Ground-based Midcourse Defense (GMD) is an element of the Ballistic Missile Defense System that engages intermediate and long-range ballistic missiles during the midcourse phase.
It is the first operational missile defense program that is capable of protecting all 50 states. GMD detects and tracks long-range ballistic missiles in their boost phase, and destroys them during their midcourse phase, i.e. while the missiles are outside the atmosphere and at their highest trajectory.
GMD utilizes an Exo-atmospheric Kill Vehicle (EKV) to destroy the incoming target. It is a sensor-propulsion package that collides with the re-entry vehicle. This hit-to-kill technology has been proven in a number of successful flight tests, including three using Ground-Based Interceptors.
Although MDA developed many of GMD’s technologies during the 1980s and 1990s, the project officially began in 1998.
GMD consists of many synchronized components: Air Force Defense Support Program (DSP) satellites; Space Based Infrared System-High (SBIRS-High) satellites; the Space Tracking and Surveillance System (STSS); Upgraded Early Warning Radars (UEWRs); a Battle Management, Command, Control and Communications (BMC3) unit; the Sea-Based X-Band Radar (SBX); and Ground-Based Interceptor (GBI) missiles. 1
The DSP and SBIRS-High satellites scan the horizon for hostile ballistic missile launches, and then estimate the missile’s flight path. The STSS system monitors the threat as it makes its way across the globe and the UWERs predict its final destination, allowing GMD to launch its interceptors as early as possible. The BMC3 unit on the ground integrates all surveillance and tracking information.
The interceptor missile itself, known as the Ground-Based Interceptor (GBI), is located in an underground silo. Once launched, the GBI travels toward the target’s predicted location, receiving in-flight updates along the way.
The Ground-Based Interceptor (GBI) is a component of the Ground-Based Midcourse Defense (GMD) System. It is launched from a silo and intercepts ballistic missiles in their midcourse, while they are outside of the atmosphere and at their highest trajectory. The GBI consists of a multi-stage rocket booster (BV – Boost Vehicle) and a kinetic kill vehicle (EKV – Exoatmospheric Kill Vehicle), which makes interception of ballistic missile warheads possible using hit-to-kill technology. It was deployed in 2004 and has been a critical part of the GMD system since. 2 Boeing is in charge of GBI’s development, and the project is currently undergoing extensive ground and flight tests. 3
At a predetermined point, the GBI releases its Exoatmospheric Kill Vehicle (EKV). The EKV is 55 inches long and weighs 140 pounds. It has its own infrared seeker, guidance system, and motor. As it closes in on its target, the EKV integrates data from the XBR with its on-board sensors and locks on to the enemy missile. The EKV continuously adjusts its flight path until it collides with the target (like a bullet hitting a bullet). The hit-to-kill impact causes complete destruction of the warhead, including any nuclear, chemical, or biological agents.
Since 1999, MDA has conducted seven hit-to-kill tests. Five have been successful. The most recent was on October 14, 2002, when a GBI from the Reagan Test Site in the central Pacific Ocean tracked and destroyed a target vehicle launched from Vandenberg Air Force Base in California at an altitude of 140 miles and a closing speed in excess of 15,000 miles per hour.
Due to these successes, the GBI program had received enthusiastic support from the Bush Administration. Currently 30 GBIs are deployed in silos, 26 in at Fort Greely in Alaska and 4 at Vandenberg Air Force Base in California. An additional 14 silos in Alaska are available, but there are currently no public plans to fill them. 4
- “Defense, Space & Security.” Boeing: Missile Defense Systems. N.p., n.d. Web. 25 Oct. 2012. <http://www.boeing.com/defense-space/space/gmd/index.html>. ↩
- “Mostlymissiledefense.” Mostlymissiledefense. N.p., n.d. Web. 11 Oct. 2012. <http://mostlymissiledefense.com/2012/07/24/ballistic-missile-defense-how-much-does-a-gbi-interceptor-cost-july-24-2012/>. ↩
- “Defense, Space & Security.” Boeing: Missile Defense Systems. N.p., n.d. Web. 11 Oct. 2012. <http://www.boeing.com/defense-space/space/gmd/>. ↩
- “Boeing Ground-Based Interceptor (GBI).” Boeing Ground-Based Interceptor. N.p., n.d. Web. 11 Oct. 2012. <http://www.designation-systems.net/dusrm/app4/gbi.html>. ↩