PLANETARY SCIENCE  行星科学

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In Situ Resource Utilization (ISRU) is the term commonly used to describe the harvesting and processing of native resources on other planetary bodies. MOXIE, the Mars Oxygen ISRU Experiment, represents the first demonstration of ISRU technology on another planetary body. An experiment inside NASA’s Mars 2020 Perseverance rover, MOXIE has successfully produced oxygen from the carbon dioxide that comprises $\sim 95\mathrm{\%}$$\sim 95\mathrm{\%}$∼95%\sim 95 \% of the martian atmosphere.
原位资源利用 （ISRU） 是通常用于描述其他行星体上原生资源的收获和加工的术语。MOXIE，即火星氧气 ISRU 实验，代表了 ISRU 技术在另一个行星体上的首次演示。作为 NASA 火星 2020 毅力号火星车内的实验，MOXIE 成功地从构成 $\sim 95\mathrm{\%}$$\sim 95\mathrm{\%}$∼95%\sim 95 \% 火星大气的二氧化碳中生产氧气。

Figure 1 shows a cutaway view of MOXIE, a full description of which is given by Hecht et al. (1). MOXIE takes in martian atmosphere through a dust-trapping HEPA filter, compresses the atmosphere via a scroll pump, heats it to ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C}, and sends it through a solid oxide electrolysis (SOXE) assembly, where ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2} flows over a nickel-based catalyzed cathode and decomposes into oxygen ions and CO. The scandia-stabilized zirconia ceramic electrolyte selectively passes oxygen ions to the anode, where the ions recombine into ${\mathrm{O}}_2$${\mathrm{O}}_2$O_(2)\mathrm{O}_{2}, which is measured for quantity and purity before being released to the Mars atmosphere. The cathode exhaust is a mixture of ${\mathrm{CO}}_2,\mathrm{CO}$${\mathrm{CO}}_2,\mathrm{CO}$CO_(2),CO\mathrm{CO}_{2}, \mathrm{CO}, and inert atmospheric gases, primarily argon and nitrogen.
图 1 显示了 MOXIE 的剖面图，Hecht 等人 （1） 对此进行了完整描述。MOXIE 通过集尘 HEPA 过滤器吸入火星大气，通过涡旋泵压缩大气，将其加热到 ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C} ，然后通过固体氧化物电解 （SOXE） 组件，流 ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2} 过镍基催化阴极并分解成氧离子和 CO。scandia 稳定的氧化锆陶瓷电解质选择性地将氧离子传递到阳极，在那里离子重新组合成 ${\mathrm{O}}_2$${\mathrm{O}}_2$O_(2)\mathrm{O}_{2} ，在释放到火星大气中之前测量其数量和纯度。阴极废气是 和惰性大气气体（主要是氩气和氮气）的 ${\mathrm{CO}}_2,\mathrm{CO}$${\mathrm{CO}}_2,\mathrm{CO}$CO_(2),CO\mathrm{CO}_{2}, \mathrm{CO} 混合物。

Numerous analyses of Mars missions (2-5) have suggested using indigenous resources to manufacture rocket propellant for the ascent vehicle that will lift a crew off the surface of Mars. Of the estimated 50 tons of total mass of a six-person oxygen-methane
对火星任务 （2-5） 的大量分析表明，利用本地资源为上升飞行器制造火箭推进剂，该火箭将把机组人员从火星表面升起。估计 50 吨的六人氧气甲烷总质量

