Would Space-Based Defenses Improve Security?

One could almost hear the gears shifting in the United States and around the world as President George W. Bush announced on December 13, 2001, that the United States would withdraw from the 1972 Anti-Ballistic Missile (ABM) Treaty on June 13, 2002. Although the formal announcement was not greatly surprising, it served notice that the United States was replacing its rhetoric regarding the deployment of missile defenses with action. The precise implications of withdrawal are still somewhat undefined, but the administration has indicated it plans to pursue an operational national missile defense system aggressively. Undoubtedly, historians will link Bush's legacy inextricably to the successes and failures in the ongoing global war on terrorism. Significant changes in the decades-long debate about national missile defense, however, will also define the first U.S. presidency of the twenty-first century. Accordingly, Bush and Secretary of Defense Donald Rumsfeld have indicated they will pursue a prominent role for space-based components in the U.S. missile defense program.

Given this near certainty, asking whether a move to use space in support of missile defenses will improve U.S. security and, if so, how is appropriate. A full understanding of the answers to these questions requires recognition of the ways space systems can contribute to the missile defense mission, as well as the strategic and operational benefits that space-based missile defense components could provide. This understanding addresses only one dimension, however, of whether such a move improves U.S. security. Determining the effects of deploying space-based missile defenses on today's geopolitical framework is also important. How will such a move affect strategic stability, and how will the international community view these actions? Finally, has technology progressed to a stage that will make space-based missile defenses possible?

Ballistic Missiles Explained

The ballistic missile defense (BMD) mission is highly complex and requires the integrated use of air-, land-, sea-, and space-based systems. From the advent of the German V-2 ballistic missile in World War II to the latest intercontinental ballistic missiles (ICBMs), planners have tried to determine how they might defend their nations against the ballistic missile threat. When the October 4, 1957, launch of Sputnik I brought the world into the space age, analysts began to examine the possibilities of using space to support BMD requirements. During the past four decades, military officials have explored many space-based missile defense concepts but have deployed very few.

Although ICBMs are highly complex weapons, their basic operational philosophy is simple. A powerful, multistage rocket boosts a nuclear payload into a ballistic trajectory calculated to deliver the payload to a specific target location. All ICBMs have three well-defined phases of their mission—the boost phase, the midcourse phase, and the terminal phase.

• Boost Phase. The missile's rocket engines accelerate the payload to speeds of more than 15,000 miles per hour in this portion of the ICBM's mission. On a typical ICBM, the boost phase consists of the sequential firing of several separate stages that lasts for four to five minutes. The ICBM must attain extremely high speeds to allow the payload to reach targets on the other side of the world—targets that can be more than 6,000 miles from the launch site. The payload of the ICBM consists of three primary elements—nuclear warheads, decoys, and a postboost vehicle. The postboost vehicle is a small satellite that automatically functions like a high-tech taxicab for its deadly cargo of warheads and decoys, maneuvering to different points in space and dropping off each warhead and decoy at the exact speed and location required for the warhead to fall along the necessary trajectory to hit its target. Some modern ICBMs can carry as many as 10 independently targetable warheads. The boost phase is completed when the last booster stage stops firing and the booster separates from the payload.
• Midcourse Phase. Once the boost phase is completed, the warheads, decoys, and...