The big Delta IV Heavy rocket will try to loft a classified mission tonight

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  Delta IV Heavy nestled in its Mobile Service Tower before launch of the NROL-44 mission for the National Reconnaissance Office. [credit: Trevor Mahlmann ]

Is anyone ready to see a heavy-lift rocket take flight? Especially one that creates a giant fireball mere seconds before liftoff?

United Launch Alliance's largest booster, the Delta IV Heavy, has not launched since January, 2019. Now the big rocket-the second-most-powerful launch vehicle in the world after SpaceX's Falcon Heavy-is back on the pad to loft a classified payload for the National Reconnaissance Office.

Liftoff of this "NROL-44" mission is scheduled for 2:12am EDT (06:12 UTC) on Thursday from Space Launch Complex-37 at Cape Canaveral Air Force Station. The weather forecast for liftoff is favorable, with only a slight concern for a chance of violating the cumulus cloud rules. Forecasters predict an 80-percent chance of good weather at the launch opportunity.

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