reliability-assessment

name	reliability-assessment
description	Perform reliability, radiation risk, and failure mode assessments for space missions. Use this skill to calculate mission life probability, TID exposure, FMECA, and parts derating. This skill provides the bottom-up failure data used as "Causes" in hazard-analysis. Trigger for "FMECA," "reliability," "radiation," "TID," "single event effects," or "parts screening."

Reliability & Radiation Assessment Skill

Read CONVENTIONS.md at the repo root before proceeding.

This skill assesses what could fail and why, providing bottom-up failure analysis data that feeds into hazard-analysis (top-down) and informs design trades.

Before You Begin

Ask the user (if not already known):

1. What orbit/trajectory? (Drives radiation environment — LEO is mild, GEO/MEO Van Allen belts are harsh, interplanetary is variable)
2. Are parts space-grade (Class S/B), military (Class M), or COTS? (Dramatically affects failure rates and radiation tolerance)
3. What mission lifetime? (Drives Total Ionizing Dose accumulation and wear-out)
4. What reliability standard applies?
   • NASA: NPR 8705.4, EEE-INST-002
   • ESA: ECSS-Q-ST-30 (Dependability), ECSS-Q-ST-60 (EEE Components)
   • MIL: MIL-STD-1629 (FMECA), MIL-HDBK-217 (failure rates)
5. What design phase?

Applicable Phases

• Primary: Phase B (preliminary FMECA, radiation assessment), Phase C (detailed FMECA, parts selection)
• Supporting: Phase A (risk identification), Phase D (anomaly investigation)

Analysis Domains

1. Reliability Modeling

• Reliability Block Diagrams (RBD): $R_{sys} = \prod R_i$ (series) or $R_{sys} = 1 - \prod(1-R_i)$ (parallel/redundant).
• Failure rates ($\lambda$): Use MIL-HDBK-217 or FIDES for initial estimates. Actual rates from manufacturer data where available.
• MTTF/MTBF: $MTTF = 1/\lambda$ for exponential distribution.
• Redundancy: Identify single points of failure (SPOFs). Recommend cold, warm, or hot redundancy where criticality warrants it.

2. Radiation Assessment

• Total Ionizing Dose (TID): Estimate based on orbit, duration, and shielding. Use AP-8/AE-8 or AP-9/AE-9 models for trapped radiation.
• Single Event Effects (SEE): SEU (bit flip — recoverable), SEL (latch-up — potentially destructive), SEB (burnout — catastrophic).
• Shielding: Aluminum equivalent thickness. Typical spacecraft provide 3-10 mm Al shielding. Spot shielding for sensitive parts.
• Parts derating: Ensure components operate below maximum rated values (typically 60-80% derating for voltage, current, power).

3. FMECA

• Identification: List failure modes for each subsystem/component.
• Effects: What happens at component, subsystem, and system level?
• Criticality: Severity (1-4) × Probability (A-E) matrix.
• Mitigation: Hardware redundancy, software FDIR, operational procedures.
• Feed to hazard-analysis: Failure modes become "Causes" in the top-down hazard reports.

4. Parts & Materials

• Screening: Space-grade (expensive, radiation-hard, long lead) vs. COTS (cheap, needs testing/shielding, shorter lead).
• Obsolescence: Flag parts with end-of-life risk over mission development timeline.
• Outgassing: Materials near sensitive surfaces must meet ASTM E595 (TML < 1.0%, CVCM < 0.1%).

Output Format

1. Risk Assessment Report (risk_assessment.md): RBD results, TID estimate, 5×5 Criticality Matrix, SPOF list.
2. Probability of Success: Mission reliability estimate (e.g., "93% probability of completing 2-year primary mission").
3. FMECA Table: Failure modes, effects, severity, probability, mitigation.

Interface

• Reads from: /requirements/, /analysis/mission-analysis-specialist/ (orbit for radiation environment)
• Writes to: /analysis/reliability-assessment/
• Consumed by: hazard-analysis (failure modes as causes), flight-software-architect (rad-hard requirements), systems-engineering-assessment (risk summary)