propelled Mars ascent vehicle (MAV), $\sim 31$$\sim 31$∼31\sim 31 tons will be oxygen and $\sim 9$$\sim 9$∼9\sim 9 tons will be methane (5). While all MAV propellant could be brought from Earth to the surface of Mars, 12 to 13 tons are required in low Earth orbit for every ton landed on Mars using current technology $(6,7)$$(6,7)$(6,7)(6,7). Thus, $\sim 500$$\sim 500$∼500\sim 500 tons would need to be launched to Earth orbit to transport the required MAV propellant from Earth for every Mars mission, a serious impediment to sustainable human exploration. Fortunately, oxygen can be produced in situ from the ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2}-rich martian atmosphere, which has a surface atmospheric pressure ranging from $\sim 5$$\sim 5$∼5\sim 5 to 10 mbar.
推进的火星上升器 （MAV） 中， $\sim 31$$\sim 31$∼31\sim 31 吨是氧气， $\sim 9$$\sim 9$∼9\sim 9 吨是甲烷 （5）。虽然所有 MAV 推进剂都可以从地球带到火星表面，但使用当前技术 $(6,7)$$(6,7)$(6,7)(6,7) ，每吨降落在火星上，在近地轨道上需要 12 到 13 吨。因此， $\sim 500$$\sim 500$∼500\sim 500 每次火星任务都需要将吨发射到地球轨道，以便从地球运输所需的 MAV 推进剂，这是人类可持续探索的严重障碍。幸运的是，可以从富含火星的 ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2} 大气中原位产生氧气，该大气层的表面大气压力从 10 mbar 不等 $\sim 5$$\sim 5$∼5\sim 5 。

Fig. 1. MOXIE with the front cover removed, showing compressor and SOXE assemblies. The inlet filter, sensor and flow control panel, and electronics are not shown. The dimensions of the MOXIE chassis are 23.9 cm by 23.9 cm by 30.9 cm .
图 1.前盖拆下的 MOXIE，显示压缩机和 SOXE 组件。未显示入口过滤器、传感器和流量控制面板以及电子设备。MOXIE 机箱的尺寸为 23.9 厘米 x 23.9 厘米 x 30.9 厘米。

Water ice is also a potential native resource for manufacturing fuel and oxidizer on Mars. In addition to the exposed polar layered deposits of water ice, permafrost is known to blanket most of Mars poleward of $\sim {50}^{\circ }$$\sim {50}^{\circ }$∼50^(@)\sim 50^{\circ} north or south latitude (8) and possibly as far equatorward as ${40}^{\circ }(9)$${40}^{\circ }(9)$40^(@)(9)40^{\circ}(9). Vestigial pockets of ice may persist at lower latitudes (10), and water could also be extracted from hydrated soils even at equatorial latitudes (11). Water and carbon dioxide can serve as reactants to produce both methane and oxygen for a MAV. However, obtaining water requires an ice-mining operation, melting the ice, purifying the water, and transporting it near the MAV for propellant production. In contrast, atmospheric ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2} can be acquired anywhere on Mars. Because oxygen makes up $\sim 78\mathrm{\%}$$\sim 78\mathrm{\%}$∼78%\sim 78 \% of the MAV propellant mass, carrying fuel from Earth while producing oxidizer on Mars still offers a substantial benefit until such time as a mining operation can be set up to obtain water (5).
水冰也是在火星上制造燃料和氧化剂的潜在原生资源。除了裸露的极地层状水冰沉积物外，众所周知，永久冻土层覆盖了火星的大部分地区，向 $\sim {50}^{\circ }$$\sim {50}^{\circ }$∼50^(@)\sim 50^{\circ} 北纬或南纬极地 （8），甚至可能远至赤道 ${40}^{\circ }(9)$${40}^{\circ }(9)$40^(@)(9)40^{\circ}(9) 。残存的冰袋可能在低纬度地区持续存在 （10），即使在赤道纬度 （11），也可以从水合土壤中提取水。水和二氧化碳可以作为反应物，为 MAV 生产甲烷和氧气。然而，获取水需要冰开采作业，融化冰，净化水，并将其运输到 MAV 附近以生产推进剂。相比之下，大气 ${\mathrm{CO}}_2$${\mathrm{CO}}_2$CO_(2)\mathrm{CO}_{2} 可以在火星的任何地方获得。由于氧气由 MAV 推进剂质量组成 $\sim 78\mathrm{\%}$$\sim 78\mathrm{\%}$∼78%\sim 78 \% ，因此在火星上生产氧化剂的同时从地球携带燃料仍然提供大量好处，直到可以建立采矿作业以获取水 （5）。

