## 3 Embedded Battery Tile Design and Construction
### Embedded Battery Tile Prototype Construction
For the structural mass ratio, it has been shown that the use of CFRP can reduce the 1U primary structure mass to 104.5 g [9] (p. 9). If the maximum total mass for a 1U is considered, 1.33 kg [2] (p. 9), the structural mass ratio is 7.8%. For the proposed multifunctional smart tile, the total mass of the tile is 79.2 g (Figure 10a) and the single battery mass is 8.9 g (\(m_{BATT}\), Figure 10c). If the mass of the solar cells, 2.3 g, is added, a total mass of 83.8 g is found. To be conservative, a value of 85 g is adopted (\(m_{BATT\,TILE}\)). The mass of the aluminum skeleton is 87.2 g ([[https://www.isspace.nl/product/1-unit-cubesat-structure/](https://www.isspace.nl/product/1-unit-cubesat-structure/)]([https://www.isspace.nl/product/1-unit-cubesat-structure/](https://www.isspace.nl/product/1-unit-cubesat-structure/)), accessed on 12 August 2022) (\(m_{SKEL}\)). The mass of other ARAMIS PCB tiles is 16.9 g, that is rounded to 17 g to be conservative (\(m_{PCBTILE}\)). This leads to the following extreme cases of structural mass ratios (SMRs):  
* One embedded battery tile and five PCB tiles (\(N=1,\,M=5\)): \[ \begin{array}{l}SMR\ \ =\frac{N\cdot(m_{BATT\,TILE}-n_{BATT\,m_{BATT}})+M\cdot m _{PCB\,TILE}+m_{SKEL}}{m_{MAX}}=\\ \ =\frac{1\cdot(85-4.89)+5\cdot 17+87.2}{130}=16.7\%\end{array} \] (17)  
Figure 10: Final result of the assembly procedure: (**a**) complete embedded battery tile prototype; (**b**) prototype fit check with the commercial frame; and (**c**) the prototype underwent mass breakdown by components. * Six embedded battery tiles (\(N=6,\ M=0\)): \[ \begin{array}{ll}SMR&=\frac{N\cdot(m_{BATTILE}-n_{BATT}m_{BATT})+M\cdot m_{ PCBTILE}+m_{SKEL}}{m_{MAX}}=\\ &=\frac{6\cdot(85-4.89)+87.2}{1330}=28.8\%\end{array} \] (18) where \(m_{MAX}\) is the aforementioned maximum mass for a 1U CubeSat and \(n_{BATT}\) is the number of batteries in the embedded battery tile. These values are major than the mass ratio of the CFRP primary structure found in the literature of 7.8% [9] (p. 9). However, the proposed structure includes multifunctional aspects that are not included in the literature example. This implies that functional materials such as copper are employed, with a considerably higher mass density with respect to CFRP, and they must be added to the structural mass since they are part of the CubeSat structure. The total mass of the prototype, including solar cells (85 g), can be compared with equivalent commercial systems having a comparable architecture. The Crystalspace P1U module ([[https://www.cubesatshop.com/product/crystalspace-plu-vasik/](https://www.cubesatshop.com/product/crystalspace-plu-vasik/)]([https://www.cubesatshop.com/product/crystalspace-plu-vasik/](https://www.cubesatshop.com/product/crystalspace-plu-vasik/)), accessed on 8 September 2023) provides a power supply, with a mass of 80 g and an electrical power storage of 11 Wh (slightly superior to the prototype energy of 7.12 Wh). To compare this mass with the mass of the prototype, the mass of a solar panel assembly must be added, for example, the SM-SP1Z 1U Cubesat Z Solar Panel ([[https://satsearch.co/products/npcspacemind-sm-sp1z](https://satsearch.co/products/npcspacemind-sm-sp1z)]([https://satsearch.co/products/npcspacemind-sm-sp1z](https://satsearch.co/products/npcspacemind-sm-sp1z)), accessed on 8 September 2023) (24 g). The mass of this assembly (104 g) is superior to the mass of the prototype that has similar performance, although commercial equipment is generally at higher development stages (in this example, the power storage module is flight-proven). Moreover, the proposed prototype has the advantages of saving internal volume for the payload and of providing more protection and containment to the batteries. Finally, a fit check was performed to ensure the mechanical compatibility of the prototype with the commercial CubeSat frame (Figure 10b). The total measured mass of 79.2 g (Figure 10a), broken down by components, is represented in Figure 10c.