Anduril Unveils Steelfin Family Of Modular Surface-To-Air Missiles

Anduril has unveiled Steelfin, a family of surface-to-air interceptor missiles designed to share a common architecture and manufacturing process while being configured for different air and missile defense missions. The company says this approach will enable high-volume production at significantly lower cost than existing weapons, though it has not disclosed prices or detailed performance specifications.

The announcement comes as the U.S. military seeks to expand air defense inventories against an increasingly diverse range of threats, from inexpensive drones to cruise missiles, ballistic missiles, and advanced maneuvering weapons, including hypersonic ones. Recent experiences from Ukraine and the Middle East make it abundantly clear that the challenge is not simply developing interceptors capable of defeating those targets but producing enough of them to sustain operations without exhausting stocks of more expensive weapons.

Using high-end interceptors against comparatively inexpensive threats can rapidly consume limited inventories, as it has in the Middle East, especially, even when engagements are necessary to protect personnel and critical infrastructure. A broader range of defensive weapons, matched to different threats and engagement requirements, could help ease that burden.

Anduril’s answer is a family of missiles built around a common two-stage design. The first stage consists of a booster, while the second is a terminal interceptor intended to share a baseline airframe, avionics, software, flight control system, and interfaces across variants. Different boosters and terminal-stage components would allow the company to tailor individual configurations to specific missions without developing an entirely new missile for each requirement. Both hit-to-kill and blast-fragmentation terminal-stage interceptors will be offered, Anduril says.

“It is an open system, so the ability to fly it with different rocket motors, different seekers, to be able to swap these components out, to be able to reconfigure the system for a range of different threats is a feature that we built into this,” explained Christian Brose, who serves as the president and chief strategy officer at Anduril. He was speaking to members of the media, including TWZ, ahead of the official unveiling of Steelfin.

The company says the family is intended to cover missions ranging from point defense and lower-tier integrated air and missile defense to upper-tier ballistic missile defense. It also identifies cruise, ballistic, and hypersonic missiles among the threats the broader family is designed to address. Overall, is an extremely ambitious goal, and something that has not been attempted previously to this degree.

The announcement does not specify which variants would address individual threats or provide engagement envelopes and performance figures with which to assess those claims.

Brose did clarify that the different ranges that the various Steelfin variants will achieve will be based on the booster sizing. “Right now, we’re looking at integrating on 10-inch, 18-inch, and 21-inch boosters, but we’re also looking at quad pack and dual pack for the Mk 41 Vertical Launch System as well for different installations, which imply different range and altitudes.”

Anduril’s emphasis on commonality is also intended to address the industrial challenges associated with conventional interceptor production. Different missile programs traditionally require specialized tooling, manufacturing processes, suppliers, and facilities, limiting opportunities to shift production rapidly as operational requirements change.

Steelfin variants are intended to use shared production lines and equipment, with mission-specific boosters and terminal-stage components incorporated during final assembly. Anduril says this would allow manufacturing capacity to be redirected toward whichever variant is in greatest demand. The company is planning near-term production on the order of several thousand missiles annually, with capacity designed to expand or shift according to requirements.

That remains a production ambition, and Anduril has not provided a detailed production schedule or contracted quantities demonstrating how quickly it could reach that scale.

The company also says Steelfin is designed to be compatible with existing land- and sea-based launch infrastructure, including the M903A2 launcher used by newer PAC-3 series interceptors, the Mk 41 Vertical Launch System, and Typhon, as well as emerging containerized launchers. It cites compatibility with established fire-control systems, including AEGIS and the Army’s Integrated Battle Command System (IBCS).

When it comes to cost, Steve Milano, the lead for Air Dominance & Strike at Anduril, suggested that the “more exquisite version” of the Steelfin would sit somewhere above the PAC-3 MSE and below THAAD, but would accomplish “100 percent of the THAAD mission at a fraction of the cost.” In a different configuration, tailored for the PAC-3-type mission, Steelfin would accomplish 80 percent of that mission at less than 50 percent of the cost, Milano added.

While THAAD is aimed at taking out short, medium, and intermediate-range ballistic missiles in the terminal phase of flight, PAC-3 provides high-altitude, hit-to-kill air and missile defense against tactical ballistic missiles, cruise missiles, and aircraft.

