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In TV and movies, when a spaceship is attacked, sparks fly in a control room filled only with people, LED lights, and iPad screens.

It seems to me that sparks generally occur in high-voltage situations such as power arc-ing or heat being generated as a by-product of whatever the electrical thing is intended to do.

If I were to build a spaceship today, I'd use as much low-voltage things as I could, as it's more efficient and modular. USB is 5v and can run basically anything. 12v should be plenty for even edge cases. Especially in the future where everything is "better" and space travel is possible.

Is this a practical way to avoid sparks and make the spaceship safer?

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    $\begingroup$ "USB is 5v and can run basically anything. 12v should be plenty for even edge cases." Sorry but no. This is not true. Significant power, like the one you need to power up your computer, would melt cables if you would try to push it @12V. Simply, too high current. Or you would need much heavier cables, but heavy is not what you want when you live under the rocket equation tyranny. That said, what is tech level of your world? What are your ships attacked with? What are their defenses? Please, give us some details to work with. $\endgroup$
    – Mołot
    Commented Oct 22, 2017 at 19:38
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    $\begingroup$ @molot and brythan - thanks so much for responding, sincerely. I love this community. molot - for powering up a computer, the computer would have an onboard battery (like an iPad) and step up to higher voltages, but the lines in the walls (getting severed in the impact) would all just be USB cables. $\endgroup$
    – Ben
    Commented Oct 22, 2017 at 20:36
  • $\begingroup$ @brythan. Yeah sorry, thanks for breaking this down so well. In the future should I just bring up my question, and leave out my "arguments" or "how I got here"? $\endgroup$
    – Ben
    Commented Oct 22, 2017 at 20:39
  • $\begingroup$ electric sparks is simply the effect of ionization of air, assuming there are a lot of instruments and each runs at max 5V but the power line attached to the source must carry high current in order to distribute the electricity. So when you combine ionization of air by high current... ta-da! $\endgroup$
    – user6760
    Commented Oct 23, 2017 at 2:02
  • $\begingroup$ They don't even have seatbelts on those ships, clearly employee safety is WAY down on the priority list! $\endgroup$
    – Jason K
    Commented Oct 23, 2017 at 14:52

3 Answers 3

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The question has changed and so my answer must change

Running everything on low voltage is one way to minimize sparks, but not the only way.

  • Design as much of the infrastructure (cabinets, bulkheads, etc) out of an electrical insulator, like plastic.

  • Ground everything. This means plating the enclosure around anything electrical with grounded conducting material. This chanels the electricity away. You do this today with, for example, light switches to better protect the user. The electricity goes somewhere other than into the user.

  • Stop the power with ultra-sensitive GFCI-style breakering, such that any current flow outside what is expected for the circuit is instantly shut off.

  • Finally, realize that you can't stop all the sparks. Sparks are more than ionization of air. They're also super-heated bits of the conductor and surrounding materials. Where there's electricity, there's spark (shuffle your feet on the floor and touch your friend. Your friend might not appreciate it, but it will be very educational).


Vacuums don't run on 5V supplies for a reason.

You are incorrect that you can reduce everything's operating voltage to create a Shangri-La of non-sparking power consumption. Lighting is a good example. You can light a small space adequately with a few volts, but a large space requires hundreds, even thousands of volts, to generate the number of required photons. Remember, LEDs are very good at producing a few high-energy photons. That's why they're great for street signals and brake lights. They're (still) lousy at producing a lot of low-energy photons, which is what ambient lighting requires. Room-filling LED lights require more than 5V.

Then there's anything that requires a motor of any kind. You can dump (figuratively) all the current you want into a low-voltage motor and the torque will be so low you can stop it with your hand. More voltage, more torque, more ability to move the car, vacuum the floor, mill the metal, etc.

And that's assuming that your power distribution isn't designed to move large amounts of power around at high voltages. The reason long-distance power lines use hundreds of thousands of volts is that it minimizes power loss and the amount of wire needed to carry the amps (Power = Current(amps) x Voltage(volts)). The display on your captain's armrest may require only 5V @ 2A to operate, but all the displays and all the controls on the bridge would need 5V @ 100's or 1,000's A. Suddenly it might make sense to trunk the energy into the bridge at 10,000 volts, thereby reducing current to 0.01's to 0.001's amps and a serious reduction in wire size.

And you'd also get sparks.

And this is ignoring the fact that behind those 5V displays might be high-energy conduits to run heaters (high voltage), fans (high voltage), water and sewer pumps (high-voltage), the engines, weapons, communications, and who knows what else. The belief that everything can be dropped to 12V or 5V is egregiously wrong.


A Real-Life Example: A long time ago I worked as an engineer for Signetics Corp building communication interface chips for satellites. One chip I designed, a 32-bit buffer (basically a signal repeater), was designed with far too small a "ground plane." The ground plane is basically the sheet of metal unused electricity was dumped onto, like the white wire used in U.S. house wiring. As a result, when all 32 bits transitioned from high-to-low simultaneously, the chip experienced a catastrophic failure: literally, it exploded. I'm told the technicians had the time of their lives blowing up my first batch of chips. How many volts were used? ONE!


I've answered the question, but here's a little background to help explain it

While using water as a metaphor for electricity is highly oversimplifying, it's useful for those who don't have an engineer's background in electricity.

  • Voltage = the speed of water running through a canal.

  • Current = the amount of water running through a canal.

  • Wire = the canal.

There's only so much water you can push through a canal before it overflows. Overflowing a canal means washing out the farm and killing the farmer and his chickens, so overflowing the canal (e.g., too much current in a wire, damaging the wire with heat) is bad.

