One Missile, Three Sizes, a Third of the Price: Anduril's Steelfin Takes On PAC-3

Air defence has a maths problem: the missiles doing the defending often cost far more than the weapons they are shooting down. On Monday, October 12, 2026, ahead of the AUSA conference, Anduril unveiled its answer — the Steelfin family of interceptors, a modular two-stage missile offered in three sizes, aimed at targets from cheap Shahed-type drones all the way up to hypersonic weapons, at what the company says could be roughly a third of the price of a PAC-3 MSE in its low-end form. If even part of that claim survives contact with testing, it would shake the most protected corner of the missile business.

Concept illustration.

One Missile, Three Sizes: How Steelfin Is Built

Steelfin's core idea is modularity. The family is a two-stage interceptor built around a common second-stage terminal interceptor — the part that does the final, hardest work of finding and hitting the target in the endgame. Underneath that common upper stage, Anduril offers swappable boosters in three diameters: 10-inch, 18-inch and 21-inch. A bigger booster means more energy, more altitude and more range; a smaller one means a cheaper, lighter round for easier targets.

The mixing does not stop at the booster. The design uses swappable seekers — radar and infrared options — and swappable motors, so the same basic family can be configured for different missions rather than forcing one expensive configuration onto every shot. In plain terms, Anduril is trying to do to interceptors what modular design did to drones: build one smart core, then scale the cheap parts up or down around it.

Why does that matter? Because today's air-defence magazine is brutally mismatched. Commanders facing a slow one-way attack drone and commanders facing a manoeuvring ballistic missile are often drawing from the same small pool of exquisite, expensive interceptors. A family that lets a battery load a right-sized round for each threat class — cheap for drones, heavy for ballistic and hypersonic targets — attacks the cost-exchange problem at the design level, not just the price tag.

Concept illustration.

The Claims: A Third of PAC-3's Price — Labelled as Claims

Now the numbers everyone will quote, stated exactly as they should be: these are Anduril's claims, made at unveiling, for a missile that has not yet flown in its final configurations. They have not been independently verified, and no customer has published a Steelfin unit price.

• Low-end configuration: Anduril says it is aiming for roughly one-third of the cost of a PAC-3 MSE.
• PAC-3-type configuration: the company claims it could deliver about 80% of that mission at under 50% of the cost.
• High-end configuration: Anduril claims a top-end Steelfin could perform the full THAAD mission at a fraction of THAAD's cost.

Read those carefully. Even Anduril's own framing concedes a trade: the mid-tier round is pitched at most of the mission for half the money, not all of the mission for half the money. That is actually the honest core of the pitch. Air defence has always been about layers and percentages — no interceptor in history has guaranteed a kill — and a cheaper round that handles the large majority of realistic threats lets commanders reserve their most expensive interceptors for the shots that truly need them. The same logic drives the Army's hunt for a cheap counter-drone interceptor in the NGCM effort: stop spending seven-figure missiles on five-figure drones.

Fits the Launchers America Already Owns

A cheap interceptor that needs all-new infrastructure would not stay cheap for long, so Anduril is claiming broad compatibility with equipment already in service. The company says Steelfin is designed to launch from PAC-3 launchers (the M903A2), the Navy's Mk 41 Vertical Launching System, the Army's Typhon mid-range capability launchers, and containerised launchers. On the fire-control side, it claims compatibility with Aegis and the Army's IBCS battle command system.

Again, these are design and compatibility claims at unveiling, not completed qualification results — integrating a new missile with Aegis and IBCS is years of testing, not a software patch. But the intent is clear and strategically smart: Steelfin is not asking any service to rip out its launchers, radars or command networks. It is asking to be loaded into them. That is the same plug-in logic Lockheed is pursuing from the incumbent side with the PAC-3 Edge interceptor unveiled on October 9 — and the fact that both the disruptor and the incumbent launched rival answers within days of each other tells you how hot this fight has become.

