# What are the risks with massive banks of batteries/capacitors?

In redesigning a large number of my ships, I've decided that having larger ships generate enough power for FTL was too convenient and made balancing the factions varied FTL methods difficult (both for writing and game development.) To work around this, I'm moving the ships towards having large banks of capacitors/batteries that store energy for later use (FTL or other power-intensive equipment.) The ships would need to recharge off their reactors between jumps/warps.

This also presents a new weak point on many of these ships, I think.

Ships are powered by fusion reactors (plural for redundancy reasons) and store the excess power that isn't running the ship into capacitors and batteries for later use. These capacitors and batteries would likely work similar to those we have today but with advances in energy storage density. Fusion reactors have the added benefit of being the "safer" forms of nuclear power in that a runaway reaction is not possible as fuel is added on demand and to maintain the reaction. If a system fails and takes away conditions needed to maintain fusion, the reaction ceases. Contained heat and energy might disperse into the local hull, but the rest of the ship would likely survive.

Batteries would be used for taking over powering ship systems in the case of a local reactor failing while the nearest reactor transitions towards higher capacity of output to compensate.

Capacitors would be used for systems that require all of that energy in an instant: massive weapons with slow firing cycles and various FTL drives being the two primary examples.

Both of these capacitors and batteries would function much like what we have presently, only with advances in energy storage density. Batteries storing energy through chemical reactions and capacitors storing the electrons themselves.

If these ships were storing massive amounts of energy, astronomical by our standards since we are talking about faster than light travel, I could imagine damage to these banks causing a catastrophic discharge of the energy contained. Something that would likely vaporize the ship in a near instant along with anything nearby.

What would likely happen if they were struck in combat or something collided with the ship? And are there means to prevent this violent discharge, protect the ship itself from it, or redirect it away from the ship?

If it could be directed, I can imagine fleet formations being set up so that friendly vessels are never in the path of these discharges.

• So your question boils down to "What happens when a charges high capacity capacitor is damaged?" – sphennings Nov 4 '17 at 1:53
• Without knowing the technology behind these capacitors, we can't possibly know what will happen, which can range from just melting down, or explode in spectacular manner. We can't also predict what safety measure should be taken to protect the ship. – Vylix Nov 4 '17 at 2:37
• @sphennings It is a lot more complicated than that. It is 'what happens if a high capacity capacitor is discharged suddenly into a highly conductive metallic ship that is capable of creating huge magnetic fields?'. In other words, a massive emp discharge. The discharging capacitor in isolation is the least of your worries. – Justin Thyme Nov 4 '17 at 17:20
• "Don't carry aluminium ladders in the battery room" ... advice from a plain old telephone exchange with plain old lead acid batteries. – Brian Drummond Nov 5 '17 at 1:52
• (Note that electric car manufacturers have had to address this issue to a limited degree, and their research and practices might inform your case.) – Hot Licks Nov 5 '17 at 3:39

Watch this overly gratuitously destructive video of some poor normal capacitors.

Those are low-voltage low-capacitance capacitors. And they still have a decent amount of force to them.

A high-voltage high-capacitance capacitor would be, in a word, cataclysmic to anything nearby. Something powerful enough to power a FTL drive would probably completely destroy the ship it was on, regardless of size.

Modern capacitors are fairly safe from exploding via impact. The linked video was done via giving them too much power. The most likely thing would be that they simply stop working, or damage causes them to short - Releasing all of the power extremely violently in a very short period of time, as seen in this video. If it's metal that's causing the short, it will heat up and melt and cause all sorts of problems - And that's only for bare metal. Other materials, especially thing with water, will expand and explode. Woe to the poor sap that ends up being the path of least resistance for a discharging capacitor.

Having a capacitor explode is, in my thoughts as an electronics tinkerer, very unlikely. Having them cause all sorts of havoc when damaged? Totally possible.

To address fleet formations and the like - Space is huge. Absurdly huge. A "Close" formation of space ships will likely be outside of visual range, with hundreds of kilometers being absurdly close. No realistic weapon or destructive event caused by even a hypermassive ship should be large enough to make even "Close" ships blink, unless those ships are moving in to dock, perhaps for boarding or rendering aid. Still, those types of actions are likely easier done via smaller craft such as shuttles.

