From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.lang.hm (syn-045-059-245-186.biz.spectrum.com [45.59.245.186]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id C11A63B2A4 for ; Wed, 4 Sep 2024 19:52:02 -0400 (EDT) Received: from dlang-mobile (unknown [10.2.3.133]) by mail.lang.hm (Postfix) with ESMTP id AE4611DE516; Wed, 4 Sep 2024 16:52:01 -0700 (PDT) Date: Wed, 4 Sep 2024 16:52:01 -0700 (PDT) From: David Lang To: Brandon Butterworth cc: Dave Taht , Dave Taht via Starlink In-Reply-To: Message-ID: <4n7s5s50-12n0-n4q4-3978-0qr743n043o9@ynat.uz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Subject: Re: [Starlink] lumen orbit X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Sep 2024 23:52:02 -0000 On Wed, 4 Sep 2024, Brandon Butterworth via Starlink wrote: > On 04/09/2024 15:48:51, "Dave Taht via Starlink" > wrote: >> They plan to build a 5GW 4k solar square for data centers in orbit, >> launched on starship: >> >> https://www.lumenorbit.com/ > > Maintenance call outs are going to be interesting > >> How are they going to cool this thing? > > With some big radiators. From > https://www.nasa.gov/wp-content/uploads/2021/02/473486main_iss_atcs_overview.pdf > > it seems that the ISS units take about 23 * 3.5m area for 35kW so > about 440 W/m^2, if they are about the same then 5GW will need > around 11 million sq metres. > > That seems a totally unfeasible number so either I messed up the > calculation, or they have way more efficient radiators than NASA, > or this is wishful thinking/investor grift. the efficiency of radiators goes up drastically as the temperature of the radiator goes up (there is a T^4 factor in the equasion, T in kelvin) so if they can get the coolant hot enough, they can shrink the radiator area by increasing the temp. but since 0c = ~273K, running the temp up to just over the melting point of aluminum would let you get to about 1000x efficiency for the radiators (@1255c) but would still need a massive radiator. 11k sq meters is still a lot. the ISS radiators are a little of 6Kg/sq meter, so you are up to around 70T worth of radiators (possible with a starship, but still massive) designing a heat pump that can pump heat from chips into molten aluminum is left as an excercise for the reader :-) David Lang