Thermal Engineering Assessment Skill

Read CONVENTIONS.md at the repo root before proceeding.

This skill performs analytical thermal modeling — calculating thermal equilibrium of spacecraft components by accounting for environmental fluxes, internal heat, and material properties.

Before You Begin

Ask the user (if not already known):

1. What is the celestial environment? (Earth orbit, lunar surface, Mars, deep space — determines environmental fluxes)
2. What are the critical components and their temperature limits? (Electronics, batteries, propellant, optics, mechanisms)
3. Is this a spinning or 3-axis stabilized spacecraft? (Affects heat distribution)
4. What thermal analysis standard applies?
   • NASA: NASA-HDBK-4002 (Thermal), GSFC-STD-7000 (GEVS Ch.14)
   • ESA: ECSS-E-ST-31 (Thermal Control)
5. What design phase? (Phase A: hand calcs; Phase B+: recommend Thermal Desktop, ESATAN-TMS, or equivalent)

Applicable Phases

• Primary: Phase A (first-order sizing), Phase B (preliminary thermal model)
• Supporting: Phase C (detailed model correlation), Phase D (TVAC test planning with ait-manager)

Analysis Domains

1. Environmental Heat Flux Calculation

Avoid hardcoded values — scale by mission:

• Solar flux ($G_s$): $1361\ W/m^2$ at 1 AU, scales as $1/d^2$.
• Albedo ($q_a$): $G_s \times a \times F_{view}$ (Earth albedo ~0.3, Moon ~0.12, Mars ~0.25).
• Planetary IR ($q_{IR}$): Based on body surface temperature and view factor.
• Deep space sink: 2.7 K cosmic microwave background.

2. Nodal Heat Balance

• Steady state: $Q_{in} + Q_{gen} = Q_{out}$
• Transient: $Q_{in} + Q_{gen} = Q_{out} + mc_p(dT/dt)$
• Conduction: $Q = kA\Delta T / L$
• Radiation: $Q = \epsilon\sigma A(T_1^4 - T_2^4)$
• Internal dissipation ($Q_{gen}$): Electronics waste heat, heater inputs.

3. Thermal Hardware Sizing

• MLI: Effective emissivity $\epsilon^*$ (typically 0.01-0.05 for good MLI).
• Radiators: Area from $Q_{reject} = \epsilon\sigma\eta A T^4$. Size for worst-case hot.
• Heaters: Power to maintain min temperature in worst-case cold.
• Heat pipes / loop heat pipes: For spreading heat from high-dissipation components.
• Thermal straps / isolators: Conductive coupling or decoupling between components.

4. Surface Properties

| Surface | Solar Absorptivity ($\alpha$) | IR Emissivity ($\epsilon$) | $\alpha/\epsilon$ | |:---|:---|:---|:---| | White paint (S13G) | 0.20 | 0.85 | 0.24 | | Black paint (Z306) | 0.95 | 0.85 | 1.12 | | Bare aluminum | 0.09 | 0.03 | 3.0 | | Gold tape | 0.23 | 0.04 | 5.75 | | OSR (Optical Solar Reflector) | 0.08 | 0.80 | 0.10 |

Note: these degrade with UV exposure and atomic oxygen over mission life (BOL vs EOL).

Verification & Margins

• Operational margin: 10°C buffer between predicted T and component hardware limits.
• Survival margin: 5°C buffer for non-operational states.
• Uncertainty: State assumptions for contact conductance and coating degradation (BOL vs EOL).

Output Format

1. Thermal Model Summary (thermal_model.md): Environment, nodes, heat loads, predicted temperature ranges, and margin status.
2. Material Recommendations: Surface treatments with $\alpha/\epsilon$ ratios.
3. Hardware List: Radiator area, heater power, MLI coverage, heat pipes.

Interface

• Reads from: /requirements/, /analysis/mission-analysis-specialist/ (eclipse duration, solar distance), /analysis/power-assessment/ (component dissipation), /analysis/structural-assessment/ (configuration)
• Writes to: /analysis/thermal-assessment/
• Consumed by: systems-engineering-assessment (thermal summary), power-assessment (battery temp limits, heater power), ait-manager (TVAC test limits), lunar-conops-manager (surface thermal environment)