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I remember when astronomers started using lasers for distortion canceling. A buddy of mine had been working on spy sats for a decade and said the government wa
by gozur88 9y ago
I remember when astronomers started using lasers for distortion canceling. A buddy of mine had been working on spy sats for a decade and said the government was using the same technology (though in the other direction) when he arrived.
- dogma1138 9y agoAdaptive optics came from the military this wasn’t a secret. Hubble was built on a spy satellite bus. Military gets the shiny toys first the reason why we have such great gyro sensors today in phones is because solid state sensors were first developed for guided missiles.
- jjoonathan 9y agoRLGs are in phones? I thought phone gyros were all still MEMS, hence the awful drift.
- dogma1138 9y agoMEMS are replacing FOGs in many applications, Fiber Optic Gyros are the low cost version of RLGs. MEMS gyros are used in military INSs today can’t say if in missiles but in guided mortar shells and field artillery for sure.
- jjoonathan 9y agoIs that because MEMS is cheap (TCO, not BOM) and good enough or is it because MEMS is better? It's obviously not as good at drift, but I'm sure there are other dimensions of performance.
- dogma1138 9y agoGood enough MEMS aren’t good as laser ring gyros, a single sensor isn’t even good as fiber optics but multiple sensors with per sensor drift bias taken into account is good enough. You can’t strap a 150,000 INS on every shell you can’t even strap a 30,000 FOG INS on a shell. Basically since we now want INS and GPS on every bloody field equipment and anything above a 20mm grenade should be guided muinitions you have to make some compromises. And MEMS aren’t that bad yes they drift but for their usecases the drift is negligible.
- jjoonathan 9y agoGood, we're on the same page. Any chance you know what's holding up integration of RLGs? I'd have thought they would be a natural fit for a cheap silicon implementation.
- dogma1138 9y agoBecause RLGs are still spin gyros the dithering motor has to spin and spin pretty darn fast (to prevent lock-in) which prevents miniaturization. MEMS operate on vibration which can be induced with solid state ultrasonics. Also since most navigation systems today are hybrid drift isn’t much of an issue over long distances anymore and for short distance applications it doesn’t matter. MEMS are much smaller, FOGS can also be made smaller especially considering you can use a single external laser injector to feed multiple sensors. So while RLGS are still probably the most accurate production gyro we can make there are technical issues on making them smaller and since we have alternatives there isn’t likely much reason to invest in miniturizing them further if it’s even possible. This is at least my educated guess.