A MOXIE-like system, scaled up several hundred times (2 to $3\mathrm{kg}/$$3\mathrm{kg}/$3kg//3 \mathrm{~kg} / hour of oxygen production versus MOXIE’s 6 to $8\mathrm{g}/\mathrm{hour}$$8\mathrm{g}/\mathrm{hour}$8g//hour8 \mathrm{~g} / \mathrm{hour} ), could produce sufficient oxygen to launch a MAV for a crew arriving one 26 -month cycle later. Producing oxygen is such a critical function for human exploration that it demands prior validation in the actual Mars environment-NASA’s Technology Readiness Level 9. This is the first purpose of MOXIE, to demonstrate successful operation of the system in the actual martian environment. The second, and equally important, purpose of MOXIE is to advance the scientific and operational knowledge of this type of ISRU system to inform the design of future, larger-scale systems.
一个类似 MOXIE 的系统，放大了几百倍（2 到 2 小时的 $3\mathrm{kg}/$$3\mathrm{kg}/$3kg//3 \mathrm{~kg} / 氧气生产，而 MOXIE 的 6 到 6 倍 $8\mathrm{g}/\mathrm{hour}$$8\mathrm{g}/\mathrm{hour}$8g//hour8 \mathrm{~g} / \mathrm{hour} ），可以产生足够的氧气，为一个 26 个月后到达的机组人员发射 MAV。产生氧气是人类探索的一项关键功能，它需要在实际的火星环境中进行事先验证——NASA 的技术成熟度 9 级。这是 MOXIE 的第一个目的，旨在展示系统在实际火星环境中的成功运行。MOXIE 的第二个也是同样重要的目的是推进此类 ISRU 系统的科学和操作知识，为未来更大规模系统的设计提供信息。

MOXIE does not require mobility, but Perseverance was MOXIE’s earliest mission opportunity. Being manifested inside the rover body led to volume, thermal, and power constraints that required compromises in MOXIE’s design. The impact of these compromises and suggestions for future scaled-up MOXIE-type systems are discussed below.
MOXIE 不需要移动性，但毅力号是 MOXIE 最早的任务机会。在漫游车体内显现会导致体积、热量和功率限制，这需要在 MOXIE 的设计中做出妥协。这些妥协的影响和对未来放大 MOXIE 型系统的建议将在下面讨论。

McClean et al. (12) describe the architecture developed for planning, testing, and executing MOXIE runs. Between landing in Jezero Crater
McClean 等人 （12） 描述了为规划、测试和执行 MOXIE 运行而开发的架构。在着陆 Jezero 陨石坑之间
on Mars in February 2021 and the end of 2021, MOXIE produced oxygen seven times. These operational cycles (OCs) are summarized in Table 1. Note that the OC number increments every time MOXIE undergoes a heating cycle, whether or not oxygen is produced. The first seven cycles, flight model (FM) OC1 to OC7 were run in laboratories on Earth as part of preflight testing and qualification. FM OC8 was a heating cycle checkout with no oxygen production.
在 2021 年 2 月和 2021 年底的火星上，MOXIE 产生了七次氧气。表 1 总结了这些操作循环 （OC）。请注意，每次 MOXIE 进行加热循环时，OC 数字都会增加，无论是否产生氧气。前七个循环，飞行模型 （FM） OC1 到 OC7 在地球上的实验室中运行，作为飞行前测试和鉴定的一部分。FM OC8 是一个没有氧气产生的加热循环检查。

