Delta IV Heavy rocket
A Delta IV Heavy rocket sits in its mobile service tower at Space Launch Complex-6 on south Vandenberg Air Force Base. The next liftoff attempt will occur at 11:05 a.m. Saturday, United Launch Alliance representatives said. (United Launch Alliance photo)

With the cause of a small but stubborn hydrogen leak found and fixed, the Delta IV Heavy rocket will shoot for a Saturday morning blastoff at Vandenberg Air Force Base.

Liftoff is planned for 11:05 a.m. Saturday from Space Launch Complex-6 on South Base, the Delta IV rocket’s manufacturer, United Launch Alliance, announced Tuesday morning.

Since the rocket will carry a top-secret payload for the National Reconnaissance Office, the actual launch window will not be released, but is expected to be less than a hour.

This mission, dubbed NROL-71, has been delayed several times since Dec. 7 due to assorted technical troubles and unfavorable weather. 

The team canceled the last countdown attempt Dec. 19 after detecting a hydrogen leak that ULA’s leader CEO Tory Bruno has since described as “stubborn to isolate.”

Bruno, a Cal Poly graduate, said the leak would only appear at cryogenic temperatures, making it more problematic to find and fix. 

“The real problem was that it didn’t leak at all at ambient (temperatures),” Bruno said on Twitter. “Had to wet the system and cool to cryo temps to get it to leak so we could find it. We had a similar issue about 10 years ago.”

What once had been a post-sunset departure now will occur in the late morning to ensure the payload’s proper placement in space.

For safety reasons, Jalama Beach County Park, just south of Vandenberg, will be evacuated for several hours prior to the launch.

Space Launch Complex-6, once planned for the West Coast space shuttle program that was canceled before any launch, sits in a valley and is not visible from off-base viewing sites.

However, several spots around the Lompoc Valley offer views of South Base launches including the peak of Harris Grade Road, the intersection of Moonglow and Stardust roads in Vandenberg Village and the western end of Ocean Avenue.

The Delta IV Heavy rocket is on track to be the second launch of 2019 from Vandenberg, following the Space Exploration Technologies Falcon 9 rocket blastoff with the final 10 Iridium Next satellites Jan. 11.

Noozhawk North County editor Janene Scully can be reached at Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.

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Janene Scully | Noozhawk North County Editor

Noozhawk North County editor Janene Scully can be reached at