Comparison of anti-ballistic missile systems

• Missile defense systems by country
• Anti-ballistic missile defense countermeasure

• System name: Many systems have numerous iterations or block upgrades, or have had multiple names. The primary or current system in use is described and noted, with the specific weapon iteration noted as appropriate.
• Period of use: ABM systems have protracted development periods. The time the system is or was in operational use is described.
• Intercept: Most systems can be used in different phases of ballistic missile flight, i.e., boost^[88] (where surface or air-launched anti-aircraft missiles might also be effective because the ballistic missile is moving relatively slowly at low altitude), requiring proximity to the launch site and immediate response, mid-course/exo-atmospheric,^[89] and re-entry/terminal.^[90] The principal intended phase of ballistic missile interception is noted. Other phases may be tried, with less effect. The earlier in flight that a missile is intercepted, the greater area a system may defend. Mid-course interception requires an ABM launch position between the ballistic missile launch site and the area defended. Terminal defense usually protects a relatively small area (i.e., Moscow, Minot Air Force Base missile fields) from projectiles in the re-entry phase.^[86][91]
• Role: Ballistic missile speed roughly corresponds to range. MRBMs move faster than SRBMs, IRBMs faster than MRBMs, and ICBMs faster than IRBMs.^[86][92] Each iteration demands greater speed, range, and targeting capability (either in accuracy or warhead power).
• Weight: Weight roughly correlates to one or more of range/ceiling, speed/acceleration, or warhead size.
• Warhead type: Lacking precision guidance systems, early systems relied on nuclear blast to destroy ballistic missiles.^[93] Systems intended for dual-role anti-aircraft/anti-SRBM and MRBM systems typically use blast/fragmentation warheads. Newer systems intended for IRBMs and ICBMs with high-altitude interception typically use hit-to-kill kinetic intercept profiles.^[94]
• Range and ceiling: Maximum range does not necessarily coincide with maximum ceiling.
• Speed: Speed, along with ceiling, correlates to intercept capability, with ICBMs demanding the greatest speed and acceleration.^[95] The terminal defense role of the Sprint system demanded extraordinary acceleration over a very brief period to intercept ICBMs that leaked through higher-altitude defense systems, or which were revealed when decoys disappeared at lower altitudes.^[96] A high speed at low altitude (as with Sprint) is much more challenging than a high speed at high altitude.^[97]
• Cost: Selected approximate costs are indicated for specific versions/blocks. These may vary significantly depending on the years procured and which upgrades they may incorporate. For instance, the cost of an SM-6 may vary by more than 100% depending on which version is examined, from about $4.25 million for Block I/IA to about $8.5 million in 2024 costs for Block IB. Costs in general appear to decline over time for United States weapons of the same version.^[98]
• Hypersonic weapons: Nearly all ballistic missiles reach hypersonic speeds during re-entry, leading to assertions that they are "hypersonic weapons." Strictly speaking, hypersonic weapons are not purely ballistic in their action, and use aerodynamic maneuvering to complicate or defeat interception by anti-ballistic missiles, rather than minor maneuvering to refine targeting accuracy, as advanced ballistic missiles may do.^[99]

The Israeli Iron Dome system is not specifically an anti-ballistic missile system, as it is intended primarily to counter unguided rockets and artillery projectiles, rather than guided missiles on trajectories that take them above Earth's atmosphere, re-entering at extreme velocities.^[100] Iron Dome uses principles that are similar to a true anti-ballistic missile system to intercept slower-moving short-range rockets and artillery projectiles, employing the Tamir missile at ranges of up to 70 km and altitudes to 10 km, at a cost of about $50,000 per missile. Iron Dome also has an anti-aircraft capability.^[101]

The U.S. Strategic Defense Initiative (SDI) investigated a variety of missile defense strategies, many involving exotic technologies such as the X-ray lasers^[102] envisioned by Project Excalibur, or the Brilliant Pebbles kinetic-kill satellite system.^[103] None of the more exotic systems were pursued to prototyping.