How Anduril's Steelfin Swaps Boosters to Undercut Patriot Prices
Anduril's new interceptor family bets that one common upper stage on 10- to 21-inch boosters can be built by the thousands. Set against the Pentagon's own PAC-3 MSE numbers, the price targets look less firm, and the missile has yet to fly.
In Anduril's rendering, Steelfin comes in two pieces. The lower half, stenciled "01," is a booster, a solid-rocket tube that throws what sits on top. The upper half, "02," carries the Anduril logo and does the hard part: finding a target and hitting it. The bet is that the top half stays the same while the bottom half changes, so one missile becomes many.
Anduril Industries unveiled Steelfin on Monday, Oct. 12, the eve of the Association of the U.S. Army's annual meeting in Washington, calling it a family of highly-configurable, mass-producible surface-to-air interceptor missiles.
Executives pitched it against Lockheed Martin's PAC-3 MSE, the Patriot interceptor the U.S. has been firing at Iranian drones and missiles faster than it can buy them. It has not flown.
Steelfin is a two-stage interceptor that pairs interchangeable 10-, 18- and 21-inch boosters with one common upper stage. Anduril says it will build on the order of several thousand
a year at a fraction of the cost of a PAC-3 MSE, which TWZ puts at about $5.3 million. So far it has done only ballistic testing with representative air vehicles
; flight tests start in 2027.
That makes the real claim industrial, not aerodynamic: one line turning out many missiles is a wager on volume, aimed at the gap the Iran fighting exposed. The prices attached are targets, and they changed depending on which outlet heard them.
A common dart rides on swappable boosters
The first stage, says Anduril's announcement, takes different solid rocket motor boosters
to suit the range and the launcher. It is the "how far, how high" half. Anduril's product page says it can be scaled up in length and diameter to maximize performance as launch platforms allow, or scaled down to trade performance for cost.
The second stage is the "find and hit" half, and it stays put. Every variant shares the same baseline airframe, avionics, software, flight control system, and interfaces.
Open interfaces let Anduril change seekers without redesigning the entire missile.
Those include radars and infrared seekers, Anduril missile executive Steve Milano told Aviation Week. TWZ reports Anduril will offer hit-to-kill stages, which destroy a target by ramming it, and blast-fragmentation stages, which burst nearby and shred it.
The booster diameters Anduril named, 10, 18 and 21 inches, map onto missiles that already exist. Per Aviation Week, PAC-3 is 10 inches across, THAAD 15.7 inches and SM-3 Block IIA 21 inches. So the smallest Steelfin booster matches the Patriot class and the largest matches SM-3 in a ship's Mk 41 cell, with 18 inches in between. Christian "Chris" Brose, Anduril's president and chief strategy officer, told TWZ the company is also looking at quad pack and dual pack
options, which stack smaller missiles in one Mk 41 cell for magazine depth.
Anduril says Steelfin fits the M903A2, Mk 41 and Typhon launchers and works with Aegis and IBCS fire control. The M903A2 is the trailer launcher for newer PAC-3 rounds, per TWZ, which says plenty about the first customer Anduril wants. The claimed reach runs from point defense to upper-tier ballistic missile defense,
short of exoatmospheric midcourse interception, TWZ notes.
"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,"
Christian Brose, Anduril
The factory logic follows: build one upper stage in volume and let final assembly decide which missile it becomes. Whether one dart works on both a 10-inch Patriot booster and a 21-inch naval one is what nobody outside Anduril has seen.
Pricing a missile that has no price
Anduril has disclosed no unit prices or detailed specs, TWZ and Defence Industry Europe report. What exists are ratios. Executives aim for Steelfin to cost a third of the price of a PAC-3 MSE, Breaking Defense reported. TWZ heard Milano say a PAC-3-type configuration would deliver 80 percent of that mission at less than 50 percent of the cost, and that Steelfin provides greater than 80 percent of the capability of an SM-2 for a third of the cost.
Here is what those ratios imply against TWZ's benchmark prices:
| Benchmark | Benchmark price | What Anduril said | What that implies for Steelfin |
|---|---|---|---|
| PAC-3 MSE | about $5.3M (TWZ) | a third of the price (Breaking Defense report) | about $1.8M |
| PAC-3 MSE, PAC-3-type mission | about $5.3M | 80% of the mission at under 50% of the cost (TWZ) | under $2.65M |
| SM-2 Block IIIC | about $2.5M (TWZ) | more than 80% of the capability for a third of the cost (TWZ) | about $830,000 |
| THAAD | about $15.5M (TWZ) | 100% of the mission "at a fraction of the cost" (TWZ) | not stated |
| For comparison: Lockheed PAC-3 ACE | n/a | "less than half the cost of a PAC-3 MSE" (Lockheed) | under $2.65M |
| For comparison: Army low-cost interceptor | n/a | target under $1M | n/a |
The two PAC-3 versions tell different competitive stories. A third of $5.3 million is about $1.8 million, below the roughly $2.5 million TWZ infers for PAC-3 ACE, the cheaper Patriot round Lockheed announced on Monday, July 20, at less than half the cost of a PAC-3 MSE per unit.
But "under 50 percent" lands at the very ceiling Lockheed already claims for ACE.
