From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.lang.hm (unknown [66.167.227.145]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 7A0583B2A4 for ; Tue, 25 Apr 2023 19:22:18 -0400 (EDT) Received: from dlang-mobile (unknown [10.2.2.69]) by mail.lang.hm (Postfix) with ESMTP id 597281893AD; Tue, 25 Apr 2023 16:22:17 -0700 (PDT) Date: Tue, 25 Apr 2023 16:22:17 -0700 (PDT) From: David Lang To: Eugene Chang cc: Bruce Perens , David Lang , Dave Taht via Starlink In-Reply-To: <4108AD1D-235D-4243-8AAD-2155DAC6D68A@alum.mit.edu> Message-ID: <41rrn842-n98o-on3s-s7oq-7720593s46rn@ynat.uz> References: <74321D7F-D914-401B-8AE7-3185D9C2009C@alum.mit.edu> <8s710on2-s8r9-4n84-s0o0-386pn0psr08p@ynat.uz> <4108AD1D-235D-4243-8AAD-2155DAC6D68A@alum.mit.edu> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="228850167-230284060-1682464937=:15245" Subject: Re: [Starlink] some post Starship launch thoughts 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: Tue, 25 Apr 2023 23:22:18 -0000 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --228850167-230284060-1682464937=:15245 Content-Type: text/plain; format=flowed; charset=ISO-8859-7 Content-Transfer-Encoding: 8BIT On Tue, 25 Apr 2023, Eugene Chang wrote: > I found this YouTube of a deluge system test. > It doesn¢t look like it uses enough water to succeed. > My intuition is the mass of water needed is approximately equal to the rocket¢s mass. nowhere close. The pad 39a where the Saturn 5 launched has a 300,000 gal take, which is ~2.4M pounds, but the Saturn 5 launch weight was around 6.5M pounds > Maybe the system doesn¢t have to fully absorb the momentum of the engine exhaust. Still, 70% would be a much greater mass than what the video shows. it doesn't, it's not absorbing the momentum of the engine exhaust, it's vaporizing to cool the area and disrupt the airflow so the exhaust is less of a blowtorch when it hits a solid surface, and absorb enough sound to prevent it from damaging the rocket. distance helps with both of these, as do the materials that the exhaust finally hits. Regular concrete has too much moisture in it and the water flashes to steam and breaks the concrete (concrete is strong in compression, weak in tension). Elon mentioned a few weeks ago that even steel plates would wear down quickly under the exhaust, and that water cooled plates were needed in the long run (and they started building water cooled plates to put under the launch mount) will that be enough? only testing will tell us for sure. not all rockets use a flame trench, and some have very little deluge David Lang --228850167-230284060-1682464937=:15245--