Hybrid rockets can be an alternative to solid and liquid propellant systems, having improved safety, controllability, and high energetic performance. One of the features characterizing hybrid propulsion is a relatively low thrust due to low regression rate of the fuel. This may be a drawback for certain missions. Fuels with a higher regression rate while maintaining good mechanical properties may be of great advantage. This article investigates experimentally and theoretically a new direction to achieve this goal: the addition of expandable graphite (EG) to the fuel. EG exists as fine particles (typically, 100–400 µm). At elevated temperatures, they expand and form strings several times longer than the original particles. When mixed with a fuel matrix they can increase the heat transfer into the fuel via conduction through the EG strings, thus increasing the regression rate. Static firing tests employing gaseous oxygen as an oxidizer and either polymeric (polyester) or liquefying (paraffin wax) fuels (plain or with 5% EG additive) have been conducted. The test results revealed an increase of 30–200% in the fuel regression rate due to EG addition, with a larger effect on the polymeric fuel and a lesser effect on the paraffin wax. Theoretical model predictions demonstrated good agreement with the experimental results.

混合火箭可以替代固体和液体推进剂系统，具有改进的安全性，可控制性和高能性能。混合动力的特征之一是由于燃料的回弹率低而推力相对较低。对于某些任务，这可能是一个缺点。在保持良好机械性能的同时，具有较高回归速率的燃料可能具有很大的优势。本文在实验和理论上研究了实现这一目标的新方向：在燃料中添加可膨胀石墨（EG）。EG以细颗粒形式存在（通常为100–400 µm）。在高温下，它们会膨胀并形成比原始颗粒长几倍的弦。当与燃料基质混合时，它们可以通过EG管柱的传导增加热量向燃料的传递，因此增加了回归率。进行了静态燃烧试验，采用气态氧气作为氧化剂，并使用了聚合（聚酯）或液化（石蜡）燃料（普通燃料或含5％EG添加剂）。测试结果表明，由于加入了EG，燃料的降解率提高了30-200％，对聚合物燃料的影响较大，对石蜡的影响较小。理论模型的预测与实验结果吻合良好。对聚合物燃料的影响较大，对石蜡的影响较小。理论模型的预测与实验结果吻合良好。对聚合物燃料的影响较大，对石蜡的影响较小。理论模型的预测与实验结果吻合良好。