Prototype & Validate

Source small-quantity Zylon (PBO) fiber for splice testing and prototype fabrication. This is a procurement step — get the material in hand before committing to lab time.

Zylon is available through Teijin Frontier USA (primary US distributor) and Avient/Fiber-Line in standard deniers (250, 500, 1000, 1500, 3000d). Hayami Industry Co. (Japan) explicitly accepts small-quantity trial orders of braided Zylon cord. For 50 splices on 1-5 m segments, total material is 50-250 m of fiber (~0.1-0.5 kg) — a trivial order at ~$100-200/kg retail.

Order both AS (standard modulus) and HM (high modulus) variants for comparison. HM has higher stiffness and lower creep but may behave differently under splice loading. Request the Toyobo technical data sheet with the order to confirm exact specs.

Before running the formal 50-splice test matrix, build a controlled splice jig and develop hand technique for working with PBO fiber. Zylon's rigid molecular structure (higher stiffness than Dyneema or Kevlar) means standard rope splicing techniques may not transfer directly — the fiber handling and interleaving process needs to be learned and refined on actual material.

The jig is a simple fixture: a board with adjustable clamps to hold both fiber ends at controlled tension, graduated markings for consistent overlap lengths (10-50 cm), guide channels to keep filaments aligned during interleaving, and a small serving tool for wrapping binding thread at even tension. Total cost under $200 in hardware store parts.

Success criteria: produce 5 consecutive splices with visually identical geometry — consistent overlap length, even filament distribution, uniform serving wrap — before advancing to formal tensile testing. This step also serves as an early filter: if PBO's stiffness makes braided overlap impractical at test scale, the formal test matrix should weight mechanical sleeve and adhesive bond methods more heavily.

With Zylon fiber in hand, fabricate 50 test splices using candidate methods (braided overlap, fusion, mechanical) on 1-5 m cable segments and load each to failure. Target: ≥95% of virgin fiber breaking strength. Document failure modes (splice slippage vs. fiber rupture) and establish minimum overlap length. This directly determines whether the 40,000 km cable is viable as a spliced assembly.

Tensile testing access: University materials labs are the most cost-effective path. Most ME, aerospace, and civil engineering departments have universal testing machines (Instron, MTS) in the 10-100 kN range and rent lab time to external users at $50-200/hr. TestResources also offers direct machine rental. Target: a 100 kN UTM with fiber/yarn grips and an extensometer.

Budget: The real costs are lab time ($1K-3K for ~20 sessions), splice fabrication tooling (braiding jig, adhesives, fixtures — $500-1K), and failure documentation (high-speed camera rental $500-1K). A university partnership or makerspace with an Instron could cut costs significantly. Save $5K-8K for this step.

Subject coated cable samples to atomic oxygen bombardment in a vacuum chamber, simulating conditions at 100 km altitude. Test at least three coating types: SiO₂ (CVD), Al₂O₃ (ALD), and aluminum foil sheath. Measure mass loss, tensile strength retention, and coating adhesion after simulated exposure equivalent to 1, 6, and 12 months. NASA Glenn Research Center and AFRL have ground-based AO exposure facilities (e.g., the MPAC&SEED or directed-beam AO sources).

Build a 1-10 km closed cable loop on the ground, tensioned between anchor points or on a circular test track. Spin the loop at scaled tension to simulate hoop stress conditions. Run continuously for weeks to test fatigue, creep, splice durability under sustained load, and coating wear. This is the cheapest way to find failure modes before going to orbit. A desert test site, abandoned airstrip, or large warehouse could host the loop.

Loft a 1-5 km cable segment to 30-35 km altitude on a stratospheric balloon. Expose the cable to near-space conditions (low pressure, UV, thermal cycling between sunlight and shadow, partial atomic oxygen exposure) for 1-4 weeks. Monitor tensile strength telemetry in real-time. This bridges the gap between ground vacuum chamber tests and actual orbital deployment. Companies like World View, Aerostar, or Near Space Corporation offer stratospheric balloon platforms for payload testing.

Test the spool unwinding mechanism at speed. Options: (1) ground-based high-speed unspool rig simulating orbital deployment rate, (2) sounding rocket carrying a small spool (100-500m of cable) that deploys during ascent/descent, (3) drop test from a high-altitude balloon. The goal is to prove the cable unspools cleanly without tangling, kinking, or uneven tension — failure modes that would be catastrophic at orbital scale. Document unspooling dynamics with onboard cameras and tension sensors.