The electrical harness serves as the "neural network" for satellite launch vehicles, providing the interfaces for all guidance, health monitoring, and control systems during a mission. This system is composed of cables, and connectors. The wires are made of metallic conductors, typically copper plated with silver or gold to enhance conductivity and prevent oxidation. These conductors are insulated with polymeric materials such as PTFE, Kapton, ETFE, or TKT. Connectors, which are the interface points for electrical circuits, consist of gold or nickel-plated copper contacts housed within a shell. A typical launch vehicle contains an extensive network of electrical harnesses, with approximately 4,200 connectors and 110,000 meters of cable, which contributes to about 30% of the vehicle's total weight. The weight is mostly due to the polymeric insulation rather than the conductors.
Challenges and Solutions for Sustainable Systems
The paper highlights several key issues with current electrical harnessing systems and the steps taken to address them. The non-expendable nature of the polymeric insulation makes the disposal of harness waste a significant environmental concern. Furthermore, some insulation materials can emit toxic gases when burned or outgas in a vacuum. Another major issue is the use of cadmium for plating connector shells, as it is a known carcinogen. Cases of cadmium bloom have been observed, prompting the need for safer alternatives.
Enhancing Safety, Reliability, and Sustainability
ISRO is implementing several measures to mitigate these challenges. Lean manufacturing practices are being adopted to minimize wastage during the production of harnesses and accessories. To reduce overall mass, the use of composite materials for connector shells and micro-miniature connectors is being explored as an alternative to current metallic parts. For human-rated missions,
TKT-insulated wires are being introduced to replace Kapton-insulated cables, which improves safety in the event of electrical failures. Additionally, plans are in place to replace cadmium-plated components with safer zinc-nickel or stainless-steel connectors to eliminate the health and environmental risks associated with cadmium.