[ELI5] How do flying/floating objects ground their electronics?


How do Submarines, Planes, Ships, Spaceships, etc. Ground their electrical systems to prevent their entire surface from becoming an electrical hazard?

In: Engineering

Carefully. Stick something out in front to act like a lightning rod when approaching some other object. When they’re out by themselves, it doesn’t matter what their electrical charge is relative to other objects, as long as it can’t arc across.

It can only be an electrical hazard if there is a nearby surface at a different voltage. By connecting the device to this surface, their voltages match and thus the device is ‘grounded’.

If not, then there is no hazard.

That said, there can be issues with grounding in space. Ships, subs, and to a lesser degree planes are inherently grounded, having such extensive contact with the ocean, but satellites and the like do not. They could, in theory, build up charge.

That said, even in space, you’ve got a lot of charged particles whipping around that you could equalize your charge with.

The flying object itself becomes the “ground” or at least the “neutral” of their circuits. It may not be the same as the *actual ground* but that’s OK because nobody is going to be touching *both the ground and the aircraft* while it’s in flight, so no current can flow through them and cause harm.

The problem with an ungrounded stereo or computer in your house is you are likely to touch the ground and the electronics at the same time, so electricity could travel *through* you from the electronics to the ground.

Electricity requires a circuit to flow and a person touching something with high voltage *but nothing else* doesn’t form a complete circuit so they won’t get zapped.

So as long as the outer body, and the seats, and any touch-able parts of the electronics in an airplane are at the same voltage, nobody’s going to be hurt, even if that voltage isn’t exactly the same as the ground.

Electronics and electrical systems in airplanes are grounded via the aircraft’s exterior body. Practically all commercial airplanes are manufactured with a conductive body, such as aluminum. When an electrical phenomenon occurs that results in excess electricity being produced, the extra electricity travels outside the aircraft to its body where it’s safely dissipated. Most airplanes are also designed with static dischargers or “static wicks” that release this excess electricity into the atmosphere.

Mostly similarly to how cars do it. Those rubber tires may be touching the ground but rubber is a fantastic insulator, meanwhile it is common for the body of the car itself (or at least the frame) to act as the ground for the electronics onboard. To that end, the negative side of the battery is pretty safe as it’s the place that wants to accept electricity rather than dish it out like the positive side, and any hot-side wiring hitting the ground *should* trip overload protection such as a fuse to keep from making the body itself an electrical hazard.

I saw a video of workers doing maintenance on high tension wires that’s a good visual proof. A helicopter flies them up to the actual live wires (thousands of volts), they hang outside the helicopter with a long cabled rod tied to the helicopter chassis, then they clip on the live wire to get everything at the same potential. Then the workers get out onto the wire and start their day at work. Someone in the helicopter unclips and they fly away to pick them up later at the end of the work day.