Ion Thruster

Description

The Ion Thruster is an electric propulsion system that uses ionized propellant to generate thrust. Unlike chemical Thrusters, ion thrusters determine required input power based on desired thrust rather than mass flow rate. The thruster integrates with an Ion Thruster Power Model to couple propulsion with the spacecraft’s electrical power system.

Example Use Cases

Low-Thrust Orbit Raising: Model gradual orbit changes using continuous low-thrust propulsion over extended periods.
Station Keeping: Simulate electric propulsion for geostationary satellite position maintenance.
Power-Limited Operations: Evaluate thruster performance when electrical power is constrained by solar array orientation or battery state.
Interplanetary Missions: Model high-efficiency propulsion for deep space trajectories.

Module Implementation

Thrust Calculation from Power

The thrust $F$ produced by an ion thruster is related to the input power $P$ , exhaust velocity $v_{e}$ , and thruster efficiency $η$ :

F = \frac{2 η P}{v _{e}}

where:

$F$ is the thrust (N)
$P$ is the available electrical power (W)
$η$ is the thruster efficiency (0 to 1)
$v_{e}$ is the exhaust velocity (m/s)

The exhaust velocity is calculated from the specific impulse:

v_{e} = I_{s p} \cdot g_{0}

where $I_{s p}$ is the specific impulse (s) and $g_{0}$ is standard gravitational acceleration (9.80665 m/s²).

Power Requirement from Desired Thrust

To determine the power required for a specified thrust, the inverse relationship is used:

P = \frac{F \cdot v _{e}}{2 η}

This value is passed to the Ion Thruster Power Model as the desired power demand.

Body-Frame Force Calculation

The thrust in the spacecraft body frame is:

F_{B} = \hat{d}_{B} \cdot F \cdot (1 - f_{dispersed})

where:

$\hat{d}_{B}$ is the thrust direction unit vector in body frame
$f_{dispersed}$ is the dispersed factor accounting for beam divergence or misalignment

Impulse Calculation

The body-frame impulse is computed from the force and exhaust velocity:

I = \frac{F ^ _{B}}{v _{e}}

This is used by the spacecraft dynamics to update velocity based on applied thrust.

Standalone Operation

When not connected to a Power Bus, the thruster operates in standalone mode with default power availability:

Parameter	Default Value
`VoltageIn`	100 V
`CurrentIn`	50 A
Available Power	5000 W

When connected to a Power Bus, these values are driven by the electrical network solution.

Assumptions/Limitations

Steady-State Operation: The thruster operates at steady state; transient startup or throttling dynamics are not modeled.
Constant Efficiency: Thruster efficiency $η$ is assumed constant and independent of power level or thrust.
Ideal Power Conversion: Power losses outside the thruster (e.g., bus inefficiencies) are not considered.
Single Propellant: The model assumes a single ionized propellant (e.g., xenon) with no chemical reactions.
Negligible Beam Divergence: The dispersed factor accounts for minor deviations; large plume effects are not modeled.
No Thermal Modeling: Thruster heating and thermal limits are not simulated.
No Plasma Physics: Ionization dynamics, space charge effects, and plasma interactions are not considered.
Zero Efficiency Handling: If Efficiency <= 0, desired power is set to zero.

References

Choueiri, E. Y. (2009). A Critical History of Electric Propulsion: The First 50 Years (1906–1956). Journal of Propulsion and Power, 20(2), 193–203.
Sutton, G. P., & Biblarz, O. (2017). Rocket Propulsion Elements (9th ed.). Wiley.
Wertz, J. R., Everett, D. F., & Puschell, J. J. (2011). Space Mission Engineering: The New SMAD (2nd ed.). Microcosm Press.