Mass closure ratio validation for ISRU economics

Background

The rq-0-28 resolution established the capacity cost model as the replacement for linear cost scaling, fundamentally changing Project Dyson's budget methodology. The new model's economics depend critically on the mass closure ratio — the fraction of a manufacturing system's mass that can be produced from in-situ materials. The consensus assumes 96% closure for Phase 3a foundries, meaning only 4% of mass must be imported from Earth. This single parameter is the highest-leverage unknown in the entire ISRU economic model: at 96% closure, costs drop by 1,000x; at 80% closure, the reduction is only 5x.

Why This Matters

The mass closure ratio determines:

• How many seed units must be launched from Earth to bootstrap the system
• The exponential growth rate of manufacturing capacity
• The steady-state import requirement (and thus ongoing Earth-launch costs)
• Whether the capacity cost model actually delivers the predicted cost reductions
• The timeline from seed deployment to self-sustaining operations

A 96% closure ratio has never been demonstrated for any manufacturing system, terrestrial or space-based. The closest analogs (biological organisms) achieve >99% mass closure but over evolutionary timescales with different material constraints.

Key Considerations

• Electronics, sensors, and control systems contain rare elements not found in asteroids
• Optical components require extreme purity not easily achieved via ISRU
• Seals, lubricants, and polymers require specific organic chemistry
• Each non-ISRU component creates an ongoing Earth-supply dependency
• Closure ratio likely improves over time as ISRU capabilities mature
• Different product types have different achievable closure ratios

Research Directions

1. Component-level closure analysis: For each BOM item in Phases 1-3, decompose into materials and classify each as asteroid-available, synthesizable from asteroid feedstock, or Earth-import-only.

2. Critical element identification: Identify the specific elements and compounds that limit closure ratio, quantifying their mass fraction in each manufactured product.

3. Closure improvement roadmap: Map the technology development path from current capabilities (0% closure) through Phase 1 (50%) to Phase 3 targets (~96%), identifying key milestones.

4. Sensitivity analysis: Model budget estimates across a range of closure ratios (50%, 70%, 85%, 96%, 99%) to understand which threshold transitions matter most economically.

5. Terrestrial analog benchmarking: Study the most self-sufficient terrestrial manufacturing facilities to establish empirical upper bounds on closure ratio with current technology.