Inside the $19.55B IRON DOME Act: What Senate Bill 435 Means for U.S. Missile Defense
Space Technology and Policy
Good morning,
This week, Senators Dan Sullivan (R-AK) and Kevin Cramer (R-ND) introduced Senate Bill 435, the IRON DOME Act, which seeks to align with President Trump’s recent executive order titled the Iron Dome for America.
We’ve already discussed the President’s E.O. in depth.
Today, we want to dig in a bit on the $19.55B IRON DOME Act, which contains both some great and some very questionable items. The bill has been referred to the SASC for consideration, and it would be surprising if the bill in some form doesn’t find its way into the NDAA.
Evaluating the Senate Missile Defense Modernization Bill
The Senate bill proposes an ambitious modernization of the U.S. missile defense architecture. By accelerating developments across space-based interceptors, advanced radar systems, and other critical technologies, the bill seeks to address a rapidly evolving threat environment. While its strategic intent is clear, a close review raises important questions regarding its assumptions, technical feasibility, cost estimates, and overall alignment with U.S. defense priorities. Below are key areas for further consideration.
Expanding Threats and Geographic Coverage
Section 2, Subsection a, Paragraph 3 acknowledges the increasing threat from China, Russia, and North Korea with regard to nuclear delivery via ballistic missiles. China has an estimated 400-600 nuclear-capable ICBMs. Further, it currently has six Jin-class (Type 094) nuclear-powered ballistic missile submarines and is building a new strategic stealth bomber (H-20) that could range to the United States; it is looking to expand its inventories of these systems.
North Korea has an estimated 50 nuclear warheads, with enough fissile material for an additional 70-90 more weapons. The Hermit Kingdom also has launched its first tactical, nuclear-armed submarine 18 months ago. Unfortunately for them, it is a diesel-powered sub and not nuclear-powered. North Korea has preferred to focus on building its land-based nuclear ballistic missile arsenal.
Russia—long our primary concern in nuclear matters—maintains the greatest arsenal of weapons, with 5,580 nuclear warheads. Further, Russia is the only adversary that has a true nuclear triad (land-based missiles, strategic bombers, and submarine-launched missiles), as China continues work on the H-20.
Notably, of these three countries, only China has a no-first-use policy, with both Russia and North Korea recently expanding their first-use policies lowering the threshold for employment. Having said that, there are legitimate concerns about ambiguity in China’s policy, particularly when Taiwan is concerned.
So, Building our Future agrees with the underlying premise underpinning the IRON DOME Act that there is an increased threat of nuclear attack.
Having said that, the bill primarily focuses on the threat posed by intercontinental ballistic missiles (ICBMs), missing broader delivery mechanism that are becoming available.
Broader Delivery Methods:
Modern nuclear threats are not limited to ballistic missiles. Adversaries may also employ submarine-launched cruise missiles or smuggled devices. Further, advanced technologies like hypersonic glide vehicles (HGVs) and hypersonic cruise missiles (HCMs) pose additional threats that are insufficiently addressed by the bill.U.S. Territorial Gaps:
The bill acknowledges threats to U.S. territories yet misfocuses protection. Strategic assets like Guam, Wake Island, and American Samoa remain outside the current coverage scope (although, there are some theater ballistic missile defenses available forward). Most importantly, the bill seems to equivocate between wanting to provide a true Iron Dome that provides protection to all Americans from ballistic missiles (the stated goal in the President’s executive order) and a far more realistic and cost-effective ballistic missile defense program aimed at critical sites / infrastructure and assuring our second-strike capabilities.
Clarifying Universal Protection from Critical Capability Protection
As mentioned in the previous section, the bill seems to conflate the assurance of a second-strike capability with total missile defense.
The U.S. already possesses a robust and secure second-strike capability that has underpinned our security for 80 years. Of course, there are concerns about the future deterrent effect of such capabilities, suggesting that the concept of Mutually Assured Destruction will not hold. This has been tested and retested through game theory, prospect theory, and other tools / frameworks—with mixed findings.
