SpaceX/xAI Reportedly Developing 'Kessel' Rack System: 84-Layer PCB Replaces NVLink Cables for Orbital Data Centers

According to a report by Tom's Hardware citing SemiAnalysis, SpaceX and xAI are developing a custom version of Nvidia's Vera Rubin NVL72 rack-scale AI system codenamed 'Kessel'. The system retains the fundamental configuration of 36 Vera CPUs, 72 Rubin GPUs, and nine NVLink switch trays but introduces a different solid-state interconnect architecture.

Unlike Nvidia's conventional arrangement using internal NVLink cable cartridges, 'Kessel' plans to position compute and switch trays back-to-back around a passive PCB midplane. The most distinctive feature is its 84-layer PCB midplane, which uses ultra-low-loss M10 copper-clad laminates (CCLs). This contrasts with Nvidia's Kyber architecture, which relied on a more complex 156-layer PCB. While reducing layer count could improve manufacturability, the advanced materials will likely increase costs.

The design is aimed at both terrestrial and orbital deployments. Furthermore, SpaceX/xAI reportedly plans to shift its procurement model, acquiring AI accelerators, CPUs, switches, and networking components directly from Nvidia while sourcing other components independently. This allows SpaceX to select its own PCB manufacturers and optimize hardware for its infrastructure, though it assumes greater responsibility for system design, validation, and supply-chain management.