L2-SSM-SHM ESSENTIAL ENVIRONMENTAL Level 2 · hardware

Structural Health Monitoring

Structural Health Monitoring Sensor Network

Embedded and surface-mounted sensor network monitoring strain, vibration, temperature, and acoustic emissions across all primary structural elements of the Ark.

Purpose

Detect structural degradation, fatigue cracking, joint loosening, seal failures, and thermal stress accumulation before they threaten Ark integrity, enabling proactive maintenance over the 100-year mission.

Context

The Ark structure endures repeated thermal cycling (280K range every 29.5-day lunar day), micrometeorite impacts, seismic loading, and long-term material creep. SHM provides the internal structural state that complements external seismic monitoring, forming a complete picture of structural health.

Principles

▸Distributed fiber optic sensing for continuous strain and temperature measurement along structural members
▸Acoustic emission monitoring for real-time crack growth detection
▸Modal analysis through ambient vibration to detect stiffness changes indicating damage
▸Comparative baseline approach: deviation from healthy reference signatures indicates damage

Typical implementations

▸Fiber Bragg grating (FBG) strain and temperature sensors on structural members
▸Distributed acoustic sensing (DAS) using fiber optic cables
▸Piezoelectric acoustic emission sensors at weld joints and high-stress regions
▸MEMS accelerometers for vibration-based structural identification
▸Capacitive displacement sensors at expansion joints and seals
▸Guided wave ultrasonic transducers for plate and pipe inspection

Lunar considerations

▸Thermal cycling causes cumulative fatigue at joints and connections
▸Vacuum environment eliminates corrosion but enables cold welding of metals
▸Radiation degrades adhesives and polymeric sensor components over time
▸Micrometeorite impacts can cause localized damage requiring rapid detection
▸Fiber optic sensors preferred for radiation tolerance and electromagnetic immunity
▸Self-powered sensors (piezoelectric energy harvesting) reduce wiring complexity

Specifications

Functional

primary function	Continuously monitor the structural health of all primary Ark structural elements
inputs	Structural strain fields, Vibration and modal responses, Acoustic emissions from material damage, Temperature distribution across structure, Joint and seal displacement
outputs	Structural health index per monitored zone, Damage detection, localization, and severity assessment, Thermal stress accumulation tracking, Seal integrity status, Maintenance priority queue
strain resolution microstrain	1
temperature resolution c	0.1
spatial resolution m	0.5
acoustic emission sensitivity db ae	40
monitoring points	2000
damage detection probability	0.95

Physical

mass kg	180
dimensions	Distributed across all primary structural elements
materials	Germanium-doped silica optical fibers, Piezoelectric PZT ceramics, Radiation-hardened silicon MEMS, Polyimide fiber coatings (radiation-resistant), Titanium sensor housings
embedded in structure	True
surface mounted	True
radiation tolerance krad	1000

Operational

power consumption w	45
thermal range c	-173, 127
lifetime years	100
mtbf hours	500000

Interfaces

Provides

→Data Processing & AnalysisStructural sensor data streamsessential
Continuous strain, vibration, acoustic emission, and temperature data from distributed sensor network
→L1-MAINTStructural damage alertsessential
Real-time notifications of detected damage events requiring maintenance action

Requires

←Power Generation SystemElectrical powercritical
45W for sensor interrogation units and local processing
←Seismometer NetworkFree-field ground motion referenceessential
External seismic input to distinguish structural damage from seismic response
←Data Processing & AnalysisData acquisition and baseline managementessential
Central processing for modal analysis and baseline comparison