tag:blogger.com,1999:blog-6568915967186844196.post2687292467046653823..comments2024-03-26T14:19:33.332-07:00Comments on Bench Grass: Postblogging 1939, July, 1, Technical Appendix: The Sky's the LimitErik Lundhttp://www.blogger.com/profile/05728486209757153685noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-6568915967186844196.post-12666390450629546042013-08-19T10:38:47.804-07:002013-08-19T10:38:47.804-07:00Next time I take a volume of the MIT Radar Handboo...Next time I take a volume of the <i>MIT Radar Handbook</i> out, I'm going to have to get myself some cheap, blue vodka to go with it. Erik Lundhttps://www.blogger.com/profile/05728486209757153685noreply@blogger.comtag:blogger.com,1999:blog-6568915967186844196.post-58678739840632114812013-08-19T09:11:00.643-07:002013-08-19T09:11:00.643-07:00A bit more Chertovblogging; the Soviets had a poli...A bit more Chertovblogging; the Soviets had a political split about it! Moiseyev at the Air Force Academy, Zhukovsky has his theory of technical stability, and the support of the powers that be, but unfortunately this doesn't actually work! Whereas the NII-88..then NII-885...then Korolev's OKB-1 (not the earlier OKB-1, the other one) gang have been reading this stuff from MIT! Which does work, but is heretical! Fortunately everyone involved is Jewish and therefore already banned from becoming too prominent, so nobody got shot in the head!<br /><br />Also, the aviation industry people discover that the artillery industry insists on technical drawings being detailed enough that series production can go ahead without ever consulting the original design team, while the aviation people tend to both change everything all the time, and also to rely on craftsmen sucking their teeth and if-it-looks-right-it-is-right a lot.<br /><br />And they keep drinking the rocket fuel. 70% ethanol coloured blue with manganese crystals.Alexhttps://www.blogger.com/profile/17153530634675543954noreply@blogger.comtag:blogger.com,1999:blog-6568915967186844196.post-359312877589206682013-08-14T12:15:00.536-07:002013-08-14T12:15:00.536-07:00The whole "control systems theory" thing...The whole "control systems theory" thing of the late 40s is so weird. You go into it with the basic problem that feedbacks are mucking up the partial differential equation that is supposed to describe the induced stable state.<br /><br />Or, as a simple analogy, the automatic steering device takes a heading from the compass. When a wave wacks the rudder, a little motor pushes it back to the proper heading. The force being proportional to the whack. Which is code for the simple harmonic equation, one of three partial differential equations that we know how to solve analytically.<br /><br />So, when feedback gets in there, suddenly we can't solve the system analytically. We fall back on numerical solutions. This is pretty well developed field of applied math, and has as its mechanical or electrical analog the insertion of other circuit elements, mostly resistors, into the loop.<br /><br />So we're doing math to figure out how big the resistor should be. It's approximate and iterative. The more calculations we do, the better the fit. So we say to ourselves, "Hey, why don't we automate this calculation?" We end up with a simulation of the original system that runs again and again, each time with a resistor-analogue element set to a different value. <br /><br />Vannnevar Bush built one of these in the 30s, to simulate the long-distance transmission lines bringing hydroelectric power down to New York. But there's not many problems that justify building a simulation. And it's just a math problem! So why not build a universal simulator?<br /><br />Okay, sure, 'universal simulator.' Impossible, but a cool idea. But wait! We're already in the realm of approximation here. One way of looking at the math is as just a series of executable instructions: yes/no. And there's these gadgets around that do that....<br /><br />The upshot is that the problem of solving complex analog problems leads to the widespread use of digital devices. Somehow, we went into it as systems engineers and came out of it as computer scientists. Erik Lundhttps://www.blogger.com/profile/05728486209757153685noreply@blogger.comtag:blogger.com,1999:blog-6568915967186844196.post-32825825910431325962013-08-14T01:51:36.111-07:002013-08-14T01:51:36.111-07:00You're going to love Boris Chertok's memoi...You're going to love Boris Chertok's memoir of the Soviet space programme, Rockets and People. All four volumes of it! and completely free from the NASA History Project.<br /><br />Especially as a major theme is how Chertok became a cybernetics/control systems engineer without ever intending to do so, and how the controls guys ended up heading the effort to reconstruct the V2 and exploit the German industry behind it because a) nobody else realised space rockets/missiles were a thing rather than engines, warheads, fuel, or controls separately and b) there wasn't a People's Commissariat of Control Systems, so unlike everyone else from the Ministry of Aviation, the Armaments Commission, the Artillery Corps, the Guards Rocket Mortar Force, the NKVD, SMERSH, and the People's State Commission of Applied Tree Climbing, his gang were able to make it up as they went along rather than referring to Berlin or Moscow, by sheer <em>Amtsanmaßung</em> and cheek.<br /><br />Also, big priority: lay hands on some of those schweeet German kreiselgeräte and messtechnik of all kinds, making good and goddamn sure someone you trust implicitly personally delivers it all to your lab back in Moscow...Alexhttps://www.blogger.com/profile/17153530634675543954noreply@blogger.com