• Great answer, but scale up the issue. Micro-farad capacitors do not explode (unless you overcharge them, per your video)... but have you ever played with the milli-farad caps used in air conditioners, or the one-farad caps used in the power industry? They can explode when breached. Scale this to the mega-farad cap needed for a ship. But... the real threat would be a discharge into the ship's infrastructure, electrocuting the whole honking crew. Less dramatic, but much more probable. And a battery would be just as dangerous. – JBH Nov 4 '17 at 3:16
• The formations would be fairly close on that scale as this setting is being used for game development, primarily for a space fighter simulator. Having every ship outside sight range would make for poor gameplay, I think. – Arvex Nov 4 '17 at 13:04
• @Arvex Being outside sight range for aerial combat is now becoming the norm, rather than the exception. Being close enough to be see would bring you far too close to survive. See any recent fighter produced by first order military powers since the early 2000's. This would scale up when it comes to spacecraft. – GOATNine Nov 4 '17 at 15:51
• @Arvex WWI and II surface ships could fight well outside of visual range. Also, their formations were wide enough that blowing a magazine usually wasn't threatening to other ships in formation. Space is also really bad for explosions. There's no medium to transmit the shockwave, which is the most destructive part. Even super close and in visual range probably wouldn't cause any issue for a ship even if the capacitors were absurdly volatile and explosive. It'd be a bright flash and wouldn't have much threat – Andon Nov 4 '17 at 18:04
• Sorry. Answer is totally wrong. First video is not from overcharging capacitors, but from reverse charging electrolytic capacitors, Energy comes from chemical reaction, not from stored energy. Main problem is that if anything goes wrong then all energy is released (almost) instantly. Place of release depends on the kind of failure and thus is very difficult to predict (assuming the whole system is designed as failproof as feasible) and may well be outside the capacitor bank as in the second video. This might be more to the point. – ZioByte Nov 5 '17 at 10:30

There is a very big difference between how traditional batteries and capacitors store electrical energy.

In a battery, the energy is stored chemically. That is, a chemical reaction occurs which produces free electrons, available to do work. This chemical reaction takes time, meaning all of the stored energy is not immediately available to do work. In a rechargeable battery, this chemical reaction is reversible. That is, when electrical energy is put into the cell, the chemicals store this energy by changing back to their original chemical composition.

In a capacitor, it is the electrons themselves that are crammed in to a small space. They are immediately available. No chemical reaction is necessary. They are, basically, like static electricity or lightning. A huge bucket of electrons, waiting to be emptied. This bucket can be emptied all at once if the path is of low enough resistance.

The difference is sort of like storing water in a water tower, immediately available (capacitor), or like storing it in ice, available only once it is slowly melted (battery).

Thus, overall, capacitors can do much more immediate damage than can batteries. However, batteries can store a lot more power overall. There is only so many electrons you an cram into a small space. Chemicals can be stored in much greater volume.

EDIT The risk from batteries is primarily from chemical reactions (exploding gases and such) but the risk from capacitors is electrical (discharge of huge quantities of electrons). Incidentally, the videos of exploding capacitors are chemical explosions from the overheating of the chemicals in the capacitor, and not directly related to electron discharge. A video of the dangers of capacitors would be, for instance, the image of a human still in shock and catatonia several minutes after accidentally discharging a capacitor through their body. Discharging a nine volt battery across your tongue is a mild jolt. Discharging the same size capacitor across your tongue is literally a mind-blowing, mind-numbing and potentially heart-stopping seizure, and definitely not recommended. A definite 'Do not try this at home' kind of thing.

Note that I said traditional batteries.

Lithium ion batteries act a lot like a capacitor. They can store huge amounts of free electrons, available for immediate release. That makes lithium ion batteries much more dangerous than traditional batteries, and why there are so many horror stories about lithium ion batteries exploding and causing severe damage and fires. They have much more electrons available for immediate delivery.

