Mass Storage

Description

The Mass Storage component models a generic mass container that holds an arbitrary payload and contributes mass properties to spacecraft dynamics. Unlike fuel-specific components, it represents any consumable or transferable mass such as water, gases, or cargo. As a state effector, the component updates the spacecraft’s mass, center of mass, and moment of inertia as payload mass changes during simulation.

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Example Use Cases

• Consumable Storage: Model water, air, or other life support consumables on crewed spacecraft.
• Cargo Transfer: Simulate payload mass changes during docking and transfer operations.
• Ballast Management: Adjust spacecraft mass distribution for center of mass control.
• Generic Mass Modeling: Represent any time-varying mass that affects spacecraft dynamics.

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Module Implementation

Mass Properties

The total component mass combines the dry mass of the container and the current payload:

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

The payload mass is constrained between zero and the configured capacity:

$$0\le m_{\text{payload}}\le C$$

where $C$ is the storage capacity.

Center of Mass

The component assumes the payload center of mass is located at the origin of the storage container in the local frame. This simplification treats the payload as centrally distributed within the container regardless of fill level.

Moment of Inertia

The moment of inertia contribution uses a spherical volume approximation. The equivalent sphere radius is derived from the configured volume:

$$r={\left(\frac{3V}{4\pi }\right)}^{1/3}$$

where $V$ is the storage volume. The inertia tensor is computed assuming uniform mass distribution within this equivalent sphere and transformed to the spacecraft body frame.

Mass Rate of Change

The payload mass rate is computed from the difference between current and previous mass each time step:

$${\dot{m}}_{\text{payload}}=\frac{m_{\text{current}}-m_{\text{previous}}}{\Delta t}$$

This derivative contributes to spacecraft dynamics through back-substitution matrices, accounting for momentum effects from mass flow into or out of the container.

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Assumptions/Limitations

• The payload center of mass is fixed at the container origin; mass distribution changes with fill level are not modeled.
• Inertia calculations use a spherical volume approximation; actual container geometry is not considered.
• The component does not connect to fuel bus networks; use Fuel Source for propellant-specific modeling.
• Payload mass is clamped to non-negative values and cannot exceed capacity.
• The dry mass is automatically determined from the initial component mass before payload is added.
• Volume and capacity are independent parameters; density constraints are not enforced.