes to space.”

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

The way the propellant flows ahead of liftoff creates a massive fireball on the launch pad.

This also marks the final ULA launch for SLC 37, which is being considered as a future home for SpaceX Starship and Super Heavy launches.

“Retiring it is obviously the future for a less expensive, higher performance rocket. It’s still sad. However it is an honor for us to serve these missions,” Bruno said.

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