1. When generation, load, and orbit combine
Sebastian Junger’s The Perfect Storm returns because thermal balance is another place where several ordinary factors add up to an extraordinary load. A hot compute task, a solar heating peak, and a neighboring cell in shadow can combine to produce temperature gradients that no single analysis predicts.
This entry defines the thermal balance test matrix.
2. The test setup
The test uses a representative desktop assembly in a thermal-vacuum chamber:
- Chamber pressure below 10⁻⁵ torr.
- Cold shrouds or walls simulating the 3 K space background.
- Solar simulators or infrared lamps for external heating.
- Heater cartridges inside cells to represent electronics dissipation.
- Thermocouples or RTDs distributed across cells, interfaces, and radiators.
3. The test matrix
| Case | Orbit phase | Internal load | External heating | Purpose |
|---|---|---|---|---|
| Hot steady-state | Full sunlight, end of eclipse | Maximum design load | Maximum solar | Verify worst-case hot temperatures |
| Cold steady-state | Eclipse | Minimum load | None | Verify worst-case cold temperatures |
| Hot transient | Sun entry after eclipse | Maximum load | Ramping solar | Verify thermal inertia and response |
| Cold transient | Eclipse entry | Minimum load | Solar drop | Verify heater and survival margins |
| Nominal orbit | Full orbit cycle | Nominal load | Nominal solar | Validate thermal model over one orbit |
| Off-nominal cooling | Nominal | One radiator degraded | Nominal | Verify margin with failed radiator |
| Off-nominal load | Nominal | One cell overloaded | Nominal | Verify heat spreading to neighbors |
| Autonomous scenario | Nominal | Dynamic load shifting | Nominal | Exercise heat-trading-ready paths |
4. What is measured
For each case the test records:
- Temperature at critical locations: electronics, batteries, radiators, interfaces.
- Time to reach steady state or to traverse transients.
- Temperature gradients across attachment interfaces.
- Whether any cell exceeds its qualification temperature limits.
- Agreement between test data and the thermal model predictions.
5. What this changes
- The thermal balance test has a concrete matrix.
- The matrix covers hot, cold, transient, and off-nominal conditions.
- The next entry will define pass and fail criteria.