Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail From: Kragen Javier Sitaker Newsgroups: sci.electronics.design Subject: Re: OT: Private German rocket makes history, reaches orbit from European soil Date: Sun, 06 Sep 2026 17:48:59 -0300 Organization: Primarily biological and memetic Lines: 33 Message-ID: <87ecf6hzr8.fsf@debian> References: <117j1og$24q9k$1@dont-email.me> <117jokm$1uut$1@solani.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Date: Sun, 06 Sep 2026 20:49:04 +0000 (UTC) Injection-Info: dont-email.me; logging-data="2804521"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/I/OsA7kAN7YSgLimV0BN2"; posting-host="d9292ac7ccfaae3f32de5406991d3862" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) Cancel-Lock: sha1:bXyQcBFl6c+ZQO+3NNf3BIqrD2Y= sha1:zyKW32c/kBrqWPrOCe9s49L1vPU= sha256:0KprhlFpCL68FUQ1fWg11AsMzbPAD3LY56yqtuzdhjc= sha1:4qoLJYc1FXjp7EWPOJ4fPj7ezoY= sha256:GGc+NhILFhon4UTqMeSflODMs3UaaZKD88cnK47OZXs= Xref: csiph.com sci.electronics.design:747295 Gerhard Hoffmann writes: > The V2 reached 100 Km, the border to space. A few Km higher is enough > for a LEO. Might have been sufficient to start it near equator instead > of Peenemünde to get another 40,000Km / 24h for free. Suborbital flight is further from orbit than you might think. Reaching 100km of altitude requires 0.98MJ/kg (100km · 9.81m/s/s), a Δv of 1.4km/s (E/m = ½v²). Mean orbital speed v ≈ √(GM/a). Earth weighs M = 5.97 × 10²⁴ kg, G = 6.67 m³/kg/s/s, and a in this case is the radius of the earth (6371km) plus our height of 100 km. This works out to 7.85km/s, a kinetic energy of 30.8MJ/kg. So, suborbital flights to the von Kármán line, as game-changing as they would have been had decent guidance systems existed in 01942, are about 18% of the way to orbit in Δv terms, or 3% of the way in energy terms. In particular, the V-2 was designed for 75%-ethanol 25%-water fuel with a cryogenic liquid-oxygen oxidizer (“Brennstoff”). Pure ethanol has 30MJ/kg, so it cannot reach orbit. Carrying the oxygen cuts that in half or more. The V-2 engines needed to be completely redesigned for more energetic rocket fuels. So trying to orbit a payload with a V-2 wouldn’t be any more effective than trying to climb a ladder to the moon. To be fair, by the end of the war, the Germans had built rockets before the end of the war that ran on various more exciting mixes like C-Stoff/T-Stoff and S-Stoff (with some reductant). Kragen