NASA Said to Tap Boeing-Lockheed’s Vulcan for Top of Moon Rocket

NASA intends to select United Launch Alliance to provide a critical component for future missions of the agency’s moon rocket, according to people familiar with the matter, replacing planned Boeing Co.-built hardware as costs ballooned to $2.8 billion.

Boeing — which manufactures the core of NASA’s massive Space Launch System, or SLS, rocket — also holds a multibillion-dollar contract from the agency to create an upgraded version of the vehicle.

That contract entailed building a powerful upper portion of the rocket, known as the Exploration Upper Stage, that was meant to debut on the rocket’s fourth flight.

But on ...