At the end of the day though, while maintaining a second-strike capability may not deter an adversary’s first-use against us, it is critical to allow us a response and to impose costs as part of a broader theory of victory.
To this end, we feel that the bill should specify its intent as being to protect critical infrastructure and capabilities of the United States including our second-strike capability. This coverage can also be extended to major population centers. This distinction from a full missile shield to protect every American will dramatically lower the expected cost of missile defense from a minimum of $1.7T to more realistic amounts, while providing reasonable protection.
Naturally, nobody wants to be the one to tell any American “you didn’t make the cut for protection” but covering major population centers of 5M+, major federal government facilities, and military installations greatly reduces the risk to the average American.
Feasibility of Drone-Based Acoustic Sensing
The Act directs the rapid fielding of a drone-based network that employs audio sensing technology to detect advanced missiles, including hypersonic weapons.
While our initial reaction was to laugh at the idea of using acoustic sensing to detect a weapon moving at least five times faster than the speed of sound, as part of a larger mesh network of sensors, it can make sense—especially for subsonic threats.
German startup Quantum Systems and Polish startup Weles Acoustics have demonstrated drone-mounted acoustic sensors than detect artillery and mortars up to 15km away. That is super-cool, and has changed the way Quantum Systems’ drones are being employed. They can now detect and cue for attacking points of origin (the actual weapon system firing a round). But if we’re using these systems to detect a passing hypersonic, they’re essentially worthless. If a hypersonic missile passes by a sensor at 15km, it will be at a minimum 75 kilometers past the sensor when it’s actually registered.
However, since most cruise missiles fly at subsonic speeds, actually become quite useful for detection as the sound wave will arrive at the sensor before the missile does. From that perspective, acoustic sensing makes quite a bit of sense—particularly in use cases such as point defense around specific forward-deployed military bases.
With all of that in mind, we believe that the language in the bill is too prescriptive and will ultimately not create the capability, for which the Senators are hoping. Instead the language should direct the development of multi-modal mesh networks of heterogenous, multi-domain sensors including but not limited to terrestrially- and airborne-based acoustic sensors. Doing such will ensure that new sensors complement other modalities including radar, IR, etc.
Next-Generation Interceptor Expansion: Costs and Timelines
Section 4, Subsection d mandates expanding interceptor fields at Fort Greely from 44 to 80 units by 2038, with an associated price tag of approximately $12B.
Basing the NGIs in Alaska largely makes sense as nearly any missile fired from China, North Korea, or Eastern Russia following a ballistic trajectory will overfly Alaska. The Missile Defense Agency was working to establish silos in the Eastern United States (Fort Drum, NY) but the effort may have netted only a In-flight Interceptor Communication System Data Terminal. So, we feel that the bill should direct some of the silos to be built in the Eastern U.S.
Now, is 80 even close to enough? No. 80 interceptors have about a 50% chance of intercepting 20 ballistic missiles. If our adversary sought to overwhelm us by firing 80 missiles (roughly 16% of China’s arsenal or 1.4% of Russia’s arsenal), then there’s 80% chance that more than 30 missiles are able to avoid interception.1 That’s a huge number. DF-5s and DF-31 missiles fired from Yulin missile field can range nearly every major metropolitan area in the United States. Meaning with nuclear yields ranging from 90kT to 3MT, they can do significant damage.
We also question the funds that would be approved under the bill. Given the rising costs of the Next-Gen Interceptor program, the historical cost overruns of major defense acquisition programs, inflation, and the impact of President Trump’s tariffs (including the 25% tariff on steel and aluminum), $19B will almost certainly be insufficient.
At the same time, a 13-year timeframe for the construction of 36 silos in Alaska is way too long. If we are to be serious about building a credible missile defense capability, then we should be building an average of 36 silos per year—at a minimum. Our adversaries are outpacing us as they build more and more missiles.
