<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> extropy-chat <extropy-chat-bounces@lists.extropy.org> <b>On Behalf Of </b>Adrian Tymes via extropy-chat<br><b>Sent:</b> Saturday, September 26, 2020 8:29 PM<br><b>To:</b> ExI chat list <extropy-chat@lists.extropy.org><br><b>Cc:</b> Adrian Tymes <atymes@gmail.com><br><b>Subject:</b> Re: [ExI] Space governance<o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Fri, Sep 25, 2020 at 11:38 AM Dave Sill via extropy-chat <<a href="mailto:extropy-chat@lists.extropy.org">extropy-chat@lists.extropy.org</a>> wrote:<o:p></o:p></p></div><div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal>On Fri, Sep 25, 2020 at 12:50 PM Adrian Tymes via extropy-chat <<a href="mailto:extropy-chat@lists.extropy.org" target="_blank">extropy-chat@lists.extropy.org</a>> wrote:<o:p></o:p></p></div><div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal>If these habitats are, say, cylinders 2 km wide, to allow them to be spun up to 1 G, that's enough of a technical (and imposed-by-human-biology) standard that people might not want to mess with it. 2 km wide suggests maybe 5 km long maximum, for structural stability.<o:p></o:p></p></div></div></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>What about rotational stability? Wouldn't want your habitats flipping when they're full of people.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><a href="https://www.youtube.com/watch?v=1VPfZ_XzisU" target="_blank">https://www.youtube.com/watch?v=1VPfZ_XzisU</a><o:p></o:p></p></div></div></div></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>>…Per that video, you weight it so the axis of rotation is not the one that's going to cause that sort of flipping…<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hi Adrian, ja. What I had in mind really is hauling fuel tanks on up to orbit to convert them to something useful there, forget re-entering the atmosphere.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When you watch that spinning wrench, what might not be obvious is that the axis about which the wrench is set to spinning is not the axis of maximum moment of inertia, but rather the axis between the minimum and maximum moments.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>You can create a maximally stable rotating object such as a disc, and there is no possible instability. If we imagine a Space Shuttle main tank, emptied of fuel and oxygen, then inhabited, we could rotate it about the transverse axis: perfectly stable. Rotate about the longitudinal axis: unstable.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So… get two of them, tie them together with a cable, get them rotating about the center of the cable.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>spike <o:p></o:p></p></div></div></div></div></body></html>