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 332AB3B2A4 for ; Tue, 25 Apr 2023 18:33:29 -0400 (EDT) Received: from dlang-mobile (unknown [10.2.2.69]) by mail.lang.hm (Postfix) with ESMTP id 28156189388; Tue, 25 Apr 2023 15:33:28 -0700 (PDT) Date: Tue, 25 Apr 2023 15:33:28 -0700 (PDT) From: David Lang To: "David P. Reed" cc: starlink@lists.bufferbloat.net In-Reply-To: <1682455200.058420642@apps.rackspace.com> Message-ID: <2oqrr341-sps4-48n0-on52-42spno4q0o40@ynat.uz> References: <1682455200.058420642@apps.rackspace.com> MIME-Version: 1.0 Content-Type: multipart/mixed; BOUNDARY="===============2791345782323500022==" 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 22:33:29 -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. --===============2791345782323500022== Content-Type: text/plain; format=flowed; charset=US-ASCII On Tue, 25 Apr 2023, David P. Reed via Starlink wrote: > Ideally, the initial acceleration of a rocket would be better imparted by an external launcher (at least on the Earth - not initially on Mars). For example, an electromagnetic linear accelerator that contains the rocket while it accelerates. (We're not talking a sub-launched missile or a carrier-launched airplane here, and even on carriers, electromagnetic catapults have been developed that work better than steam ones - despite Trump's Musk-like idiotic statement that "steam is the best way" for carriers). > > The reusability of an electromagnetic launcher is clearly far better than for the "reusable" launch stage that holds the equivalent energy in fuel form. (snark: and Musk is a genius who "invented" a whole system for using tubes and magnets called Hyperloop). > > It doesn't need to be a tube, it could be a "rail" (railguns work, and are cool in SF, too). > Powering it just needs a way to store and release electrical energy fast - a battery, basically, which can be wired up as a collection of storage cells in parallel. > > And this wouldn't pollute the atmosphere anywhere near as much, I'd guess. also not a rocket engineer, but I've been paying attention for a while are you aware of spinlaunch? they are trying to get their initial velocity with electricity, via spinning the rocket at the end of an arm rather than a linear accelerator. re: linear accelerator 1. you want to gain alititude quickly to get out of the thickest air, that takes a launch up the side of a mountain, not something horizontal. 2. having your velocity really high as you leave the launch facility (as opposed to as you gain speed at higher altitudes) will significantly increase your aerodynamic forces 3. good mountains don't tend to have ocean to the east for problems to fall into, even on islands you tend to have population pretty close 4. this is a LOT of mass to move, yes, the more you can power with the linear accelerator, the less you need in the rocket, but you still need to move a LOT of mass. 5. rockets aren't stressed to be on their side (at least not when fully assembled and fueled), adding structure to support this will reduce your gains 6. you will need to mount the rocket to a sled, there's not a lot of ferris metal in a rocket for magnets to grab 7. there are a lot of delicate electronics on a rocket, how will they handle the very strong magnetic fields (even if you have them focused on a sled, they will need to be strong enough that they could be a risk even further away all these things said, I would love to see someone try it. I think that an accelerator up the side of a mountain could do wonders for unmanned cargo. Possibly not electronics, but a lot of structure, and more importantly fuel, could be launched this way. But until we have a much more substantial presense in space, I don't see it worth anyone investing the money to make it work. The F9 reusability was criticised as being unneded, the Starship is being criticised as being unneeded. (both with the argument that there wasn't enough demand to need them). I expect demand to grow with capacity, and as the cost comes down, outstripping the capacity, but we have a ways to go. David Lang --===============2791345782323500022== Content-Type: text/plain; CHARSET=utf-8 Content-Transfer-Encoding: BASE64 Content-ID: <7nr41931-7804-sr29-084n-84s3255pq151@ynat.uz> Content-Description: Content-Disposition: INLINE X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KU3Rhcmxpbmsg bWFpbGluZyBsaXN0ClN0YXJsaW5rQGxpc3RzLmJ1ZmZlcmJsb2F0Lm5ldApodHRwczovL2xpc3Rz LmJ1ZmZlcmJsb2F0Lm5ldC9saXN0aW5mby9zdGFybGluawo= --===============2791345782323500022==--