Just launching the satellites could cost between $161 billion and $542 billion, the Congressional Budget Office warned two weeks ago. Both estimates were based on the old SDI proposal; Golden Dome will likely require more satellites and more money for costs that could rise to $831 billion over two decades.

The Pentagon has submitted small, medium and large options to the White House for developing “Golden Dome,” President Donald Trump’s vision for a cutting-edge missile shield that can protect ...