WSF_SAM_LAUNCH_COMPUTER

launch_computer WSF_SAM_LAUNCH_COMPUTER

launch_computer <name> WSF_SAM_LAUNCH_COMPUTER
   ... launch_computer Commands ...
   ... WSF_LAUNCH_COMPUTER Commands ...
   ... WSF_SAM_LAUNCH_COMPUTER Commands ..
end_launch_computer

Overview

WSF_SAM_LAUNCH_COMPUTER implements a launch computer for a surface-to-air missile system, and tabulates the expected time to intercept for a missile fired at some down-range and altitude away from the shooter, assuming the target does not maneuver during missile flight. Expected time of flight is obtained as an interpolated four-dimensional table lookup. The independent value arrays (lateral offsets, altitudes, ranges, speeds) are provided prior to the intercept results (within the intercept_envelope block) obtained under the defined set of independent conditions.

The weapon_tools application assists with creation of launch computers of this type. (See SAM_LAUNCH_COMPUTER_GENERATOR).

Commands

lateral_offsets <distance-values> end_lateral_offsets

Provides a listing of the lateral offsets used as the first independent variable (slowest-changing index) in the intercept_envelope which follows. Lateral offset is the horizontal distance with which the target would overfly the launcher if the current track is maintained. Values are to be provided in increasing order, and the effect is assumed symmetrical about the launcher’s line-of-sight axis.

altitudes <altitude-values> end_altitudes

Specifies the target altitudes used as the second independent variable in the intercept_envelope below. May be uneven but must be in increasing numerical order.

ranges <range-values> end_ranges

Specifies the ground ranges used as the third independent variable in the intercept_envelope. May be uneven but must be in increasing numerical order.

speeds <speed-values> end_speeds

Specifies the target speeds used as the fourth independent variable in the intercept_envelope. May be uneven but must be in increasing numerical order.

intercept_envelope … end_intercept_envelope

This block contains the data that defines the intercept envelope. By convention, any unsuccessful intercept point may be omitted from the tabulation, and a time-of-flight of -1.0 seconds (a miss) is assumed. The five index values given in the example below are printed out by the class weapon_tools generator, and are used to assure proper indexing when the data is read in by the stream parser.

intercept_envelope
   # "intercept" intercept_index lateral_offset_index
   #    lateral_offset_value altitude_index altitude_value
   #    ground_range_index ground_range_value speed_index
   #    speed_value time_of_flight_value
   intercept 0 0 0 m 0 300 m 0 0 m 1 50 m/s 31.3536 sec
   intercept 1 0 0 m 0 300 m 0 0 m 4 200 m/s 19.9911 sec
   intercept 2 0 0 m 0 300 m 0 0 m 5 250 m/s 20.5551 sec
   intercept 3 0 0 m 0 300 m 0 0 m 6 300 m/s 21.9581 sec
   intercept 4 0 0 m 0 300 m 0 0 m 7 350 m/s 23.5001 sec          .
   .
   .
   .
end_intercept_envelope

interpolation_test … end_interpolation_test

For debug purposes only, and optional. Inside this block one may place one or more ‘lateral_offset <distance-value>’, ‘altitude <distance-value>’, ‘target_speed <speed_value>’ and ‘ground_range <distance_value>’ specifications. Each time the keyword ‘test’ appears, the most recent value of (offset, altitude, speed, range) is saved off as a test point, and stored into a test point array. After the launch computer is initialized, each of these test points will be evaluated, and the corresponding interpolated time-of-flight value will be printed to the screen. The example given below saves off three points for testing.

interpolation_test
   lateral_offset 4000 m
   altitude       2000 m
   ground_range  10000 m
   target_speed    120 m/s
           test
   ground_range  20000 m
           test
   lateral_offset 2000 m
           test
end_interpolation_test