reusability-analysis - SKILL.md Agent Skill

name: reusability-analysis description: Analyze reusability of launch vehicles and spacecraft systems. Use this skill to size recovery hardware, estimate refurbishment costs, model reuse degradation, and calculate flight-rate economics. Trigger for "reusability," "landing propellant," "recovery system," "refurbishment," "turnaround time," "flight rate economics," "booster recovery," or "reuse degradation."

Reusability Analysis Skill

Read CONVENTIONS.md at the repo root before proceeding.

This skill evaluates whether reusing a vehicle element is economically and technically viable. Reusability is the single largest cost lever in spaceflight — but only if the recovery penalties and refurbishment costs don't erase the savings.

Before You Begin

Ask the user (if not already known):

What element is being reused? (First stage booster, upper stage, fairing, spacecraft, capsule)
Recovery method? (Propulsive landing, parachute + ocean recovery, parachute + land, glide-back, mid-air capture)
Target reuse count? (1x = expendable baseline, 10x = Falcon 9 class, 100x+ = Starship ambition)
Flight rate? (Launches per year — amortization only works above a minimum cadence)
What design phase?

Applicable Phases

Primary: Phase A (reusability vs. expendable trade), Phase B (recovery system preliminary design)
Supporting: Phase C (detailed refurbishment planning), Phase D (operational reuse tracking)

Analysis Domains

1. Recovery System Sizing

Propulsive Landing

Landing propellant reserve: Typically 10-15% of stage propellant for boostback + entry burn + landing burn.
Performance penalty: Payload reduction = $\Delta m_{payload} \approx m_{prop,landing} \cdot (1 + k_{structural})$ where $k_{structural}$ accounts for landing legs, grid fins, and additional avionics.
Reference: Falcon 9 loses ~30-40% payload to LEO for RTLS, ~15-20% for ASDS (downrange landing).
Landing hardware mass: Legs (1-3% of stage dry mass), grid fins (0.5-1%), additional avionics and sensors.

Parachute / Splashdown

Parachute system mass: Typically 1-3% of recovered mass.
Salt water exposure: Drives refurbishment scope — engines, avionics, and structures all affected.
Recovery fleet: Ship + crane + logistics per recovery (operational cost).

Fairing Recovery

Parafoil + GPS guidance: Fairing halves, ~1000 kg each.
Economic value: Each fairing costs $5-6M; recovery saves ~$3-4M per flight after capture costs.

2. Reuse Degradation Modeling

Components degrade with each flight cycle:

System	Degradation Driver	Typical Limit	Inspection
Engines	Turbopump wear, chamber erosion, injector coking	10-100+ flights (depends on engine)	Borescope, flow testing
Structures	Fatigue (launch + landing loads), thermal cycling	Fatigue life analysis per MIL-STD	NDT (UT, X-ray)
Thermal Protection	Ablation, tile damage, heat shield erosion	Per-flight mass loss tracking	Visual + thickness gauge
Avionics	Vibration fatigue, connector wear	Typically not the limiter	Functional test
Tanks	Pressure cycling, cryo-cycling fatigue	COPV cycle life (design dependent)	Proof test, acoustic emission

3. Refurbishment Cost Model

Level 0 — Inspect & Fly: Visual inspection, functional test, propellant reload. (Target: <5% of new-build cost)
Level 1 — Minor Refurb: Replace consumables (igniters, seals, pyros), touch-up coatings. (Target: 5-15%)
Level 2 — Major Refurb: Engine teardown/rebuild, structural repair, avionics replacement. (Target: 15-40%)
Level 3 — Overhaul: Comparable to new build — if you're here regularly, reuse isn't saving money.
Turnaround time: Days (inspect & fly) to months (major refurb). This directly limits flight rate.

4. Flight-Rate Economics

The break-even calculation:

Expendable cost per flight: $C_{exp}$
Reusable cost per flight: $C_{reuse} = (C_{vehicle} / N_{flights}) + C_{refurb} + C_{recovery} + C_{ops}$
Break-even flight count: $N_{break} = C_{vehicle} / (C_{exp} - C_{refurb} - C_{recovery} - C_{ops})$
Payload penalty cost: If reuse reduces payload, some missions need a larger (more expensive) vehicle — factor this in.

Key insight: Reuse only wins if $N_{flights}$ exceeds $N_{break}$ AND the flight rate is high enough to amortize fixed costs (facilities, recovery fleet, refurb workforce).

5. Design-for-Reuse Checklist

Landing load cases added to structural design
Engine designed for multiple ignition cycles (bearing life, seal life)
TPS designed for multi-flight thermal cycling
Avionics designed for rapid functional test (automatable)
Propellant system designed for rapid drain/purge/reload
Access panels for inspection without extensive disassembly
Data recording (flight loads, temperatures) to support health monitoring

Output Format

Reusability Trade Report (reusability_report.md): Expendable vs. reusable comparison with performance penalty, break-even analysis, and economic model.
Recovery System Summary: Hardware mass, propellant reserves, and mission impact.
Refurbishment Plan: Per-flight and periodic maintenance requirements.
🟢 / 🟡 / 🔴 status: Economic viability at projected flight rate.

Interface

Reads from: /requirements/, /analysis/propulsion-assessment/ (engine specs, propellant), /analysis/structural-assessment/ (fatigue life), /analysis/cost-modeling/ (expendable baseline cost)
Writes to: /analysis/reusability-analysis/
Consumed by: cost-modeling (reuse economics), trade-study-manager (reuse as architecture option), systems-engineering-assessment (mass/performance impact)