Why It Matters

The Senate Armed Services Committee's Subcommittee on Strategic Forces held a Sept. 29 hearing to review an update on the Trump administration's Golden Dome missile-defense initiative. The hearing focused on the program's costs and whether building the system could trigger an arms race.

The hearing revealed a stark divide between the administration's cost estimate and CBO's estimate for the hypothetical national missile defense system, even though the two figures cover different time periods and potentially different architectures. The Golden Dome program office estimates the objective architecture will cost about $185 billion through 2035, while the administration requested about $17.5 billion for Golden Dome in fiscal 2027.

However, CBO estimated that a national missile defense system with capabilities broadly consistent with President Donald Trump's executive order would cost about $1.2 trillion to develop, deploy, and operate over 20 years. CBO produced that estimate without access to the Pentagon's objective architecture, which remains classified. CBO also acknowledged that the Defense Department's $185 billion figure covers a shorter time frame and may reflect a different scope of activities and budget categories.

The Big Picture

The hearing stemmed from uncertainty about Golden Dome's architecture, cost, effectiveness, and schedule, with the program's classified design limiting lawmakers' ability to evaluate it. Reuters reported that, one year after the initiative launched, Golden Dome had shown little visible progress because of technical disputes and disagreements over space-based components. In April, the U.S. Space Force awarded contracts worth up to $3.2 billion to 12 companies to develop space-based interceptors. The Federal News Network reported that lawmakers remained largely in the dark about the program's architecture more than a year after it was announced. CBO Director of National Security Analysis David E. Mosher told the hearing that CBO received its first briefing from the Golden Dome program office only the Friday before the session.

What They're Saying

Mosher said CBO estimated the system "would cost about 1.2 trillion dollars to build and operate over 20 years," broken down as $740 billion for a space-based boost-phase interceptor layer, $270 billion for ground-based defenses, and $180 billion for other activities, including deploying a sensor system and conducting research and development. He acknowledged the figure is "very different than" the $185 billion estimate and stressed that it carries "considerable uncertainty."

David J. Trachtenberg, a senior scholar at the National Institute for Public Policy, said, "There is also an unfortunate tendency to confuse cost with value," and called it "disingenuous" to suggest that extreme cost estimates make Golden Dome unaffordable.

Sen. Mark Kelly (D-AZ) raised the concern that if Russia and China believe Golden Dome could reduce the effectiveness of their retaliatory forces, they could respond by expanding their arsenals or developing new ways to penetrate U.S. defenses. Trachtenberg said, "I think the logical thing for them to do would be not to consider attack in the first place." Kelly countered: "We spent $1.2 trillion on a system that then becomes irrelevant… People don't have health care coverage. They can't afford their lives anymore."

Thomas O. Karako, director of the Missile Defense Project at the Center for Strategic and International Studies (CSIS), said Golden Dome "suffers from a serious lack of strategic messaging, an explanation of what it is and what it's trying to do."

Political Stakes

Chair Sen. Deb Fischer (R-NE) asserted the committee's ownership of the concept: "While President Trump has named Golden Dome, the focus for this layered missile defense system came from the Senate Armed Services Committee… So it came from us." Federal News Network reported Fischer said "a lot of work has to be done" to build broad congressional support.

Sen. Christopher Murphy (D-CT) tied the program's viability to alliance management, saying: "It's unrealistic to expect that you can treat an ally badly in one domain on the economy… but expect… we really need to work cooperatively in terms of our defense." Mosher added that, to his understanding, "an agreement hasn't been reached with Canada yet on Golden Dome."

The strategic debate extends beyond the hearing. CBO said a national missile defense system could prompt regional adversaries to increase their long-range missile inventories or pursue more effective countermeasures. It said Russia and China could already overwhelm the notional system it analyzed with large-scale attacks, although they could still increase their arsenals to ensure they retained that capability.

The Bottom Line

As of Oct. 1, the hearing record lists no associated legislation or formal follow-up outcome. The government is operating under a continuing resolution through Dec. 11, generally continuing funding at prior-year levels while Congress considers full-year appropriations. That leaves fiscal 2027 funding as a central near-term issue for Golden Dome. Karako warned that "all these efforts will stand or fall on 2027 funding."

The hearing leaves a central question raised by senators unresolved: how Congress should evaluate and fund a program whose underlying design remains classified. The cost debate is also unsettled: the Pentagon's estimate of approximately $185 billion and CBO's estimate of $1.2 trillion cover different time frames and may assume substantially different missile-defense architectures.

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