SM-3 Block IB vs Khorramshahr-4: Cost-Exchange Ratio & Combat Analysis
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2026-03-21
3 min read
Overview
This analysis compares the SM-3 Block IB, a US Mid-course BMD system costing $15.0M per unit, against the Khorramshahr-4, an Iranian Heavy MRBM costing $2.5M per unit. The cost-exchange ratio of 6.0:1 favors the attacker — meaning it costs the defender 6.0x more to intercept than the missile cost Iran to produce. Earlier-generation midcourse BMD interceptor with unitary kill vehicle Iran's heaviest MRBM — liquid-fueled, 3,000km range, 1,500kg warhead
Side-by-Side Specifications
| Dimension | Sm 3 Block Ib | Khorramshahr 4 |
|---|
| Unit Cost |
$15.0M |
$2.5M |
| Cost-Exchange Ratio |
6.0:1 |
6.0:1 |
| Range |
Mid-course BMD |
3000 km |
| Inventory |
~194 |
~50 |
| Annual Production |
18/yr |
— |
| Role |
Mid-course BMD |
Heavy MRBM |
| Manufacturer |
RTX/Raytheon |
Iran / IRGC |
| Fuel |
Solid rocket |
— |
Head-to-Head Analysis
Cost-Exchange Economics
The SM-3 Block IB costs $15.0M per unit while the Khorramshahr-4 costs just $2.5M, creating a 6.0:1 cost-exchange ratio. Unfavorable for the defender. The attacker has significant cost advantage. Iran can produce 6 Khorramshahr-4 units for the price of a single SM-3 Block IB interceptor.
The Khorramshahr-4 has a 6.0:1 cost advantage over the SM-3 Block IB. This asymmetry is a key factor in the conflict's economic sustainability.
Inventory & Depletion
Coalition forces have approximately 194 SM-3 Block IB interceptors with annual production of 18 units. Iran maintains an estimated 50 Khorramshahr-4 units. The SM-3 Block IB is already 20% depleted vs operational requirements.
Coalition holds an inventory advantage, but at 6.0:1 cost ratio, this is offset by economics.
Tactical Engagement
The SM-3 Block IB engages the Khorramshahr-4 during the flight phase. With 3000km range, the Khorramshahr-4 can be launched from deep within Iranian territory, complicating launch detection. CSIS Dec 2025: part of 414 SM-3 total. Reinstated Feb 2026. $475M allocation.
The SM-3 Block IB is designed to counter threats like the Khorramshahr-4, but sustained engagement at 6.0:1 cost ratios creates long-term sustainability challenges.
Scenario Analysis
Mass salvo of Khorramshahr-4 missiles
In a saturation attack using Khorramshahr-4 systems, the SM-3 Block IB battery would need to engage multiple targets simultaneously. At $15.0M per interceptor, a salvo of 1 Khorramshahr-4 missiles would cost $2.5M to launch but $15.0M to intercept.
Khorramshahr-4
Extended conflict (30+ days)
Over 30 days of sustained combat, the SM-3 Block IB inventory faces significant depletion pressure. Annual production of 18 units translates to just 0.0 per day — far below consumption rates during active operations. Meanwhile, Iran produces approximately 3.3 ballistic missiles and 6.7 drones per day.
Attacker (Iran) — production outpaces defender replenishment
Complementary Use
The SM-3 Block IB should be integrated into a layered defense architecture, not relied upon as a standalone solution against Khorramshahr-4 threats. Cost-effective lower-tier systems (Iron Dome at $80K, or Iron Beam laser at $2/shot) should handle cheaper threats when possible, preserving expensive SM-3 Block IB interceptors for high-value targets.
Overall Verdict
The SM-3 Block IB vs Khorramshahr-4 matchup produces a 6.0:1 cost-exchange ratio favoring the attacker. For sustained conflict planning, interceptor production ramp-up and cost-reduction programs are critical to maintaining defensive capability.
Frequently Asked Questions
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