The Congressional Budget Office estimates that a hypothetical space-based interceptor constellation for a national missile defense system could cost approximately $720 billion to develop, deploy, and maintain over 20 years.

The estimate comes from a May 2026 CBO report examining the potential cost of a missile defense architecture broadly consistent with the objectives outlined in President Donald Trump’s executive order establishing the Golden Dome for America. The Pentagon has not publicly released the full architecture it intends to build, so CBO developed a notional system to illustrate potential costs.

CBO estimates the complete four-layer system would cost approximately $1.2 trillion over 20 years, with the space-based interceptor layer accounting for roughly 60% of total costs and about 70% of acquisition costs.

The hypothetical space-based layer would consist of approximately 7,800 satellites in low-Earth orbit, positioned roughly 300 to 500 kilometers above Earth. CBO designed the constellation to defend against a scenario involving 10 nearly simultaneous intercontinental ballistic missile launches, with two interceptor shots assigned to each missile.

Each satellite would cost an average of approximately $22 million. Because atmospheric drag would limit the satellites' operational lifespans to roughly five years, CBO estimates that about 1,600 replacements would be needed each year. Maintaining 7,800 satellites in orbit for two decades would therefore require roughly 30,000 satellites over the life of the system.

CBO estimates that operating the space-based interceptor layer would cost an additional $1 billion annually. Launch expenses would account for less than 5% of the layer's total cost under CBO's assumptions, which use a launch price of $500 per kilogram—below current typical costs but potentially achievable with newer heavy-lift rockets.

The remaining components of CBO's hypothetical system would be considerably less expensive. The agency estimated approximately $69 billion for a space-based missile tracking constellation, while the various surface-based interceptor layers would account for hundreds of billions more.

The CBO estimate is substantially higher than the $185 billion figure publicly cited by the Golden Dome program office for an architecture to be deployed over a decade. CBO said the difference could indicate that the government's planned system will be more limited than the hypothetical architecture it modeled, that other federal accounts would cover some expenses, or both.

CBO also emphasized that its estimate carries substantial uncertainty. Space-based interceptors have never been deployed, and the costs could change significantly depending on technological advances, production rates, and the size of the constellation ultimately selected.

The report therefore does not establish that President Trump's Golden Dome program will cost $1.2 trillion or that its space-based component will cost $720 billion. Instead, it provides an estimate for one potential national missile defense architecture while the administration continues developing its plans.