1. The equations, written down before the flight

Tom Godwin’s “The Cold Equations” returns because the only way to respect a hard margin is to compute it before the crisis. The desktop’s power autonomy must be tested the same way: not by hoping the numbers work out, but by running the numbers through every scenario that orbit can produce. This entry defines the test matrix for autonomous power management.

2. Test environment

The test should use a hardware-in-the-loop power testbed that includes:

  • a representative solar array simulator with variable illumination and angle;
  • a representative battery pack with adjustable state of charge and temperature;
  • representative DC-DC converters, charge regulators, and protection circuits;
  • switchable loads that model housekeeping, thermal control, communications, compute, and payloads;
  • a fault-injection unit capable of creating shorts, opens, overcurrents, and sensor errors;
  • a simulated orbit and attitude source so the autonomy sees realistic Sun vectors and eclipse events.

The software under test is the actual flight power manager: the state estimator, the forecast scheduler, the load-shedding policy, and the fault-protection state machine.

3. Matrix: estimation and forecasting

Test Purpose Pass criterion
State-of-charge convergence Battery model learns true state Estimated SoC converges to calibrated reference within 5%
Temperature compensation Cold and hot battery behavior SoC estimate remains within tolerance across -20°C to +40°C
Eclipse prediction Forecast matches simulated shadow Predicted array power drops to zero within one minute of true eclipse entry and exit
Degradation tracking Long-life fade model Estimated remaining capacity tracks injected cell fade within 10%
Load forecast Scheduled demand matches actual Predicted load profile matches measured load within 5% RMS

4. Matrix: scheduling and load shedding

Test Purpose Pass criterion
Nominal scheduling Value-aware load planning High-value tasks run; low-value tasks defer when margin is tight
Eclipse survival Battery carries critical loads Critical loads remain powered through longest expected eclipse
Generation shortfall Array output lower than forecast Non-critical loads shed in order of value; critical loads survive
Priority override Ground command changes plan Autonomy accepts override, verifies feasibility, and reports conflicts
Battery preservation Deep-discharge avoidance Autonomy limits depth of discharge to agreed threshold unless emergency override is active

5. Matrix: fault protection and recovery

Test Purpose Pass criterion
Undervoltage response Bus droops below threshold Autonomy sheds loads and enters survival mode within defined time
Overvoltage clamp Regulator fails high Protection circuit clamps or isolates source before load damage
Overcurrent isolation Short on non-critical load Faulty load isolated; bus remains above minimum voltage
Latch-up recovery Radiation-induced short Device power-cycled and re-integrated if current returns to normal
Sensor fault Current or voltage sensor fails Autonomy detects disagreement, switches to redundant sensor, and logs the event
Recovery sequencing Generation returns after fault Loads re-enabled in priority order only after stable voltage and positive margin are confirmed

6. Matrix: integration with other subsystems

Test Purpose Pass criterion
ADCS conflict Safe mode needs power while autonomy wants to shed Coordination policy keeps ADCS alive long enough to stabilize attitude
Thermal conflict Heater demand spikes during eclipse Autonomy forecasts thermal need and preserves battery margin for heaters
Communications conflict High-power transmit window coincides with low margin Autonomy defers transmit or requests shorter pass
Attachment change New payload changes load profile Autonomy re-learns load model and updates schedule without manual reconfiguration

7. What this changes

  • The power autonomy test is a structured matrix, not a single pass/fail run.
  • Each row tests one failure mode or operational transition that could kill or degrade the mission.
  • The next entry will define success and failure criteria for the matrix as a whole.