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yexuqing木蟲之王 (文學(xué)泰斗)
太陽系系主任
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[交流]
Photophoretic flight of perforated structures in near-space conditions
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Photophoretic flight of perforated structures in near-space conditions 近地太陽能飛行器來了 ▲ 作者：Benjamin C. Schafer, Jong-hyoung Kim, Felix Sharipov, Gyeong-Seok Hwang, Joost J. Vlassak & David W. Keith ▲鏈接： https://www.nature.com/articles/s41586-025-09281-8 ▲摘要： 光泳是一種氣體（或液體）中懸浮的顆粒被光加熱后產(chǎn)生的運動力。人們已經(jīng)知道這種原理超過百年，但直到近期才開始探索它的實際用途。在地球大氣層上層，空氣十分稀薄，光泳的力強到足以讓小型物體漂浮。但迄今為止，大多數(shù)實驗都集中在非常小而輕的材料上，將之?dāng)U展到更大、更實用的大型設(shè)備一直是個挑戰(zhàn)。 美國哈佛大學(xué)的Benjamin Schafer與合作者研究了一種小型太陽能漂浮裝置，由兩片薄而多孔的膜通過微小的垂直支撐連接而成。結(jié)合計算機建模和實驗室實驗優(yōu)化光泳力后，他們制作了一個寬1厘米的圓盤，能夠在與高空陽光強度相當(dāng)?shù)墓庹障聭腋�。他們還提出了一種3厘米寬的版本，計算機模型顯示它白天在75公里高空能夠攜帶10毫克的載重（足以支撐包含射頻天線、太陽能電池和集成電路的小型通信系統(tǒng)）。 這些發(fā)現(xiàn)凸顯了光泳飛行作為監(jiān)測地球大氣甚至探索其他行星的工具的潛力。作者認(rèn)為，現(xiàn)在的火星運輸成本每公斤超過10萬美元，而相比專門的火星衛(wèi)星，光泳裝置在尺寸、重量和功耗方面均有顯著優(yōu)勢，未來可用于執(zhí)行傳感和通信任務(wù)。未來的設(shè)計可以包含導(dǎo)航系統(tǒng)、增加載荷能力和運行時長，以及執(zhí)行更大規(guī)模的任務(wù)。 ▲ Abstract： Lightweight nanofabricated structures could photophoretically loft payloads in near-space. Proposed structures range from microscale engineered aerosols, to centimetre-scale thin disks with variations in surface accommodation coefficients, to sandwich structures with nanoscale thickness that might be extended to metre-scale width. Quantitative understanding of how structural and surface properties determine photophoretic lofting forces is necessary to develop a practical flying device. Here we focus on thermal transpiration as the most promising photophoretic mechanism for lofting large devices and present a hybrid analytical–numerical model of the lofting force on a structure that consists of two perforated membranes spaced a small distance apart. We identify optimal structural parameters, including device size, membrane perforation density and distribution of the vertical ligaments that connect the two membranes, each as a function of atmospheric altitude. Targeting these optimal parameters, we fabricate structures with a heterogeneous ligament distribution, which efficiently compromises between structural rigidity and photophoretic performance. We measure how lofting forces generated by these structures depend on pressure using gases with three different molecular weights. We observed photophoretic levitation of a 1-cm-wide structure at an air pressure of 26.7 Pa when illuminated by 750 W m-2, about 55% the intensity of sunlight. Lastly, we describe the preliminary design of a 3-cm-radius device with 10-mg payload capacity at 75-km altitudes and discuss horizontal motion control, overnight settling, and applications in climate sensing, communications and Martian exploration. 12,433個實用裝置的大氣懸浮。向上推力由熱對流氣流通過裝置膜上的434個微尺度孔洞產(chǎn)生。回流發(fā)生在遠(yuǎn)離裝置的位置。 |
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