The Frozen-Design Methodology

At defined points we freeze a complete, self-consistent design so that everyone works from one set of numbers under formal change control.

One design point, held still

A frozen design is a complete, internally consistent snapshot of the machine: every headline number, every input, every assumption, fixed at a moment and treated as the single source of truth until formally changed. Freezing prevents the slow drift where different documents quote slightly different figures and no one can say which is real.

Why freeze at all

Design is coupled: change the field and the current shifts, change the geometry and the breeding ratio moves. If numbers float freely, documents silently disagree and analyses built on last month's figure are silently invalid. A freeze guarantees that Q_sci 3.424, fusion power 88.7 MW, plasma current 9.86 MA, and peak field 16.84 T all describe the same machine at the same time.

The freeze is dated and enumerated

Each freeze is a specific, dated set of entries, so any claim can be traced to the freeze it came from. This is what lets us compare a future FOAK measurement against exactly the design that predicted it, rather than a moving target.

Freezing is not rigidity. It is the precondition for disciplined change: you can only control a change against a fixed baseline. A freeze is therefore not a claim that the design is finished; it is a claim that, as of a specific date, these particular numbers describe one coherent machine and can be tested as such. Everything downstream -- documents, analyses, predictions, and the eventual comparison with hardware -- inherits its integrity from that single, dated, reconcilable baseline.