The whole idea of a NMD system is to provide a type of shield that will guard against a light ballistic-missile attack. Tracking enemy missiles by radar is all well and good, but the point of the NMD system is to shoot them down before they get to U.S. air space. This will be no small task for the American military, and there is still much testing to do. Let's take a look at one of the NMD's ground-based interceptors.
The ground-based interceptors include two parts:
- Payload Vehicle (PLV) - Flight tests have been conducted with a PLV designed by Lockheed Martin. It consists of the second and third stages of retired Minuteman II boosters. The Minuteman II PLV will later be replaced with a more advanced model for one-site coverage of the entire United States. In addition to the two booster stages on the PLV, there is also a payload shroud attached to the top. The payload shroud contains the EKV.
- Exoatmospheric Kill Vehicle (EKV) - The kill vehicle is the bullet of NMD's weapon system. This device is intended to impact the targeted missile at a velocity of 15,000 mph (24,140 kph). The force of the collision should destroy any ballistic missile, according to defense officials.
The Battle Management, Command, Control and Communications (BMC3) is the nerve center of the NMD system. It begins tracking the threatening ballistic missile as soon as it is launched by an enemy state. Information about the enemy missile, including trajectory and probable impact point, is relayed to the BMC3 from space-based sensors and ground-based radar. In about 20 minutes after the enemy missile is launched, an interceptor takes off. This interceptor is programmed with information gained from the radar.
Approximately two-and-a-half minutes after take-off, the kill vehicle will separate from the booster. Just prior to this separation, the kill vehicle will be given a final update about the target. The kill vehicle will be about 1,400 miles (2,253 km) away from its target when it separates. It will then begin a set of maneuvers to calibrate its sensors. One way it calibrates itself is by doing a star shot. A star shot involves the EKV comparing itself to a constellation that it is programmed to look for.
After the EKV is finished with calibration, it will seek out, acquire and guide itself toward the target without any external guidance or communications. This happens about six minutes after takeoff. Then, the EKV draws a figurative bull's eye on the targeted ICBM and begins a collision course. If everything goes according to plan, the EKV will collide with the target 120 miles (193 km) above Earth.
The process of pinpointing, aiming an interceptor at and then killing the target with an EKV is very complex. There are many components that have to be coordinated in real time, and the entire procedure is completed less than 30 minutes after the enemy missile takes off. Some critics have said that the system is too complex to work effectively. The military has had mixed success in testing the system.