[ESD] (in space) ground to earth vs. eliminating local potential difference - Page 1
Forum section: electronics / beginners

author: faekjarz
author_rank: Regular Contributor
timestamp: August 25, 2018, 12:08:59 pm
content: Hey there, enginerds!I was thinking about electrostatic discharge / ESD; what it is and how it works. I just watched a YouTube video about servers. Those servers have been decommissioned and unplugged from mains grid. The videographer touched some exposed RAM modules without wearing an ESD protection device, but he touched the metal case 1st, and therefore created equilibrium.That got me thinking. What kills / damages ICs is the discharge, the arking and sparking, caused by a potential difference. But if the handler and the handled device have reached potential equilibrium, by touching the case, there'll be no discharge / ark / spark. So, the now connected system (handler + device) still has an electrostatic charge, a potential difference to earth ground.Wouldn't that be a safe scenario, without actually being grounded to earth?I guess it's safe, until the workspace system (bench + handler + device) suddenly connects to earth ground potential, right?My point is, that grounding to mains earth is not actually necessary, as long as all parts of the whole workspace system "floats"(?) at the same potential.Right? Correct me if i'm wrong.A few more thoughts:While i was writing this post, i thought about relevance; is this actually relevant, or am i answering my questions by investing thought in order to ask said same question. Then i thought about manual satellite maintenance, where there's no way one could possibly ground to earth. I guess, it comes down to potential difference.Another question:Are EVA tethers conductive; i mean, there are two entities in non-conductive vacuum, very likely to have a differential in static charge…? …there's probably a physical contact protocol; something similar to what helicopter crews have for high voltage cable maintenance. (EVA: Extra Vehicular Activity, in space flight, satellite maintenance) I'll forward this post to Scott Manley on twitter, maybe he gets a video idea out of it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2018, 12:47:43 pm
content: Right, the only reason grounding is ever used is because of convenience and simplicity.When you have to educate a billion workers about electricity, it's a lot easier to tell them to grab a pipe (or some more abstract version thereof, like a wrist strap) and use grounded work mats, than to teach and certify each and every one about something they'll probably never fully understand anyway, and also never use again.Dunno about tethers. There can be quite large voltages generated on them (if conductive), due to induction at the great velocities crossing through Earth's magnetic field. Which in turn generates large currents, due to (I suppose) field emission, and what little gas and plasma there is out there (the mean free path in LEO is, what, a bit less than a meter, right?).Tim

author: Rerouter
author_rank: Super Contributor
timestamp: August 25, 2018, 12:56:12 pm
content: In space tethers also get interesting due to charged solar wind particles,EVA tethers generally still use a foil thermal insulation which acts as a ground wire out to the astronaut, not to mention there gloves are made out of very good insulators,Scott manly recently did a video about the gyroscopes failing in satellites, this was in effect a solar wind driven ESD event into a mechanical system, the charge caused enough current to melt parts of the metal on a bearing surface.Similar things happen to IC's, the power dissipated from the current flowing over an isolation gap generally melts both sides a little and leaves growths that extend towards the start and end point of that arc.