(mass flow rate).These components allow you to model the thrust and specific impulse (Isp) of a rocket engine.
ComponentBrowser */ SetValue "Engine Models" {Component} {Attribute} <Value> [{Unit}]
ComponentBrowser */ Duplicate "Engine Models" {Component} <Duplicate Component Name>
The Engine Models components are:
| Component | Description |
|---|---|
| Constant Thrust and Isp | This model employs user-supplied, constant values for thrust and Isp. |
| Custom Engine | Engine that uses Custom Functions to compute values |
| Ion Engine | Engine that uses ion propulsion |
| Plugin Engine | Engine that uses a COM interface to compute values |
| Polynomial Thrust and Isp | Engine with polynomial functions for Thrust and Isp |
The attributes for each component are described individually below.
Note:The default value is the value the model will have if you do not send a command.
| Attribute | Description | Values |
|---|---|---|
| g | Gravitational acceleration constant at sea level on the Earth.
Enter a value in the selected distance unit per the selected time
unit squared (e.g. km/sec^2). This is the value used to convert
Isp to exhaust velocity Ve:
Ve = Isp(g) |
<Numerical> Default: 0.00980665 km/sec^2 |
| Thrust | The thrust for this engine. Enter a value in the selected force unit, e.g., in Newtons (N). | <Numerical> Default: 500 N |
| Isp | The specific impulse for this engine. Enter a value in the scenario specific impulse unit (seconds). | <Numerical> Default: 300 s |
| Attribute | Description | Values |
|---|---|---|
| g | Earth surface gravity acceleration for Isp conversions. | <Numerical> Default: 0.00980665 km/sec^2 |
| PreFunction | Custom function to call before any propagation begins. | <Custom Function Component> |
| SegStartFunction | Custom function to call at the beginning of each segment. | <Custom Function Component> |
| UpdateFunction | Custom function to call at the beginning of each integration step. | <Custom Function Component> |
| EvalFunction | Custom function to call at every thrust evaluation. | <Custom Function Component> |
| PostFunction | Custom function to call at the beginning of each integration step. | <Custom Function Component> |
The Ion Engine model calculates three parameters: Thrust,
Ve (Exhaust Velocity) and(mass flow rate).
Ve = Ispg
where Isp is specific impulse (in seconds), and g is the gravitational acceleration on the surface of the Earth.
where MassFlowRate is described below. Note thatshould be negative; this
represents the loss of mass when the engine is on. The MassFlowRate
coefficients should return a positive number, and STK enforces the
correct sign.
where D is the degradation factor (PercentageDegradationPerYear) measured from the reference epoch.
Note that bothand Thrust are affected by the throttle setting. The
input power is clipped based on the minimum and maximum power
attributes.
| Attribute | Description | Values |
|---|---|---|
| g | Gravitational acceleration constant at sea level on the Earth. Enter a value in the selected distance unit per the selected time unit squared (e.g. km/sec^2). | <Numerical> Default: 0.00980665 km/sec^2 |
| InputPowerSource | Object that computes the power input to the engine. | "InternalPower", "ProcessedPower", "SolarArrayPower", or a custom Power Source component. Default: ProcessedPower |
| MinRequiredPower | Minimum power required for the engine to produce thrust. | <Numerical> Default: 27 dBW |
| MaxInputPower | Maximum power that can be used by the engine to produce thrust. | <Numerical> Default: 33.6 dBW |
| PercentDegradationPerYear | The degradation factor is (1 - x)n, where n is the time since epoch in years, and x is the percent degradation per year. | <Numerical> Default: 0 |
| ReferenceEpoch | Date and time used as a reference epoch for degradation. | <Date and time> Default: 1 Jan 1992 00:00:00.000 UTCG |
| PercentThrottle | Percentage of available thrust to use (100 is full on, 0 is off). | <Numerical> Default: 100 |
| IspModel.C0 | Constant coefficient | <Numerical> Default: 3800 |
| IspModel.C1 | Linear coefficient | <Numerical> Default: 0 |
| IspModel.C2 | Quadratic coefficient | <Numerical> Default: 0 |
| IspModel.C3 | Cubic coefficient | <Numerical> Default: 0 |
| FlowRateModel.EquationType | "Isp", "Power", "PowerAndIsp" | |
| FlowRateModel.C0 | Constant coefficient | <Numerical> Default: 4.43e-008 |
| FlowRateModel.C1 | Linear coefficient | <Numerical> Default: 0 |
| FlowRateModel.C2 | Quadratic coefficient | <Numerical> Default: 0 |
| FlowRateModel.C3 | Cubic coefficient | <Numerical> Default: 0 |
| MassFlowEfficiencyModel.IndependentVar | "Power", "Isp" | |
| MassFlowEfficiencyModel.C0 | Constant coefficient | <Numerical> Default: 1 |
| MassFlowEfficiencyModel.C1 | Linear coefficient | <Numerical> Default: 0 |
| MassFlowEfficiencyModel.C2 | Quadratic coefficient | <Numerical> Default: 0 |
| MassFlowEfficiencyModel.C3 | Cubic coefficient | <Numerical> Default: 0 |
| PowerEfficiencyModel.IndependentVar | "Power", "Isp" | |
| PowerEfficiencyModel.C0 | Constant coefficient | <Numerical> Default: 1 |
| PowerEfficiencyModel.C1 | Linear coefficient | <Numerical> Default: 0 |
| PowerEfficiencyModel.C2 | Quadratic coefficient | <Numerical> Default: 0 |
| PowerEfficiencyModel.C3 | Cubic coefficient | <Numerical> Default: 0 |
Note: For details on testing coefficients, see the Astrogator graphical user interface (GUI) help.
