Dynamics: Thruster

Description

The Thruster is used to produce a propulsive force on the spacecraft it is attached to. The following is an example of a thruster in a spacecraft. A thruster is commonly used in a spacecraft to increase its maneuverability either in terms of its attitude or its orbital properties.

Example Use Cases

Delta V Functional Chain: The \(\Delta V\) functional chain implementation uses a thruster to produce a change in the spacecraft's orbital velocity which results in orbital maneuvers
Attitude Feedback Thrusters: A chain of thrusters is configured in this scenario to produce a torque in the spacecraft body which increases its ability to control its attitude.

Module Implementation

The configuration of a thruster requires a ThrusterConfigMessage with the following data

Name	Description
RThrust_B	[m] Location of the thruster in the Spacecraft
THatThrust_B	Unit Vector of the Thrust direction
MaxThrust	[N] Maximum Thrust produced by the Thruster
MaxImpulse	[Ns] Steady state maximum impulse
SpecificImpulse	[s] Specific Impulse of the Thruster
MinFireDuration	[s] Minimum fire duration of the Thruster
MaxThrustDuration	[s] Duration for thruster to achieve maximum thrust

The firing of the thruster is controlled using a ThrustFireRequestMessage which controls the parameters of the Start time of the thruster and its duration of fire. The required thrust force is then calculated with respect to the firing procedure of the thruster and its fire up ramp of which a thrust factor is outputted. The required fuel for that specific amount of thrust is then calculated as follows

\[ \begin{equation}\dot{m}=\frac{F}{I_{sp}g_{0}}\end{equation} \]

where,

\(F\): Thrust Force
\(\dot{m}\): Mass flow rate
\(I_{sp}\): Specific Impulse
\(g_0\): Gravitational Acceleration Constant ( \(9.8 ms^{-2}\))

The mass flow rate required for the burn is requested from a fuel source and the thrust is applied depending on the amount of fuel provided with respect to the flow rate requested and the specific impulse.

Assumptions/Limitations

If a fuel source is not connected to the spacecraft maximum requested fuel will be assumed to be provided.
Free stream pressure is assumed to be zero due to simulation in space.

References