Space-Based Interceptors and Directed Energy
The bill directs accelerated development of proliferated space-based interceptors for boost-phase intercept while allocating separate funds for directed energy research.
Given that directed energy systems promise reusability, lower cost per shot, and reduced orbital debris risks (mitigating the potential for Kessler syndrome), there is a strong argument for merging these efforts under a unified development strategy.
Aegis Ashore Systems: Siting and Threat Focus
The IRON DOME Act would direct the establishment of Aegis Ashore systems in Alaska, Hawaii, and on the East Coast, presumably to protect against short- to medium-range ballistic missile threats (the Aegis system’s SM-3 Block IB and IIA missiles offer some limited, untested capabilities against ICBMs) and against low-altitude hypersonic, supersonic, and subsonic missiles and threats.
If the intent of these Aegis Ashore systems is to protect specific critical locations (e.g., Joint Base Pearl Harbor - Hickam in Hawaii, Cobra Dane in Alaska, and Washington D.C.) then the siting makes sense. If we’re seeking broad coverage protection against the threats listed in the previous paragraph or protection for the continental U.S., then the sites make little sense.
The AN/SPY-1 radar currently used in Aegis Ashore systems has a detection range of about 230 miles. If we use the AN/SPY-6 radar (replacing the AN/SPY-1 on Aegis afloat systems), that detection / discrimination range extends significantly. With 30x more power and 15dB more sensitivity than the AN/SPY-1, the AN-SPY-6 should have a range of approximately 720 miles. The SM-3 Block IIA missile has an operational range of about 1,200 miles.
The shortest distance between Hawaii and Alaska is about 2,200 miles. This means that while the section of the Pacific can be curtained by SM-3s, there’s still a 760 mile gap in the coverage of the AN/SPY-6 radars, meaning that a missile can easily sneak through it.
Of course, that’s assuming that only the AN/SPY-6 would be effective against the threat, which is unlikely, as there are other radars operating, albeit in different bands.
We recommend the following concerning these capabilities:
Conduct an analysis of alternatives to determine the best site locations for Aegis Ashore systems without the limitations of placement in Alaska and Hawaii.
Outline clearly the threat that we want these systems to protect against to better inform the siting.
Include language about adding additional radar capabilities in both the S-band (like the AN/SPY-6) and X-band (better for target discrimination and detecting smaller targets).
Include protections of these critically important sections of the electromagnetic spectrum to ensure availability for critical military use-cases.
Conclusion
The Senate missile defense modernization bill represents a robust effort to update the nation’s defensive posture by integrating advanced interceptors, state-of-the-art sensors, and emerging technologies into a multi-layered architecture. However, the critical observations outlined above reveal several areas where further analysis and clarification are essential.
We have plenty of other thoughts about the bill, but want as most of them are what may be called ‘happy-to-glad’ changes, we’ll omit them from this post.
Addressing the concerns that we’ve raised will ensure that investments in missile defense modernization are both cost-effective and operationally sound. As the Senate bill moves forward, collaborative dialogue among DoD leadership, military planners, legislative staff, and industry stakeholders will be key to refining these initiatives and realizing a resilient, future-proof missile defense architecture.
Alright, enough ballistic missile defense geekery. On to the news!
