THAAD has absolutely nothing to do with the aforementioned SDI
system. It does not employ lasers
and orbiting satellites
to shoot down threatening missiles
It is amazing in the numbers of people that constantly deride the concept of body-to-body intercept. They claim that it is a pipe dream, or idiotic, while all the time this concept has been consistently proven to work in a multitude of flight tests and real life demonstrations. Most of these people have a poor background in physics and mathematics, and have not paid attention to the vast amounts of public information there is on the developmental status of missile defense projects. It is not the fact that people are critical of THAAD (or NMD related issues) that is bothersome; rather it is that more often than not, few scientific or technical reasons are presented to argue the point *why* it is idiotic and a pipe dream. Also, I rarely hear such people provide any examples of why such a system might be beneficial. Please consider the issue from both sides.
THAAD employs a ground-based interceptor missile which is designed to defeat theater, or medium-to-long range ballistic missiles. This interceptor missile does not employ a kill vehicle, it instead destroys the target by sheer force of impact. The interceptor itself uses infrared guidance. Track and discrimination are performed by the very sophisticated THAAD RADAR, located on the ground with the interceptor launcher and various other units.
THAAD can be considered the second in a tier of missile defenses. The first tier might be the NMD system, which has an extremely long range. If the NMD interceptor misses, the THAAD system might be employed later in the flight of the threat to attempt an intercept in exo, or at the threshhold of atmosphere. If THAAD was to fail, the next tier being the Patriot system might be called into action. We all remember how well the Patriot missile system shot down Scuds in the Gulf War.
I will put to rest a couple of misconceptions about THAAD. The interceptor is not an immature or drawing-board technology. The missile is a solid design, and many production-level interceptors have already been built by Lockheed Martin for testing and demonstration. The interceptor and THAAD radar system have been proven very successful in the last several flight tests in which intercepts were successfully made and the threatening missiles destroyed.