Power Assessment Skill (EPS)

Read CONVENTIONS.md at the repo root before proceeding.

This skill performs detailed Electrical Power System analysis. It provides sized solar arrays, batteries, and bus architecture — going beyond the summary-level power budget in systems-engineering-assessment.

Before You Begin

Ask the user (if not already known):

1. What is the primary power source? (Solar, RTG, fuel cells, primary batteries — driven by mission type and distance from Sun)
2. What is the orbit? (Eclipse duration from mission-analysis-specialist is a critical input)
3. What is the mission lifetime? (Drives degradation and cycle-life calculations)
4. What is the bus voltage? (28V regulated is common; ask if there's a heritage constraint)
5. What design phase?

Applicable Phases

• Primary: Phase A (first-order sizing), Phase B (detailed energy balance)
• Supporting: Phase C (power profile verification), Phase D (solar array deployment test planning)

Core Analysis Workflows

1. Solar Array Sizing (BOL/EOL)

• Inputs: Required power ($P_{req}$), solar constant ($1361\ W/m^2$ at 1 AU), cell efficiency ($\eta$), sun incidence angle ($\theta$), degradation rate ($F_d$), mission life ($L$), packing factor.
• For non-Earth missions: Scale solar flux by $1/d^2$ from Sun. Mars: ~589 W/m², Jupiter: ~50 W/m².
• EOL factor: $L_d = (1 - F_d)^L$
• Required area: $A = P_{req} / (S \cdot \eta \cdot \cos\theta \cdot I_d \cdot L_d)$
• If solar is not viable (e.g., outer planets, permanent shadow): Recommend RTG or nuclear and flag for user decision.

2. Battery & Energy Storage

• Inputs: Eclipse power ($P_{ecl}$), eclipse duration ($t_{ecl}$ from mission-analysis-specialist), DOD, battery efficiency, transmission efficiency.
• Sizing: $E_{req} = (P_{ecl} \cdot t_{ecl}) / (\eta_{bat} \cdot \eta_{trans} \cdot DOD)$
• DOD policy:
  • LEO (high cycle count): 20-40% DOD for Li-ion
  • GEO (low cycle count): up to 80% DOD
  • Lunar night (~14 days): batteries alone are typically insufficient — flag this
• Thermal: Battery charge typically 0°C to 30°C — coordinate with thermal-assessment.

3. Power Distribution & Architecture

• Bus regulation: Regulated (28V typical) vs. unregulated (battery voltage varies).
• Peak power tracking: MPPT vs. Direct Energy Transfer (DET).
• Harness losses: Typically < 2% voltage drop budget.

4. Alternative Power Sources

For missions where solar power is insufficient:

• RTG: ~120W per unit, multi-decade lifetime, ~4.8% efficiency. Subject to nuclear safety review.
• Fuel Cells: Short-duration high-power missions (e.g., crewed lunar sortie).
• Primary Batteries: Very short missions only (< days).

Output Format

1. Power Analysis Report (power_analysis.md):
   • Solar array: BOL/EOL power, required area, degradation assumptions
   • Battery: capacity (Wh/Ah), DOD, cycle life
   • 🟢 / 🟡 / 🔴 status
2. EPS Configuration (eps_config.csv): Solar area, battery Wh, bus voltage.

Reference Data

• Solar Flux: Earth/Moon ~1361 W/m², Mars ~589 W/m², Jupiter ~50 W/m²
• Li-ion energy density: 150-250 Wh/kg
• Solar cell efficiency: Triple-junction GaAs 28-32%, Silicon 15-20%, advanced multi-junction >35%

Interface

• Reads from: /requirements/, /analysis/mission-analysis-specialist/ (eclipse duration, solar distance), /analysis/thermal-assessment/ (battery temp limits)
• Writes to: /analysis/power-assessment/
• Consumed by: systems-engineering-assessment (power budget summary), propulsion-assessment (EP power availability), gnc-assessment (actuator power)