Wickman L A, Luna B
Lockheed-Martin Missiles & Space Company, Sunnyvale, CA, USA.
Aviat Space Environ Med. 1996 Oct;67(10):940-6.
Supporting the mass of a protective suit and portable life support system (PLSS) will impose an energy requirement on planetary astronauts. To design extravehicular protective equipment for planetary missions, scientists must learn more about human physical capabilities while load-carrying in reduced gravities. In this study, an underwater treadmill and weighting system were used to simulate reduced-gravity locomotion while load-carrying. The test matrix included 3 gravity levels, 6 subjects, 2 locomotion speeds, and a range of load sizes. Energy expenditure, calculated from measured oxygen consumption, is positively correlated with gravity level, speed, and load size. The data are used to project that individuals in average physical condition will be able to walk for 8 h on the Moon while carrying up to 170% of their body mass without undue fatigue, and on Mars with up to 50% of their body mass. These approximate limits, especially for Martian gravity, may prove quite a challenge for designers of advanced protective systems. Requirements for regenerable and non-venting PLSS components have been driving the total projected masses of advanced PLSSs increasingly higher, perhaps beyond what is reasonable to carry. However, the larger mass can be beneficial in maintaining bone mass. Using Whalen's model (1988), the daily planetary walking times required to maintain bone mass were calculated for a range of carried load sizes. The calculated times were unattainably high, suggesting that some combination of loads carrying and supplemental bone maintenance measures will likely be required to maintain bone mass in reduced gravity environments.
支撑防护服和便携式生命保障系统（PLSS）的重量会给执行行星任务的宇航员带来能量需求。为了设计用于行星任务的舱外防护装备，科学家们必须更多地了解人类在低重力环境下负重行走时的身体能力。在这项研究中，使用水下跑步机和配重系统来模拟低重力环境下的负重行走。测试矩阵包括3个重力水平、6名受试者、2种行走速度以及一系列负载大小。根据测得的氧气消耗量计算出的能量消耗与重力水平、速度和负载大小呈正相关。这些数据被用来预测，身体状况一般的人在月球上携带高达其体重170%的负载时能够行走8小时而不会过度疲劳，在火星上携带高达其体重50%的负载时也能如此。这些大致的限制，尤其是对于火星重力环境而言，可能对先进防护系统的设计者来说是一个相当大的挑战。对可再生且无通风的PLSS组件的要求使得先进PLSS的预计总质量越来越高，可能超出了合理的携带范围。然而，更大的质量在维持骨量方面可能是有益的。使用Whalen（1988年）的模型，计算了一系列负载大小下维持骨量所需的每日行星行走时间。计算出的时间高得难以实现，这表明在低重力环境下可能需要结合负载携带和补充性骨量维持措施来维持骨量。
