4 ms·

Is 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

Is 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 ago
Good 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 ago
  Good, 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 ago
    Because 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.

4 ms·

Is 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

by jjoonathan 9y ago

Is 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 ago
Good 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 ago
  Good, 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 ago
    Because 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.