News Headlines:
Trump kills the penny, which costs more to make than it's worth (BBC)
Pentagon acquisition office orders review of Space Development Agency (DN)
U.S. announced 25% tariffs on steel and aluminum (BBC)
Elon Musk leds consortium offering to buy-out rival OpenAI for $97.4B; Sam Altman say 'no, thank you' as offer is less than 1/3 of the company's likely next valuation (AP)
China drafts list of tech companies to sanction in looming trade war with the U.S. (WSJ)
Judge extends pause on 'deferred resignation' offer (FNN)
VP and DOGE question authority of the courts as Trump's agenda faces legal pushback (AP)
SECDEF: No plans to drawdown troops in Europe, for now (MT)
'Trump trades' start to misfire as dollar weakens (FT)
Satellites:
Launches:
Upcoming Launches:
Space News:
GOP senators back Trump's s[pace-based 'Iron Dome' plan with $19.5B bill (SN)
Council on Foreign Relations' report urges U.S.-China dialogue, responsible decision making, and peace (CFR)
Space Force pushes forward with acquisition reforms (SN)
Investors: don't compete with or emulate SpaceX (SN)
Falling space debris is increasingly threatening airplanes (ABC)
DIU is studying applications of SpaceX Starship in-space refueling (SN)
Senators reintroduce bill to authorize Commerce Department's space traffic coordination system (SN)
SKY Perfect JSAT is the customer behind Planet's $230M LEO order (SN)
After a wrenching decision by NASA, private lunar lander finds a new customer (AT)
Boeing's Starliner losses mount, now totaling more than $2B (ET)
Astrolab to fly its FLIP lunar rover on Astrobotic's Griffin-1 lander (SN)
Geost sues Sierra Space over breach of contract in military satellite program (SN)
Lockeed, Boeing compete for military satellite contract amid commercial disruption (SN)
Texas awards $47.7M in grants to Blue Origin, Firefly, Intuitive Machines, SpaceX, and Starlab Space through its Space Exploration and Aeronautics research Fund (SN)
Redwire lands new satellite contract for Space Force in-orbit refueling experiment (SN)
MDA Space signs $768M contract with Globalstar to build next-gen LEO constellation (PRN)
Investors advise caution in defense-focused space boom (SN)
Foreign Space News
First launch of China's Long March 8A sends second group of Guowang megaconstellation satellites into orbit (SN)
China builds space alliances across Africa as Trump cuts foreign aid (RT)
Russian scientists prototype plasma electric rocket engine that could slash travel time to Mars to 1-2 months (WNN)
Kremlin replaces Russian space boss after tenure scarred by failed moonshot (RT)
Thales Alenia Space wins contract for gateway airlock (SN)
Japan puts new U.S. Space Force capability into orbit (ASF)
Germany's Atmos Space Cargo secures regulatory approvals for first reentry mission using inflatable heat shield (SN)
Europe signs contract for its first moon lander (SP)
EU's EUCLID satellite finds rare 'Einstein Ring' of light in nearby galaxy (NPR)
Deal Flow:
PE / M&A / Exits / Other
Karman Holdings, a payload protection and propulsion systems firm, is targeting a value of $2.6B in its IPO (BS)
Indra acquires European satellite firm Hispasat for $748M (DCD)
Satellite experts SES secured a $130M loan agreement from the European Investment Bank (VS)
Opportunities
The military's TRANSCOM is looking for partners to work on commercial global delivery directly from space for DoD cargo (SAM)
NASA is seeking info from potential sources that could work on building ground stations in New Mexico, South Africa, and Western Australia for communicating with space craft in cislunar space (including on the Moon) (SAM)
NASA will host an industry week for parties interested in working on the Landsat Next mission to ensure sustained access to high-quality, global, land-imaging measurements (SAM)
Space Force is looking for an integrator to manage the Resilient MEO Missile Warning and Tracking program (SAM)
NASA is seeking partners to land its VIPER lunar lander, operate it at the lunar poles, and share science results (SAM)
Editor’s Picks
Victoria Samson and Jessica West warn how the pursuit of space-based interceptors and total missile defense are inherently escalatory and the Iron Dome for America will lead to an arms race.
Space Law expert Ana Laura Villicaña explains what DeepSeek means for space tech.
Scott Firsing and Zolana Joao call for increased U.S.-African cooperation for space.
Lighter Side:
Keep Building,
BOF
Please note that our calculations two weeks ago were wrong. We acknowledge and apologize for that.
An autonomous maritime capability could be useful for early detect/engagement capability if these assets were stationed hundreds of miles of U.S. shores and connected into the MD network.