Golden Dome would cost $1.2 trillion under current plans, CBO finds

The Golden Dome missile-defense system would cost $1.2 trillion to build out, far more than the White House has budgeted, according to a new estimate by Congressional researchers.

The figure is roughly double the Congressional Budget Office’s initial assessment of Golden Dome, based on the expansive yet vague executive order issued in the busy first week of the second Trump administration. It’s nearly seven times larger than President Trump’s original promise to build it for $175 billion.

And it’s fifteen times larger than the $79 billion the administration plans to spend in the Golden Dome for America account over the next five years, which excludes other-related missile defense funding.

“The system would provide significantly expanded defensive capabilities but would not be impenetrable, particularly against large-scale attacks from peer adversaries,” the office said in an emailed statement. “CBO’s estimate is substantially higher than publicly cited administration figures, which may reflect differences in scope, time frame, and assumptions.”

In the last two months, Golden Dome’s budget has swelled by $10 billion. And the program’s leader has conceded that space-based interceptors, a cornerstone of the proposed missile shield, may be too costly to build.

The bulk of the funds—about $730 billion—would purchase only enough space-based interceptors to destroy about 10 incoming ballistic missiles.

The new CBO assessment was requested by Sen. Jeff Merkley, D-Oregon.

The $1.2 trillion estimate is not far off from a projection published by Todd Harrison, a defense budget analyst and space expert with AEI. In September, Harrison wrote that roughly $1 trillion over two decades could buy enough space-based interceptors to take out five missiles in the boost phase, 50 hypersonic weapons in the glide phase, and 50 warheads in midcourse. The sum would also purchase nearly 150 missile-warning and -tracking satellites, 10 Ground-Based Midcourse Defense battalions, 10 Patriot batteries, eight THAAD batteries, and two Aegis Ashore sites.

But the administration’s $185 billion budget won’t buy anywhere close to that, Harrison said.

“The fact that CBO’s estimate is almost an order of magnitude higher than what the administration says it will cost can only mean one thing: the administration is not actually building what the executive order described,” he said. “The CBO analysis and my previous analysis both demonstrate that the homeland missile defense you can buy for $185 billion is an incremental improvement over what we have today but not an impenetrable shield that will forever end the missile threat to the United States.”

The Trump administration has leaned heavily on funds outside the baseline defense budget to make Golden Dome a reality. Last year, the Pentagon netted $24 billion in reconciliation funds for the program. For the 2027 defense budget, the administration requested more than $17 billion from the same funding source and just $400 million from the annual Pentagon budget.

Additional reconciliation funds are not guaranteed, but the administration has projected future support in the baseline budget — the Pentagon plans to request an estimated $14.7 billion in the 2028 budget and projects it to rise to $16 billion by 2031, according to the American Enterprise Institute data.

Last year’s Golden Dome executive order called for fielding the “development and deployment” of space-based interceptors that can hit a missile within minutes of its initial launch. But physics shows that weaving a defensive web to stop any number of missiles from anywhere would require tens or hundreds of thousands of satellites.

Space interceptors, as the CBO’s estimate points out, are the most expensive component. Space Force Gen. Michael Guetlein, the program’s leader, told lawmakers last month that he’s focused on staying within the budget and said, “If we cannot do it affordabl[ly], we will not go into production” on boost-phase space-based interceptors.

In light of the new estimate, Harrison said, Congress should have serious doubts about prioritizing and funding space-based interceptors instead of focusing on more attainable homeland security defenses.

“One of the lingering questions for Congress is: why are we still funding [space-based interceptor] development? Prototyping the system and maturing the technology will not prove or disprove its ability to scale with the threat—scalability is a matter of orbital mechanics, and the prototyping effort does nothing to change that,” Harrison said. “SBIs do not scale. We are throwing away billions of dollars on a system with no future, when that money could instead be used to buy more of the ground-based interceptors and drone defenses we are in desperate need of today that do scale with threats.”