Editing CubeSat (section)

===Structure===

The number of joined units classifies the size of CubeSats and according to the CubeSat Design Specification are [[Scalability|scalable]] along only one axis to fit the forms of 0.5U, 1U, 1.5U, 2U, or 3U. All the standard sizes of CubeSat have been built and launched, and represent the form factors for nearly all launched CubeSats as of 2015.<ref>{{Cite web| title = CubeSat| url = http://space.skyrocket.de/doc_sat/cubesat.htm| website = space.skyrocket.de| access-date = 2015-10-18}}</ref> Materials used in the structure must feature the same [[coefficient of thermal expansion]] as the deployer to prevent jamming. Specifically, allowed materials are four aluminum alloys: [[7075 aluminium alloy|7075]], [[6061 aluminium alloy|6061]], [[5005 aluminium alloy|5005]], and [[5052 aluminium alloy|5052]]. Aluminum used on the structure which contacts the P-POD must be [[anodize]]d to prevent [[cold welding]], and other materials may be used for the structure if a waiver is obtained.<ref name='specs'/> Beyond cold welding, further consideration is put into material selection as not all materials can be [[Materials for use in vacuum|used in vacuums]]. Structures often feature soft dampers at each end, typically made of rubber, to lessen the effects of impacting other CubeSats in the P-POD.

Protrusions beyond the maximum dimensions are allowed by the standard specification, to a maximum of {{cvt|6.5|mm}} beyond each side. Any protrusions may not interfere with the deployment rails and are typically occupied by antennas and solar panels. In Revision 13 of the CubeSat Design Specification an extra available volume was defined for use on 3U projects. The additional volume is made possible by space typically wasted in the P-POD Mk III's spring mechanism. 3U CubeSats which utilize the space are designated 3U+ and may place components in a cylindrical volume centered on one end of the CubeSat. The cylindrical space has a maximum diameter of {{cvt|6.4|cm}} and a height no greater than {{cvt|3.6|cm}} while not allowing for any increase in mass beyond the 3U's maximum of {{cvt|4|kg}}. Propulsion systems and antennas are the most common components that might require the additional volume, though the payload sometimes extends into this volume. Deviations from the dimension and mass requirements can be waived following application and negotiation with the [[launch service provider]].<ref name='specs'/>

CubeSat structures do not have all the same strength concerns as larger satellites do, as they have the added benefit of the deployer supporting them structurally during launch.<ref>{{Cite journal |last=Thomas |first=Daniel |date=2021-11-01 |title=Enhancing the electrical and mechanical properties of graphene nanoplatelet composites for 3D printed microsatellite structures |url=https://www.sciencedirect.com/science/article/pii/S2214860421003754 |journal=Additive Manufacturing |volume=47 |pages=102215 |doi=10.1016/j.addma.2021.102215 |issn=2214-8604|url-access=subscription }}</ref> Still, some CubeSats will undergo [[Structural dynamics|vibration analysis]] or [[structural analysis]] to ensure that components unsupported by the P-POD remain structurally sound throughout the launch.<ref>{{Cite journal| title = Stress and Thermal Analysis of CubeSat Structure | journal = Applied Mechanics and Materials| pages = 426–430| volume = 554| doi = 10.4028/www.scientific.net/amm.554.426| first1 = Nur| last1 = Athirah| first2 = Mohd| last2 = Afendi| first3 = Ku| last3 = Hafizan| first4 = N.A.M.| last4 = Amin| first5 = M.S. Abdul| last5 = Majid|year = 2014| s2cid = 110559952}}</ref> Despite rarely undergoing the analysis that larger satellites do, CubeSats rarely fail due to mechanical issues.<ref>{{Cite journal| url=http://web.csulb.edu/~hill/ee400d/Project%20Folder/CubeSat/The%20First%20One%20Hundred%20Cubesats.pdf| title=The First One Hundred CubeSats: A Statistical Look| last=Swartwout| first=Michael| date=December 2013| journal=Journal of Small Satellites| volume=2| issue=2| pages=213| bibcode=2013JSSat...2..213S| access-date=28 November 2015| archive-date=8 December 2015| archive-url=https://web.archive.org/web/20151208093346/http://web.csulb.edu/~hill/ee400d/Project%20Folder/CubeSat/The%20First%20One%20Hundred%20Cubesats.pdf| url-status=dead}}</ref>