Initial thermal calculations are based on a seven node blackbody analysis (six sides and the insides).

**Thermal**

The sun is modelled as a black body.

A node is a finite sub-division of the thermal system so that thermal balance and heat flow may be calculated in unsimilar components.

There are 2 elements to each node, and 3 types of node.

The elements are the Temperature **T**, which is analogous to potential.

and thermal mass **C**, or capacitance.

The 3 types are,

**Diffusion
Arithmetic
Boundary**

**Errors** that can occur are due to,

Material Thermal Properties

Boundary Conditions

Node Size (smaller the better)

Node Centre Placement

and Time Increment of Dynamic Calculations

**Diffusion**

-for normal materials

-heat flow in or out of materials

-involves potential, capacitance value, net heat flow, and time.

**Arithmetic**

-has zero capacitance

-useful for small components, such as bolts, thin films, gas contents of tubes and low-mass insulation

-but should only form a minority of the number of nodes

**Boundary**

-has infinite capacitance

-for constant temperature boundaries or heat sinks (such as space)

-it can be used for nodes that have a large thermal capacitance (lots of mass) though this is not realistic for cubesat

Nodes typically sub-divide the main structure into simple volumes that are easy to calculate.

In the case of a simple seven node model each of the solar panels, and the internal components are nodes.

The solar panels are modelled for **3 cases**,

-in **full sunlight**, where the maximum number (3) of panels are illuminated

-in **partial sunlight**, where only 1 panel is illuminated

-and in **shadow**, where no panels are illuminated