Another safer type of electrical energy storage is the hydrogen-oxygen rechargeable fuel cell. In this storage device, hydrogen and oxygen are combined to produce water, and lots of free electrons. The water can be chemically broken down back to oxygen and hydrogen by passing electricity through it. In this case, the storage element - hydrogen and oxygen - can be stored a bit more safely in pressurized tanks. However, hydrogen still goes boom in the presence of oxygen.

So, in summary, you have a trade-off in storage techniques. The electrical energy can be more safely stored in larger amounts using chemical batteries, but it is not immediately available all at once. On the other hand, electrons can be stored directly, and available for immediate release, but much more dangerously and in smaller quantities.

• This is not addressing the question. Explaining tge difference between capacitor and battery is not what was asked, and you never mention risks or failure modes, at all. – JDługosz Nov 4 '17 at 15:16
• It would seem that it has direct relevance on the question, in terms of the safety of batteries vs capacitors. Batteries have lower risk, but lower immediate output power, due to the necessity to produce free electrons. Capacitors have higher risk, but higher immediate output power, due to the immediate availability of free electrons. It is very useful information to understand the fundamentals underlying the risks between various methods when considering the risks and hazards of each method. That addresses exactly what the OP is questioning - risk mitigation. – Justin Thyme Nov 4 '17 at 16:11
• You have everything right, but you seem to mis one crucial factor: All proposed methods, but the reversible chemical storage, have no "ignition energy threshold", so whatever (possibly huge) quantity of energy will be released in a rather short time. OTOH chemical reactants will release energy only if brought together and a (possibly minimal) amount of energy is provided. Coupled with separate and jettisonable external containers this increases safety several orders of magnitude, especially on the long run. – ZioByte Nov 5 '17 at 19:56
• @ZioByte I seem to remember something about a tank of 'reversible chemical storage' fuel for a fuel cell going boom in a very catastrophic fashion during a certain famous moon mission. – Justin Thyme Nov 6 '17 at 15:42
• @JustinThyme: the "problem" reported by Swigert was due to an Oxygen tank completely busted and had no impact beyond fact that Hydrogen without Oxygen is pretty much useless. Of course remaining without power while on course for the Moon isn't exactly "nice". If Apollo 13 would have had a super-giga-capacitor bank instead (assuming they had technology to store the same amount of energy in the same weight/space) there would have been no "problem", just a blinding flash. That episode is factual confirmation chemicals are less dangerous. – ZioByte Nov 6 '17 at 16:03

You could have your storage units blow up, or melt, or whatever you like.

But here is an idea for prevention: These energy storage units put their energy into the FTL mover - warp drive or what have you. Any energy output from them warps that battery and the surrounding area of ship a distance corresponding to the energy output.

To move the entire ship, the storage units are triggered in unison and the ship moves as a piece. If one battery triggers accidentally or via damage, it will warp off on its own, carrying its section of ship with it. Bad for whomever is in that section of the ship with the damaged battery but good for the rest of the ship, because the damaged battery moves off through warp space and is at a distance if it melts or explodes.

A ship like this would be modular with sections closed off from each other. The ship would still function with pieces missing due to battery damage. If this is for a game one could calculate exactly the damage done because that piece of ship with damaged battery would just be missing.

A damaged battery moving FTL with a piece of ship around it might whack into something, or whack into something and then explode. It would be fun to have the direction of warp be random.

The damaged battery might not blow up, and crew members who move off FTL might not be killed. They could wait in their ship section and hope for rescue. Or if that piece of ship has weapons or engines the crew might be able to do more.

This decentralized aspect of this ship means these sections could also used as escape pods - if the ship is boarded and soon to be overrun the crew could trigger each battery and adjacent unit and have them warp randomly away. Under these controlled circumstances the modules (and crew if they are lucky) might be recovered later and go back to war.

The modular ship structure will make it easy to improve and augment ships with additional modules. A badly damaged ship could hook its useful remaining modules onto another ship mid battle - salvage on the fly. It would be painful if your expensive new weapons module got the battery damaged and warped itself off into space. It would be delightful if you found a mysterious derelict weapons module adrift in space after its ship destructed - hook it on, charge it up and you are good to go (if you can read the instruction manual...).

