The final flight of United Launch Alliance's Delta IV Heavy rocket took off Tuesday from Cape Canaveral, Florida, with a classified spy satellite for the National Reconnaissance Office.
The Delta IV Heavy, one of the world's most powerful rockets, launched for the 16th and final time Tuesday. It was the 45th and last flight of a Delta IV launcher and the final rocket named Delta to ever launch, ending a string of 389 missions dating back to 1960.
United Launch Alliance (ULA) tried to launch this rocket on March 28 but aborted the countdown about four minutes prior to liftoff due to trouble with nitrogen pumps at an off-site facility at Cape Canaveral. The nitrogen is necessary for purging parts inside the Delta IV rocket before launch, reducing the risk of a fire or explosion during the countdown.
The pumps, operated by Air Liquide, are part of a network that distributes nitrogen to different launch pads at the Florida spaceport. The nitrogen network has caused problems before, most notably during the first launch campaign for NASA's Space Launch System rocket in 2022. Air Liquide did not respond to questions from Ars.
A flawless liftoff
With a solution in place, ULA gave the go-ahead for another launch attempt Tuesday. After a smooth countdown, the final Delta IV Heavy lifted off from Cape Canaveral Space Force Station at 12:53 pm EDT (16:53 UTC).
Three hydrogen-fueled RS-68A engines made by Aerojet Rocketdyne flashed to life in the final seconds before launch and throttled up to produce more than 2 million pounds of thrust. The ignition sequence was accompanied by a dramatic hydrogen fireball, a hallmark of Delta IV Heavy launches, that singed the bottom of the 235-foot-tall (71.6-meter) rocket, turning a patch of its orange insulation black. Then, 12 hold-down bolts fired and freed the Delta IV Heavy for its climb into space with a top-secret payload for the US government's spy satellite agency.