Anduril unveils Steelfin interceptor family it says could cost a third of a PAC-3 MSE

Anduril on Monday, 12 October 2026, unveiled Steelfin, a family of surface-to-air interceptor missiles that company executives said they are aiming to sell for about a third of the price of the Patriot air defence system's current PAC-3 Missile Segment Enhancement interceptor.

The company briefed reporters on the eve of the opening day of the Association of the US Army's annual meeting, three days after Lockheed Martin unveiled its own next-generation Patriot interceptor, the PAC-3 Edge. Both launches come as the United States and its allies try to expand missile production while demand for air and missile defence strains American stockpiles.

One design in several sizes

Anduril describes Steelfin as a configurable, mass-producible family built on a common two-stage design. A first-stage booster sets range, performance and launch configuration, while the second-stage terminal interceptor shares its airframe, avionics and flight controls across variants, so every version can move down the same production line. The company says the family is meant to cover point defence, lower-tier air and missile defence and upper-tier ballistic missile defence, against cruise, ballistic and hypersonic missiles.

Aviation Week reported that Steelfin will be offered with booster diameters of 10, 18 and 21 inches, matching the range of advanced interceptors in the US inventory, from the 10-inch PAC-3 through the 15.7-inch THAAD interceptor to the 21-inch SM-3 Block IIA. The upper stage is designed to carry different sensors, including radar and infrared seekers.

Anduril says the variants are compatible with existing land and sea launch systems, including the M903A2 Patriot launcher, the Mk 41 vertical launch system and the Typhon launcher, as well as newer containerised launchers, and that they can plug into fielded fire control systems such as Aegis and the Army's IBCS battle command system.

Aiming at the Army's next Patriot missile

Stephen Milano, an Anduril missile executive, told reporters that the smallest Steelfin is a natural fit for the Army's Future Interceptor programme, which is meant to fill a range gap between the PAC-3 MSE and the THAAD interceptor. Breaking Defense reported on Friday that Lockheed Martin and one undisclosed company had been selected for that programme, and Anduril declined to say whether it was the second firm.

Milano said the Army wants a terminal interceptor of seven to 10 inches with a booster of 10 to 13 inches that fits both the existing Patriot launcher and the Common Autonomous Multi-domain Launcher, and that Steelfin meets those requirements. Anduril is also competing for the Army's separate low-cost interceptor effort, having been picked with other vendors for further testing after the service's xTech Apex Intercept competition.

Chris Brose, Anduril's president and chief strategy officer, said US and allied forces depend on legacy interceptors that cannot be built at the scale needed to match the number of drones and missiles now fired at them. Milano said the modular design would let commanders use a cheaper missile against Shahed-type one-way attack drones instead of firing their most capable interceptor at every threat.

Testing and production

Anduril says it has completed ballistic testing with representative air vehicles and will begin flight testing Steelfin variants next year. Milano said he expects full-rate production at the end of 2028 or early 2029, with output of several thousand a year at the low end and possibly far more, depending on demand from the US military and foreign customers.

Most subassemblies are to be built at Anduril's Arsenal-1 factory in Ohio, with final integration done with a handful of partners. Solid rocket motors will come both from Anduril and from other suppliers.

For now Steelfin has not flown, and its cost goal is a company target rather than a contract price. Whether the Army chooses it for either interceptor programme will decide whether it becomes a real, cheaper option for the many armed forces that already rely on Patriot launchers and are short of missiles to fire from them.