Paddle wheels are useful for doing work. Some paddlewheels are light duty, they turn a small fan to keep the chickens cool. It almost doesn't matter how much water there is because the paddle wheel is light and easy to turn. What really matters is the water's speed (voltage). Too little speed and the wheel doesn't turn and the chickens die of heat stroke. Too much speed and the grease on the axel burns away, breaking the paddle wheel (killing both the chickens and the little orphan boy who was collecting eggs). You need the correct speed to turn the wheel efficiently.

A large paddle wheel, however, needs both speed and volume. The farm's large wheel is used to turn the grinding stone for flour and, by shifting gears, runs a really neat tool that punches, drills, saws, and hammers for quick wood and metal manufacture. Like the light wheel, there needs to be the proper speed to turn the wheel, but you also need volume or the wheel just sits there getting wet.

In real life, a circuit will only use as much current as it needs, but too little voltage and the circuit fails to operate or too much voltage and the circuit burns up. See my real-life example, above.

Gearing (called a transformer in the world of electricity) allows us to compensate for what kind of water source we have. We have a big canal the entire community has access to but we want to run a light wheel at a higher speed than the large but slow moving canal can provide. So we use gears to speed the little wheel up. HOWEVER there's only so much you can do with a small but fast moving canal. Anyone who's used a garden hose to clean their driveway knows a little water at high pressure will move the dirt, often better than a lot of water at low pressure --- but you can't move a large rock that way. You need a lot of water to displace a rock. The same is basically true for electricity.

As you can see, it's not all about voltage. If it were, you could (as you suggest) simply design the circuits for lower voltage and off you go, no sparks, everybody's safe. In reality, it's all about power (P = I * V). Sometimes you can't deal with the huge wire you need for a large "I" because you want a small "V." This means increasing "V" and that means sparks.

FOR THE RECORD: all those cool Hollywood effects are for your entertainment and don't reflect reality in any way, shape, or form. They're not showering their actors with electrical sparks, they're using pyrotechnics --- better known as fireworks --- to make the moment more dramatic. When Apollo 1 shorted out, igniting the pure oxygen atmosphere of the cabin and killing the astronauts, there was one spark followed by a cascade of non-spark problems. That's how electricity works... and fails....

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Voltage is not the main consideration in electric wiring. Current and power are. If I have a computer that draws 500w, and run it at 5v, I need 100 amps. Having worked on a robot running at around 100 amps when under load, I can mention you'd need about a centimeter thick wire. That's going to weigh and cost a lot on a spaceship. Why so thick? To reduce resistance in the wire, which reduces energy loss/heat buildup, and stops it burning out under load. So for anything bigger than a laptop or desk-lamp, you're going to need higher voltages. (Power loss through resistance is only a function of current, so for the same power, higher voltages have less losses. This is why long distance powerlines are high voltages)

Also, you can get sparks from surprisingly low voltages. As a kid I had great fun making short-lived carbon arc lamps running at 12v DC.

There's another effect you should know about called ... flyback. If you have a motor happily running at 12v, and suddenly pull out the plug, the inductance in the motor coils can generate a large voltage (not because of the motors motion, but because of the coils magnetic field collapsing). How much? Depends on how fast you pulled the plug, and how big the motor is. For reference, I gave myself a nasty shock by building a poorly (self) designed motor driver for a 12v cordless drill motor. I didn't have a flyback diode, the FET was rated up to the thousands of volts (so it didn't burn out), so when PWM'ing the motor, the heatsink would go live to probably a couple hundred volts - enough to give me a nice surprise when I touched it! If you had a bigger motor, you could easily get into the kv range, even from a 12vdc supply.

Also, electricity isn't required for sparks. Electricity is required for arcs. An arc is where the air is turned into a plasma, a spark is a small glowing hot thing. You can make sparks by banging rocks together, or grinding steel on a powered grindstone. The ferrocerium in a lighter creates sparks from the power of your thumb. If you pull a piece if steel in half fast enough, you generate heat and may get some 'sparks.'

But as to why control panels in movies generate sparks when the spacecraft is hit? It's the rule of cool [insert tvtropes link]

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  • $\begingroup$ I've drawn sparks off capacitive discharges at a mere few volts DC (was probing at the back of a CPU socket on a PIII MB) $\endgroup$
    – Shalvenay
    Commented Oct 22, 2017 at 23:13
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    $\begingroup$ "Having worked on a robot running at around 100 amps when under load, I can mention you'd need about a centimeter thick wire" Assuming room temperature superconductors have not been invented in this fictional world. $\endgroup$
    – MichaelK
    Commented Oct 23, 2017 at 10:10
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The problem is that "USB is 5v and can run basically anything" today, and that statement isn't actually even close to true. USB runs 5 volts with a max of around 2 Amps for some charging setups, so max power of ~ 10 Watts, even if you bump it up to 12V your still looking at less than 100 Watts at any reasonable amperage. Most devices these days "work" on USB power by charging powerful onboard batteries over hours (which have other safety concerns). These power levels are not going to be enough power to run a powerful computer or large view screen display today and forget about holographic interfaces or supercomputers of the future.

The extreme end of this is the Star Trek route of running a plasma conduit directly to every workstation, probably overkill and it has definitely shown the dangers of running high power adjacent to where people work, but it has the flexibility and convenience of providing more than enough power to run anything the crewman might want, including high power draw items like charging a phaser, or running a replicator.

So yes you could probably go for safer low powered controls and interfaces, but there will be limits: very small display screens, limited local computing power, no charging devices, etc; and forget about any future tech, like running a holo-deck, main view screen, drive monitoring, navigation software, etc.

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