• I had been considering that possibility as one of the factions already have modular capital ships with external hull segments that could be seen as safely distanced from the crew. – Arvex Nov 4 '17 at 12:34

Capacitors store lots of energy. All that energy desperately wants to just be at equilibrium with the rest of the universe. Normally, we make it work hard to reach that equilibrium by powering laser guns or FTL drives. But, should a short happen in the capacitor, all that energy will equalize as quickly as possible.

While the following isn't a spaceship, it's a pretty good idea of what will happen. This is a better idea of the results. Now, confine all those hot gases in a big metal tube that can't dump heat (space is a great insulator) and that spaceship is going to have a really really bad day.

# Prevention

Just like with modern warships, the powerplant is the most protected area of the ship. The citadel is the most protect portion of the ship. I see no reason why spaceships will be any different. Emergency capacitor ejection options would certainly be installed too.

You have an immediate risk with capacitors, referred to as an RCL or CL tank circuit. It is the circuit used in Taser-like devices to amplify the voltage of a battery to huge values.

A capacitor stores a great quantity of electrons, available for almost instantaneous release (the C). Coils store a great deal of electrical power in the magnetic fields around the coil windings (flux, or the L), but only while current is flowing. When the field collapses suddenly, there is a tremendous voltage induced - giga-volts potentially. Thus, in an CL circuit, the capacitor slowly accumulates the electrons as it charges. They are suddenly dumped (discharged) into the coil, building up a huge field. The capacitor then fully discharges, no longer sustaining current flow to energize the field, and the field collapses suddenly. This collapsing field produces an induced EMF that 'pushes' the electrons back into the capacitor, charging it again, but at a higher voltage. The cycle continues over and over, and with a minimal resistance (R) the charge can be kept resonating for a very long time. In a super-conductor, for years. In a Taser, this tank (as in storage tank) circuit is taped to produce a huge current flow at a very high voltage.

Here is the thing. This tank circuit resonates at a particular frequency. If just a very small voltage and current are applied at the mid-point, in each cycle, the circuit will continue to build up higher and higher current and voltages (like a small push on a swing makes it go higher and higher).

So, back to your risk factor. A spaceship has all kinds of sources of circuits that produce magnetic fields. Motors, generators, wiring throughout the ship, even the steel hull itself. If a capacitor were to suddenly discharge into the ship generally, an astronomically huge field would be instantly created surrounding the entire ship. When this field collapses just as suddenly, the voltages produced would be in the tera volt range. Read: a massive EMP discharge. It would fry and take out even the most hardened of circuits, and produce a great amount of heat everywhere instantaneously.

I can imagine the weapons systems would make extensive use of CL circuits to build up the necessary energies required to instantly discharge and fire them.

So, the trick is to keep your capacitors completely isolated electrically from the rest of the ship, so they can not somehow short and discharge into the ship's systems generally. I expect that they would probably be put in isolation pods separate from the ship by a long mast that could be instantly severed. This, coincidentally, makes them very vulnerable to attack. Alternately, they would have to be placed in a thickly electrically insulated (probably meters thick) compartment in the ship, so that sharp projectiles of metal could not pierce the capacitor and short it out into the rest of the ship.

Incidentally, this CL circuit is of great concern to automotive designers of electrical vehicles. Li ion batteries are like capacitors, and the rest of the car is like one big coil. A potentially huge CL tank circuit. Short out the battery into the metal of the car, creating an instantaneous magnetic field, and you have one enormous Taser discharge as the field collapses - substantial enough to create current flow at extremely high (kilo or mega) voltages at multiple places throughout the car. This creates sparking, arcing, and overheating conditions throughout the car instantaneously. It also presents a severe risk to fire fighters and other first responders. Water is an excellent conductor, and will discharge (short) these batteries very quickly. Insulating and isolating these batteries, and waterproofing them, is a great concern to the designers, and a major consideration in getting them approved by safety regulators.