The 80 percent caveat matters too. Under half the cost for 80 percent of the mission works out to at most about 63 percent of an MSE's cost per unit of capability. The saving per round is bigger than the saving per kill, because a lesser round may need more shots.
Then there is the Army's own bar. Its low-cost interceptor must come in under $1 million, roughly one-fifth of an MSE. Even the friendliest reading of Anduril's PAC-3-class targets, about $1.8 million, sits well above that. Only the SM-2-class configuration, at roughly $830,000, would fall under it.
The yardstick itself wobbles. TWZ reported in May that $5.3 million is up from a historical average of around $4 million, and dividing the PAC-3 MSE line in the Pentagon's fiscal 2027 budget, $13,960.3 million for 3,203 missiles, gives about $4.36 million each. That average folds in support costs and is a different measure from TWZ's unit price, but it shows how much the benchmark depends on who is counting.
What Anduril is really selling is a fix for mismatch. Long-range kamikaze drones carry unit prices measured in tens or hundreds of thousands of dollars,
TWZ notes, and defenders keep answering them with multimillion-dollar rounds. Anduril calls that trade punishing
over a sustained fight. Milano put it plainly: You have the flexibility to be able to engage Shahed-like things with the appropriate-cost missile, as opposed to firing the most exquisite system at the threat every time.
The factory is the pitch
Price makes headlines, but supply is the crisis. Lockheed delivered 620 PAC-3 MSEs in 2025. Under a seven-year framework announced Tuesday, Jan. 6, it plans to lift annual capacity from roughly 600 to 2,000, a ramp CEO Jim Taiclet said will be accomplished by the end of 2030.
On Monday, Oct. 5, Boeing got a contract worth about $14.7 billion from Lockheed to expand seeker production, AeroTime reported. The scramble has even pulled in carmakers, as GM and Lockheed's June manufacturing deal showed.
The fiscal 2027 request asks for 3,203 MSEs for the Army and Navy, 5.2 times Lockheed's 2025 deliveries. The money is arriving faster than factories can turn it into missiles.
The hole is deep. CSIS estimated the U.S. had about 2,300 Patriot interceptors before Operation Epic Fury. By July 27, TWZ reported, citing CSIS, that was down to between 759 and 827. THAAD fell from 452 to between 234 and 278.
That Patriot drop, 1,473 to 1,541 interceptors, equals roughly 2.4 to 2.5 years of Lockheed's entire 2025 output. Partners are stretched too: last month regional officials told AP that Saudi Arabia was running low on missile interceptors.
CENTCOM's Adm. Brad Cooper told Congress in May that regional air defenses intercepted over 6,000 one-way attack drones and more than 1,500 ballistic missiles.
The carrier USS Abraham Lincoln came home to San Diego with 103 attack drones painted on its side. Lt. Gen. John Rafferty, commander of Army Space and Missile Defense Command, has been blunt: I cannot add anything to the emphasis on magazine depth… or for the need for cheaper and wide-ranging mix of interceptors.
Anduril answers with volume on paper. Milano expects full-rate production at the end of 2028 or the beginning of 2029, Breaking Defense reported, with multiple thousands
a year at the low end and closer to hundreds of thousands
at the high end. Most subassemblies would come from Anduril's Arsenal-1 plant in Ohio, with final integration by partners. No contracted quantity or customer order has been published.
That puts Steelfin's full-rate start roughly two years ahead of Lockheed's 2,000-a-year finish line, an opening that narrows every quarter Lockheed stays on schedule.
The contracts are already moving. In May the Army sought a Patriot-compatible Low Cost Interceptor under $1 million a round, in four component groups capped at $250,000 each. Milano said Anduril is pursuing it with Steelfin. The bigger prize is the Future Interceptor, which Milano described to Aviation Week as filling the range gap between PAC-3 MSE and THAAD. Breaking Defense reported on Friday, Oct. 9 that Lockheed and one undisclosed company were selected; Anduril would not say whether it was the other. Milano called Steelfin a natural fit in that domain space.
The same day, Lockheed rolled out PAC-3 Edge for that program, with a Northrop Grumman multi-pulse motor, testing in 2027 and deployment by 2031.
Nor is the booster-swap idea Anduril's alone: the Navy's Naval Modular Missile concept pairs a common terminal stage with different boosters, aiming for 1,000 a year within five years of a contract, TWZ reports.
Strip away the ratios and what is proven is thin. Anduril has yet to develop or produce a surface-to-air missile,
TWZ notes, though its Roadrunner and the motor it supplies for Boeing's IFPC entry are related experience. No fielding date exists. TWZ's verdict is fair: modular designs are attractive, but realizing the benefits has historically proved difficult, and fraught with compromises.
Taiclet, describing the missile Steelfin is chasing, supplied the contrast himself:
"this is a known technology. This is not experimental. We're not on the edge of science here."
Jim Taiclet, chairman, president and CEO, Lockheed Martin, Jan. 6, 2026 briefing
Three things will settle it: the 2027 flight tests, an Army award that names Steelfin and a contracted price. Until then this is a proven missile built 620 a year against an unflown one promised by the thousands, and Steelfin's price targets are worth only what next year's tests prove about one dart riding many boosters.
