Class in Zendir.Classes | Inherits from PowerNodeModel
Declaration
class IonThrusterPowerModel;Description
Power model for an ion thruster. Implements a Constant Power Load (CPL) pattern where the Power Processing Unit (PPU) adjusts its effective input impedance to maintain constant power draw from the bus.
The ion thruster’s power consumption consists of:
- StandbyPower: cathode keep-warm, housekeeping, and control electronics
- BeamPower / PPUEfficiency: when ignited (DesiredPower >= MinIgnitionPower)
The model uses quasi-static iteration where resistance is computed from the previous tick’s solved voltage: R = V_solved² / P_dc. This allows the linear SPICE resistor to converge on the true CPL operating point across successive time-steps.
AvailablePower (the beam power output) is derived from absorbed branch power after accounting for StandbyPower and PPU losses. If the thruster is in brownout or hasn’t reached MinIgnitionPower, AvailablePower is zero and IonThruster.CalculateBodyFrameForce naturally produces no thrust.
Properties
| Declared | Description |
|---|---|
| AvailablePower | The actual beam power that the system can supply this frame [W].Computed from absorbed branch power after accounting for StandbyPower and PPU losses.Zero if the thruster is in brownout or has not reached MinIgnitionPower. |
| DesiredPower | The beam power requested by the ion thruster [W].This is the power that will be delivered to the propellant for thrustgeneration. The actual DC power draw is higher due to PPU losses andstandby power requirements. |
| LastSolvedVoltage | The last SPICE-solved acrossthis thruster. This is fed back into the next tick’s resistancecalculation so the model converges toward true constant-power behavior(R = V_solved² / P_dc) despite the underlying SPICE resistor being linear.Zero means no valid solve has been captured yet and the next resistancecalculation will seed from . |
| MaxOperatingPower | The maximum beam power the thruster can process [W].DesiredPower is clamped to this value before computing DC draw.Default ~150 W is representative of compact electric propulsion on 6U–small-sat platforms;increase for high-power EP missions. |
| MinIgnitionPower | The minimum beam power required to ignite the thruster [W].Below this threshold, DesiredPower is ignored and the thrusterstays in standby mode, drawing only StandbyPower.Default ~40 W reflects a lower-throughput CubeSat / nanosat ion class (tens of watts),versus hundred-watt to kW-class flight hardware on larger spacecraft. |
| MinOperationalVoltageRatio | Minimum fraction of required onthe node for the thruster to remain powered. If the SPICE-solvedfalls below this fraction,AvailablePower is set to zero (thruster produces no thrust). |
| MinPowerRatio | Minimum fraction of the expected DC power draw that must appear as absorbedbranch power |
| NominalOperationalVoltage | The nominal DC voltage at the thruster PPU input for CPL seeding and brownout thresholds.Default 28 V is representative of CubeSat / small-sat EPS buses feedingelectric propulsion PPUs (missions vary widely; large satellites often use much higher rails). |
| Power | The Power Consumption of the Ion Thruster based on its current state.When connected to a PowerBus (not SelfSolve), returns CurrentIn * VoltageNode.Otherwise returns the calculated DC power draw. |
| PPUEfficiency | The efficiency of the Power Processing Unit (PPU) [0..1].Real ion thruster PPUs typically have 85-95% efficiency.The actual DC power draw is StandbyPower + BeamPower / PPUEfficiency. |
| StandbyPower | The power consumption when the thruster is in standby mode [W].Represents cathode keep-warm, housekeeping, and control electronics.Default ~8 W biases toward CubeSat / small-sat PPUs (large-flight ion systems are often higher). |
| Inherited | Description |
|---|---|
| CurrentIn | The current flowing into this node at the In terminal.Under flow-through convention, positive means current enters at In and exits at Out.Equal to CurrentOut in steady state for two-terminal elements. |
| CurrentOut | The current flowing out of this node at the Out terminal.Under flow-through convention, positive means current exits at Out (entered at In).Equal to CurrentIn in steady state for two-terminal elements. |
| IsEnabled | Is true if the object is currently enabled. |
| IsOpenCircuit | A flag if the power node is currently open and no power willbe transferred to the next component. |
| Name | The display name or tag of this object. |
| NetPower | Net power this node contributes to the bus, calculated directly from thevoltages and currents at the In and Out terminals:NetPower = VoltageOut * CurrentOut - VoltageIn * CurrentInThis is the power delivered to the external circuit by this node (the negativeof the power absorbed by it). Under the flow-through convention, positiveCurrentIn represents current entering at the In terminal and positiveCurrentOut represents current exiting at the Out terminal.A positive NetPower means the node is adding power to the bus (e.g. a solarpanel producing power, a discharging battery). A negative NetPower means thenode is consuming power from the bus (e.g. a power sink, a charging battery,resistive losses in a fuse/switch/component).For a two-terminal element CurrentIn == CurrentOut, so this reduces to(VoltageOut - VoltageIn) * I. When one terminal is connected to ground andthe bus has ZeroGroundPlane enabled, that terminal’s voltage and current areboth zero, so the formula still represents the true energy exchange at thenon-grounded terminal (e.g. V_out * I_out for a ground-referenced source orbattery, -V_in * I_in for a ground-referenced load). |
| Out_PowerNodeMsg | The power node message that stores all the properties ofthe node. |
| Parent | The currently attached parent object. |
| Resistance | The Resistance of the node. |
| SelfSolve | A Flag to determine if the Power Node Model should update Output parameters itself if not connected to a PowerBus |
| VoltageIn | The voltage at the In (negative) terminal of this node.For a load connected between a source and ground, this is the higher potential side. |
| VoltageNode | The voltage drop across the node: VoltageIn - VoltageOut.Positive for a load (current flows from higher to lower potential).Negative for a source (Out terminal at higher potential than In). |
| VoltageOut | The voltage at the Out (positive) terminal of this node.For a load connected between a source and ground, this is the lower potential side. |
Methods
| Inherited | Description |
|---|---|
| Clear | Clear the Power Node Model if the circuit is open |
| FindParentWithID | Returns an attached parent that satisfies the specified ID. |
| FindParentWithType | Returns an attached parent that satisfies the specified type. |
| FindRootWithID | Returns a root object that satisfies the specified ID. |
| FindRootWithType | Returns a root object that satisfies the specified type. |