US defence technology company Anduril Industries has unveiled a new family of surface-to-air interceptor missiles, dubbed Steelfin, designed to offer a cheaper alternative to the Patriot PAC-3 MSE while countering a range of aerial threats, including drones, cruise missiles and ballistic missiles.According to Defence Express, the Steelfin family features a modular design that allows different configurations to be developed for different missions, potentially reducing manufacturing costs and enabling higher production volumes.Anduril is targeting a price of around one-third that of the PAC-3 MSE, although the cost advantage and operational capabilities have yet to be independently demonstrated.The development of Steelfin comes amid growing concerns over the cost and availability of air-defence interceptors, as militaries face repeated drone and missile attacks. Modern air-defence systems often have to use expensive interceptors to destroy relatively inexpensive incoming weapons, creating an unfavourable cost exchange for the defender.The problem becomes more acute during sustained attacks, when large numbers of drones and missiles can force defenders to expend their interceptor stocks rapidly. Replenishing these weapons can take time, particularly when production capacity is limited and several countries are competing for supplies.Steelfin missileThe Steelfin family uses a two-stage architecture, combining interchangeable first-stage solid-rocket boosters with a second-stage terminal interceptor that shares a common airframe, avionics, software and flight-control system across variants.According to Anduril’s official announcement, the modular design also allows different seekers and mission-specific components to be integrated without redesigning the entire missile. The company says Steelfin is designed to work with existing launch infrastructure, including the M903A2, Mk 41 Vertical Launch System and Typhon.Anduril has completed ballistic testing using representative air vehicles and plans to begin flight testing the missile variants in 2027. According to Breaking Defense, the company is targeting full-rate production by late 2028 or early 2029, with output dependent on demand.The manufacturer lists Steelfin’s speed as ranging from supersonic to hypersonic, depending on the booster, while its engagement range is also configuration-dependent.