Forwarded from Andy Price, and with the kind permission of Dr. Edwards, following are his initial thoughts on the Pugno study;
\n<\/p>\n
“The paper by Pugno has been beaten around a bit.\u00a0 I just read the paper, very interesting.\u00a0 Let me run through a few thoughts on it.<\/p>\n
I start off worrying when someone creates his own theory and simulation to model everything from nanoscale to megascale (nanotubes to Earth) especially when there are plenty of molecular models out there.\u00a0 But having said that, let me assume his simulation is perfect for a nanotube.\u00a0 He appears to have scripted the paper to claim the cable will break (he repeats this claim at least four times throughout the paper often with the note that it is his opinion) \u2013 a second worry when an author appears to be trying to prove a conclusion.\u00a0 Here are a few notes I made on his discussion:
\n– references and then ignores coatings to eliminate atomic oxygen erosion.
\n– states radiation damage will cause defects but doesn\u2019t discuss the amount.\u00a0 Damage seen in experiments is minimal for carbon fibers in the radiation fields around Earth.
\n– I may be wrong but it appeared to me that Pugno was using a macroscopic model to represent a damaged nanotube as a solid tube with a physical hole in it.\u00a0 He certainly discusses this and then discusses missing bonds so I would be curious to know which one he went with.\u00a0 I will need to look at this again.
\n– uses an erroneous theoretical maximum of 100GPa for the tensile strength of CNTs.\u00a0 CNTs have been measured at strengths from 150GPa to 200 GPa and he references one that is at 109GPa.\u00a0 His final 30GPa is directly related to this.
\n– uses the strength of long CNT bundles to prove his arguments.\u00a0 CNT bundles are not a valid comparison because they can have very short CNTs and limited interaction.
\n– assumes that all CNTs will be damaged (it appears to be on a 100 nm length) and that none of them interact with each other in a supportive manner.
\nThis is from a quick read of the paper but essentially as far as I understand, Pugno makes some poor assumptions to argue that there will be damage to all the CNTs in a ribbon, calculates that each CNT will degrade 70% and then jumps to the conclusion that the ribbon will degrade 70%.\u00a0 As far as I can tell he doesn\u2019t look at or consider the structure of the CNT threads, the interactions of the CNTs, real defect type and frequency, techniques to reduce defects in production, the real defect production rates in space, the maximum measured CNT strengths, \u2026\u00a0 The paper didn\u2019t strike me as very good scientific work.
\nHaving said all of this, people will view my remarks as biased \u2013 a reasonable assumption.\u00a0 I have attempted to be objective because I would like to know the answers as well.\u00a0 I would like to request that others examine this material as well.
\nI applaud the attempt to examine the materials issue, but don\u2019t think Pugno has provided a good analysis in this paper.”<\/p><\/blockquote>\nThank you Andy and Dr. Edwards.<\/p>\n","protected":false},"excerpt":{"rendered":"
Forwarded from Andy Price, and with the kind permission of Dr. Edwards, following are his initial thoughts on the Pugno study; “The paper by Pugno has been beaten around a bit.\u00a0 I just read the paper, very interesting.\u00a0 Let me run through a few thoughts on it. I start off worrying when someone creates his […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":["post-269","post","type-post","status-publish","format-standard","hentry","category-news-announcements"],"_links":{"self":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/269","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=269"}],"version-history":[{"count":0,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/269\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=269"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}