Remember the 'flux capacitor' of 'Back to the future' fame? The CL tank circuit is it. Flux is another term for magnetic lines of force. Combine a capacitor with a flux-producing device (coil) and you can deliver unimaginable quantities of instantly available voltage and current - the gigajoules of the movie - from low voltage sources. Getting it small enough to fit in a car is the challenge.

Your problem isnt the battery getting damaged. In fact, that isnt even a big deal. The problem is one of charge and electrical field.

Did you know there is such a thing as an electrical black hole? They can theoretically exist. In fact the equation for electric is identical to gravity. We just don't have negative mass. Thats all. The only reason we dont see them in nature is because the charge would almost instantly be balanced out by the opposite charge. Consider the sheer charge. Its enough to accelerate to 3 * 10^8 meters per second. Simply put, you are dealing with energy on the level of general relativity. Your bettery doesnt need to be blown up. If it so much as has one of its plates (assuming a parallel plate battery) tilts then every negative or positive particle (proton or electron) will be instantly ripped toward the battery.

There is no defense here. If the battery is damaged you dont have an emp or an explosion. You'll have a violent implosion resulting in potential nuclear fission from protons/electrons bombarding your hull at the speed of light.

If your hull can survive that then by all means you dont need offense. Just use your batteries as a weapon.

I should also point out that charge goes both ways so your ship will also have all its electrons ripped away and flung at light speed. Once again, there is no defense.

To put it simply, encase your batteries in the hardest most defending point in your ship. If they get dented, you and the surrounding mile radius can be obliterated by what can only be deemed as a weapon of planetary destruction.

• I think it would be funnier to stick with the classical phrase "weapon of MASS destruction" – steverino Nov 5 '17 at 8:41
• A reference would be very, very useful here. I must confess I have never heard about an electrical black hole. Gravitational black holes work because there is no opposite gravitational charge to negate the pull of gravity. – Justin Thyme Nov 5 '17 at 15:35
• @JustinThyme Thats why they don't naturally occur. One could only occur if we managed to create that much charge in one spot. I.E. the charge is on the order of magnitude of the mass of a black hole. Therefore, it will have the same effect but with charge. It isnt really something needing a reference. Both charge forces and gravitational forces operate under the same equation pretty much but with different ranges and constants. As a result both can have black hole like entities. Whether they actually occur in nature is a different story. – user64742 Nov 5 '17 at 17:50
• @JustinThyme and I dont know of any reference. Im actually a Math and Computer Science major. The readon I know of this is because the professir teaching the physics class Im in (an elective) mentioned that when we were studying Coulomb's law and that such a thing can occur given the right circumstances but have never been observed due to them being unlikely to form in nature and also because they will almost instantly and violently balance out. However I could speculate that a highly enough charged battery mildly damaged might produce such an electric field. – user64742 Nov 5 '17 at 17:52
• @Typhon I always thought that they should make Professor Coulomb an honorary token in the game of Clue. 'Professor Coulomb with the capacitor in the laboratory'. – Justin Thyme Nov 5 '17 at 19:34

The main problem with direct electrical storage (capacitors), kinetic storage (flywheels) and localized chemical (batteries), when used to store huge amount of energy, is all that energy may be discharged (almost) instantly in case of disruptive failure either internal to battery pack or even external to it.

Such a failure is bound to have catastrophic consequences and is very difficult to prevent because actual place of release depends on specifics of failure.

The only (currently available or conceivable) way to limit damage is to use chemical storage with separate storage of reagents and use a reversible process, possibly in the form of power cells.

As explained in another answer to a similar question, (currently) easiest is $2 H_2 O \Leftrightarrow 2 H_2 + O_2$ which can be efficiently performed by electrolysis/fuel-cell and necessitates of three independent, separate and possibly jettisonable containers.

Note this is actually quite similar to Justin Tyme answer (which I upvoted) but it apparently didn't appear to answer question, which was about Batteries/capacitor risks and ways to prevent them.

• I did edit my answer to better clarify that I was analyzing and comparing the risk assessment of the three methods - batteries, capacitors, and fuel cells - in terms of how they function.. – Justin Thyme Nov 5 '17 at 16:24

If you have fusion, then you can pretty safely assume a couple of requisite technical capabilities.

