Sulkowski Christina M, Gilkey Kelly M, Lewandowski Beth E, Samorezov Sergey, Myers Jerry G
NASA Glenn Research Center, 21000 Brookpark Rd., MS 110-3, Cleveland, OH 44135, USA.
Aviat Space Environ Med. 2011 Apr;82(4):455-62. doi: 10.3357/asem.2855.2011.
Understanding the contributions to the risk of bone fracture during spaceflight is essential for mission success.
A pressurized extravehicular activity (EVA) suit analogue test bed was developed, impact load attenuation data were obtained, and the load at the hip of an astronaut who falls to the side during an EVA was characterized. Offset (representing the gap between the EVA suit and the astronaut's body), impact load magnitude, and EVA suit operating pressure were factors varied in the study. The attenuation data were incorporated into a probabilistic model of bone fracture risk during spaceflight, replacing the previous load attenuation value that was based on commercial hip protector data.
Load attenuation was more dependent on offset than on pressurization or load magnitude, especially at small offset values. Load attenuation factors for offsets between 0.1-1.5 cm were 0.69 +/- 0.15, 0.49 +/- 0.22, and 0.35 +/- 0.18 for mean impact forces of 4827, 6400, and 8467 N, respectively. Load attenuation factors for offsets of 2.8-5.3 cm were 0.93 +/- 0.2, 0.94 +/- 0.1, and 0.84 +/- 0.5 for the same mean impact forces. The mean and 95th percentile bone fracture risk index predictions were each reduced by 65-83%. The mean and 95th percentile bone fracture probability predictions were both reduced approximately 20-50%.
The reduction in uncertainty and improved confidence in bone fracture predictions increased the fidelity and credibility of the fracture risk model and its benefit to mission design and in-flight operational decisions.
了解太空飞行期间对骨折风险的影响因素对于任务成功至关重要。
开发了一个加压舱外活动（EVA）航天服模拟试验台，获取了冲击载荷衰减数据，并对EVA期间向一侧摔倒的宇航员髋部的载荷进行了表征。研究中改变的因素包括偏移量（代表EVA航天服与宇航员身体之间的间隙）、冲击载荷大小和EVA航天服工作压力。将衰减数据纳入太空飞行期间骨折风险的概率模型，取代了之前基于商用髋部保护器数据的载荷衰减值。
载荷衰减对偏移量的依赖性比对增压或载荷大小的依赖性更大，尤其是在小偏移量值时。对于平均冲击力分别为4827、6400和8467 N的情况，偏移量在0.1 - 1.5 cm之间时的载荷衰减系数分别为0.69±0.15、0.49±0.22和0.35±0.18。对于相同的平均冲击力，偏移量为2.8 - 5.3 cm时的载荷衰减系数分别为0.93±0.2、0.94±0.1和0.84±0.5。平均骨折风险指数预测值和第95百分位数骨折风险指数预测值均降低了65 - 83%。平均骨折概率预测值和第95百分位数骨折概率预测值均降低了约20 - 50%。
骨折预测中不确定性的降低和信心的提高增加了骨折风险模型的保真度和可信度及其对任务设计和飞行中操作决策的益处。
