April 2: This article has been updated to include a new launch date.
The Delta IV Heavy rocket’s ignition is probably the most visible liftoff you’ll ever see — the rocket appears to burn itself up on the launchpad before it heads into space. Today, the latest Delta IV Heavy is on the launchpad.
Liftoff is scheduled for 2:45 pm Eastern time from Cape Canaveral, Fla. Less than four minutes before launch, flight controllers paused the countdown due to an issue with a component that provides pneumatic pressure to the rocket.
After a Friday launch time was announced, United Launch Alliance, the rocket’s maker, provided an update Thursday evening in a statement, saying “more time is needed to instill confidence in the system,” before another flight attempt. In an email released Tuesday, the company said it will try to launch the rocket again on April 9 at 12:53 pm Eastern time.
Before Thursday’s scrubbed flight, ULA officials shared their feelings about the Delta IV Heavy, which will carry a secret spy satellite for the National Reconnaissance Office on its final mission.
“It’s a bittersweet moment for us,” Tory Bruno, the company’s chief executive, said at a news conference Wednesday. “It’s an amazing piece of technology. Twenty-three stories high. Half a million gallons of propellant. Two and a quarter million pounds of thrust.”
When it launches, it will look like it’s on fire, with fire billowing out the sides. That is by design.
The Delta IV Heavy burns ultracold liquid hydrogen, which is a high-performance fuel. In the final part of the countdown, to cool the engines and prevent sudden temperature shocks that could cause cracks, liquid hydrogen begins to flow through the engine into the flame trench.
But when hydrogen is heated above its boiling temperature of minus 423.2 degrees Fahrenheit, it turns into a gas. Hydrogen is lighter than air and rises upward. When the engines ignite, so does the hydrogen cloud – like a space-age Hindenburg.
“A very dramatic effect,” Mr. Bruno said.
Of course, the rocket designers took this into account and applied enough insulation to the boosters to keep the rocket from burning. The orange shade of that exterior takes on a burnt-marshmallow glow as the rocket leaves Earth.
“And he left,” said Mr. Bruno.
United Launch Alliance images. Mobile photo illustration by Antonio de Luca.