First you have superconductors to generate the high gauss fields to contain a plasma, and second you have magnetic containment "bottles" for said plasma.

This puts you in the ballpark of having the means to store anti matter. Since you have a 100% conversion of matter to energy when hydrogen meets anti hydrogen, the only obstacle to solve for a ridiculously high gravimetric energy density is how to get the increase the density of stored anti matter.

Strictly on a speculation basis, I would propose the following solution: Your FTL drives operate continuously in one of two modes. Travel mode generates a displacement used to move the ship. This mode requires a great deal of power. Storage mode also generates a displacement field that is merely used to make a heavily curved spatial area such that the inside is a lot larger than the outside. A much smaller high gauss field can then store a large quantity of antimatter made by accelerators fed from other fusion drives. A big magnetic bottle in a small space, as it were.

So the ship makes an FTL transit and changes FTL drive to storage mode. The drop in power requirements allow for diverting power to linear accelerators. Antimatter production commences. Magnetic confinement is established to hold the antimatter contents inside the cubic antimatter box that internally is a hypercube. This should allow you to run up the metric prefixes a bit as you should be able to hit exa, zetta or yotta joule scales on storage easily.

However the whole idea is predicated on the notion that if an FTL drive can "warp" space so that FTL travel is possible; that it should also be possible to make the same effect on a much smaller field and with lower power requirements so that a large scale anti matter battery is feasible.

## Speed matters, and in space, speed differences can be astronomical.

In the mid-60s during the ramp-up of NASA's Apollo program, there was a lot of research being done on the Moon. And a lot was still unknown: what was the surface really like? Was it rocky and hard, or was it so soft & dusty that a lander's legs would sink right in?

Geologists at the time were arguing about the origin of the Moon's craters. There were two competing theories, that they were formed by meteor impacts, or that they were formed by volcanic eruptions blasting holes in the surface.

Volcanists argued that when you look closely at the Moon's surface, nearly every single crater is perfectly round. In fact, it's hard to find one that's not.

So how could it be that in the chaos of space, with meteors being flung about at all different angles, that all the craters are perfectly round? There's not a single elliptical or elongated crater shape to be found.

To learn more we had to study impact craters, and meteors sometimes hit Earth too. Like Meteor Crater in Arizona. Originally this was also thought to be caused by a volcanic explosion, a fair point since the San Francisco volcanic field is only about 40 miles away.

However, meteorite fragments had been found around the rim and basin of the crater, and the theory was proposed that this was a real meteor impact site. This led Daniel Barringer on a business venture: a crater this size (>1km across) must be caused by an equally huge meteor filled with precious metals, right?

So in 1903 Barringer's mining company, the Standard Iron Company, purchased the land with the idea that due to ~30 tons of iron meteorite fragments laying about the basin, the meteor itself must be buried somewhere under the crater floor.

Barringer spent 27 years searching, but no significant iron deposits were ever found.

Where was the giant meteor? It would take several decades before science matured enough to answer.

# $E=mc^2$ or, the equivalence of mass and energy

Einstein to the rescue!

This equation may be so familiar to most people by now that it's jaw-dropping, awe-inspiring everyday significance must be lost on you.

But take another moment right now to really let it soak in. This mind-bogglingly simple equation is telling us that energy and mass are equivalent. To put it another way, mass is energy.

(And energy has mass. If you stretched out a rubber band, and somehow were able to weigh it like that, the rubber band would weigh more while stretched out than it would at rest.)

## Speed is also energy

And in space with nothing to slow you down, objects can get thrown around at scary-fast speeds, right? Speeds so fast we usually measure them in km/s, or kilometers per second.

So what happens when a meteor already traveling at several dozen km/s gets pulled in even faster by the Moon's gravity? It literally explodes.

To put it in technical terms, the impact force is so great it breaks apart the bonds of the atoms holding the meteor together, and all that mass gets converted to energy.

