# Solar-electric spacecraft schematic CAD package

This is an editable parametric CadQuery/OpenCascade model prepared to explain the basic parts and arrangement of a solar-electric spacecraft. It is a CAD-authored schematic, not an engineering design or build plan. Its 47 named positive-volume solids represent two solar-array wings with simple cell layout markers and supports, a bus enclosure and generic internal placeholders, a generic carried-propellant tank, a generic electric-thruster housing/exit ring, a separate radiator with fins, and illustrative harness routes.

The desktop PNG is an isometric view rendered from the model's tessellated solids. The mobile PNG is a model-derived section view: the modeled bus front access cover is hidden in that view only, exposing three generic placeholder blocks. These blocks do not specify real spacecraft electronics, payload layout, or component architecture. The axis arrows in the isometric image simply explain the source drawing's intended thrust/exhaust directions; no centre of mass is computed to validate alignment.

## Units and complete parameter values

Every length below is an arbitrary display proportion expressed in millimetres solely to support CAD exchange. The concept layout supplied no engineering dimensions, so none of these values represents a real spacecraft size, a validated ratio, or a manufacturing tolerance. Per-component axis-aligned bounding extents are recorded in `solar-electric-spacecraft-components.csv`.

| Parameter | Value | Meaning in this visualization |
|---|---:|---|
| `bus_width_x` | 42 mm | Bus enclosure outside width along X |
| `bus_width_y` | 48 mm | Bus enclosure outside depth along Y |
| `bus_height_z` | 76 mm | Bus enclosure outside length along Z |
| `bus_center_z` | 0 mm | Arbitrary datum for bus centre |
| `bus_shell_wall` | 3 mm | Bus panel thickness |
| `array_panel_dx` | 58 mm | Each array wing's span along X |
| `array_panel_dz` | 68 mm | Each array wing's span along Z |
| `array_panel_t` | 2 mm | Array substrate thickness along Y |
| `array_center_x` | ±72 mm | Port/starboard wing centre offsets |
| `array_center_z` | 5 mm | Shared array centre height |
| `cell_dx` | 17.5 mm | One cell-tile width along X |
| `cell_dz` | 30 mm | One cell-tile height along Z |
| `cell_t` | 1.2 mm | Cell-tile thickness along Y |
| `tank_radius` | 13 mm | Generic tank body radius |
| `tank_height` | 30 mm | Generic tank body length |
| `thruster_ring_outer_radius` | 13 mm | Generic exit-ring outer radius |
| `thruster_ring_inner_radius` | 8.5 mm | Generic exit-ring inner radius |
| `radiator_dx` | 28 mm | Separate radiator span along X |
| `radiator_dy` | 2 mm | Radiator panel thickness along Y |
| `radiator_dz` | 40 mm | Radiator panel span along Z |

Additional display-only choices in the source are: six cell layout markers per array face (3 columns × 2 rows on each of two faces); array support booms radius 1.8 mm; harness-route markers radius 0.8 mm; thruster housing radius 11 mm and length 17 mm; exit-ring thickness 3 mm; four radiator fins, each 31 × 4 × 1.3 mm. Three interior blocks use extents 19 × 15 × 14 mm, 20 × 16 × 20 mm, and 17 × 14 × 10 mm. These are placeholders, not real parts. Cell layout markers are duplicated on both faces solely so that the rendered surface pattern stays legible in alternate views; this is not a claim that the spacecraft has bifacial photovoltaic cells.

## Scientific limits

- The thruster is intentionally generic. The model does not choose Hall, gridded-ion, or another thruster architecture and contains no functional internal thruster geometry.
- The propellant vessel is a shape only. No propellant, pressure, feed system, valve, tank mass, or depletion is modeled.
- The solar cells, support booms, harness, radiator, and generic bus boxes are schematic solids. No deployment mechanism, photovoltaic conversion, electrical conditioning, heat load, radiator sizing, structural check, mass properties, trajectory, power, thrust, efficiency, or mission result is calculated.
- The central reference line shows an intended arrangement only. The model does not calculate centre of mass or establish that thrust passes through it.
- STEP preserves editable boundary-representation solids but not the original CadQuery feature history; the Python source is the editable parametric definition. STL is a faceted view mesh.
- No image is a source photograph or a measured vehicle. No matching to a specific flown spacecraft is claimed.

## Rebuild

Use Python 3.12, then run these commands from this directory:

```text
python -m pip install -r solar-electric-spacecraft-cad-requirements.txt
python build_solar_electric_spacecraft_cad.py
```

The script regenerates the STEP and STL files, CSV component inventory, and both PNG views. It checks all generated solids for positive volume and OpenCascade validity before export.