aircraft needs to support the missile guidance until missile seeker acquisition. No-escape zone The no-escape zone is the zone within which there is a high (defined) kill probability against a target even if it has been alerted. This zone is defined as a conical shape with the tip at the missile launch. The cone's length and width are determined by the missile and seeker performance. A missile's speed, range and seeker sensitivity will mostly determine the length of this imaginary cone, while its agility (turn rate) and seeker complexity (speed of detection and ability to detect off axis targets) will determine the width of the cone. Dogfight Short-range air-to-air missiles used in "dogfighting" are usually classified into five "generations" according to the historical technological advances. Most of these advances were in infrared seeker technology (later combined with digital signal processing). First generation Early short-range missiles such as the early Sidewinders and K-13 (missile) (AA-2 Atoll) had infrared seekers with a narrow (30-degree) field of view and required the attacker to position himself behind the target (rear aspect engagement). This meant that the target aircraft only had to perform a slight turn to move outside the missile seeker's field of view and cause the missile to lose track of the target ("break lock"). Second generation Second-generation missiles utilized more effective seekers that improved the field of view to 45 degrees. Third generation This generation introduced "all aspect" missiles, because more sensitive seekers allowed the attacker to fire at a target which was side-on to itself, i.e. from all aspects not just the rear. This meant that while the field-of-view was still restricted to a fairly narrow cone, the attack at least did not have to be behind the target. Fourth generation The R-73 (missile) (AA-11 Archer) entered service in 1985 and marked a new generation of dogfight missile. It had a wider field of view and could be cued onto a target using a helmet mounted sight. This allowed it to be launched at targets that would otherwise not be seen by older generation missiles that generally stared forward while waiting to be launched. This capability, combined with a more powerful motor that allows the missile to maneuver against crossing targets and launch at greater ranges, gives the launching aircraft improved tactical freedom. Other members of the 4th generation use focal plane arrays to offer greatly improved scanning and countermeasures resistance