The AstroForge PGM model structures supply into three cost tiers cleared through Vensim's FIND MARKET PRICE function, driven by a named reinforcing/balancing feedback-loop pair ("R1 Gold Rush" / "B2 Falling Price")

Nachtrieb and Smith's system-dynamics model (arXiv:2607.06806) is not an exogenously scripted price path stitched to fit the paper's narrative; it is a stock-and-flow structure with a specific mechanical implementation. Supply is split into three cost-ranked stocks: High Cost (HC, small terrestrial capacity such as U.S. mines), Medium Cost (MC, the bulk of terrestrial supply — the paper names South Africa and Russia), and Low Cost (LC, off-world/asteroid supply, small initially and variable based on the investment flow driven by entities such as AstroForge). The market-clearing price across these three tiers is computed with a built-in Vensim allocation function: "we use the built-in Vensim function FIND MARKET PRICE to satisfy the allocation of supply to demand."

The peak-then-collapse shape is generated by a named pair of feedback loops rather than asserted directly. A reinforcing loop, "R1 Gold Rush," runs on above-industry-norm margins attracting exponentially growing investment into low-cost capacity; a balancing loop, "B2 Falling Price," activates once that growing low-cost supply is large enough to depress the market price, which then slows the growth rate of new investment. This is the same trajectory claim-asteroid-pgm-price-holds-then-collapses already documents from Table III's numbers (60→60→11 MUSD/ton, profit peaking near 8x); this note adds the specific stock-flow structure and loop mechanics producing it.

Provenance: source_url: https://arxiv.org/pdf/2607.06806; source_author: Robert T. Nachtrieb and Steven J. Smith; source_date: 2026-07-07 (v1); source_tier: 1. The actual equations behind these tiers and Vensim's allocation function live in the ancillary AstroForge_v5.mdl file, not yet read verbatim — see question-verify-astroforge-pgm-model-dynamics.