WsfLaunchComputer

WsfLaunchComputer

The WsfLaunchComputer object provides support to WsfWeapon to decide if a weapon can be launched, and if so, some of the conditions about the launch.

Methods

bool CanIntercept(WsfTrack aTrack)

bool CanIntercept(WsfTrack aTrack, double aLaunchDelayTime)

Initiates a launch computer calculation to determine if an intercept can occur against the specified target.

bool HaveResultsFor(WsfTrackId aTrackId)

Returns whether the launch computer has computed a launch solution against the given track id.

Data Validity Methods

bool BurnTimeIsValid()

Returns whether a valid burn time was computed.

bool EndPointIsValid()

Returns whether a valid weapon end point has been computed.

bool EndTimeIsValid()

Returns whether a valid weapon end time has been computed.

bool InterceptPointIsValid()

Returns whether a valid intercept point has been computed.

bool InterceptTimeIsValid()

Returns whether a valid intercept time has been computed.

bool LauncherBearingIsValid()

Returns whether a valid bearing was computed.

bool LauncherElevationIsValid()

Returns whether a valid launcher elevation angle was computed.

bool LaunchTimeIsValid()

Returns whether a valid launch time has been computed.

bool LoftAngleIsValid()

Returns whether a valid loft angle was computed.

bool TargetImpactPointIsValid()

Returns whether a valid target impact point has been computed.

bool TargetImpactTimeIsValid()

Returns whether a valid target impact time has been computed.

bool TimeOfFlightIsValid()

Returns whether a valid time of flight has been computed.

Data Retrieval Methods

double BurnTime()

Returns the computed burn time (seconds).

WsfGeoPoint InterceptPoint()

Returns the computed intercept point.

double InterceptTime()

Returns the simulation time at which intercept is expected to occur (seconds).

double LauncherBearing()

Returns the computed launcher bearing.

double LauncherElevation()

Returns the computed launcher elevation.

double LaunchTime()

Returns the simulation time at which launch should occur (seconds).

double LoftAngle()

Returns the computed loft angle (decimal degrees).

double TimeOfFlight()

Returns the computed time of flight (seconds).

Additional Methods for WSF_BALLISTIC_MISSILE_LAUNCH_COMPUTER

Launch Window Computations

Normally WSF_BALLISTIC_MISSILE_LAUNCH_COMPUTER will compute only the first available solution for surface-to-air intercepts. By enabling WsfLaunchComputer.ComputeLaunchWindows before calling WsfLaunchComputer.CanIntercept, the launch computer will determine the ‘launch windows’ or the ranges of times in which a launch can occur that will result in an intercept.

Enabling launch window computation requires more processor time, so it should be used only when needed.

Note

These methods only apply to surface-air-air intercept calculations.

void ComputeLaunchWindows()

Indicates launch windows should be computed on the next call to CanIntercept.

This is a ‘single-shot’ request. It is applicable only to the next call to CanIntercept and is cleared after the call. The results should be captured immediately after the call the CanIntercept by using the methods below.

int LaunchWindowCount()

Returns the number of launch windows.

double FirstLaunchTime(int aIndex)

Returns the first launch time for the launch window with the specified index.

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

double FirstInterceptTime(int aIndex)

Returns the predicted intercept time for a launch that occurs at FirstLaunchTime(aIndex).

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

WsfGeoPoint FirstInterceptPoint(int aIndex)

Returns the predicted intercept location for a launch that occurs at FirstLaunchTime(aIndex).

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

double LastLaunchTime(int aIndex)

Returns the last possible launch time for the launch window with the specified index.

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

double LastInterceptTime(int aIndex)

Returns the predicted intercept time for a launch that occurs at LastLaunchTime(aIndex).

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

WsfGeoPoint LastInterceptPoint(int aIndex)

Returns the predicted intercept location for a launch that occurs at FirstLaunchTime(aIndex).

Note

aIndex must be in the range [ 0 .. LaunchWindowCount()-1 ]

Target Methods

These methods are valid only for surface-to-air intercept predictions. They refer to the incoming ballistic missile, not the interceptor. .. method:: double TargetApogeeTime()

Returns the simulation time at which the target is expected to reach apogee during its trajectory.

WsfGeoPoint TargetApogeePoint()

Returns the point at which the target is predicted to reach apogee during its trajectory.

double TargetImpactTime()

Returns the simulation time at which the target is expected to impact its target location.

WsfGeoPoint TargetImpactPoint()

Returns the point at which the target is predicted to impact.

