Directory of U.S. Military Rockets and Missiles|
Appendix 4: Undesignated Vehicles
|Copyright © 2003 Andreas Parsch|
In the late 1970s, the development of nuclear-armed ABMs (Anti-Ballistic Missiles), which had culminated in the operationally deployed Safeguard system with LIM-49 Spartan and Sprint missiles, was increasingly regarded as a dead end. The U.S. Army began studies about the feasibility of hit-to-kill vehicles, where an interceptor missile would destroy an incoming ballistic missile just by colliding with it head-on.
The first program, which actually tested a hit-to-kill missile interceptor, was the Army's HOE (Homing Overlay Experiment). The HOE vehicle consisted of the first two stages (Thiokol M55E1 + Aerojet General M56A1) of a LGM-30A/B Minuteman I ICBM, which boosted a large KKV (Kinetic Kill Vehicle) to high altitude. The KKV was equipped with an infrared seeker, guidance electronics and a propulsion system. Once in space, the KKV could extend a folded structure similar to an umbrella skeleton of 4 m (13 ft) diameter to enhance its effective cross section. This device, which also had weights attached to the ribs, would destroy the ICBM reentry vehicle on collision.
|Photo & Image: Lockheed Martin Missiles and Space|
|HOE||HOE (kill vehicle)|
A total of four intercepts were attempted in the HOE test program. In each test, a Minuteman ICBM with a dummy warhead served as the target. The first attempt on 7 February 1983 missed because a failure in the IR sensor prevented proper target tracking. The next two flights in May and December 1983 failed, too, because of malfunctions in the guidance system. However, the fourth and final test on 10 June 1984 was successful, intercepting the Minuteman RV with a closing speed of about 6.1 km/s (20000 fps) at an altitude of more than 160 km (100 miles).
The successful test came right on time for the SDI (Strategic Defense Initiative) program, which had been officially established in January 1984. One of the primary elements of SDI were ground-based reentry vehicle interceptors without nuclear warheads. The technology tested by HOE formed the base for ERIS (Exoatmospheric Reentry Interceptor Subsystem), the upper-tier component of SDI's ground-based missile defense.
I have no data about the exact physical characteristics of the HOE test vehicles. For data on the Minuteman I 1st and 2nd stage motors, refer to the LGM-30 Minuteman page.
 Bernard Blake (ed.): "Jane's Weapon Systems 1987-88", Jane's, 1988
 Missile Defense Agency Website
 Chronology of Missile Defense Tests
Back to Directory of U.S. Military Rockets and Missiles, Appendix 4