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How cheap can guidance go?
Earl Colby Pottinger wrote:
(John Carmack) : I would note that we have had quite a few issues with our electronics. Building rocket engines is easier than the mythology, but all of the issues and problems with electronics are for real -- we have had connector problems, electrical noise problems, thermal problems, vibration problems, RF interference problems, pretty much the whole spectrum of classic issues. There are a lot of mil-spec things at the component level that are a really good idea to buy -- using good tefzel wire and double crimp terminals and splices, for instance. Question, does it have to really be mil-spec or will high end commerial equipment work as well? And even if it does is the cost diffirence worth it or would you say go mil-spec always to be sure as the money savings just is not there for reliable equipment? A lot of Johns problems sound like problems resulting from bolting hardware together. At least some of the problems would go away if you designed it from the ground up. However, this probably isn't cheaper if you'r building ones. -- http://inquisitor.i.am/ | | Ian Stirling. ---------------------------+-------------------------+-------------------------- 'Where subtlety fails, we must simply make do with cream pies' -- David Brin |
#3
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How cheap can guidance go?
For a rocket, yes. Cheaper things will work for things like RC
planes, but non light based strapdown rate gyros will have acceleration biases and other issues to fret about. Some of them can be compensated for, but it is really really really nice to know that those issues just don't exist for your sensors. There are, of course, more expensive options, like RLG's (ring laser gyros), but rocket flight times are so short (relative to, say, a submarine trip) that they would be pointless for flight control. John Carmack www.armadilloaerospace.com I have a publication that I wrote on guidance and reliability issues. http://www.vtol.net/guidance.htm I don't believe wiring should be used at all. Wiring is obsolete for anything but the shortest connections. I have designed processor boards, motor driver control electronics, fiber optic links etc. After a design is complete it costs about 200 dollars for a processor board and another 300 dollars worth of parts on it. For a complete guidance system I would estimate at least 10k in addition to the cost of the FOG of which I would want to have maybe 3. Zoltan |
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