The Griffiths Free-Flying EVA Logistics Sled (NGLS) is a purpose-built EVA logistics vehicle designed to solve a capability gap that traditional astronaut maneuvering units were never intended to address. Systems like SAFER and the historical MMU were built for personal mobility and emergency return, not for transporting heavy equipment, structural components, or modular payloads across the exterior of large deep‑space habitats and propulsion modules. As spacecraft scale upward and distributed construction becomes routine, EVA logistics becomes its own operational domain. The NGLS formalises that domain.

The sled is a lightweight composite-frame vehicle, 3.2 metres long, with dual high‑pressure nitrogen COPV tanks feeding a cold‑gas propulsion system. It provides 6‑degree‑of‑freedom control authority through a combination of gimballed nozzles and micro‑thruster clusters. Total thrust ranges from 2 to 6 newtons, with specific impulse of 65–75 seconds and exhaust velocity around 700 m/s. With 30 kg of nitrogen propellant, the sled delivers approximately 21,000 N·s of total impulse, enabling operational delta‑v of 50–150 m/s depending on payload mass and sortie profile. Payload capacity ranges from 50 to 200 kg, allowing the sled to move tools, radiator panels, replacement coils, structural elements, and fabricated components that would otherwise require robotic arms or multiple EVA sorties.

The structural architecture uses carbon‑fibre composite for the primary spine and load rails, titanium alloy for load‑bearing joints and thruster hardpoints, and aluminium‑lithium for secondary brackets. EVA‑safe edge treatments, integrated handholds, and ISS‑compatible cargo interfaces ensure compatibility with existing EVA tools and procedures. Shock‑isolated mounts protect sensitive payloads during manoeuvres.

The propulsion subsystem is built around safety-first principles. All valves are fast‑response solenoids configured to fail closed. Redundant regulators and distribution manifolds ensure that either tank can independently support a controlled return-to-base. Thruster clusters provide multiple independent pathways for attitude and translation control, allowing the autonomy stack to isolate a failed nozzle and redistribute control authority without losing stability.

The autonomy architecture is layered. The inner loop runs at 100 Hz for high‑frequency attitude control using triple‑redundant IMUs. The outer loop at 10 Hz handles position control, drift correction, and collision avoidance using fused LIDAR, stereo vision, and ultrasonic sensors. A supervisory layer governs dead‑man stabilisation, safe‑mode damping, and autonomous return-to-base. If the pilot becomes incapacitated or releases the control handle, the sled immediately nulls rotation and translation, stabilises, and prepares for autonomous docking with the habitat.

Safety and predictive diagnostics are central. The sled continuously monitors thrust-vector deviation, valve response times, tank pressure decay, sensor disagreement, thermal excursions, and structural load signatures. All telemetry streams to the habitat’s DI‑HCL predictive safety system, enabling early detection of anomalies and coordinated EVA safety management.

Within the broader Griffiths Canon, the NGLS becomes the logistics backbone: delivering components fabricated by DIMDCP, supporting propulsion-module maintenance for GNMT and MSH‑Drive, and enabling exterior servicing of the Dual‑Ring Habitat. It transforms EVA from a physically taxing, manually constrained activity into a predictable, governed logistics operation.