The United States is estimated to have spent more than $400 billion on the kinds of antimissile goals that the president now says will provide “for the common defense.”

The first Trump administration floated a space weapon concept in March 2018: a neutral particle beam in space. But it ultimately shelved the idea because of the massive amount of power needed to destroy a missile with directed energy.

Producing an Iron Dome large enough to cover the continental United States would be a very costly project. U.S. president Donald Trump has followed through on his earlier pledge to develop a homegrown “Iron Dome-like shield” for missile defense in America.