Two Years of Work, Ballistic Tests Done, Flight Tests Next Year

Anduril says Steelfin is not a render. The company states it has been working on the family for about two years, and that it has completed ballistic testing with representative vehicles — ground and ballistic work short of full guided flight. Flight testing of the variants is planned to start next year. That timeline matters for how seriously to take the claims: the cost and performance numbers above are targets and modelling until a Steelfin actually flies, guides and hits something under test conditions.

The commercial context is just as real as the technical caveats. Anduril is competing in the Army's low-cost interceptor effort and the wider Future Interceptor space, following the xTech Apex Intercept competition. Meanwhile the incumbent is not standing still: PAC-3 production is being ramped toward 2,000 missiles a year under a framework worth up to $58.6 billion. Steelfin is swimming directly into the strongest current in the missile industry — with wars in Ukraine and the Middle East burning through interceptor stockpiles faster than factories can refill them.

The Production Ambition: Several Thousand a Year

Anduril says it aims to produce several thousand Steelfins a year in the short term. Be precise about what that is: a production ambition, stated by the company, not a contracted quantity. No Steelfin production contract with published numbers is in hand at unveiling. Still, the ambition itself is the strategy. The Pentagon's deepest air-defence anxiety is not whether its best interceptor works — it is whether it can ever own enough of them. A design built from modular, swappable parts is meant to be manufactured at rates the exquisite-missile model has never achieved, and Anduril has built its reputation on betting its own money on factory capacity ahead of contracts.

Why It Matters

First, the cost curve is the battlefield. Attackers have learned to build cheap mass — Shahed-type drones, cruise missiles and ballistic salvos designed to exhaust magazines. A defender whose cheapest credible shot costs a third of today's standard changes every exchange calculation an attacker makes.

Second, one family across three sizes simplifies everything downstream — training, logistics, stockpile planning and upgrades. When the terminal interceptor is common, improving the seeker or the software improves the whole family at once.

Third, this is a direct challenge to the prime-contractor model in the Army's most urgent mission area. If Steelfin flies well next year and prices anywhere near its claims, the pressure on every legacy interceptor program to cut cost and raise production rates becomes irresistible. If it stumbles, the episode still proves how badly the Pentagon wants a second source.

Frequently Asked Questions

What is Anduril Steelfin?

Steelfin is a modular two-stage interceptor family unveiled by Anduril on October 12, 2026, ahead of AUSA. It uses a common second-stage terminal interceptor with swappable boosters in 10-inch, 18-inch and 21-inch diameters, plus swappable radar and infrared seekers and motors, covering targets from Shahed-type drones to ballistic, cruise and hypersonic weapons.

Is Steelfin really a third of the price of PAC-3?

That is Anduril's stated aim for the low-end configuration, and the company claims a PAC-3-type configuration could deliver about 80% of that mission at under 50% of the cost. These are company claims made at unveiling; they are not independently verified, and no Steelfin variant has flown yet. Flight testing is planned for next year.

What can launch Steelfin?

Anduril claims launch compatibility with PAC-3 M903A2 launchers, the Mk 41 Vertical Launching System, Typhon launchers and containerised launchers, with fire control through Aegis and the Army's IBCS. These are design claims at unveiling; full qualification testing lies ahead.

When will Steelfin be operational?

There is no announced operational date. Anduril says it has worked on the family for about two years, has completed ballistic testing with representative vehicles, and plans flight testing of variants starting next year. The company aims to produce several thousand a year in the short term, but that is an ambition, not a contract quantity.

Our Take

Steelfin's unveiling is best read as a well-aimed bet, not a finished weapon. The modular logic is sound, the launcher-compatibility pitch is exactly what a challenger should offer, and the cost problem it attacks is the most real problem in air defence today. But the discipline this subject demands is simple: claims are claims until interceptors fly. PAC-3's price buys a combat-proven record that no slide deck can replicate, and Lockheed's production ramp and PAC-3 Edge show the incumbent fighting back hard. Watch next year's flight tests. If Steelfin hits its targets at anything near its promised prices, October 12, 2026 will be remembered as the day the interceptor market cracked open. If it does not, it will be remembered as a very expensive press release. Either way, the era of the unchallenged seven-figure interceptor is over.

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