An important goal of MOXIE is to demonstrate successful operation during day and night throughout all martian seasons, showing robustness to variations in atmospheric pressure and temperature. Figure 2 shows predicted diurnal maximum (nighttime) and minimum (daytime) atmospheric densities throughout Mars year at the Perseverance landing site (13). Superimposed are MOXIE’s seven oxygen-producing runs performed in 2021. A run will be scheduled during the annual maximum density period, shown as a star in Fig. 2. Other runs will be spaced out between the minimum and maximum extremes.
MOXIE 的一个重要目标是证明在所有火星季节的昼夜成功运行，显示出对大气压力和温度变化的稳健性。图 2 显示了毅力号着陆点 （13） 在整个火星年中预测的最大（夜间）和最小（白天）大气密度。叠加的是 MOXIE 在 2021 年进行的七次产氧运行。在年度最大密度期间将安排一次运行，如图 2 中的星星所示。其他运行将在最小和最大极端之间间隔。

The Nernst potential $\left(V_{\mathrm{N}}\right)$$\left(V_{\mathrm{N}}\right)$(V_(N))\left(V_{\mathrm{N}}\right) for an electrolysis reaction is the voltage above which the reaction can be initiated. To produce oxygen safely, MOXIE must operate at a voltage above $V_{\mathrm{N}}$$V_{\mathrm{N}}$V_(N)V_{\mathrm{N}} for the oxygen-producing reaction, $V_{\mathrm{N}}(2{\mathrm{CO}}_2\to 2\mathrm{CO}+{\mathrm{O}}_2)$$V_{\mathrm{N}}\left(2{\mathrm{CO}}_2\to 2\mathrm{CO}+{\mathrm{O}}_2\right)$V_(N)(2CO_(2)rarr2CO+O_(2))V_{\mathrm{N}}\left(2 \mathrm{CO}_{2} \rightarrow 2 \mathrm{CO}+\mathrm{O}_{2}\right), and below $V_{\mathrm{N}}$$V_{\mathrm{N}}$V_(N)V_{\mathrm{N}} for carbon formation, ${\mathrm{V}}_{\mathrm{N}}(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2)$${\mathrm{V}}_{\mathrm{N}}\left(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2\right)$V_(N)(2COrarr2C+O_(2))\mathrm{V}_{\mathrm{N}}\left(2 \mathrm{CO} \rightarrow 2 \mathrm{C}+\mathrm{O}_{2}\right), both of which depend on the partial pressures and temperature of the reactants $(1,12)$$(1,12)$(1,12)(1,12). The latter process must be avoided to prevent coking (carbon deposition) in the SOXE cathode, which raises the resistance of cells by reducing their active area and may possibly fracture the cathode, causing an inability to produce oxygen. Experience in the laboratory and on Mars indicates that, with sufficient attention to these limits, MOXIE’s electrolysis stack can be operated safely over many cycles.
电解反应的能斯特电位 $\left(V_{\mathrm{N}}\right)$$\left(V_{\mathrm{N}}\right)$(V_(N))\left(V_{\mathrm{N}}\right) 是可以引发反应的电压。为了安全地生产氧气，MOXIE 必须在高于 $V_{\mathrm{N}}$$V_{\mathrm{N}}$V_(N)V_{\mathrm{N}} 产氧反应 $V_{\mathrm{N}}(2{\mathrm{CO}}_2\to 2\mathrm{CO}+{\mathrm{O}}_2)$$V_{\mathrm{N}}\left(2{\mathrm{CO}}_2\to 2\mathrm{CO}+{\mathrm{O}}_2\right)$V_(N)(2CO_(2)rarr2CO+O_(2))V_{\mathrm{N}}\left(2 \mathrm{CO}_{2} \rightarrow 2 \mathrm{CO}+\mathrm{O}_{2}\right) 的电压和低于 $V_{\mathrm{N}}$$V_{\mathrm{N}}$V_(N)V_{\mathrm{N}} 碳形成的电压下运行， ${\mathrm{V}}_{\mathrm{N}}(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2)$${\mathrm{V}}_{\mathrm{N}}\left(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2\right)$V_(N)(2COrarr2C+O_(2))\mathrm{V}_{\mathrm{N}}\left(2 \mathrm{CO} \rightarrow 2 \mathrm{C}+\mathrm{O}_{2}\right) 这两者都取决于反应物 $(1,12)$$(1,12)$(1,12)(1,12) 的分压和温度。必须避免后一个过程，以防止 SOXE 阴极中的焦化（碳沉积），这会通过减小电池的活性面积来提高电池的电阻，并可能使阴极破裂，导致无法产生氧气。实验室和火星的经验表明，如果充分注意这些限制，MOXIE 的电解堆栈可以在多个循环中安全运行。

