From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x22a.google.com (mail-qt0-x22a.google.com [IPv6:2607:f8b0:400d:c0d::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 797103CB35 for ; Tue, 13 Mar 2018 14:06:57 -0400 (EDT) Received: by mail-qt0-x22a.google.com with SMTP id z14so607387qti.2 for ; Tue, 13 Mar 2018 11:06:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=RUJ2JyKJILDJa8IqXcxgnh//pWmAJSchqGDxnbqsSPc=; b=utSCb65a9qw2B3+CA7f0rQfTDOfQDpRuR4s/CHrrwgtCCK7g3L6QwHk79anEdKjGtp 7FXL+jjG9b6aQB2w86Dbc8tGQuMK0DqqB109FdQnG/jUhD7PH+mb7tqdtNI1Ag/hP7Z8 tftBXylKJXfB/BC1F8ppHa2uDCXaC9lzodMvzZ+aA38+oWBKo4iUSY/iYT4I4ONm6m5D FL3Ppxm1x6FVH157LBIedcLWcLmXkjAg4/Q6TtvF10oUZD8Klak6NGpoM2MqmrnFyYb8 e9QzwOYrQT5TFNWrBajws2MmuNOfDedWmk1Do+EvEGpxXQDzmH656wZep1JJzFvG71hE KUqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=RUJ2JyKJILDJa8IqXcxgnh//pWmAJSchqGDxnbqsSPc=; b=stBC/jevWv45m+Uzd3QOBW+WTbCqeBTUmE1O457w6RiAif3IY5YDR7oMe6quSTZg5u aaRozXm8lzhN10/C8MjkfnZVf6gWLK+3cWq+n4x0y92uGr6d2+JN2cEqDOk9sFJCBZbS dEMQwyf97PtpYQAST/q0XBxLjHZHsYHgfxpleFm4Zkm0FDPHGrfO2lGhHxHovoSpcpfb LqB2QtY0ThdRH31clc1EztUWjKOzKuRK3wxgZ1Pt6H62iVJk/xPGZwlvyxvhaXVoznFA 42EQre+HVBuIQnPYlDzAd2ncbJvfMErv2Krf4PIpWMj19alOLwSpF/3rFhKtmAeXgRYR 5Seg== X-Gm-Message-State: AElRT7Eqz0mW/93090Rw8hs7b2DZrWY24pCeu0dXLZ4b52Tg96xuxzcr bankTNogqw9TLqzZ/03wrt68/4BLBMK+dW7+q0A= X-Google-Smtp-Source: AG47ELuvpfi1Xfu+YUkc/nEjPb+8FlUrMYRx3gfPS58Pf/OmpNpx/CRYNasQvabv9mqnnHdW0KMwuSPHCjmV4qEju0s= X-Received: by 10.200.42.177 with SMTP id b46mr2455872qta.321.1520964416985; Tue, 13 Mar 2018 11:06:56 -0700 (PDT) MIME-Version: 1.0 Received: by 10.12.191.15 with HTTP; Tue, 13 Mar 2018 11:06:56 -0700 (PDT) In-Reply-To: <123694.1520963365@turing-police.cc.vt.edu> References: <1520875105.31683592@apps.rackspace.com> <1520881804.31539998@apps.rackspace.com> <123694.1520963365@turing-police.cc.vt.edu> From: Dave Taht Date: Tue, 13 Mar 2018 11:06:56 -0700 Message-ID: To: Valdis Kletnieks Cc: Jim Gettys , cerowrt-devel@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 18:06:57 -0000 On Tue, Mar 13, 2018 at 10:49 AM, wrote: > 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! 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 ^2. So that bolt ends up whacking you with a= bout > 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). "U.S. space agency NASA estimated that the satellite collision created approximately 1,000 pieces of debris larger than 10 centimeters (4 inches), in addition to many smaller ones" Can you run the probability of a hit for two objects 10 centimeters in size in the 2009 orbital conflict vs, say, 2 meters, with a margin of measurement error of 500 meters? > 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= "one > half em vee squared" and we get 17000^2 / 100^2 - or a baseball in orbit > has 28,900 times the kinetic energy. I am painfully aware of this. On of my big fears in the SDI 80s was that someone would deploy pebbles in a reverse or polar GEO orbit, rigged to explode in a war extending to space. It could render GEO useless in a matter of weeks. The technique (I can't remember the codename) is so obvious (and so essentially MAD), that I've long assumed every spacefaring nation had one or more stealthy sats rigged that way on the drawing boards at some point or another. > 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. It was a sat from the early 90s. The collision took place in 2009. I remember (early 00s) how n-body sims took weeks, nowadays that's thoroughly parallized on gpus. > > 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 thx for the pointer! > 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. Yes we should worry about creating sea lanes for > --=20 Dave T=C3=A4ht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619