Abstract Nuclear thermal propulsion (NTP) is an in-space propulsion technology capable of both high specific impulse (850–1000 s) and thrust (44–1112 kN), which can help reduce trip times for crewed missions beyond low Earth orbit. NTP technology has been demonstrated during historic programs. Over 20 ground test reactor experiments were performed, which demonstrated the prototypic reactor operations, during the Nuclear Engine for Rocket Vehicle Application (NERVA)/Rover program (1955–1972). Although historical programs have shown that NTP is a viable in-space propulsion technology, developing NTP in modern programs is contingent on the development and qualification of ultrahigh-temperature nuclear fuel technologies that can withstand engine operating conditions. In historical NTP development programs such as NERVA/Rover, prototypic reactor/engine schemes were ground tested to assess the overall system feasibility and to qualify the reactor fuel forms for eventual flight systems. Although this approach is effective to verify fuel performance under prototypic conditions, relying solely on full-scale NTP reactor tests as the pathway for verifying or qualifying fuel is inefficient and cost prohibitive today. Additionally, modern nuclear licensing requirements state that before test reactor approval, reactor components and fuel elements should be qualified via non-nuclear (out-of-pile) and nuclear (in-pile) testing under representative operating conditions. Using this methodology, fuel matures as production scale fabrication methods are established, and as produced fuel performance is demonstrated. This paper provides an overview of historical approaches to NTP fuel performance maturation, including fuel screening and qualification needs, and provides insight for establishing an efficient testing paradigm that can be implemented to rapidly and affordably develop NTP fuel forms for eventual qualification.

中文翻译：

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核热推进系统近期燃料筛选和鉴定需求的评估

摘要 核热推进 (NTP) 是一种空间推进技术，具有高比冲 (850–1000 s) 和推力 (44–1112 kN)，有助于减少载人飞行任务的飞行时间。NTP 技术已在历史项目中得到展示。在火箭车辆应用核发动机 (NERVA)/漫游者计划 (1955–1972) 期间，进行了 20 多个地面测试反应堆实验，展示了原型反应堆的运行。尽管历史项目表明 NTP 是一种可行的空间推进技术，但在现代项目中开发 NTP 取决于能够承受发动机运行条件的超高温核燃料技术的开发和认证。在 NERVA/Rover 等历史 NTP 开发项目中，原型反应堆/发动机方案经过地面测试，以评估整个系统的可行性，并使反应堆燃料形式符合最终飞行系统的要求。尽管这种方法在原型条件下验证燃料性能是有效的，但今天仅依靠全尺寸 NTP 反应堆测试作为验证或鉴定燃料的途径效率低下且成本高昂。此外，现代核许可要求规定，在试验反应堆批准之前，反应堆组件和燃料元件应在有代表性的运行条件下通过非核（堆外）和核（堆内）测试进行鉴定。使用这种方法，随着生产规模制造方法的建立，燃料变得成熟，并且生产的燃料性能得到证明。