Milano continued: “Looking at the lower end of the the spectrum, as far as low-cost interceptors are concerned, I just saw an article on the [aircraft carrier USS Abraham] Lincoln coming back with all of the Shahed markings on the side, and I was contemplating the number of SM-2s that were fired against those assets. When I think of that cost exchange, the Steelfin enters into that market and provides greater than 80 percent of the capability of an SM-2 for a third of the cost.”

For reference, a single THAAD interceptor costs around $15.5 million. The unit price of each PAC-3 MSE interceptor now stands at approximately $5.3 million, according to the Army’s latest proposed budget for the 2027 Fiscal Year. Meanwhile, the price of a single SM-2 Block IIIC interceptor, the most advanced version of that missile currently in service, is around $2.5 million. 

Steelfin is entering a market in which the U.S. military is already pursuing several approaches to expanding its low-cost interceptor inventory.

In May, the U.S. Army sought industry proposals for a Patriot-compatible interceptor with a target unit cost below $1 million. The effort reflects the service’s desire for a less expensive weapon for appropriate engagements, preserving higher-end interceptors for targets that warrant their cost and capabilities. The Army’s solicitation also emphasizes component-level cost targets and competition among suppliers, including for rocket motors, seekers, and guidance systems.

Lockheed Martin has offered a separate industry response with its PAC-3 Adapted Capability Effector (ACE), a lower-cost interceptor intended to operate within the Patriot ecosystem. Unveiled in July, the weapon is intended to cost less than half as much as the PAC-3 Missile Segment Enhancement (MSE), according to the company. The MSE’s unit price is approximately $5.3 million in the Army’s fiscal 2027 budget request, putting the ACE’s implied price at around $2.5 million if Lockheed’s comparison holds.

Its projected price would still be well above the Army’s separate sub-$1 million target, reflecting the different objectives and requirements behind the two efforts.

The Navy, meanwhile, is pursuing a potentially broader shift toward modular interceptor architectures. Its Naval Modular Missile initiative envisions a family of surface-to-air weapons built around a common Terminal Stage Interceptor, with different boosters and canisters producing configurations for different missions and platforms. The plans include variants intended to fit multiple missiles within a Mk 41 launcher cell, as well as a version designed for launch from Virginia class submarines equipped with the Virginia Payload Module.

The Navy’s longer-term vision is to replace its existing Standard Missile family with modular variants, although the effort remains in development. The concept highlights potential operational benefits beyond manufacturing: smaller interceptors could increase the number of weapons carried aboard ships, while other configurations could preserve longer-range capabilities. The Navy has also outlined an ambition to reach production of 1,000 missiles annually within five years of a contract award.

Both the Navy’s modular missile initiative and Steelfin reflect a push toward common architectures that can support multiple interceptor configurations without requiring an entirely new missile for every mission. Steelfin’s stated scope is particularly broad, with Anduril pitching the family for missions spanning point defense through lower-tier air and missile defense to upper-tier ballistic missile defense. That would cover much of the air and missile defense spectrum, although it does not extend to exoatmospheric midcourse interception. Whether the family can deliver that breadth of capability at the promised cost and scale remains to be demonstrated.

Anduril says it has been developing Steelfin for several years with investment from multiple customers and has completed ballistic testing using representative air vehicles. Flight testing of Steelfin variants is planned for 2027.

Already, Anduril says it is working closely with “a number of different customers to to get into the field.” Brose continued: “We feel like this is going to be a critical component of the U.S. and allied inventories to complement the range of exquisite capabilities that all of us are familiar with and know by name.”

Steelfin underscores what is now a broader trend toward lower-cost interceptors that can be manufactured at scale, and plugged into existing ecosystems, often with at least a degree of modularity to tackle new and emerging target sets. Steelfin adds Anduril’s proposal to combine that modularity with a common production system designed to support thousands of weapons annually.

Anduril has yet to develop or produce a surface-to-air missile, although its Roadrunner system gives it experience in the related field of countering aerial threats, including loitering munitions. The company’s ambitions for Steelfin are significant, and modular architectures are certainly attractive. After all, a common baseline should simplify production, reduce costs, and allow interceptors to be tailored to different missions. In practice, however, realizing those benefits has historically proved difficult, and fraught with compromises. Whether Anduril can avoid those pitfalls while delivering the promised combination of capability, affordability, and production scale remains an open question. If it can, Steelfin could put the company in a strong position in the future surface-to-air missile market.

Contact the author: thomas@thewarzone.com