Project 33

C4 — Material mass accounting

Field	Value
Status	UNRESOLVED — An open question, conflict, or missing measurement blocks a stronger statement.
Strongest accepted evidence	MODEL ONLY
Evidence classes cited	SPECIFICATION, IMPLEMENTATION, TEST PROCEDURE, ANALYTICAL
Gate reached	SOFTWARE REPRODUCTION (next: SYNTHETIC TEST)
Last review	CURRENT — snapshot recorded 2026-09-28 by tooling snapshot (no human review)

Question. Does substituting CFRP and Ti-6Al-4V for the baseline materials reduce mass by 30-40%?

Current statement. For the four parts listed in parts.yaml, substituting CFRP and Ti-6Al-4V for 7075-T6 reduces calculated mass by 36.0% (98.1 g to 62.8 g). No part has been weighed, the listed baseline is not the PLA/PETG prototype, and the listed fin volume is inconsistent with the fin mass used by C6 and C8.

Requirements

ID	Requirement	Check	Bound	Observed	Result
R-C4-REDUCTION	Candidate materials reduce total mass by 30-40% relative to the baseline.	machine	≥ 0.3 and ≤ 0.4 fraction	0.359949	SATISFIED (analytical)
R-C4-SCOPE	The mass rollup’s parts, volumes, and baseline materials describe the assembly being claimed.	human review	none stated	judgement, not a value	REQUIRES HUMAN REVIEW

Known contradictions

• None on record.

Open questions

• The rollup’s fin (about 5 g in CFRP) and the 154 g fin used by C6 and C8 cannot both describe the same design (D-010).
• The 7075-T6 baseline is not the printed prototype (D-022).

Discrepancies

• D-010 (OPEN) No shared design point across the mass, spring, reliability, and structural models
• D-022 (OPEN) The C4 baseline is not the printed prototype

Assumptions

• Part volumes, densities, and the four-part scope represent the assembly the claim is about.

Limitations

• Calculated differences are not measured savings.
• Electronics, servos, fasteners, motor, and manufacturing variation are excluded.
• The candidate materials have not been built.

Measurement needed to close the next gate

• One reconciled design point shared by C4, C6, C7, and C8.
• As-built part masses on a calibrated scale for whatever is actually built.

Pre-registered experiments

• None.

What this claim does not establish

• Any inert physical measurement: none has been accepted for this claim.
• Physical performance of any hardware.
• Flight readiness or safety for live propulsion.

Evidence

Artifact	Class	SHA-256 (first 12)	What it is
materials/mass_rollup.py	IMPLEMENTATION	7e8b8ca2b46b	Volume-times-density mass rollup.
materials/parts.yaml	IMPLEMENTATION	b2b65a256c6b	Authored part volumes and material choices for four parts.
docs/EVIDENCE/C4_mass_baseline.csv	ANALYTICAL	aa54a78f60d0	Calculated baseline masses. Nothing was weighed.
docs/EVIDENCE/C4_mass_optimized.csv	ANALYTICAL	c6dff1a044a6	Calculated candidate masses. Nothing was weighed.
docs/EVIDENCE/C4_mass_summary.json	ANALYTICAL	f2987d389601	Totals, reduction fraction, and the explicit list of what the rollup excludes.
tests/test_mass_rollup.py	TEST PROCEDURE	a553cf030873	Regression checks against the committed summary.
docs/CAD_ASSEMBLIES.md	SPECIFICATION	4352bd376b30	Prototype material plan: PLA+/PETG printed airframe and fins.

Earlier versions (failure archive)

• evidence/archive/notes-v1/C4_delta.md — Historical C4 note.

A change to any of these files makes the last review insufficient

• docs/CAD_ASSEMBLIES.md
• docs/EVIDENCE/C4_mass_baseline.csv
• docs/EVIDENCE/C4_mass_optimized.csv
• docs/EVIDENCE/C4_mass_summary.json
• materials/mass_rollup.py
• materials/parts.yaml
• tests/test_mass_rollup.py

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All claims · Traceability · Discrepancies · Evidence Observatory

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