The ignition of the Delta IV Heavy rocket might be essentially the most visually striking launch you’ll ever see – the rocket seemingly burns up on the launch pad before flying into space. Now on the launch pad is the last-ever Delta IV Heavy.
Liftoff is scheduled for two:45 p.m. ET from Cape Canaveral, Florida. Less than 4 minutes before the scheduled launch, flight controllers suspended the countdown because of an issue with a component that gives air pressure to the rocket.
After announcing the launch time on Friday, United Launch Alliance, the rocket’s manufacturer, provided an update on Thursday evening in a press release saying that “more time is needed to establish confidence in the system” before one other flight attempt. It didn’t specify a timetable for completing this work.
Ahead of Thursday’s cleared flight, ULA officials shared their impressions of the Delta IV Heavy, which is scheduled to hold a secret spy satellite for the National Reconnaissance Office on its final mission.
“This is a bittersweet moment for us,” Tory Bruno, the corporate’s CEO, said during a press conference Wednesday. “It’s an amazing piece of technology. Twenty-three stories high. Half a million gallons of fuel. Two and a quarter million pounds of thrust.
Once it takes off, it will look like it’s on fire, with flames running down the sides. This is by design.
Delta IV Heavy burns ultra-cold liquid hydrogen, which is a high-performance fuel. At the end of the countdown, to cool the engines and prevent a sudden temperature shock that could cause cracks, liquid hydrogen begins to flow through the engine into the flame trench.
But when hydrogen is heated above its boiling point of minus 423.2 degrees Fahrenheit, it turns into a gas. Hydrogen is lighter than air and floats upwards. When the engines ignite, a cloud of hydrogen ignites – like a space-age Hindenburg.
“A very dramatic effect,” Mr. Bruno said.
The rocket designers, of course, took this into consideration and added enough insulation to the boosters to forestall the rocket from burning up. As the rocket leaves Earth, the orange hue of this surface takes on the sheen of burnt marshmallow.
“And she leaves,” Mr. Bruno said.
Photos: United Launch Alliance. Mobile illustration by Antonio de Luca.
