The ignition of the Delta IV Heavy rocket is perhaps the most visually impressive launch ever seen. The rocket appears to burn up on the launch pad before heading into space. Now, the last Delta IV Heavy in history is on the launch pad.
The launch was scheduled for 2:45 p.m. ET from Cape Canaveral, Florida. Flight controllers paused the countdown four minutes before liftoff due to a problem with a component that provides air pressure to the rocket.
After Friday's launch time was announced, the rocket's manufacturer, United Launch Alliance, provided an update in a statement Thursday night, saying it would take “more time to instill confidence in the system” before the next flight attempt. It's necessary.'' No schedule was set for when the work would be completed.
Ahead of Thursday's unmanned flight, ULA officials shared their thoughts on the Delta IV Heavy, which will carry the National Reconnaissance Agency's secret reconnaissance satellite on its final mission.
“This is a bittersweet moment for us,” CEO Tori Bruno said at a press conference Wednesday. “This is a very impressive piece of technology. Twenty-three stories high. 500,000 gallons of propellant. 2.5 million pounds of thrust.”
When fired, flames come out from the sides, making it look like it's on fire. That's by specification.
The Delta IV Heavy burns cryogenic liquid hydrogen, a high-performance fuel. During the final part of the countdown, liquid hydrogen begins to flow through the engine and into the flame groove to cool the engine and prevent sudden temperature shocks that could cause cracks.
However, when hydrogen exceeds its boiling temperature of -423.2 degrees Fahrenheit, it turns into a gas. Hydrogen is lighter than air, so it rises to the top. When the engine ignites, it also ignites a cloud of hydrogen, like a space-age Hindenburg.
“It's a very dramatic effect,” Bruno said.
Rocket designers naturally took this into account and put enough insulation in the booster to prevent the rocket from actually burning out. As the rocket leaves Earth, its outer orange hue takes on a burnished marshmallow-like sheen.
“And then she leaves,” Bruno said.
Photo courtesy of United Launch Alliance. Mobile photography illustration by Antonio De Luca.