Safe and clean propulsion systems for small-scale rocket launchers

进入太空的途径正在迅速发展，部分原因是对小型卫星（smallsats）的需求激增。这些通常是在大型火箭上与更大的有效载荷共享，在轨道和时间表灵活性方面施加限制。这是火箭推进系统范式转变的一个机会，转向由安全、清洁燃烧和可再生推进剂提供动力的小型发射器。提出的研究计划侧重于自燃混合推进，一种可以大大降低发射器复杂性的发动机设计。混合火箭发动机结构简单，因为其中一种推进剂（通常是燃料）以固体形式储存在燃烧室中，与液体燃料替代品相比，泵送需求减半。我们的工作考虑自燃推进剂，这意味着燃料在与氧化剂接触时自发点燃，消除了对点火系统的需要。这种自燃混合方法有可能将复杂的液体燃料发动机的关键优势带到简单的小型发射器上：高比冲、高推力和控制推力或在部分燃烧后重新点火的能力。目前提供这些特性的小规模推进方法通常依赖于肼和富氮氧化剂。这些推进剂具有极强的毒性，燃烧后会形成污染性的氮氧化物。因此，实现自燃混合火箭推进的长期目标有可能减少空间工业和地面大推力推进系统（探空火箭、烟火技术等）的环境足迹。在拟议的工作中解决的目标将增加三个关键的反应流体力学问题的基本理解，阻碍了环境友好的混合动力推进的发展。首先，我们将研究新的生物源燃料基质，有可能是碳中性的，从山梨糖醇和热塑性生物聚合物开始。其次，我们将使用高测试过氧化氢（HTP，90%H2O2）作为无毒和无氮氧化剂进行自燃点火实验。对于这前两个目标，我们将获得燃烧性能，通过模拟和实验，在我们独特的研究设施，允许自燃燃烧混合火箭发动机的代表条件下观察。第三个目标涉及HTP反应气氛对碳基材料的侵蚀，在混合发动机燃烧室结构和喷嘴中起着关键作用。这项工作的结果将有助于为小卫星市场建立一个清洁、安全和负担得起的空间工业，这是使加拿大拥有本国发射能力的一个理想机会。此外，由此产生的培训环境将使11名HQP（3名博士，3名硕士和5名本科实习生）获得进入航空航天领域高影响力职业所需的技能。

Access to space is evolving quickly, partly driven by a surge in demand for small satellites (smallsats). These are often launched ride-sharing with bigger payloads on large rockets, imposing limitations in terms of orbit and schedule flexibility. This is an opportunity for a paradigm shift in rocket propulsion systems, towards small launchers powered by safe, clean-burning and renewable propellants. The research program proposed focuses on hypergolic hybrid propulsion, an engine design that can drastically decrease launcher complexity. Hybrid rocket engines have simple construction as one of the propellants, typically the fuel, is stored as a solid in what becomes the combustion chamber, halving pumping needs compared to liquid-fueled alternatives. Our work considers hypergolic propellants, meaning that the fuel ignites spontaneously on contact with the oxidizer, removing the need for an ignition system. This hypergolic hybrid approach has the potential to bring key advantages associated with complex liquid-fueled engines to simple small-scale launchers: high specific impulse, high thrust and the ability to control thrust or re-ignite following partial burns. Current small-scale propulsion approaches providing these characteristics often rely on hydrazines and nitrogen-rich oxidizers. These propellants are extremely toxic and form polluting nitrogen oxides upon combustion. The long-term objective of enabling hypergolic hybrid rocket propulsion therefore has the potential to reduce the environmental footprint of the space industry and of terrestrial high-thrust propulsion systems (sounding rockets, pyrotechnics, etc.). The objectives addressed in the proposed work will increase the fundamental understanding of three critical reactive fluid mechanics problems hindering the development of environmentally friendly hybrid propulsion. First, we will investigate novel bio-sourced fuel matrices that have the potential to be carbon neutral, starting with sorbitol and thermoplastic biopolymers. Second, we will carry out experiments on hypergolic ignition using high-test hydrogen peroxide (HTP, 90% H2O2) as a non-toxic and nitrogen-free oxidizer. For these first two objectives, we will obtain combustion properties through simulation and experiments in our unique research facility allowing hypergolic combustion to be observed in conditions representative of hybrid rocket engines. The third objective pertains to the erosion induced by HTP reactive atmospheres on carbon-based materials, playing a critical role in hybrid engines combustion chamber structures and nozzles. The results of this work will contribute to the emergence of a clean, safe and affordable space industry for the smallsat market, an ideal opportunity to give Canada its own domestic launch capabilities. Moreover, the resulting training environment will enable 11 HQP (3 PhD, 3 MSc and 5 undergraduate interns) to acquire the skills needed to enter high-impact careers in the aerospace sector.