While Pentagon officials have revealed some details about the architecture behind the Golden Dome missile defense project, crafting an independent cost estimate for a largely classified program remains a challenge, experts said Aug. 19.
President Donald Trump issued an executive order in January 2025 directing the Pentagon to build a multilayered missile defense shield to protect the U.S. from traditional and advanced missile threats, to include hypersonic weapons. Defense Department officials have said the system will consist of command-and-control nodes, satellite sensors, and ground-and- space-based interceptors, but the finer details of that architecture—including numbers of satellites and interceptors—remain shrouded in secrecy.
The Pentagon has said it expects the program to cost $185 billion to build over the next 10 years, but think tank experts and government analysis have argued the bill for what Trump’s executive order articulated will likely be much higher. One of the first outside estimates, released last year by the American Enterprise Institute, projected costs ranging anywhere from $250 billion to $2.4 trillion. In May, the Congressional Budget Office pegged the program’s cost at $1.2 trillion.
These wide-ranging projections point to the lack of a common, unclassified understanding of what systems and technology will underpin the program, which experts said is the fundamental challenge of estimating Golden Dome’s cost.
Speaking at a Brookings Institute event, CBO’s Director of National Security Analysis David Mosher said the organization was tasked by lawmakers to put a price tag on the scope laid out in Trump’s initial executive order rather than try to estimate what the Golden Dome program office is actually building—an important distinction.
“The Golden Dome they’re building is perhaps different than the Golden Dome in the executive order,” Mosher said. “We couldn’t have costed what they’re building because nobody knows what they’re building yet.”
With the executive order as the baseline, the report constructed an architecture with the elements included in Trump’s directive and then sized it “to protect what we thought was a sort of plausible, relatively large attack from North Korea, or a modest attack from Russia or China,” Mosher said. The resulting notional architecture features four interceptor layers designed to target multiple missile types and to operate either independently or in concert with an associated command-and-control network:
- A space-based constellation of 7,800 satellites designed to take out up to 10 intercontinental ballistic missiles launched near simultaneously as well as hypersonic glide vehicle threats
- An upper wide-area surface layer comprised of three Ground-Based Midcourse Defense sites, each with 60 Next-Generation Interceptors or Ground-Based Interceptors focused on engaging ICBM threats
- A lower wide-area surface layer with four U.S.-based sites, each equipped with 48 SM-3 Block IIA interceptors to defeat ICBMs or hypersonic glide vehicles
- A “regional sector” layer with 35 interceptor and radar sites loaded with THAAD, SM-6 Block IB, and Patriot interceptors that can target ICBMs, glide vehicles, and cruise missiles
The space-based interceptor constellation would be the most expensive element of this architecture by far, costing $743 billion over 20 years, or 60 percent of the total cost. The report, which calls its architecture a “middle ground” between more limited and high-end alternatives, estimates each SBI-equipped satellite would cost $22 million and have a five-year service life.
CBO’s report also includes the cost of a satellite sensing layer—which it projects would require about $90 billion to develop, field, and maintain—as well as the battle management and communication systems needed to coordinate the broader architecture. The sensing layer would include satellites such as the Hypersonic and Ballistic Tracking Space Sensor, which the Space Development Agency is fielding as part of its low-Earth orbit missile-tracking constellation, and space-based air moving target indication satellites, which the Space Force is currently developing.
Golden Dome Director Gen. Michael Guetlein has pushed back on CBO’s estimates, saying they’re built on inaccurate assumptions about what his team is actually building. According to Guetlein, the report’s assumptions are based on technology envisioned in the early 2000s “for a different fight”—one focused on point defense, or defense of a limited area, rather than the regional, homeland defense mission that underpins Golden Dome.
“That is not what we need for the homeland,” he said in May. “In a regional defense, there’s a different architecture. And you can’t just take what we’ve done in the past and multiply it forward or you’re going to get large numbers like CBO got.”
Mosher acknowledged the report is detached from the program office’s architecture, pointing out multiple times that CBO and the general public do not have access to those details. He said CBO has asked for briefings but hasn’t been able to meet with program officials.
“I know nothing about what they’re actually building except what I read in publications,” Mosher said.
According to Guetlein, a key difference between the architecture envisioned in the CBO report and what the Pentagon is pursuing through Golden Dome is the use of “next-generation” technology like AI, advanced computing, and directed energy.
Mosher said that for the most part, the report used existing systems as a baseline because they’re a known quantity. He said it’s true that harnessing advanced technology could lower costs over time, especially for some space-based elements of the architecture. However, other technologies like high-energy lasers in space aren’t yet ready for prime time, which means it’s likely not a near-term differentiator.
“We tend to estimate what we see,” he said. “New technologies might provide the opportunity for that, I think we mentioned that as a possibility, but it’s not what you would have in the near term, which is what they’re trying to do.”