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U.S. President Donald Trump set high expectations for “Golden Dome.” His executive order directing development of this homeland air and missile defense system lists a broad range of threats: “ballistic, hypersonic, advanced cruise missiles, and other next-generation aerial attacks from peer, near-peer, and rogue adversaries.” At an Oval Office event, he went further, claiming Golden Dome would be “very close to 100 percent” effective, completed “in about three years,” and cost “about $175 billion.” The problem with setting expectations this high is that it can only lead to disappointment. The capabilities Trump promised for Golden Dome are fundamentally misaligned with the cost and schedule he asserted. Although reports suggest that an initial architecture has been selected, unless expectations are recalibrated, Golden Dome risks being built to promises rather than requirements, eroding the transparency and confidence needed to make the program sustainable.
Breaking the Iron Triangle
Acquisition programs are governed by the “iron triangle” of cost, schedule, and performance. Improving one of these inherently requires sacrifices in one or both of the others. In his executive order and subsequent statements, President Trump attempted to fix all three sides at once before the architecture was even decided. He set the cost at $175 billion, without specifying what it included, over what period, or where the figure came from. He set the performance as being nearly 100 percent effective and capable of intercepting virtually all aerial threats to the homeland. And perhaps most astonishingly, he said it would be completed before he leaves office in just three years. Even someone with only a passing familiarity with defense acquisitions would recognize that this triangle cannot close.
An enduring truth in defense acquisitions is that cost scales with ambition. Despite the administration’s rhetoric, Golden Dome’s cost depends on the architecture chosen and the detailed requirements that will follow in the coming months, namely the level of geographic coverage, the types and numbers of threats it must address, and the degree of resilience it is expected to achieve. To illuminate the tradeoffs involved, I published a paper that estimates the costs of dozens of potential Golden Dome components, ranging from Patriot batteries and uncrewed ships armed with missiles to space-based interceptors and counter-drone systems. The paper assembles these building blocks in different combinations and quantities to form alternative architectures that span the spectrum from fiscally constrained to strategically ambitious. This analysis shows that even slight changes in ambition can alter costs by hundreds of billions of dollars. Which naturally raises the question: How much will Golden Dome actually cost?
Alternative Architectures
The paper uses six example architectures to explore a range of alternatives, but it stops short of recommending what the architecture should be. Each architecture’s cost represents the additional funding required beyond what is already funded or planned in the current baseline, including development, procurement, construction, and operations and support funding. Total costs are shown for a 20-year period (Fiscal Years 26-45) in constant FY26 dollars.
The first architecture (Accelerated Homeland Defense) prioritizes the president’s schedule and cost constraints, with capability being a secondary priority. It invests in programs that can begin fielding capabilities within the next three to five years — generally items that are already in production or development — and includes a limited deployment of boost-phase space-based interceptors. While it does not strictly adhere to the president’s three-year schedule, it remains within the $175 billion funding limit for the first five years and allows for ongoing operations and support as well as satellite replenishment costs in later years. This architecture is estimated to cost $471 billion over 20 years.
The second architecture (Space-centric Strategic Defense) prioritizes defending against strategic threats to the homeland, specifically long-range ballistic missiles, fractional orbital bombardment systems, and hypersonic weapons. The layered defense in this architecture relies primarily on space-based interceptors capable of engaging long-range ballistic and hypersonic threats in multiple phases of flight. The resulting architecture provides global coverage but at a high cost: roughly $2.4 trillion over 20 years, with 96 percent of the funding going to the Space Force.
By contrast, the third architecture (Ground-centric Strategic Defense) provides similar protection against strategic threats to the homeland but relies primarily on terrestrial systems rather than space-based interceptors. With a large expansion of ground-based midcourse defense battalions, terminal high altitude area defense batteries, and Aegis Ashore sites (among other investments), it totals about $406 billion — one-sixth the cost of its space-centric counterpart, although it lacks the global protection inherent to space-based capabilities.
The fourth architecture (Limited Tactical Defense) focuses instead on the lower end of the threat spectrum: drones, cruise missiles, and aircraft. It invests in directed energy weapons, aerostats, and large numbers of short- and medium-range interceptors to protect major population centers, key military installations, ports, and other strategic infrastructure while leaving long-range strategic threats largely unaddressed. At $252 billion (nearly half of which would go to the Army), it is the lowest-cost of the six architectures.
Two final architectures attempt to balance across the threat spectrum. The fifth architecture (Balanced All-Threat Defense) provides moderate protection against all types of aerial threats within a budget cap of $1 trillion over 20 years (an average of $50 billion per year). It blends different types of space-based interceptors with expanded ground-based defenses and counter-drone systems to provide broad coverage but limited depth of capacity.
Architecture 6 (Robust All-Threat Defense) attempts to align with Trump’s performance goal of “very close to 100 percent” effectiveness against the full spectrum of aerial threats. It invests in all types of ground- and space-based interceptors and is scaled to defeat salvos of hundreds of missiles, with the sole constraint that annual costs not exceed 25 percent of the current defense budget (~$220 billion per year) in any single year. While this architecture costs an estimated $3.6 trillion over 20 years, it still falls short of creating a nearly impenetrable shield.
