reliability-assessment - SKILL.md Agent Skill

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):

What orbit/trajectory? (Drives radiation environment — LEO is mild, GEO/MEO Van Allen belts are harsh, interplanetary is variable)
Are parts space-grade (Class S/B), military (Class M), or COTS? (Dramatically affects failure rates and radiation tolerance)
What mission lifetime? (Drives Total Ionizing Dose accumulation and wear-out)
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)
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

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