Missile Models

Aviator Pro

Aviator Pro allows you to model the performance characteristics of missiles in addition to aircraft. You can create a missile model in the User Missile Models catalog of the Aviator catalog interface or catalog manager.

The Missile properties window is used to define the global settings and performance models of a missile model in your User Missile Models catalog. Any changes that you make in this window will be applied to the missile's definition in the catalog.

The Missile properties window is comprised of three tabs - Performance Models, Aerodynamics, and Propulsion. The Performance Models tab defines the basic turning, climb and descent transition, cruising, and attitude transition characteristics of the missile, while the Aerodynamics and Propulsion tabs allow you to select and define strategies to model attitude and propulsion characteristics, respectively.

When you are done editing the missile's properties, click Save to save any changes you have made and click Close to close the window; you will be prompted to save any changes before closing the window.

Performance Models

The Performance Models tab is comprised of five sections - Level Turns, Attitude Transitions, Climb, Cruise, and Descent - as described below. As they do with aircraft models, performance models define the behavior of the missile in flight.

Level Turns

Define the Max Load Factor that the missile can withstand while maneuvering. The value specified for this parameter is the level turn value for the missile. Aviator will adhere to this value when possible, but in procedures where the turn is non-level the value may be adjusted to maintain the correct relationship between this and other interrelated parameters.

Attitude Transitions

Missile attitude is determined using a 123 Euler angle sequence of Bank, Angle of Attack, and Sideslip, originating from a velocity aligned, nadir constrained set of axes. Attitude rates may be violated in the case of very short - or zero distance - procedures.

Table - Attitude Transitions Parameters

Parameter	Description
Roll Rate	Defines the standard roll rate - the rate at which the missile bank angle changes - of the missile in a turn. When Aviator violates the specified Turn Roll Rate, the probable cause is an unrealistic climb or descent model, or the use of climb, descent, level turn and speed change parameters that aren't well matched to the roll rate parameters of the missile.
AOA/Pitch Rate	Defines the pitch rate when transitioning between attitude modes, between procedures, and between uncoordinated maneuvers when necessary.
Sideslip/Yaw Rate	Defines the yaw rate when transitioning between attitude modes, either triggered by changes in the acceleration performance model or between takeoff/landing, normal flight, weight-on-wheels, or hover mode.

Climb

The Climb performance model is comprised of a simple set of parameters that define the flight characteristics of the missile while climbing.

Table - Attitude Transitions Parameters

Parameter	Description
Airspeed	Defines the standard airspeed of the missile while climbing. You can select the airspeed reference of the performance model - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number - using the drop-down menu.
Min Flight Path Angle	Defines the minimum pitch angle of the missile's flight path while climbing.
Max Flight Path Angle	Defines the maximum pitch angle of the missile's flight path while climbing.

Cruise

The Cruise performance model is comprised of a simple set of parameters that define the flight characteristics of the missile while cruising.

Table - Attitude Transitions Parameters

Parameter	Description
Max Airspeed	Defines the maximum airspeed of the missile while cruising. You can select the airspeed reference of the performance model - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number - using the drop-down menu.
Default Cruise Altitude	Defines the missile's default cruising altitude. You cannot specify an altitude below sea level (0). If a procedure is specified that requires the missile to fly below sea level, the performance models in effect at sea level will be applied to that procedure.

Descent

The Descent performance model is comprised of a simple set of parameters that define the flight characteristics of the missile while descending.

Table - Attitude Transitions Parameters

Parameter	Description
Airspeed	Defines the standard airspeed of the missile while descending. You can select the airspeed reference of the performance model - true airspeed (TAS), calibrated airspeed (CAS), equivalent airspeed (EAS), or Mach number - using the drop-down menu.
Min Flight Path Angle	Defines the minimum pitch angle of the missile's flight path while descending.
Max Flight Path Angle	Defines the maximum pitch angle of the missile's flight path while descending.

Aerodynamics and Propulsion Analysis

The Aerodynamics and Propulsion tabs of a missile model function together as an analysis system that performs a trim calculation - as the missile flies - to compute lift, drag, thrust, throttle, and fuel consumption parameters at any given flight condition for the specified trajectory. The input to this system is the mission flight path while the outputs are the aerodynamics and propulsion data. The fuel flow is integrated into the weight of the missile, but these values do not directly influence the flight path.

The system will generate warnings when AOA limits are exceeded or when thrust deficits exist indicating the missile design is not capable of flying the path specified, but the path will still be flown as designed; this feature allows users to explore a missile design (perhaps based on high accuracy wind tunnel and engine test data) and its suitability to perform a desired mission.

Aerodynamics

The Aerodynamics tab is used to define the methods used to compute lift, drag, angle of attack, sideslip and intermediate / derived values. There are two aerodynamics strategies to choose from - Simple Missile and Advanced Missile. Each of these strategies is defined below.

Simple Missile

The Simple aerodynamics strategy uses several parameters to define the aerodynamic performance of the missile in terms of a single lifting surface.

Table - Simple Missile Aerodynamics Strategy Parameters

Parameter	Description
Reference Surface Area	The area of the lifting surface of the missile.
Cl Max	The maximum coefficient of lift.
Cd	The coefficient of drag of the lifting surface, representing Cd0 in the equation, Cd = Cd0 + K * Cl^2.
Angle of Attack	By default, the missile's Angle of Attack is 0. Select Calculate AOA to allow the value to be determined by Aviator and, if so, define a Max AOA value. Aviator will compute the lift curve slope as: Cl Max / Max AOA

Advanced Missile

The Advanced Missile aerodynamics strategy allows you to enter the dimensions of the missile's body, wings, and tail, and calculates the aerodynamic performance of the missile in terms of the specific size and shape that has been defined.

Propulsion

The Propulsion tab is used to define the rate at which the missile will speed up or slow down and provides a method for computing the fuel flow; this involves computing the thrust requirements and the throttle setting for any given flight condition which in turn requires a full aerodynamics calculation.

The propulsion models provided with STK separate the acceleration and deceleration speed changes from the thrust available as computed by the models. This is done for ease of use and to allow for quick construction of flight paths without constraints imposed by the propulsion system. AGI recommends that you fine tune these separate parameters so that they result in a faithful representation of actual performance.

There are four propulsion strategies to choose from - Simple Missile, Missile - Ramjet, Missile - Rocket, and Missile - Turbojet. The Simple Missile propulsion strategy uses basic Max Thrust and Fuel Flow parameters to define the thrust performance of the missile, while the other strategies allow you to define the properties of a specific type of propulsion system. For any strategy, select No Thrust When No Fuel to prevent the missile from thrusting once it has expended all of its fuel.