Take a look at the Moon's craters again. Yes, they're all perfectly round, but that's because each time an impactor hit, it exploded like TNT. The Moon is showing scars of literal bombardment.

Why did Daniel Barringer never find his giant meteorite? Because we wouldn't discover until later that when a meteor hits at high speed, it hits with so much force that most of its mass vaporizes into energy.

# Kinetic kill weapons

The irony of weapons in space is that in space everything is a weapon.

If you have the capability to get up to orbital speed, or even faster, your vehicle itself is a weapon. If you could for example, approach the speed of light, your vehicle could easily destroy an entire planet.

You don't need bombs or warheads, any regular matter like debris or asteroids will do.

It's worth mentioning that the Chinese have already done tests like this on their own satellites. No warhead required, just a big, pointy steel rod, AKA a "kinetic kill vehicle". (Also worth noting that this test in particular did not vaporize everything, it actually scattered large pieces of debris everywhere much to the dislike of every nation with a space agency.)

## The rule of cool

To answer your question, it doesn't really matter if capacitors explode when being shot at, because everything explodes if it's going fast enough! (As long as it has mass, i.e. a projectile, not a laser weapon)

Use this to your advantage when designing, or ignore it if it's not. If this is for a game most people won't notice anyways. The reality is even tiny micro-meteorites can turn into bombs if you're traveling fast through space, leaving Moon-like craters in the hull of your ship.

(You'd need auto-targeting lasers or something to handle micro-meteorites and debris while traveling fast through interstellar space.)

Cheers!

Based on today's known science, the most efficient future technology for storing energy is superconductors. Basically, you trap energy in the circuit, with current endlessly turning around in it. This should allow much higher energy density than chemical batteries, and very fast charge time.

There are two main limits with it. One, you can only put so much energy into it before it stops superconducting. Two, the more energy you put in it, the more the circuit will try to expand, meaning that you have to brace your superconductor ring to prevent bursting.

When a superconductor ring is compromised (by the above, or because someone shot at your ship and put a hole in it) and it stops being superconductive, you now have a very strong current flowing through a not-that-conductive circuit, and the energy of said current starts being transformed into heat. At those levels, it is less like "electrical heat radiator" and more like "massive explosion with bits flying around very fast". Which may very well compromise nearby rings, causing a chain reaction, unless you put them very far away and shielded them from damage.

So the result would be ships spectacularly blowing up when their superconductive batteries are damaged.

A much more far-fetched but still not-forbidden-by-physics option (think cold fusion) is nuclear batteries, where atomic nucleus absorb gamma rays and stay in an excited state for a long time - decades for, say, Hafnium. If you could somehow goad those nuclei to release gamma ray at will, say by bathing it with the right X-ray frequency, you would get a nuclear battery of immense energy density. The problem is, no-one actually has an idea how you're supposed to do that. But hey, future-tech.

This would be much less exciting, as it would mostly act as a boring, mildly toxic heavy metal. If you want safer ships for your story, it may be a good option.

• Would it be possible to have a failsafe that directs the energy from one superconductor to the next in case of said failure? – Arvex Nov 9 '17 at 20:17
• @Arvex To some extent yes, most probably. If one element is about to overcharge or risks being damaged, there should be automated systems that will drain it of as much energy as possible - assuming other elements are available and the circuit is working (something for maintenance and damage control crew to do!). For example, if there is an explosion and a few elements are about to be shredded, the system will try and drain them before the shockwave/fragments reach them. Once a given element is compromised, though, it will probably blow up too fast for energy transfer. – Eth Nov 10 '17 at 12:16

Other answers point out that sudden capacitor discharge & other failures would be pretty catastrophic. However, I think the biggest risk would be excess heat generated in normal operation making the ship too hot for crew to survive.

Massive banks of capacitors/batteries based on existing tech would add a huge amount of weight, take up lots of space, & generate insane heat levels, all without adding any concrete advantage. Converting thermal/kinetic energy from fusion to electricity always loses some energy as heat. Same for converting electrical energy to kinetic energy.

Batteries & capacitors based on existing technology are not competitive with fusion for capacity to store energy. They have no way to be safer or more efficient at storing energy than leaving it as unreacted fusion fuel, so the battery premise doesn't make sense.

