(Brett Rowland, The Center Square) – President Donald Trump‘s plans for a $175 billion missile defense shield include significant technical challenges and political risks.

Trump outlined plans for his Golden Dome in the Oval Office last week. The system Trump envisions would protect the U.S. and Canada using multiple layers of defense against diverse potential attacks, making it much more complex than previous proposals. The Golden Dome would also include space-based sensors and interceptors that the president said would be able to intercept missiles “even if they are launched from other sides of the world and even if they are launched from space.” 

The president said the missile defense system would be operational before he leaves office in 2029. Trump’s plan is loosely modeled after Israel’s Iron Dome – but on a much larger scale. Israel’s Iron Dome defends a nation the size of New Jersey against short-range missiles built in underground tunnels. Trump’s system would protect a much larger area – North America – against more challenging threats, including intercontinental ballistic missiles and hypersonic weapons.

The Congressional Budget Office, which helps Congress understand the cost of budget proposals, said in a letter earlier this month that lower launch costs could reduce the price tag for deploying a constellation of space-based interceptors designed to defeat one or two intercontinental ballistic missiles fired at the U.S. by a regional adversary, such as North Korea, a nation with limited resources.

CBO noted that a reduction in launch costs would “cause the total estimated cost of deploying and operating the SBI constellation for 20 years to fall from $264 billion to $161 billion (in 2025 dollars),” according to the letter. On the high side, the total estimate would fall from $831 billion to $542 billion, CBO said.

However, the system discussed in the CBO letter has little resemblance to what Trump is planning. Trump’s executive order on the Golden Dome called for deploying a missile defense system to protect the United States from attacks by regional adversaries and attacks by peer or near-peer adversaries, including those with military capabilities similar to the U.S.

“Such a defense could require a more expansive SBI capability than the systems examined in the previous studies,” CBO noted. “Quantifying those recent changes will require further analysis.” 

Nearly every president since Ronald Reagan has discussed a missile defense system for the U.S. In 1992, the U.S. Government Accountability Office concluded that a proposed space-based interceptor system known as “Brilliant Pebbles” was based on immature simulations that “use many unproven assumptions.” Some such projects cost taxpayers billions before being scrapped.

The Missile Defense Agency, a U.S. Department of Defense component, has been working on a Ground-Based Midcourse Defense system to defend the U.S. against a limited ballistic missile attack from potential adversaries such as North Korea and Iran since 2002.

Its latest project, called the Next Generation Interceptor, was designed to respond to new threats and eventually replace aging Ground-Based Interceptors. DOD’s Director for Cost Assessment and Program Evaluation estimated the total cost to design, develop, produce, operate and sustain an initial capability of 20 production unit NGIs and additional test articles would exceed $17 billion, according to a 2024 report from the Government Accountability Office. 

“MDA is making progress developing NGI and the program is currently estimating initial interceptor deliveries will occur by the fourth quarter of fiscal year 2027, 1 year ahead of schedule,” the GAO report noted. “However, we found that NGI’s schedule is optimistic when compared to DOD’s historical performance developing and testing systems similar to NGI.”

That GAO report further noted that the NGI “program’s prime contract development costs have increased by hundreds of millions of dollars in the last year (specific details are sensitive) but remain within the program’s current budget.”

Todd Harrison, a senior fellow at the American Enterprise Institute, said Trump’s ambitious project comes with challenges and risks. Scale will be a key challenge, he said. 

“The physics of space-based interceptors mean that they inherently have an absenteeism problem – each interceptor spends the vast majority of its time each orbit out of range of any missiles it could intercept,” Harrison wrote for AEI. “According to my calculations and using fairly generous assumptions for the performance of each interceptor, it takes about 950 interceptors spread out in orbit around the Earth to ensure that at least one is always in range to intercept a missile during its boost phase. If an adversary launches ten missiles in a salvo, it requires some 9,500 interceptors in space to ensure at least ten are within range to intercept all of the incoming missiles.”

The numbers get much bigger very quickly, Harrison said.

“Given that China has about 350 ICBMs and Russia has 306, not including their sub-launched ballistic missiles, scaling a space-based interceptor system to meet the threat quickly becomes impractical,” he wrote. “In peacetime competition, this means an adversary can build missiles faster and more affordably than we can build the space-based interceptors needed to counter them.”

Harrison said lawmakers should put expectations in check. 

“No matter how many different layers are included in Golden Dome, whether space-based or not, homeland missile defense will never be iron clad. Policymakers should limit their expectations for what can be deployed by the end of 2030,” he said. “The objective should be a system that can reliably defeat an attack by North Korea or Iran and merely blunt a large-scale attack by China or Russia. This much is technically feasible, but it will require substantial and sustained funding on the order of tens of billions of dollars over the next decade and beyond.”

Harrison noted the Golden Project faces political challenges as well. 

“Golden Dome is technically feasible and strategically sound overall, with the notable exception of space-based interceptors, which the laws of physics continue to render impractical,” he wrote. “The main mark against Golden Dome is the political risk that a future Congress or new administration will terminate it … The U.S. military could spend billions of dollars developing it only to have a subsequent administration kill the effort before it bears fruit. Golden Dome could become the poster child for waste and inefficiency in defense.”

Defense contractors are eager to join the effort. Lockheed Martin has already launched a Golden Dome website, suggesting how the company could help make it a reality.