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Radioprotective effects of induced astronaut torpor and advanced propulsion systems during deep space travel

机译：深度空间旅行中诱导宇航员与先进推进系统的辐射防护作用

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Background.Human metabolic suppression is not a new concept, with 1950s scientific literature and movies demonstrating its potential use for deep space travel (Hock, 1960). An artificially induced state of metabolic suppression in the form of torpor would improve the amount of supplies required and therefore lessen weight and fuel required for missions to Mars and beyond (Choukèr et al., 2019). Transfer habitats for human stasis to Mars have been conceived (Bradford et al., 2018). Evidence suggests that animals, when hibernating, demonstrate relative radioprotection compared to their awake state. Experiments have also demonstrated relative radioprotection in conditions of hypothermia as well as during sleep (Bellesi et al., 2016 and Andersen et al., 2009). Circadian rhythm disrupted cells also appear to be more susceptible to radiation damage compared to those that are under a rhythmic control (Dakup et al., 2018).An induced torpor state for astronauts on deep space missions may provide a biological radioprotective state due to a decreased metabolism and hypothermic conditions. A regular enforced circadian rhythm might further limit DNA damage from radiation.The As Low As Reasonably Achievable (A.L.A.R.A.) radiation protection concept defines time, distance and shielding as ways to decrease radiation exposure. Whilst distance cannot be altered in space and shielding either passively or actively may be beneficial, time of exposure may be drastically decreased with improved propulsion systems. Whilst chemical propulsion systems have superior thrust to other systems, they lack high changes in velocity and fuel efficiency which can be achieved with nuclear or electric based propulsion systems.Radiation toxicity could be limited by reduced transit times, combined with the radioprotective effects of enforced circadian rhythms during a state of torpor or hibernation.Objectives.1. Investigate how the circadian clock and body temperature may contribute to radioprotection during human torpor on deep space missions.2. Estimate radiation dose received by astronauts during a transit to Mars with varying propulsion systems.Methods.We simulated three types of conditions to investigate the potential radioprotective effect of the circadian clock and decreased temperature on cells being exposed to radiation such that may be the case during astronaut torpor. These conditions were:- Circadian clock strength: strong vs weak.- Light exposure: dark-dark vs light-dark cycle- Body temperature: 37C vs hypothermia vs torpor.We estimated transit times for a mission to Mars from Earth utilizing chemical, nuclear and electrical propulsion systems. Transit times were generated using the General Mission Analysis Tool (GMAT) and Matlab. These times were then input into the National Aeronautics and Space Administration (NASA) Online Tool for the Assessment of Radiation In Space (OLTARIS) computer simulator to estimate doses received by an astronaut for the three propulsion methods.Results.Our simulation demonstrated an increase in radioprotection with decreasing temperature. The greatest degree of radioprotection was shown in cells that maintained a strong circadian clock during torpor. This was in contrast to relatively lower radioprotection in cells with a weak clock during normothermia. We were also able to demonstrate that if torpor weakened the circadian clock, a protective effect could be partially restored by an external drive such as lighting schedules to aid entrainment i.e.: Blue light exposure for periods of awake and no light for rest timesFor the propulsion simulation, estimated transit times from Earth to Mars were 258 days for chemical propulsion with 165.9mSv received, 209 days for nuclear propulsion with 134.4mSv received and 80 days for electrical propulsion with 51.4mSv received.Conclusion.A state of torpor for astronauts on deep space missions may not only improve weight, fuel and storage requirements but also provide a potential biological radiation protection strategy. Moreover, maintaining a controlled circadian rhythm during torpor conditions may aid radioprotection. In the not too distant future, propulsion techniques will be improved to limit transit time and hence decrease radiation dose to astronauts. Limiting exposure time and enhancing physiological radioprotection during transit could provide superior radioprotection benefits compared with active and passive radiation shielding strategies alone.
机译：背景生来来的代谢抑制不是一个新的概念，20世纪50年代的科学文学和电影证明了其对深空旅行的潜在用途（Hock，1960）。人工诱导的托麦特形式的代谢抑制状态将改善所需的供应量，从而减轻法官和超越的特派团所需的重量和燃料（Choukèr等，2019）。已经构思了人类瘀滞的转移栖息地（Bradford等，2018）。证据表明，与他们的醒着状态相比，动物在冬眠时表现出相对放射保护。实验还在体温过低以及睡眠期间展示了相对放射保护（Bellesi等，2016和Andersen等，2009）。与节奏控制下的那些相​​比，昼夜节律中断细胞也似乎更容易受到辐射损伤（Dakup等，2018）。and诱导的宇航员在深度空间任务中的刺激状态可能提供生物辐射保护状态降低新陈代谢和低温条件。常规强制昼夜节律可能进一步限制辐射的DNA损伤。与合理可取的（A.L.A.R.A.）辐射保护概念的辐射保护概念与减少辐射曝光的方法定义时间，距离和屏蔽。虽然在太空中不能改变距离并且被动地或主动屏蔽可能是有益的，但是通过改进的推进系统，暴露的时间可以大大降低。虽然化学推进系统对其他系统具有优异的推力，但它们缺乏速度和燃料效率的高变化，这些速度和燃料效率可以通过核或电力的推进系统实现。毒性可能会限制通过减少的运输时间，结合强制昼夜强制性昼夜辐射反应效应在麻木或冬眠状态期间的节奏.1。调查昼夜钟表和体温如何在人类托波间在深度空间任务中有助于放射保护。宇航员在具有不同推进系统的过渡到火星期间估算宇航员的辐射剂量。方法。我们模拟了三种类型的条件来研究昼夜节点的潜在放射性应对效果，并降低暴露于辐射的细胞的温度，这可能是如此宇航员麻木。这些条件是： - 昼夜节日时钟强度：强大的弱弱.-曝光：黑暗的vs浅黑循环 - 体温：37C与低温vs torpor.We估计来自地球的使命，利用化学，核的使命估计运输时间和电气推进系统。使用普通任务分析工具（GMAT）和Matlab生成过境时间。然后将这些时间输入国家航空航天局（NASA）在线工具，用于评估空间（Oltaris）计算机模拟器的辐射，以估计由宇航员接收的三种推进方法的剂量。结果。我们的模拟显示增加辐射辐射随温度降低。最大程度的辐射保护在细胞中显示，在托麦特期间保持强烈的昼夜昼夜时钟。这与常温期间具有弱时钟的细胞中相对较低的辐射保护相反。我们还能够证明，如果托麦托削弱了昼夜节点，则可以通过外部驱动器（例如照明时间表）部分恢复保护效果，以帮助夹带，即：蓝色光曝光，用于唤醒的时期，对于推进仿真，休息时的休息时间，从地球到火星的估计时间是258天的化学推进，165.9msv接受，核推进209天，收到的134.4msv，电气推进80天，有51.4msv收到的电力推进。结论。托尔康纳宇航员在深空中的刺激状态任务不仅可以提高重量，燃料和储存要求，还可以提供潜在的生物辐射保护策略。此外，在扭力条件下保持受控的昼夜节律可能有助于辐射防护。在不太遥远的未来，将改善推进技术以限制运输时间，因此减少辐射剂量给宇航员。与单独的主动和被动辐射屏蔽策略相比，在运输过程中限制过度的接触时间和增强的生理放射应激可以提供卓越的放射保护效益。

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