{"id":1910,"date":"2014-10-31T00:05:31","date_gmt":"2014-10-31T05:05:31","guid":{"rendered":"http:\/\/www.spaceelevatorblog.com\/?p=1910"},"modified":"2014-10-30T20:51:49","modified_gmt":"2014-10-31T01:51:49","slug":"space-debris-2","status":"publish","type":"post","link":"https:\/\/www.spaceelevatorblog.com\/?p=1910","title":{"rendered":"Space Debris"},"content":{"rendered":"<p>The <a href=\"http:\/\/us1.campaign-archive1.com\/?u=b04fe6a717cb201602c57bc5c&amp;id=f66727bca7&amp;e=eef9cd0384\" target=\"_blank\">October 29th issue<\/a> of the most-excellent <strong>SpaceRef<\/strong> newsletter contains a link to a new video that NASA has posted showing the space debris field orbiting our planet.\u00a0 It&#8217;s the most complete such video I&#8217;ve seen, zooming through various orbit levels and showing different viewpoints and perspectives of the debris.<\/p>\n<p><iframe loading=\"lazy\" title=\"Space Debris in Motion\" width=\"625\" height=\"469\" src=\"https:\/\/www.youtube.com\/embed\/IOwv1j-fUbo?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n<p>Of course this video only shows the space debris that is known &amp; tracked.\u00a0 The amount of items too small to be tracked greatly exceed what you see in the video.\u00a0 It&#8217;s important to keep in mind, however, that videos such as this cannot show the vast distances that actually exist between pieces of space debris.\u00a0 It&#8217;s kind of like the pictures you see of the asteroid belt showing asteroids constantly bumping into each other, that&#8217;s just not realistic.\u00a0 Incidentally, on the topic of the distance between asteroids, <a href=\"http:\/\/spacemath.gsfc.nasa.gov\/weekly\/6Page141.pdf\" target=\"_blank\">here is a paper<\/a> put out by NASA on the probabilities of a collision between asteroids 100 meters or larger in diameter (estimated to be at 30 billion) &#8211; they calculate that such occurrences will only happen once every 1.2 million years!\u00a0 They also give the formulas and assumptions they use so you can have fun figuring out your own asteroid collision scenarios \ud83d\ude42\u00a0 And, as a bonus, <a href=\"http:\/\/spacemath.gsfc.nasa.gov\/weekly\/6Page141.pdf\" target=\"_blank\">the paper<\/a> shows a picture of two asteroids after a collision.<\/p>\n<p>Anyway, back to earth&#8217;s space debris field.\u00a0 According to the ISEC Report on <strong>Space Debris Mitigation<\/strong> (available at the <a href=\"http:\/\/www.isec.org\/index.php\/store\/isec-reports\" target=\"_blank\">ISEC Store<\/a>), in Low-Earth-Orbit (LEO), the area with the highest concentration of space debris, there is only piece of space debris (10 cm or larger) ON AVERAGE per 730,000 cubic kilometers.\u00a0 To put that into perspective, imagine an enclosed corridor, 4.25 km wide and 4.25 km tall, that circles the earth at the equator, a distance of about about 40,000 km.\u00a0 In that entire area, you would find ONE PIECE of space debris 10cm or larger.\u00a0 Of course that is an average as there are, alternatively, clouds and voids of space debris.\u00a0 And the quantity of smaller space debris is, of course, larger.<\/p>\n<p>What does this mean for a Space Elevator?\u00a0 Well, unlike pieces of space debris that may collide with each other or with a satellite, the Space Elevator is much more vulnerable.\u00a0 Given enough time, a very long time, EVERY piece of space debris will, sooner or later, impact a space elevator.\u00a0 Referring again to the ISEC report on <strong>Space Debris Mitigation<\/strong>, calculations show that the most vulnerable part of the space elevator to space debris is that portion equivalent to LEO, approximately 200 to 2000 km above the earth.\u00a0 In that zone, the ISEC report shows that satellites would impact the elevator once every five years, space debris 10 cm or larger would impact the space elevator once per 100 days and space debris smaller than 10 cm would impact the space elevator once every 10 days.\u00a0 All of these are, again, average numbers.<\/p>\n<p>Does that sound the death knell for the idea of a space elevator?\u00a0 No, not at all.\u00a0 What it does mean is that the elevator tether must be designed to cope with this hazard and that CAN be done.\u00a0 The tether must be robust, able to cope with multiple small impacts and the occasional large one and it must be rigorously monitored and maintained.\u00a0 I can imagine a scenario where every meter of the tether has multiple monitors viewing it, with Climbers that also examine the tether as it ascends and descends.\u00a0 As the conclusion of the ISEC <strong>Space Debris Mitigation<\/strong> report states;<\/p>\n<blockquote><p>Space debris mitigation is an engineering problem with definable quantities such as density of debris and lengths\/widths of targets.\u00a0 With proper knowledge and good operational procedures, the threat of space debris is not a show stopper by any means.\u00a0 However, mitigation approaches must be accepted and implemented robustly to ensure that engineering problems do not become a catastrophic failure event.<\/p><\/blockquote>\n<p>If you want to learn more about this, visit the <a href=\"http:\/\/www.isec.org\/index.php\/store\/isec-reports\" target=\"_blank\">ISEC Store<\/a> to purchase the entire report.\u00a0 You can use information from it the next time one of your friends tells you that a space elevator is not feasible because &#8220;<em>space debris<\/em>&#8220;&#8230;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The October 29th issue of the most-excellent SpaceRef newsletter contains a link to a new video that NASA has posted showing the space debris field orbiting our planet.\u00a0 It&#8217;s the most complete such video I&#8217;ve seen, zooming through various orbit levels and showing different viewpoints and perspectives of the debris. Of course this video only [&hellip;]<\/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-1910","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\/1910","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=1910"}],"version-history":[{"count":17,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/1910\/revisions"}],"predecessor-version":[{"id":1912,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/1910\/revisions\/1912"}],"wp:attachment":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1910"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1910"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1910"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}