| Attribute | Description | Values |
|---|---|---|
| g | Gravitational acceleration constant at sea level on the Earth.
Enter a value in the selected distance unit per the selected time
unit squared (e.g. km/sec^2). This is the value used to convert
Isp to exhaust velocity Ve:
Ve = Isp(g) |
<Numerical> |
| PluginIdentifier | The ProgID of the COM component you are using for this model. | <Prog Id for Plugin Engine Model> |
| PluginConfig.<Attribute> | Typically multiple attributes, each one displaying an attribute of the selected COM component. | Dependent on attribute |
| Attribute | Description | Values |
|---|---|---|
| g | Gravitational acceleration constant at sea level on the Earth. Enter a value in the selected distance unit per the selected time unit squared (e.g. km/sec^2). | <Numerical> Default: 0.00980665000 km/sec^2 |
| Thrust.ReferenceTemp | Enter the appropriate value for each coefficient, depending upon the thrust equation you are using. | <Numerical> Defaults: C0: 490; T/Tr: 293 K |
| Thrust.C0 | <Numerical> | |
| Thrust.C1 | <Numerical> | |
| Thrust.C2 | <Numerical> | |
| Thrust.C3 | <Numerical> | |
| Thrust.C4 | <Numerical> | |
| Thrust.C5 | <Numerical> | |
| Thrust.C6 | <Numerical> | |
| Thrust.C7 | <Numerical> | |
| Thrust.E4 | <Numerical> | |
| Thrust.E5 | <Numerical> | |
| Thrust.E6 | <Numerical> | |
| Thrust.E7 | <Numerical> | |
| Thrust.B7 | <Numerical> | |
| Thrust.K0 | <Numerical> | |
| Thrust.K1 | <Numerical> | |
| Isp.ReferenceTemp | Enter the appropriate value for each coefficient, depending
upon the Isp equation you are using.
Note: Thrust coefficients must be entered in terms of Newtons and Pascals, regardless of the selected unit settings. Similarly, Isp coefficients must be entered in terms of seconds and Pascals. |
<Numerical> Defaults: C0: 300; T/Tr: 293 K |
| Isp.C0 | <Numerical> | |
| Isp.C1 | <Numerical> | |
| Isp.C2 | <Numerical> | |
| Isp.C3 | <Numerical> | |
| Isp.C4 | <Numerical> | |
| Isp.C5 | <Numerical> | |
| Isp.C6 | <Numerical> | |
| Isp.C7 | <Numerical> | |
| Isp.E4 | <Numerical> | |
| Isp.E5 | <Numerical> | |
| Isp.E6 | <Numerical> | |
| Isp.E7 | <Numerical> | |
| Isp.B7 | <Numerical> | |
| Isp.K0 | <Numerical> | |
| Isp.K1 | <Numerical> |
ComponentBrowser */ Duplicate "Engine Models" "Ion Engine" "My Ion Engine"
ComponentBrowser */ SetValue "Engine Models" "My Ion Engine" InputPowerSource InternalPower
ComponentBrowser */ SetValue "Engine Models" "My Polynomial Engine" Isp.ReferenceTemp 290 K
ComponentBrowser */ SetValue "Engine Models" "My CustomEngine" SegStartFunction “my engine segment start custom function”
STK Programming Interface 11.0.1