The Space-Based Interceptor Problem
Across the range of architectures considered, space-based interceptors emerge as the single largest cost driver. They account for 92 percent of the total cost for the second architecture and roughly 90 percent of the cost difference between the fifth and sixth architectures. To put this in perspective, the sixth architecture would increase the Space Force’s discretionary budget by more than a factor of six above its current level. The reason space-based interceptors are so expensive is rooted in physics and orbital mechanics.
As detailed in an appendix to the paper, space-based interceptors are constantly moving in and out of range as they orbit the Earth — what is known as the absenteeism problem. A constellation of interceptors must be designed to ensure that enough are in range of every potential launch site at all times. One of the most important performance parameters used in designing a constellation is the flyout time for the interceptors. Flyout time is the interval between when the command is given to fire an interceptor and the latest point at which it can intercept a target. Boost-phase interceptors are particularly sensitive to this parameter because the boost phase of a solid-propellant inter-continental ballistic missile can be less than three minutes. Including time that gets used up detecting the launch, establishing a track, and making the decision to fire, the flyout time for a boost-phase interceptor can be as short at 120 seconds.
A shorter flyout time reduces each interceptor’s effective range and therefore increases the total number of interceptors required in the constellation to maintain continuous coverage. The relationship between flyout time and the number of interceptors in a constellation is non-linear, meaning a slight reduction in the assumed flyout time results in a large increase in the number of interceptors needed and in the total cost.
Depending on the specific performance characteristics used, boost-phase interceptors require roughly 1,000 interceptors in orbit for every missile launched in a salvo (a 1,000:1 ratio). If an adversary launches 10 missiles in a salvo, it requires 10,000 interceptors in orbit. For ground-based interceptors, the ratio is typically in the range of 2:1 to 4:1.
An inherent advantage of space-based interceptors, however, is that a constellation sized to protect the U.S. homeland will inherently protect allies, partners, and forward-deployed U.S. forces as well. That may be an advantage or a liability, depending on one’s view of America’s strategic commitments.
Rhetoric Meets Reality
The analysis highlights a striking gap between administration rhetoric and fiscal reality. The sixth architecture comes the closest to meeting the performance objectives set by the administration, but this architecture costs more than 20 times the president’s price tag and would require nearly two decades to complete. An architecture that fits roughly within the president’s $175 billion funding constraint (over the first five years) only buys a limited, stopgap system incapable of defending against the large and growing missile inventories of China and Russia — and still requires more than three years to complete.
The examples used in this analysis are just a sample of the countless architectures possible. Readers can explore cost, schedule, and performance tradeoffs themselves with the Defense Futures Simulator (DFS). Anyone can make an account at defensefutures.aei.org, create a new scenario using the “Build Your Own Golden Dome” baseline, and experiment with different cost constraints and strategic tradeoffs. DFS allows users to save scenarios, share them with others, and compare results across scenarios.
Attempting to build your own Golden Dome architecture makes clear what policy debates often obscure: Golden Dome can be almost anything — small or large, tactical or strategic, ground-based or space-based — but it cannot be everything at once. It also illustrates that Golden Dome is not a binary choice between building a homeland missile defense system or doing nothing. The real choice is what kind of system to build and at what cost.
While no architecture can deliver total protection from every threat, this analysis demonstrates that even small shifts in ambition can produce outsized changes in cost, and the largest cost driver by far is space-based interceptors. The issue for policymakers is one of balancing risks. With potentially trillions of dollars at stake over the next 20 years, the risks involved in Golden Dome are broader than homeland defense alone. Spending more to reduce risks to the homeland can increase risks elsewhere — through higher borrowing and taxes that impose economic risks, or through cuts to other defense and non-defense funding that carry security and political risks of their own.
Golden Dome is not merely a technical or budgetary problem to be solved, but a political issue that must be managed. Policymakers must decide how much risk they are willing to mitigate, how much they can shift elsewhere, and how much they are prepared to simply accept. Doing so requires setting realistic expectations from the outset and maintaining transparency about the costs and capabilities the system can actually deliver. Otherwise, Golden Dome risks collapsing under the weight of promises it cannot keep.
Todd Harrison is a senior fellow at the American Enterprise Institute, where he focuses on defense strategy, defense budgeting, and space policy. He has published extensively on issues such as the future of the Space Force, trade-offs in defense spending, and military readiness. Previously, he was senior fellow and director of Defense Budget Analysis and the Aerospace Security Project at the Center for Strategic and International Studies, and senior fellow for defense budget studies at the Center for Strategic and Budgetary Assessments. He has also worked in the defense industry, served as a captain in the U.S. Air Force Reserves, and taught classes at Johns Hopkins University’s School of Advanced International Studies and George Washington University’s Elliott School of International Affairs. Mr. Harrison received a B.S. and M.S. in aeronautics and astronautics from the Massachusetts Institute of Technology.
Image: Tech. Sgt. Elora McCutcheon via DVIDS.