End Point Methods

These methods are valid only for surface-to-air intercept predictions. They return the estimated time and location at which the launched weapon (interceptor) would hit the surface of the Earth if it followed a ballistic trajectory and did not hit the intended target.

Note

See the documentation for compute_end_point in WSF_BALLISTIC_MISSILE_LAUNCH_COMPUTER for additional information prior to using this capability.

void ComputeEndPoint()

Specifies that the end time and point should be computed on the next call to CanIntercept.

This is a ‘single-shot’ request. It is applicable only to the next call to CanIntercept and is reset to the value of the compute_end_point from WSF_BALLISTIC_MISSILE_LAUNCH_COMPUTER after the call. The results should be captured immediately after the call the CanIntercept by using the methods below.

double EndTime()

Returns the estimated simulation time at which the weapon would hit the surface of the Earth. The value will be less than or equal to zero if a value was not determined.

WsfGeoPoint EndPoint()

Returns the estimated point at which the weapon would hit the surface of the Earth. The results are valid only if EndTime() returned a value greater than zero.

After launch, the data may be accessed from the the launched weapon platform as follows:

WsfPlatform weapon = *<weapon-platform-reference>*;
WsfTrack track = weapon.MasterRawTrackList().Entry(0);
if (track.IsValid() &&
    (track.AuxDataDouble("LC_END_TIME") > 0.0))
{
   WsfGeoPoint endPoint = WsfGeoPoint.Construct(track.AuxDataDouble("LC_END_LAT"),
                                                track.AuxDataDouble("LC_END_LON"),
                                                track.AuxDataDouble("LC_END_ALT"));
   writeln("  EndTime=", track.AuxDataDouble("LC_END_TIME"), " EndPoint=", endPoint);
}

Other Methods

double LateralTargetOffset(WsfTrack aTrack)

Returns the lateral offset in meters (cross range) between the launcher and predicted target trajectory. Another way of looking at it is that this is the shortest ground range to the target along the predicted trajectory.

If this method is called after the target has passed by the launcher and the predicted trajectory for the target has yet to be computed (i.e., there was no prior call to this method or ComputeIntercept) then the return value will be the ground range to the current location of the target.

Note

This is valid only for surface-to-air engagements.

Additional Methods for WSF_AIR_TO_AIR_LAUNCH_COMPUTER

Internally, the WSF_AIR_TO_AIR_LAUNCH_COMPUTER contains a reference to a precomputed six-dimensional table of expected missile engagement shot results. For each combination of (shooter altitude, shooter speed, target altitude, target speed, target aspect (nose on = 0) and target lead angle) the table provides the expected (minimum range, min range time-of-flight, no escape range, no escape range time-of-flight, maximum range, maximum range time-of-flight) results. Be aware that some tabulated results may yield “no engagement possible,” represented by all dependent variable equal to -1.0. Also know that the precomputed predictions make simplifying assumptions on target motion; results in an actual engagement may vary from prediction. Because of this variability, it is desirable to incorporate conservatism into missile launch logic. This conservatism will typically be placed in user-defined scripts, and will often involve artificially increasing the minimum range distance, and/or artificially reducing the maximum range distance. The script methods documented below provide the predicted results and allow the user to make whatever “trigger pull” decisions that are required.

Note

The track must have valid WCS location and velocity.

Array<double> LookupResult(WsfTrack aTrack)

Returns an array with the expected engagement envelope ranges and times-of-flight:

0 = Maximum Range (m)
1 = Maximum Range Time Of Flight (sec)
2 = No Escape Range (m)
3 = No Escape Range Time Of Flight (sec)
4 = Minimum Range (min)
5 = Minimum Range Time Of Flight (sec)

Additional Methods for WSF_SCRIPT_LAUNCH_COMPUTER

WSF_SCRIPT_LAUNCH_COMPUTER allows the user to compute the intercept using the scripting language. As such, it must have the means to communicate its results. This is done using the methods defined below. Note that SetInterceptTime is required if a predicted intercept is to be reported. All other methods are optional.

void SetInterceptTime(double aInterceptTime)

Set the simulation time when the intercept has been predicted to occur.

Note

This method must be called if a predicted intercept is to be reported.

void SetInterceptPoint(WsfGeoPoint aInterceptPoint)

Set the location where the intercept has been predicted occur.

Note

This is not required, but a weapon system may desire to have this for orienting the weapon at launch.

void SetLaunchTime(double aLaunchTime)

Set the simulation time when the launch command should be issued.

void SetTimeOfFlight(double aTimeOfFlight)

Set the predicted time of flight (the predicted time of intercept minus the predicted time of launch).