Delta IV Heavy set to launch on farewell flight from Cape Canaveral Tuesday

Again, the time has come.

The Delta IV Heavy rocket is stated to make its final flight at 12:53 p.m. on Tuesday, April 9, from Cape Canaveral Space Force Launch Complex 37.

This comes after its first attempt at a finale flight scubbed four minutes before the planned March 28 launch. There was hope the problem of gaseous nitrogen pump failure would be a quick fix, and the rocket would fly within days but now more than a week later, it's ready.

With the FAA airspace showing a cleared range for the launch window, and a 90% chance of favorable launch weather as of Monday, the question remains: Will Tuesday be the day Delta IV Heavy flies for the final time?

Delta IV Heavy launch: Updates from historic last flight from Cape Canaveral, Florida

What caused the Delta IV Heavy's scrub last month?

During the last launch attempt on March 28, rain, wind, and cloud cover made itself known over the Cape Canaveral area during much of the early afternoon. For stretches of time, it appeared weather would not cooperate.

But as the countdown clock continued to move, spectators waited with high hopes as the troublesome weather began to push out of the area. Those hopes turned into skepticism as a weather hold was placed at T- 4 minutes to launch.

After announcing the countdown would resume, ULA announced a scrub before the clock even had a chance to move. Spectators were left wondering what had gone wrong.

What originally was called a possible 24-hour turn around became an indefinite wait as Tory Bruno, ULA’s CEO and President, took to X (formerly Twitter) to announce that the "GN2 pipeline ground pump had failed" during the T-4 minute weather hold.

Don't miss another launch: Is there a launch today? Upcoming rocket launch schedule for SpaceX, ULA, NASA in Florida

A next day attempt was soon unlikely to happen, as Bruno announced on X later that evening that the pump had failed yet again. ULA stated that a new launch date was uncertain at the time.

Bueno said on X, "NASA operates a GN2 pipeline as a service to several pads. And, yes, there is a 'gas meter' so companies pay for what they use. The issue is with pumps on that pipeline. They are working it hard right now," explaining that this was not an issue with the rocket itself.

The final Delta IV Heavy launch date and the rise of the Vulcan

The Delta IV Heavy set to take its final flight is, in simple terms, three Delta IV rockets bolted together to make a super-lift rocket. Onboard is a secretive payload for the NRO, making this mission's name NROL-70. Very little information is available about the mission. What is known: its emblem is a snow leopard.

“The snow leopard illustrates the quiet strength with which we provide an advantage to the nation and its allies," the NRO said in a press release.

Read more about the Delta IV: Final Flight: What made ULA's Delta IV Heavy stand apart from other rockets?

This will be not only the last Delta IV Heavy to fly, but the final in ULA’s Delta family of rockets.

The Deltas have been workhorses, and the Delta IV Heavy in particular. Among its claim to fame: transportation of the NASA Parker Solar Probe in 2018 and the first orbital test flight of the Orion crew capsule in 2014. The rocket has never carried astronauts to space.

ULA is retiring the Delta, and soon the Atlas, to focus on its newest vehicle, the Vulcan.

Introducing Delta’s successor: the Vulcan rocket

ULA is counting on the Vulcan to outpreform both former rockets, having powerful lift, the ability to carry both crewed and payload launches, and even to carry two payloads. According to ULA, rocket reusability is also a goal – that's an area in which SpaceX has paved the way among space companies. Reusability is important as it cuts down the cost of launching dramatically.

The Vulcan had a successful flight earlier this year, as it launched the ill-fated Intuitive Machines Lunar Lander, an uncrewed payload mission to the Moon. In the lander’s payload were NASA and student experiments. The Vulcan rocket performed but the Lunar Lander, Odysseus, tipped over after landing on the moon. Still, it became the first U.S. soft landing on the moon since 1972.

Intuitive Machines was just selected by NASA to work on the team which develops their next Lunar Terrain Vehicle (LTV), which would be used by astronauts on Artemis V, according to NASA. The other companies selected were Lunar Outpost and Venturi Astrolab.

ULA has not yet confirmed the next launch date for the Vulcan, but it is slated to carry Sierra Space’s Dream Chaser spaceplane this year.

Delta IV Heavy farewell flight - visible far beyond Space Coast.

On Tuesday, eyes will be on the skies at 12:53 p.m. as ULA has previously said the rocket may be visible from as far as Jacksonville and Miami. Even on the Gulf Coast, there may be sightings.

Rocket enthusiasts have come from all across the country to see this "most metal" rocket launch for one last time. As its three rocket engines fire up, Delta IV Heavy promises a fiery performance before liftoff, as the liquid hydrogen it uses to cool the engines, burns. This makes the rocket appear to set itself on fire before rising up off the launch pad.

FLORIDA TODAY will provide live updates on Tuesday, beginning at least two hours before launch at FloridaToday.com/space. Downloading the FLORIDA TODAY mobile app will also send real time launch alerts to subscribers' smartphones.

As the Delta IV heavy carries its NRO payload into its intended orbit, those who witness this launch are likely to remember it for a lifetime.

Brooke Edwards is a Space Reporter for Florida Today. Contact her at [email protected] or on X: @brookeofstars.

This article originally appeared on Florida Today: ULA's Delta IV Heavy rocket set for fiery final flight Tuesday