In the journey of aerospace propulsion technology towards higher speeds and deeper space, extreme temperature fluctuations, strong oxidation atmospheres, and high-speed airflow erosion pose strict challenges to material performance. With unique molecular structure stability, wide-temperature adaptability, and chemical inertness, silicone rubber and silicone oil have become the "invisible guardians" of aero-engines and spacecraft propulsion systems. From combustion chamber sealing to rocket nozzle protection, from fuel pipeline corrosion resistance to turbine bearing lubrication, they are solving technical problems under extreme conditions through material innovation, providing key support for human exploration of the starry sky.
一、Extreme Environment Challenges in Propulsion Systems
（一）Performance Tests in Ultra-Wide Temperature Ranges
The combustion chamber temperature of an aero-engine surges from -50°C to 1800°C during startup, and the rocket engine nozzle faces alternating impacts of 3000°C high temperature and -200°C plume low temperature in an instant of ignition. Traditional materials are prone to thermal fatigue cracking in such extreme temperature changes, while the silicon-oxygen bond backbone of silicone rubber remains elastic in the range of -100°C to 300°C. With the introduction of special ceramic fillers, it can withstand 1200°C high temperature in the short term. Silicone oil maintains fluid stability in the wide temperature range of -60°C to 250°C through molecular design.
（二）Strong Oxidation and Corrosion Protection
The oxygen-rich environment in LOX-kerosene engines, the extreme low-temperature hydrogen embrittlement in hydrogen-oxygen engines, and the strong corrosiveness of new green propellants require materials to have multiple protective capabilities. The chemical inertness of silicone rubber makes it not easy to age in strong oxidants, and the low surface energy characteristics of silicone oil can resist the penetration and erosion of propellants, forming a stable protective barrier.
二、Silicone Rubber: Sealing Protection and Structural Support for Propulsion Systems
（一）Technological Breakthroughs in High-Temperature Sealing
Silicone rubber seals for aero-engine combustion chambers achieve breakthroughs through special crosslinking processes: silicone rubber filled with nanoscale aluminum oxide still maintains 70% of sealing performance at 1000°C high temperature. Combined with a multi-layer sealing structure with gradient density design, it successfully solves the air leakage problem of the high-pressure compressor of the turbofan engine. After a certain type of military aero-engine applied this material, the overhaul cycle was extended from 800 hours to 1500 hours.
（二）Thermal Protection Innovations for Rocket Components
In the expansion section of the rocket nozzle, silicone rubber-based composites show unique advantages: silicone rubber coatings added with silicon carbide whiskers can dissipate 30% of heat through thermal radiation, and combined with the internal micro-channel design, realize the composite protection of "passive heat dissipation + active cooling". After the second-stage engine of a launch vehicle adopted this technology, the nozzle thermal protection efficiency was increased by 40%, and the weight was reduced by 15%.
三、Silicone Oil: Fluid Management and Lubrication Revolution in Propulsion Systems
（一）Lubrication Innovations under Extreme Conditions
The silicone oil lubrication system for aero-engine turbine bearings achieves breakthroughs through molecular modification: phenyl silicone oil introduced with long-chain alkyl groups still maintains a stable oil film under high-speed shearing. After a commercial aero-engine adopted it, the bearing temperature rise was reduced by 20°C, and the service life was extended to 10,000 hours. In the rocket attitude control engine, the low freezing point characteristic of perfluorinated silicone oil ensures normal lubrication in the -196°C liquid oxygen environment.
（二）Fluid Wisdom in Propellant Management
In the spacecraft propellant tank, silicone oil as an anti-slosh medium shows multiple values: its viscous characteristics can suppress fuel sloshing. Combined with the oil-repellent treated silicone rubber baffle, the satellite attitude control accuracy is increased by 50%. In the fuel pipeline of reusable rockets, the silicone oil-based anti-corrosion coating forms a molecular-level protective film to resist the long-term erosion of sulfur components in kerosene fuel.
四、Future Innovation Directions of Aerospace Materials
（一）R&D of Intelligent Response Silicone Rubber
Researchers are developing temperature-pressure dual-response materials: silicone rubber embedded with shape memory alloy fibers can automatically adjust the sealing pressure when the engine starts; silicone rubber introduced with self-healing microcapsules can realize structural regeneration through catalytic reactions after thermal damage, providing material 保障 (guarantee) for long-term deep space exploration.
（二）Breakthroughs of Multifunctional Integrated Silicone Oil
New silicone oils are integrating multiple functions: silicone oil added with nano-thermal conductive fillers realizes efficient heat dissipation and electrical insulation at the same time; silicone oil doped with rare earth compounds can absorb radioactive particles in the propulsion system, providing additional protection for manned spaceflight missions.
（三）Material-System Collaborative Design
Optimize material applications through digital twin technology: establish a service environment simulation model for silicone rubber seals to predict the stress distribution under extreme temperature changes; use AI algorithms to optimize the silicone oil formula to achieve precise control of lubrication performance for different propellant characteristics, and promote aerospace propulsion technology to move towards higher efficiency and lower cost.
From supersonic fighters to deep space detectors, silicone rubber and silicone oil are promoting the iterative upgrading of aerospace propulsion systems through material innovation. They are not only the performance guarantee in extreme environments but also the "material cornerstones" for human exploration of the universe. With the vigorous development of commercial aerospace and the advancement of deep space exploration plans, these silicon-based materials will continue to break through in frontier fields such as reusable rockets, nuclear thermal propulsion, and interstellar spacecraft, providing unlimited possibilities for humanity to pursue the dream of the starry sea.
Silicone Rubber for ultra-high voltage cable-Mingyi Silicone
