Since many systems have developed in stages or have many iterations or upgrades, only the most notable versions are described.
For example, David's Sling is a system that employs the Stunner missile.
Legend for ABM system status in below table: Operational In development Inactive Unknown status 2017-present 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.
[85] 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 70km and altitudes to 10km, at a cost of about $50,000 per missile.
[86] The U.S. Strategic Defense Initiative (SDI) investigated a variety of missile defense strategies, many involving exotic technologies such as the X-ray lasers[87] envisioned by Project Excalibur, or the Brilliant Pebbles kinetic-kill satellite system.