The Ground-Based Interceptor (GBI) is the interceptor component of the Ground-Based Midcourse Defense System (GMD) administered by the Missile Defense Agency. The GBI’s role is to intercept missile threats outside of the Earth’s atmosphere and destroy them by the kinetic force. GBIs are deployed as dormant missiles that launch from underground silos in the event of a ballistic missile attack. As of 2009, GMD is the only defensive system that can intercept Intercontinental-Range Ballistic Missiles in their midcourse phase of flight.

The GBI is made up of a three-stage, solid fuel booster and an exoatmospheric kill vehicle (EKV.) When launched, the booster missile carries the EKV toward the target’s predicted location in space. As the missile closes in on its target, the GBI launches the EKV, armed with a high-sensitivity infrared seeker and an agile divert system, it carries. Once released from the booster, the 152 pound kill vehicle uses data received in-flight from ground-based radars and its own on-board sensors to close with and destroy the target using only the force of the impact.

• GBIs are deployed at Fort Greely, Alaska (22) and Vandenberg Air Force Base, California (3).
• Ground-Based Midcourse Defense fire control centers have been established in Colorado and Alaska.
• Several existing early warning radars located around the world, including one on Shemya Island in the Alaskan Aleutian chain, have been upgraded to support flight tests and to provide tracking information in the event of a hostile missile attack.
• Plans to deploy two-stage GBIs to Poland and accompanying radar systems to the Czech Republic were cancelled.
• Boeing introduced concept models for a two-stage interceptor that would be capable of deployment within 24 hours in August 2009 in response to political constraints to fixed GBI deployment.
• Up to 30 GBIs are scheduled to be deployed by the end of 2010.

Specifications

• Length: 16.8 m (55 ft)
• Diameter: 1.27 m (50 in)
• Weight: 12700 kg (28000 lb)
• Ceiling: 2000 km (1250 miles)

• 1st stage: Alliant Tech Orion 50SXLG solid-fueled rocket; 441 kN (99000 lb)
• 2nd stage: Alliant Tech Orion 50XL solid-fueled rocket; 153 kN (34500 lb)
• 3rd stage: Alliant Tech Orion 38 solid-fueled rocket; 32 kN (7200 lb)
• Warhead: EKV "hit-to-kill" vehicle