Fuel Source

Description

The Fuel Source represents a propellant tank that stores fuel and contributes mass properties to spacecraft dynamics. As a state effector, it updates the spacecraft’s mass, center of mass, and moment of inertia as fuel is consumed or transferred. The component connects to the fuel network via the Fuel Bus, allowing flow to consumers, pumps, valves, and other tanks.

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Example Use Cases

• Propellant Storage: Model fuel and oxidizer tanks for chemical propulsion systems.
• Mass Property Evolution: Simulate changing spacecraft dynamics as propellant is consumed during maneuvers.
• Tank-to-Tank Transfer: Move propellant between tanks for center of mass management or redundancy.
• Thermal Protection: Halt transfer operations when tank temperature exceeds safe limits.

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Module Implementation

Mass Properties

The fuel source contributes to spacecraft mass properties based on tank geometry and current fuel amount. The total component mass combines dry mass and fuel:

$$m_{\text{total}}=m_{\text{dry}}+m_{\text{fuel}}$$

The moment of inertia is computed from tank geometry and transformed to the spacecraft body frame. As fuel depletes, the inertia tensor evolves according to the selected fuel model.

Flow Rates

The fuel source tracks ingoing and outgoing flow rates separately:

$${\dot{m}}_{\text{total}}={\dot{m}}_{\text{in}}+{\dot{m}}_{\text{out}}$$

where ${\dot{m}}_{\text{in}}\ge 0$ represents fuel entering the tank and ${\dot{m}}_{\text{out}}\le 0$ represents fuel leaving. The outgoing flow is constrained by a configurable maximum rate:

$$|{\dot{m}}_{\text{out}}|\le {\dot{m}}_{\text{max}}$$

Fuel Models

The fuel source supports different depletion models that determine how mass properties evolve:

Model Type	Description
Constant Volume	Tank volume remains fixed; density varies with fuel amount
Constant Density	Fuel density remains fixed; effective volume varies

The model type affects inertia calculations and center of mass tracking as fuel depletes.

Network Connections

The fuel source exposes a Tank port for connecting to the fuel network:

Connected Component	Connection
Fuel Consumer	Tank → Intake
Fuel Valve	Tank → Inlet/Outlet
Fuel Pump	Tank → Upstream/Downstream
Fuel Source	Tank → Tank

Thermal Protection

Optional thermal limits can halt transfer operations when ullage temperature exceeds safe thresholds. When the maximum allowable temperature is exceeded, the tank enters thermal shutoff and blocks incoming flow. Transfer resumes when temperature falls to the restart threshold:

$$\text{Shutoff active if }T>T_{\text{max}}\text{ until }T\le T_{\text{restart}}$$

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Assumptions/Limitations

• Tank geometry is modeled as a cylinder; complex tank shapes require equivalent parameters.
• The fuel amount is clamped between zero and capacity; negative fuel is not permitted.
• Mass properties update each simulation step; rapid flow transients may require small time steps for accuracy.
• Thermal shutoff requires a thermal model to be attached for temperature monitoring.
• The maximum outgoing flow rate applies regardless of downstream demand; flow is limited at the source.
• Fuel density and other fluid properties are implicit in the selected fuel model.