Laser-induced propulsion of graphene lightsails in microgravity
- Paper number
IAC-19,C2,8,x52952
- Year
2019
- Abstract
Light from the Sun or a laser beam can be used to transfer momentum to matter and displace low-mass objects. Space agencies have successfully tested the solar sail technology for low-Earth orbit applications, navigation control, and Solar System exploration~[1,2,3], JAXA's mission \textit{IKAROS}~[4] (2010) being the first demonstration of spacecraft with a sail contributing to its propulsion. However, the thrust from radiation pressure is too low for standalone propulsion unless we use ultrathin sails made of optically-suitable materials with low mass density yet mechanically strong and stiff to reduce issues with sail deployment and space particle bombardment~[5,6]. Graphene, a one atom thick allotrope of graphite~[7,8], has the ultimate low mass density with exceptional properties: large stiffness ($1$~TPa) and tensile strength ($130$~GPa) for a 20\% stretchability~[9]; and excellent electrical ($350000$~cm$^2$V$^{-1}$s$^{-1}$)~[10,11] and thermal ($2500$~Wm$^{-1}$K$^{-1}$) conductivity~[12]. Despite promising great material performance for lightsail material, its large optical absorption (2.3\% in the visible and near infrared spectrum)~[13] and low reflectivity need to be engineered if wants to be used as the lightsail interface. In this work, we propose and experimentally study a lightsail design where graphene layers cover a holey copper grid. Such a compounded structure allows to reduce the average mass density of the sail substrate while deriving from graphene its mechanical rigidity and full-surface availability to sustain a reflective thin film. Furthermore, we made a laser setup to demonstrate the light-induced acceleration of these 2D sails in microgravity at ZARM Drop Tower (Germany). By using lasers with different wavelengths and optical powers (up to 1~W), we observe thrusts of $8-248$~nN, one order of magnitude higher than the theoretical calculations for a radiation pressure mechanism. References: \newline [1] Friedman et al, 16th Aerospace Sciences Meeting (1978). \newline [2] Tsu, ARS Journal 29, 422 (1959). \newline [3] Johnson et al, Acta Astronautica 68, 571 (2011). \newline [4] Tsuda, Acta Astronautica 69, 833 (2011). \newline [5] Fernandez et al, Acta Astronautica 103, 204 (2014). \newline [6] Hoang et al, The Astrophysical Journal 1, 837 (2017). \newline [7] Novoselov et al, Science 306, 666 (2004). \newline [8] Novoselov et al, Nature Materials 3, 6 (2007). \newline [9] Lee et al, Science 321, 385 (2008). \newline [10] Novoselov et al, Nature 7065, 438 (2005). \newline [11] Neto et al, Reviews of modern physics 81, 109 (2009). \newline [12] Balandin et al, Nano Letters 3, 8 (2008). \newline [13] Nair et al, Science 5881, 320 (2008).- Abstract document
- Manuscript document
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