Orbiting in space, American satellites detect the bright flames. While the missile is still in its “boost” phase, one of a network of space-based interceptors fires down a laser, or alternative munition, to blow up the threat. America sleeps soundly, protected by its Golden Dome.

US President Donald Trump's plan for a nationwide missile defense system -- dubbed "Golden Dome" -- faces significant technical and political challenges, and it could cost far more than he has estimated to achieve its goals.