The US defence technology company Anduril says Steelfin’s modular design can be adapted for different missions by changing components such as rocket motors and seekers, while retaining a common core architecture. The company is positioning the system as a lower-cost complement to established interceptors, including the Patriot PAC-3 Missile Segment Enhancement (MSE), at a time when militaries face growing demand for air-defence munitions.
Anduril executives have said they are targeting a price around one-third that of a PAC-3 MSE. That is a company target, not a published contract price or independently verified cost estimate. The actual cost would depend on configuration, production volume, customer requirements and procurement terms, none of which have been disclosed.
Steelfin is built around two stages. The booster can be tailored with different solid-rocket motors to meet mission and launch requirements. The terminal interceptor-the section intended to engage the target-uses a common baseline airframe, avionics, software, flight controls and interfaces across variants, according to reporting on Anduril’s announcement. Sensors, including radar or infrared seekers, can be selected for different missions.
That approach is intended to let the company adapt performance without designing an entirely new missile for each role. Anduril says the family could address a range of threats, including one-way attack drones, cruise missiles and ballistic missiles. It has also discussed configurations aimed at more advanced, high-speed threats. Those are design aims; the company has not published detailed performance figures for every variant or demonstrated that the family can defeat all the threats listed.
Compatibility is another central feature. Anduril says Steelfin is designed to work with existing launchers and fire-control networks, including Patriot’s M903A2 launcher, the Navy’s Mk 41 Vertical Launch System and the Army’s Typhon system. The company has also described potential integration with Aegis and the Army’s Integrated Battle Command System. Successful integration would depend on testing, certification and customer approval.
The design reflects a persistent problem for air-defence planners: a defender can expend a costly interceptor against a comparatively inexpensive incoming weapon. A lower-priced option could improve the economics of defending against larger numbers of threats, while preserving high-end interceptors for targets that demand them. But price alone does not determine value. Reliability, probability of intercept, sensor performance, stock availability and the cost of supporting a new system all matter.
Production plans remain ambitious but conditional. Anduril executives told reporters they expect full-rate production to begin at the end of 2028 or early 2029. The company anticipates producing several thousand units annually in the short term, with substantially higher output possible if demand warrants it. Most sub-assemblies are expected to be made at Anduril’s Arsenal-1 facility in Ohio, with final integration involving partners. These are company projections, not current production figures.
The announcement comes as the US Army seeks affordable interceptor technologies. Its xTech|Apex Intercept competition is intended to identify solutions that can augment the Patriot air- and missile-defence mission against aerial threats, cruise missiles and short-range ballistic missiles. The Army’s competition lists Anduril among the finalists in the low-cost interceptor category; finalist selection is not a purchase award or a guarantee that Steelfin will enter service.
Anduril has reportedly completed ballistic testing with representative air vehicles, while flight testing of Steelfin variants is planned to begin next year. The next milestones will test whether the modular concept can meet operational requirements and be manufactured at scale. Until those trials and procurement decisions advance, Steelfin remains a proposed answer to the cost-and-capacity challenge-not a fielded replacement for existing systems.
