Structural Assessment

• Primary: Phase A (mass budget, first-order stiffness), Phase B (preliminary structural design)
• Supporting: Phase C (detailed FEA, coupled loads analysis), Phase D (structural testing)

Analysis Domains

1. Mass Properties

• Center of Gravity (CG): $CG = \sum(m_i \cdot r_i) / \sum m_i$. Calculate for both stowed (launch) and deployed configurations.
• Moments of Inertia (MOI): $I = \sum(m_i \cdot d_i^2)$ using Parallel Axis Theorem. Essential input for gnc-assessment.
• Products of Inertia: Identify principal axis misalignments (causes nutation during spin-stabilized phases).
• Mass growth tracking: Phase A budgets should include 20-30% margin. Track current best estimate (CBE) vs. allocation.

2. Structural Integrity

• Quasi-static loads: Apply launch vehicle G-loads (typically 6-10G axial, 2-5G lateral, combined).
• Dynamic loads: Random vibration and acoustic environments per LV User Manual.
• Stress: $\sigma = F/A$ (axial) or $\sigma = Mc/I$ (bending).
• Margin of Safety: $MoS = \frac{F_{allowable}}{F_{applied} \times SF} - 1$
  • SF = 1.25 for Yield, 1.5 for Ultimate (ask user — standards vary)
  • Negative MoS = structural failure — must redesign.

3. Fundamental Frequency (Stiffness)

• Estimate: $f = \frac{1}{2\pi}\sqrt{k/m}$ for simple models.
• Requirement: First natural frequency must be above LV "kick" frequency:
  • Typically > 25 Hz lateral, > 35 Hz axial for small satellites
  • Large spacecraft: check LV manual for specific requirements
• If below threshold: Stiffen the structure or add mass constraints.

4. Launch Vehicle Interface

• Adapter: Separation system type (clamp band, Lightband, motorized), bolt circle diameter.
• CG envelope: LV specifies maximum CG height above separation plane.
• Coupled Loads Analysis (CLA): At Phase C, a formal CLA with the LV provider is typically required.

Output Format

1. Structural Report (structural_report.md): CG position (stowed/deployed), MOI matrix, MoS table for critical components.
2. Mass Properties Summary: CBE mass, allocation, margin, CG coordinates.
3. Configuration Notes: Ballast requirements, deployment sequence constraints.

Interface

• Reads from: /requirements/, subsystem mass estimates from all domain skills
• Writes to: /analysis/structural-assessment/
• Consumed by: systems-engineering-assessment (mass budget), gnc-assessment (MOI, CG-CP offset), ait-manager (structural test levels)