Hydroxylammonium nitrate (HAN; NHOH NO), a green and non-toxic monopropellant, finds wide application in liquid and controllable solid propulsion. Gel propulsion enjoys advantages such as a high throttling capacity and encouraging operational safety. This study prepared three HAN-based gel propellant samples with gelling agent contents ranging from 2 to 4 wt%. Their decomposition processes were analyzed using thermogravimetry (TG), differential scanning calorimetry (DSC), and mass spectrometry (MS), and a microthruster was designed to investigate their combustion characteristics under varying voltages and flow rates. Results reveal the presence of three exothermic peaks in the HAN-based gel propellants at temperatures of 204, 306 °C and 441 °C. The gel propellants experienced violent decomposition between 100 °C and 400 °C, producing low-molecular-weight organics such as CH, CH, HO, O, and NH. For the initial ignition, the flow rate exerts a greater effect of reducing the delay time than the voltage. The reignition exhibited a shorter delay time than the initial ignition, and increasing voltage led to a more significant decrease in the reignition delay time than increasing the flow rate. Under a gelling agent content of approximately 4 wt%, the reignition delay time decreased from 2.35 s to 0.65 s as the voltage increased from 150 V to 250 V, with the flame length and light intensity during the reignition greater than those in the initial ignition. At the end of combustion, the extinguishment delay time changed insignificantly under high voltage. As revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses, residues with numerous cavities emerged due to incomplete combustion and the severe agglomeration of the gel propellants, exhibiting a maximum chlorine content of up to 77.73%.

中文翻译：

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硝酸羟铵基凝胶推进剂重燃和燃烧性能的双重控制

硝酸羟铵（HAN；NHOH NO）是一种绿色无毒的单组元推进剂，在液体和可控固体推进领域有着广泛的应用。凝胶推进具有节流能力高、运行安全等优点。本研究制备了三种基于 HAN 的凝胶推进剂样品，其胶凝剂含量范围为 2 至 4 wt%。使用热重分析（TG）、差示扫描量热分析（DSC）和质谱分析（MS）分析它们的分解过程，并设计微型推进器来研究它们在不同电压和流量下的燃烧特性。结果表明，HAN 基凝胶推进剂在 204、306 °C 和 441 °C 温度下存在三个放热峰。凝胶推进剂在 100 °C 至 400 °C 之间经历剧烈分解，产生低分子量有机物，如 CH、CH、H2O、O 和 NH。对于初始点火来说，流量对延迟时间的缩短作用比电压更大。重燃表现出比初始点火更短的延迟时间，并且增加电压导致重燃延迟时间比增加流量更显着的减少。在胶凝剂含量约为4 wt%的情况下，随着电压从150 V增加到250 V，重燃延迟时间从2.35 s减少到0.65 s，重燃时的火焰长度和光强均大于初次点燃时的火焰长度和光强。燃烧结束时，高压下熄火延迟时间变化不大。扫描电子显微镜（SEM）和能谱（EDS）分析表明，由于凝胶推进剂燃烧不完全和严重团聚，出现了许多空洞的残留物，其氯含量最高高达77.73%。