1.  Field of the Invention
The present invention relates to defense systems for atmospheric and extraterrestrial vehicles.  More particularly, the present invention relates to a method and system for defending a vehicle which involves deployment of a body from the vehicle which can either serve as a decoy, by diverting an approaching threat, and/or serve as a kinetic kill device by positioning itself to collide with the threat. 
2.  Description of the Related Art
Defensive strategies used by aircraft to defend against approaching threats include passive defense to avoid a threat, active defense to deceive a threat, and lethal defense to kill the source of the threat.  Methods currently being used to implement these defensive strategies include low altitude sanctuary, terrain masking, expendable countermeasures, electronic countermeasures (ECM), air-to-air missiles, air-to-surface missiles, and most recently, low observable, or "stealth" technology.  These methods provide a substantial measure of survivability in a very hostile threat environment, but face continual pressure to keep pace with threat upgrades.  Examples of prior art decoys/targets are included in the following references:
U.S. Pat.  No.  2,957,417, issued to D. D. Musgrave, entitled "Missile Decoy", discloses a decoy system comprising a shroud fixed to the fins of a missile having an internal reflective surface of partial parabolic shape. 
U.S. Pat.  No.  2,898,588, issued to C. L. Graham, entitled "Attack Deviation Device", discloses a device comprising a hollow elongated member which is towed behind an aircraft.  There is structure in the member for reflecting radar signals impinging thereon. 
U.S. Pat.  No.  4,808,999, issued to D. Toman, entitled "Towed Decoy with Fiber Optic Link", discloses a decoy which is towed behind an aircraft using a tow line which incorporates a fiber optic link through which signals are transmitted. 
U.S. Pat.  No.  4,419,669, issued to D. M. Slager, entitled "Controlled Scintillation Rate Decoy", discloses a decoy having a spherical body with microwave reflectors for reflecting incident radar energy in a manner to provide the decoy with the selected radar cross section. 
U.S. Pat.  No.  3,290,681, issued to R. H. Beteille, entitled "Device for Jamming Radar Detection and Interception of Ballistic Missiles", discloses the use of decoys consisting of metallized inflatable balloons. 
U.S. Pat.  No.  3,568,191, issued to J. C. Hiester, entitled "Method for Defending an Aircraft Against a Frontal Attack", discloses a method of launching a rocket in the direction of travel of an aircraft, the rocket containing, in a collapsed, condition a collapsible reflector having three orthogonal surfaces of wire mesh.  The reflector is ejected from the rocket, expanded, and thereby towed, the reflector serving as a target for attracting the interceptor. 
U.S. Pat.  No.  3,126,544, issued to W. H. Greatbatch, Jr., entitled "Method of Deception for an Aircraft", discloses deployment of a spherically shaped decoy that is provided with a plurality of target plates.  The decoy is illuminated with RF energy, the interceptor being deceived into following the decoy target. 
U.S. Pat.  No.  3,045,596 entitled "Guided Missile", issued to R. S. Rae discloses a controlled missile having structure including a spherical body having spaced ports for the discharge of jets in such a manner so as to lift and propel the missile.  The guided missile is launched and controlled in aerial flight by the operator from the time of launching to the time of contact with a target.  The Rae device weighs on the order of 300 pounds and is two feet in diameter.  It carries explosives. 
None of the aforementioned references disclose a defense system or apparatus having 1) a guidance system capable of operating independently of the launch vehicle and/or operator, and 2) a propulsion system having the ability to accurately maneuver the body relative to the threat in the absence of a substantial axial velocity so as to eliminate the threat. 
As will be disclosed below, present applicants have developed a novel system and method for defending a vehicle against an approaching threat which provides these capabilities.  This patent application is related to patent application Ser.  No.  07/493,088, entitled "Killer Volleyball For Vehicle Defense" filed concurrently herewith and patent application Ser.  No.  07/493,087, entitled "Killer Volleyball Launcher".  All three patent applications are assigned to the present assignee, Rockwell International Corporation
The term "Killer Volleyball" or "KV", as used herein and in the aforementioned, concurrently filed patent applications, refers to the presently disclosed apparatus for defending a vehicle, which is specifically claimed in Ser.  No.  07/493,088.  This is the terminology used during the KV's development by Rockwell International Corporation.