The Delta IV Heavy, a rocket whose time has come and gone, will fly once last time.

Good night, sweet prince. 🫡

Launch pushed back a day..

This is the best summary I could come up with:

Now, United Launch Alliance's last Delta IV Heavy rocket is set to lift off Thursday from Cape Canaveral Space Force Station, Florida, with a classified payload for the National Reconnaissance Office, the US government's spy satellite agency.

"This is such an amazing piece of technology, 23 stories tall, a half-million gallons of propellant and a quarter-million pounds of thrust, and the most metal of all rockets, setting itself on fire before it goes to space," said Tory Bruno, ULA's president and CEO.

Weather permitting, the Delta IV Heavy will light up its three hydrogen-fueled RS-68A engines at 1:40 pm EDT (17:40 UTC) Thursday, the opening of a four-hour launch window.

When the engines are finally full and ready to go and we start spinning up the pumps, then we actually drop the main load (of propellant), we ignite it, and that flame carries on up that ... plume of hydrogen, which is clinging to the side of the booster and rising up.”

One of the reasons for this is to protect the rocket from the fireball, leading to a "very dramatic effect of a self-immolating booster" that has the appearance of a "toasted marshmallow" as it heads to space.

Once the Delta IV lets go of its side boosters and falls into the Atlantic Ocean, the center core throttles up and burns for another minute and a half.

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