Figure 3 shows the two Nernst potentials as a function of the gas intake and the amount of oxygen produced at an operating temperature of ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C}. The two circles and light vertical line indicate the “reference segment” condition of $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / hour of intake with $6\mathrm{g}/\mathrm{hour}$$6\mathrm{g}/\mathrm{hour}$6g//hour6 \mathrm{~g} / \mathrm{hour} of oxygen production (see discussion of generic runs below). The safe operating zone is indicated in Fig. 3 by dark arrows, assuming nominal operating conditions. To ensure operation in this zone, parameters used to control MOXIE are validated using well-tested models and verified on the engineering model (EM) before each
图 3 显示了两个能斯特电位与气体进气量和在工作温度 下产生的氧气量的函数关系。 ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C} 两个圆圈和浅垂直线表示进气 $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / 小时和 $6\mathrm{g}/\mathrm{hour}$$6\mathrm{g}/\mathrm{hour}$6g//hour6 \mathrm{~g} / \mathrm{hour} 氧气产生的“参考段”条件（参见下面对通用运行的讨论）。安全操作区在图 3 中用深色箭头表示，假设标称操作条件。为确保在该区域内运行，用于控制 MOXIE 的参数使用经过充分测试的模型进行验证，并在每个模型 （EM） 之前在工程模型 （EM） 上进行验证

Table 1. Seven oxygen-producing cycles successfully completed by MOXIE in 2021. Sols are martian days, counted from Perseverance landing on 18 February 2021 (sol 0). “FM” refers to the flight model of MOXIE, on Mars, to distinguish from Earth-based engineering model (EM), on which all runs are verified before being executed on the FM.
表 1.MOXIE 在 2021 年成功完成了七个制氧周期。Sols 是火星日，从 2021 年 2 月 18 日毅力号着陆 （sol 0） 开始计算。“FM”是指 MOXIE 在火星上的飞行模型，以区别于地球工程模型 （EM），在地球上执行之前，所有运行都经过验证。

Fig. 2. Diurnal maximum (nighttime) and minimum (daytime) atmospheric density predicted (13) at the Perseverance landing site, Jezero crater, over one Mars year ( 668 sols). The circles show MOXIE runs completed in 2021, FM OC9 to OC15. The star shows the anticipated MOXIE run during the annual maximum atmospheric density.
图 2.毅力号着陆点 Jezero 陨石坑在火星一年（668 个溶胶）的昼夜最大（夜间）和最小（白天）大气密度预测 （13）。圆圈显示 2021 年完成的 MOXIE 运行，FM OC9 至 OC15。星星显示年度最大大气密度期间的预期 MOXIE 运行。
run on Mars. In addition to coking, governed by the Nernst potential, there is also a potential risk of oxidation of the nickel at the very entrance of the cathode, before CO production makes the overall gas mixture reducing. This has been mitigated, however, by a design that recirculates $\sim 6\mathrm{\%}$$\sim 6\mathrm{\%}$∼6%\sim 6 \% of the CO-rich cathode exhaust to the intake to prevent Ni oxidation.
在火星上运行。除了受能斯特电位控制的焦化之外，在 CO 产生使整体气体混合物减少之前，在阴极入口处还存在镍氧化的潜在风险。然而，通过一种设计，将富含 CO 的阴极废气再循环 $\sim 6\mathrm{\%}$$\sim 6\mathrm{\%}$∼6%\sim 6 \% 到进气口以防止镍氧化，这种情况已经得到缓解。

