WASHINGTON — The Congressional Budget Office estimates that a national missile defense system broadly aligned with President Donald Trump’s Golden Dome executive order could cost roughly $1.2 trillion over 20 years, a figure that dramatically exceeds the Pentagon’s public estimate of about $185 billion.
The largest driver of that cost is a proposed constellation of space-based interceptors, or SBIs, which alone would account for about $743 billion. The interceptors would consist of satellites in low Earth orbit designed to destroy ballistic missiles during the “boost phase,” the first few minutes after launch while a missile’s rocket motor is still burning.
The report, released May 12, was prepared at the request of Sen. Jeff Merkley, the ranking Democrat on the Senate Budget Committee. CBO emphasized that the study was not based on a detailed administration blueprint because the Defense Department has not publicly released the architecture it intends to build. Instead, the agency modeled a notional missile defense system derived from the language of Trump’s January 2025 executive order directing the Pentagon to pursue what became known as Golden Dome.
That distinction highlights a disconnect between Congress and the administration over the program. Because CBO works at the direction of Congress, the absence of a detailed Pentagon plan suggests lawmakers still have not received a comprehensive explanation of what the administration intends to field or how it plans to build it.
