Trump estimated the Golden Dome project to cost $175 billion, with a $25 billion down payment. A recent Congressional Budget Office estimate put the total cost of deploying and operating a constellation of space-based interceptors for 20 years at anywhere from $161 billion to $831 billion.

A key part of the new missile defense system, which Trump described as "Golden Dome" in a speech earlier this year, will likely be space-based interceptors, according to experts and an executive ...