The Nernst potentials also exhibit considerable significant sensitivity to temperature. For example, decreasing the operating temperature by ${30}^{\circ }\mathrm{C}$${30}^{\circ }\mathrm{C}$30^(@)C30^{\circ} \mathrm{C} lowers $V_{\mathrm{N}}(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2)$$V_{\mathrm{N}}\left(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2\right)$V_(N)(2COrarr2C+O_(2))V_{\mathrm{N}}\left(2 \mathrm{CO} \rightarrow 2 \mathrm{C}+\mathrm{O}_{2}\right) and raises $V_{\mathrm{N}}(2{\mathrm{CO}}_2\to$$V_{\mathrm{N}}\left(2{\mathrm{CO}}_2\to \right.$V_(N)(2CO_(2)rarr:}V_{\mathrm{N}}\left(2 \mathrm{CO}_{2} \rightarrow\right. $2\mathrm{CO}+{\mathrm{O}}_2$$2\mathrm{CO}+{\mathrm{O}}_2$2CO+O_(2)2 \mathrm{CO}+\mathrm{O}_{2} ), effectively reducing the safe voltage zone by 0.027 V . A temperature increase similarly expands the safe voltage zone. Initial tests of the SOXE, performed in an oven, suggested that an operating temperature of ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C} is an optimal compromise between efficient operation and the risk of damaging heat-sensitive materials. Inside the Perseverance rover, however, volume and power constraints precluded an oven, so, instead, MOXIE’s SOXE is heated by two heater plates at the top and bottom of the electrolysis stacks with insulation partially covering its sides. This configuration results in thermal gradients of up to ${10}^{\circ }\mathrm{C}$${10}^{\circ }\mathrm{C}$10^(@)C10^{\circ} \mathrm{C} between the cooler cells in the center of the stack and the warmer cells nearer the heaters. Cooler cells have both a higher resistance and a smaller safe voltage zone and are, thus, at greater risk of coking. MOXIE runs are operated conservatively, assuming worst-case (lowest) temperature in the middle cells and setting the voltages accordingly. The warmer cells, thus, will not produce as much oxygen as they potentially could.
能斯特电位对温度也表现出相当大的敏感性。例如，通过 ${30}^{\circ }\mathrm{C}$${30}^{\circ }\mathrm{C}$30^(@)C30^{\circ} \mathrm{C} 降低 $V_{\mathrm{N}}(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2)$$V_{\mathrm{N}}\left(2\mathrm{CO}\to 2\mathrm{C}+{\mathrm{O}}_2\right)$V_(N)(2COrarr2C+O_(2))V_{\mathrm{N}}\left(2 \mathrm{CO} \rightarrow 2 \mathrm{C}+\mathrm{O}_{2}\right) 和升高 $V_{\mathrm{N}}(2{\mathrm{CO}}_2\to$$V_{\mathrm{N}}\left(2{\mathrm{CO}}_2\to \right.$V_(N)(2CO_(2)rarr:}V_{\mathrm{N}}\left(2 \mathrm{CO}_{2} \rightarrow\right. 来降低工作温度 $2\mathrm{CO}+{\mathrm{O}}_2$$2\mathrm{CO}+{\mathrm{O}}_2$2CO+O_(2)2 \mathrm{CO}+\mathrm{O}_{2} ），有效地将安全电压区减少 0.027 V。温度升高同样会扩大安全电压区。在烘箱中对 SOXE 进行的初步测试表明，工作温度 ${800}^{\circ }\mathrm{C}$${800}^{\circ }\mathrm{C}$800^(@)C800^{\circ} \mathrm{C} 是高效运行和损坏热敏材料风险之间的最佳折衷方案。然而，在毅力号火星车内部，体积和功率限制排除了烘箱，因此，MOXIE 的 SOXE 由电解堆顶部和底部的两个加热板加热，绝缘层部分覆盖其侧面。这种配置导致堆垛中心的冷却器单元与靠近加热器的较暖单元 ${10}^{\circ }\mathrm{C}$${10}^{\circ }\mathrm{C}$10^(@)C10^{\circ} \mathrm{C} 之间的热梯度高达。较冷的电池具有更高的电阻和较小的安全电压区，因此具有更大的结焦风险。MOXIE 运行采用保守操作，假设中间电池处于最坏情况（最低）温度，并相应地设置电压。因此，较热的电池不会产生尽可能多的氧气。

