China's Dong Feng-21D medium-range ballistic missile — otherwise known as the "carrier killer" — looms large in people's minds as a weapon of ultimate destruction.
It's designed to do exactly what the name implies: kill American and allied carriers, sending thousands of sailors to a watery grave.
But the Navy has been working to protect carriers from enemy ballistic missiles for decades. Here are three missiles that could stop a DF-21D in its tracks.
1. The Standard Missile-3
The SM-3 is the Navy's preferred tool for defeating an incoming ballistic missile. The system is deployed on Aegis ballistic missile defense ships in the U.S. Navy and KONGO-class destroyers in Japan's navy.
These missiles primarily engage their targets in space at the height of the ballistic missile's flight path. To hit a DF-21D, the Aegis system will need to be on or near the projected flight path. Keeping carriers safe may require keeping an Aegis ship equipped with SM-3s permanently co-located with the carrier.
2. Standard Missile-6
The SM-6 is really designed to take down cruise missiles and perhaps the occasional jet, but the Navy has been testing its capability when pressed into an anti-ballistic missile role. In a Dec. 14 test, an updated SM-6 fired from an aegis destroyer successfully struck down a medium-range ballistic missile.
These are much cheaper than SM-3s, but the SM-6 is a final, last-ditch defense while the SM-3 is still the first call. That's because SM-6s engage targeted missiles during their terminal phase, the final moments before the incoming missile kills its target. If the SM-6 misses, there isn't time to do anything else.
3. The Army's THAAD missile
The Terminal, High-Altitude Air Defense missile is a radar-guided, hit-to-kill missile that engages ballistic missiles either in the edge of space or soon after they enter the atmosphere. It might be capable of engaging a DF-21D after it begins its descent to the carrier.
The system is rapidly deployable and the Army has already stood up five air defense artillery batteries with the new missiles. One battery is deployed to Guam and plans are ongoing to deploy another to South Korea.
The main problem for the Navy when using THAAD to protect its ships is that the THAAD system is deployed on trucks, not ships. It's hard to keep land-based missiles in position to protect ships sailing on the open sea.