From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from omr2.cc.vt.edu (omr2.cc.ipv6.vt.edu [IPv6:2607:b400:92:8400:0:33:fb76:806e]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 4237F3CB48 for ; Tue, 13 Mar 2018 13:49:34 -0400 (EDT) Received: from mr2.cc.vt.edu (mail.ipv6.vt.edu [IPv6:2607:b400:92:9:0:9d:8fcb:4116]) by omr2.cc.vt.edu (8.14.4/8.14.4) with ESMTP id w2DHnXBE008849 for ; Tue, 13 Mar 2018 13:49:33 -0400 Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by mr2.cc.vt.edu (8.14.7/8.14.7) with ESMTP id w2DHnSO0005203 for ; Tue, 13 Mar 2018 13:49:33 -0400 Received: by mail-qk0-f199.google.com with SMTP id h128so258059qke.8 for ; Tue, 13 Mar 2018 10:49:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:in-reply-to:references :mime-version:content-transfer-encoding:date:message-id; bh=FZtZMWgu3gsiwXmeNUCG/LePzqj4fa7pCgYNfsXLFeg=; b=owHA1Cp3Jap+Nj9+zk0x9kSqvnKMQ53YnSaM19JhIQDfE12IW2R4659iYBBTvL4ldn xXx20M2PC6IsQA/UrrPsPE8RBf2v0Lu6+6g6rZkB6HSl1IxBM5Ew61dbnAGd+BSa2baY gEt/NgnTd1KRcS4ZsEWCtaX7i03CCPO1d1eaphCL8Cs1GBuR5PkF0E0CYJEINbAK4u6z uE9RL1y+2avyVrns+Yy84hAsDNDjFFly/sDoanX8Cth5MDfqyPkN2fXoS/adGa9UXUv9 w5rM89HxEc6IRZXBlWLC6V+RDDbC3220v6DUL0yMm95SUrMrF4G/1+1tOIh/tW68dBYk 8wrg== X-Gm-Message-State: AElRT7HXKm4C30Qsx2G6iVMKH67THOWTviBIPfFFvGIzmrENAKP3S90e FqoroVTmODtS/1vrR2WP711gf2s0zh6fOCbAHWJjit919zb4sgcThYFxRTbjpd/8cCi+cYVb/ym JjwAYPqu4TK1afcppJ+C0zvn6yn9UJQLi9REh9p8Nj9pO X-Received: by 10.200.55.157 with SMTP id d29mr2357670qtc.61.1520963368343; Tue, 13 Mar 2018 10:49:28 -0700 (PDT) X-Google-Smtp-Source: AG47ELsL42pt2OpgubRe8UIyPi1ccL+dgBVm4AjPeCjLBxeKzdYH3K+uOV2vBywNivYHFthLYdt81w== X-Received: by 10.200.55.157 with SMTP id d29mr2357644qtc.61.1520963367991; Tue, 13 Mar 2018 10:49:27 -0700 (PDT) Received: from turing-police.cc.vt.edu ([2601:5c0:c001:4342:c430:e38f:d48e:a275]) by smtp.gmail.com with ESMTPSA id q187sm178423qke.13.2018.03.13.10.49.25 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 13 Mar 2018 10:49:26 -0700 (PDT) Sender: Valdis Kletnieks From: valdis.kletnieks@vt.edu X-Google-Original-From: Valdis.Kletnieks@vt.edu X-Mailer: exmh version 2.8.0 04/21/2017 with nmh-1.7+dev To: Dave Taht Cc: Jim Gettys , cerowrt-devel@lists.bufferbloat.net In-Reply-To: References: <1520875105.31683592@apps.rackspace.com> <1520881804.31539998@apps.rackspace.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1520963365_3866P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 13 Mar 2018 13:49:25 -0400 Message-ID: <123694.1520963365@turing-police.cc.vt.edu> Subject: Re: [Cerowrt-devel] spacebee X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Mar 2018 17:49:34 -0000 --==_Exmh_1520963365_3866P Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable On Tue, 13 Mar 2018 09:52:53 -0700, Dave Taht said: > Spacebee - Having a payload 1/4th the size of a cubesat *work* and be > useable=21 is a major advance. And is 1/4th the space junk. Worrying > about something smaller than baseball hitting anything strikes me as > control freakery at the FCC. For the purposes of this example, we'll assume that a large bolt sized pi= ece of space debris is about the same size as a 50 caliber sniper round. That le= aves the rifle going about 4,000 feet per second. A piece of space debris can hit at anywhere from almost zero to twice the= orbital speed, depending on relative orbit angles (the 2009 Iridium incid= ent they hit at almost exactly 90 degrees, so 17000 mph times sqrt(2)). For that configuration, they collided at around 25,000 feet per second. = And kinetic energy is 0.5 * m v =5E2. So that bolt ends up whacking you with= about 40 times the force of a 50 caliber round. That's gonna mess up your day = unless you have some serious armor - which is the last thing anything in orbit h= as due to the cost of launching per pound (even the ISS is only armored enou= gh to stop something up to 1.5cm or so). If you want to use a baseball as the example, find the video of Randy Joh= nson pegging a stray pigeon. And his baseball was going around 100mph. Apply= =22one half em vee squared=22 and we get 17000=5E2 / 100=5E2 - or a baseball in = orbit has 28,900 times the kinetic energy. The Iridium constellation of 66 satellites already has to deal with some = 400 incidents *per week* where known space junk passes within 5km. And in mo= st cases, the exact orbitals for at least one of the bodies aren't exactly k= nown - in the 2009 incident, they had been predicted to miss by 500 meters. And NASA has an in-progress experiment to measure how often the really small stuff hits: https://www.nasa.gov/mission_pages/station/research/news/sensor_to_monito= r_orbital_debris_outside_ISS Sure, the chances of any given piece of debris hitting something is prett= y low. But you get enough crap in orbit, the cumulative risk over time starts ge= tting into territories that make your risk management team start drinking heavi= ly. --==_Exmh_1520963365_3866P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.8.0 04/21/2017 iQEVAwUBWqgPJY0DS38y7CIcAQImVAf/TR/Se/WNlMST5x7yxndW2qCzOAXgCRIe TeOjEuswr5MqW9BEiJJ+FmNLe0uCG6+TsZBphu+7U/LXnDMevMU4fwBnqaViMGOA vtg9Hn7jzkkRud5Wu7c2Sg5HhuE2h8T9pkaygddMqW2J8YDIuo/U2DRPnlzlu6Ag /Az0WNAR0U61e76S9Qfgp6OyvCq78NLG99hFl1O9XruDaichJvVxnwCkb25zzLC8 HTVkXSwLBsYhjmxMOLuaKaxw2NlWDFJBM2P8fq7JolnxvpMKQb+CNJGv4RIDIQc8 iiJ+p7bAxnZDMak67+m11e2hsjXFQcgNMe5MrkbCeltpaLerARxSjg== =Igm8 -----END PGP SIGNATURE----- --==_Exmh_1520963365_3866P--