Runs FM OC9 to OC13 were performed at a semiannual high-density season (northern hemisphere spring). FM OC14 was executed as the atmospheric density was decreasing, and OC15 took place near the annual minimum density. OC10, OC11, OC14, and OC15 were generic runs, essentially identical except for the time of sol they were run and the seasonal atmospheric density. Generic MOXIE runs start with a reference segment, described by McClean et al. (12), in which MOXIE’s compressor is commanded to a revolution per minute calculated to input $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / hour of martian atmosphere into the system ( $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / hour is the maximum reliable intake during annual atmospheric
FM OC9 到 OC13 的运行是在半年一次的高密度季节（北半球春季）进行的。FM OC14 是在大气密度降低时执行的，而 OC15 发生在年最低密度附近。OC10、OC11、OC14 和 OC15 是通用运行，除了它们的运行时间和季节性大气密度外，基本相同。通用 MOXIE 运行从 McClean 等人 （12） 描述的参考段开始，其中 MOXIE 的压缩机被命令每分钟转一圈，计算将火星大气的小时输入 $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / 系统（ $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / 小时是年度大气期间的最大可靠摄入量

Fig. 3. Nernst potentials for oxygen and carbon formation versus input mass flow for several rates of oxygen production at an operating temperature of $\mathbf{8}\mathbf{0}\mathbf{0}{}^{\circ }\mathrm{C}$$\mathbf{8}\mathbf{0}\mathbf{0}{}^{\circ }\mathrm{C}$800^(@)C\mathbf{8 0 0}{ }^{\circ} \mathrm{C}. The two circles and the vertical line show reference segment conditions of $55\mathrm{g}/\mathrm{hour}$$55\mathrm{g}/\mathrm{hour}$55g//hour55 \mathrm{~g} / \mathrm{hour} of intake and $6\mathrm{g}/$$6\mathrm{g}/$6g//6 \mathrm{~g} / hour of oxygen production. The dark arrows show the safe voltage zone for oxygen production, with no coking under these conditions. The vertical error bar reflects the effect of uncertainty in the lead resistance (see in the “Diagnostic runs” section) on the voltage applied to the cells. The horizontal error bar shows the uncertainty in determining the mass flow rate.
图 3.在工作温度 下 $\mathbf{8}\mathbf{0}\mathbf{0}{}^{\circ }\mathrm{C}$$\mathbf{8}\mathbf{0}\mathbf{0}{}^{\circ }\mathrm{C}$800^(@)C\mathbf{8 0 0}{ }^{\circ} \mathrm{C} ，几种氧气生产速率下氧气和碳形成的能斯特电位与输入质量流量的关系。两个圆圈和垂直线表示进气口和 $6\mathrm{g}/$$6\mathrm{g}/$6g//6 \mathrm{~g} / 氧气生产小时的参考段条件 $55\mathrm{g}/\mathrm{hour}$$55\mathrm{g}/\mathrm{hour}$55g//hour55 \mathrm{~g} / \mathrm{hour} 。深色箭头表示氧气生产的安全电压区，在这些条件下没有焦化。垂直误差条反映了铅电阻的不确定性（参见“诊断运行”部分）对施加到电池上的电压的影响。水平误差条显示了确定质量流量的不确定性。
density minimum with MOXIE’s compressor at its 3500 rpm maximum). The reference segment starts with a 16 -min “equilibration” step with 2-A electrolysis current ( $6\mathrm{g}/$$6\mathrm{g}/$6g//6 \mathrm{~g} / hour of oxygen), during which time, the internal operating temperature stabilizes. This is followed by $3.5-\min$$3.5-\min$3.5-min3.5-\mathrm{min} steps at 1.6 A and 1.2 A ( 4.8 and $3.6\mathrm{g}/$$3.6\mathrm{g}/$3.6g//3.6 \mathrm{~g} / hour of oxygen, respectively), providing a voltage-current ( $V-I$$V-I$V-IV-I ) sweep to determine the internal resistance of the SOXE, an important instrument health parameter. The current returns to 2 A to end the reference segment. Running identical reference segments at the beginning of every MOXIE run allows for tracking changes in MOXIE performance. The intake of $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / hour and points of $6\mathrm{g}/\mathrm{hour}$$6\mathrm{g}/\mathrm{hour}$6g//hour6 \mathrm{~g} / \mathrm{hour} are indicated in Fig. 3.
密度最低，MOXIE 压缩机最大转速为 3500 rpm）。参考段从 16 分钟的“平衡”步骤开始，电解电流为 2-A（ $6\mathrm{g}/$$6\mathrm{g}/$6g//6 \mathrm{~g} / 氧气小时），在此期间，内部工作温度稳定。接下来是 $3.5-\min$$3.5-\min$3.5-min3.5-\mathrm{min} 1.6 A 和 1.2 A（分别为 4.8 和 $3.6\mathrm{g}/$$3.6\mathrm{g}/$3.6g//3.6 \mathrm{~g} / 氧气小时）的步骤，提供电压-电流 （ $V-I$$V-I$V-IV-I ） 扫描以确定 SOXE 的内阻，这是一个重要的仪器健康参数。电流返回 2 A 以结束参考段。在每次 MOXIE 运行开始时运行相同的参考段可以跟踪 MOXIE 性能的变化。 $55\mathrm{g}/$$55\mathrm{g}/$55g//55 \mathrm{~g} / 小时和点的 $6\mathrm{g}/\mathrm{hour}$$6\mathrm{g}/\mathrm{hour}$6g//hour6 \mathrm{~g} / \mathrm{hour} 摄入量如图 3 所示。

