Fleet-level contamination acceptability threshold for excavation operations

Background

The rq-0-26 bucket-wheel design includes integrated housing for particle containment during excavation. The target is >99% containment efficiency, but at 20,000+ tonnes of material processed per robot per year across a fleet of 20 robots, even 1% escape represents 4,000+ tonnes of ejected particles annually. These particles can contaminate optical surfaces, jam mechanisms, degrade solar arrays, and create collision hazards for nearby spacecraft.

Why This Matters

The contamination threshold determines:

• Required containment housing design complexity and mass
• Operational spacing between robots and other assets
• Maintenance intervals for optical and mechanical systems
• Whether prospecting satellites can operate in proximity to active mining
• Long-term asteroid environment degradation affecting future operations

At fleet scale, the cumulative debris environment around a mining operation could become self-sustaining if ejection rates exceed natural dispersal rates, creating a persistent contamination cloud that affects all operations.

Key Considerations

• Particle ejection velocities may exceed asteroid escape velocity (cm/s to m/s)
• Electrostatic charging of ejected particles complicates prediction and mitigation
• Optical surfaces (solar arrays, sensors, cameras) are most sensitive to contamination
• Particle sizes range from microns to centimeters with different hazard profiles
• Multiple robots operating simultaneously create overlapping contamination zones
• Self-cleaning mechanisms add mass and complexity to all nearby systems

Research Directions

1. Debris environment modeling: Simulate the particle population around an asteroid with 20 active excavators at various containment efficiencies, predicting steady-state debris density.

2. Containment efficiency testing: Measure actual particle escape rates from enclosed bucket-wheel prototypes using various housing designs and sealing approaches.

3. Fleet spacing optimization: Determine minimum safe operating distances between excavators and between excavators and other assets as a function of containment efficiency.

4. Contamination impact assessment: Quantify degradation rates for solar arrays, optical sensors, and mechanical systems as a function of particle flux exposure.

5. Mitigation hierarchy: Define a tiered approach from source containment (housing design) to path control (electrostatic barriers) to receiver protection (self-cleaning surfaces).