U.S. Missile Defense in the 21st Century: Part 2

In light of the ballistic missile threats facing the United States, the question of missile defense is a serious one. The cost of failure could be at least thousands of lives and hundreds of billions of dollars. The wise course of action is to prevent such detrimental consequences as effectively as possible, so some experts have advocated a space based missile defense program.

Current U.S. missile defense capabilties are primarily ground-based. Recently, the United States has tested sea based missile defense options with Japan, but the most recent test failed according to a November 26 article on RFDesign.com. The two main alternatives for missile defense include a ground based boost-phase intercept system and a ground based midcourse intercept system.

Before you get lost in the jargon, let's back up a little bit. To understand U.S. missile defense, the first thing to focus on is the three phases of a missile's flight. According to the Missile Defense Agency (MDA), the first phase of a missile's flight begins with the boost phase. This phase begins as soon as the missile is launched and ends once the missile has entered into an eliptical orbit above the earth--roughly a 3-5 minute timeframe. Once this occurs, a new phase begins called the midcourse phase which describes the time in which the missile is in orbit. Obviously, the distance between targets plays a factor in the time of the midcourse phase, but the MDA points out that the phase can last up to 20 minutes. Once the missile nears its target, it will leave orbit and begin the terminal phase. During this final phase, it picks up speed as it approaches its (by now) doomed target. Within approximately 30 seconds, the missile makes its impact and ends the terminal phase of its flight.

Though the casual observer can tell that the midcourse phase is the longest part of the missile trajectory (and therefore, presumably the most vulnerable part of the flight), this is not the case. Jeremy Singer at SpaceNews.com reported that, "Ballistic missiles in theory are far easier to track and shoot down during liftoff, when they move relatively slowly and emit superhot exhaust plumes that are easily spotted by overhead infrared sensors. In addition, countermeasures such as decoys, a major headache for designers of midcourse defenses, are not much of a factor during the boost phase."

As we can see, although the midcourse phase is longer, the missile produces much less heat and also releases deocys that make it harder to target and hit while it is in the midcourse phase. Plus, the missile in midcourse travels faster than the missile in the boost phase. In other words, the missile is most exposed when in its 3-5 minute boost phase, not when it is in the midcourse phase.

A good understanding of the three phases of missile flight is essential to the understanding of interception capabilities, whether the discussion revolves around ground, sea, or space based defense systems. To cover for these phases of missile flight, Steven Lambakis notes in his article "Missile Defense from Space," that the current U.S. missile defense system includes "...space-based detection sensors, ground-based and seaborne early warning and tracking sensors, ground-based interceptors in Alaska and California for long-range defense, transportable ground-based Patriot Advanced Capability-3 units, and sea-based interceptors to engage short- and medium-range ballistic missiles." In other words, the U.S. boasts a mutli-layered system which, theoretically, gives it the capability to shoot down missiles in the boost and midcourse phase before they enter the terminal phase.

To clarify, advocates of space based missile defense do not simply advocate space based sensors as the United States already possesses those. Rather, they advocate a whole new missile shield that is based in space to compliment the current ground and sea based shields that the United States fields. Therefore, in the next article, we will look at current U.S. missile defense capabilities and determine whether or not a space based interception system (specifically designed to target enemy missiles in their boost phase) would enhance the current ground and sea based interception capabilities that Lambakis highlights.