MOXIE software allows either specifying a desired current through the stack (“current-control mode,” which effectively specifies the oxygen production rate) or specifying the desired voltage across the top and bottom parts of the stack (“voltage-control mode”). All runs described in this paper were run in current-control mode, where a feedback loop adjusts the stack voltage to obtain the desired current. Estimates of the internal resistance of the stack, obtained from the $V-I$$V-I$V-IV-I sweeps described above, are used to predict the required voltages to ensure that the operation remains in the safe voltage zone. Voltagecontrolled runs are planned for the future.
MOXIE 软件允许指定通过堆栈的所需电流（“电流控制模式”，有效地指定氧气生成速率）或指定堆栈顶部和底部所需的电压（“电压控制模式”）。本文中描述的所有运行均在电流控制模式下运行，其中反馈回路调整堆栈电压以获得所需的电流。从上述 $V-I$$V-I$V-IV-I 扫描中获得的堆栈内阻估计值用于预测所需的电压，以确保操作保持在安全电压区。电压控制运行计划在未来进行。

Following the reference segment, a generic MOXIE run steps the compressor up to its 3500 rpm maximum speed, implements another $V-I$$V-I$V-IV-I sweep, and then sets the current to as high a value as possible for this maximum gas intake while keeping the estimated electrolysis voltage at least 0.1 V below the Nernst potential for carbon formation. At the end of a run, the compressor speed and electrolysis current are reset for 5 min to the values used in the reference segment to compare the system behavior at the beginning and at the end of the run.
在参考段之后，通用 MOXIE 运行将压缩机提高到 3500 rpm 的最大速度，实施另一次 $V-I$$V-I$V-IV-I 扫描，然后将电流设置为尽可能高的值，以达到该最大气体摄入量，同时保持估计的电解电压至少比能斯特电位低 0.1 V 形成碳。在运行结束时，压缩机速度和电解电流将重置 5 分钟，重置为参考段中使用的值，以比较运行开始和结束时的系统行为。