If you want something with the FTL that requires building up power reserves (with associated risks), I think you can do better than the capacitor idea. Consider going with a FTL drive that inherently requires a buildup of power (maybe a disc of unobtanium that has to be sped up until its edge reaches 0.999C, for instance?)

Since you tagged this with , let's consider one of the reasons we don't put a heck of a lot of batteries parallel of each other in the real world:

## Short circuit current

The capacity of a battery bank (in Ah) goes up linearly by each battery you place. 2 batteries is 2 times the capacity of 1. 400 batteries is 400 times the capacity of 1.

The short circuit current follows the same rule.

If a battery holds 100 Ah, discharging it at a rate of 1 C pulls 100 A from it for one hour. Discharging it twice as fast (200A/h, 2 C) can only be sustained for half an hour.

The higher the C, the higher your discharge speed, the shorter it can sustain this power. The maximum safe discharge rate of a battery is, depending on it's type, usually between 1 and 5 C.

A short circuit is only limited by the impedance of the battery itself, the object causing the short circuit and the wires connecting the battery with the object (if any).

Let's throw in a couple of estimates to get a feel for what you're trying to do:

A modern, fully charged battery of an Electric Vehicle has a voltage of around 400 Vdc and a capacity of at least 100 Ah (40 kWh). That's slightly more than for example that of a BMW i3. The short circuit current of such a battery is at least 500 Ah.

Now, I don't know how much power your FTL and weapons are going to require, but probably more than one battery can produce. Let's use another example.

The power usage of a the Enterprise-D could be at least 12.75 billion gigawatts. The exact numbers don't matter and it was a fairly large ship, but let's say at least 1 TWh is required for emergency actions. You'll probably need a lot more.

That's 25,000,000 batteries already. The short circuit current of something that powerful should be enough to vaporize your ship.

Long story short: if you do this, make sure you have measures in place to protect your batteries and their power distribution.

• Your three limitations on the short circuit current are not quite complete. Short a 12 volt lead acid automotive battery and a 12 volt zinc-carbon mini battery and the current will be very different. The cranking amps rating of a battery is a measure of the number of immediately available electrons before the chemical action has time to replace them. Alternately, it is the number of electrons the chemical reaction can sustain. The maximum current output of the battery. Basically, the short circuit current. – Justin Thyme Nov 5 '17 at 16:09
• ctd edit This diminishes as the battery drains in some (lead-acid) but stays consistent in others (Li-Ion). The battery impedance would seem to cover this (voltage divided by current) however, as the battery drains, this impedance obviously changes. A drained battery delivers less current for the same voltage, and the impedance has gone up. Thus you need to know the impedance performance characteristics over the discharge time – Justin Thyme Nov 5 '17 at 16:42
• @JustinThyme I'm aware of the shortcuts I took to prevent this answer from turning into something highly technical and 4 times it's current length. We're dealing with a highly hypothetical situation in OP's case, for all we know batteries work somewhat differently in his setting because the materials use are even more exotic. At the end though, the higher throughput the battery has, the worse the problem gets. So that isn't going to change. – Mast Nov 5 '17 at 18:22
• I would have let it go except for your reference to the science-based tag. – Justin Thyme Nov 5 '17 at 19:21

You could go the other way, and design it so it provides more protection than risks. Using a multi cell battery banks as a protective covering over the hull with the ability to switch out damaged sections means the weight of the batteries is doing two jobs - one for whatever battery storage you need and two to provide radiation and physical protection. I think I read somewhere that one of the U-boat models used that principle and where harder to kill because of it, but I can't find a reference with my quick google search.

Note I am referring to batteries which arn't a big risk when physically damaged, ie where the energy release takes some time like lead acid, rather than those that can discharge very quickly. Likewise capacitors would normally be only charged when impulse power (say a phasor style weapon) required it.

# FIRE

First, a bit of backstory:

UPS Airlines Flight 6 was a 747 traveling from a city in Germany to Dubai. There were no passengers (as it was a shipment flight, as is all the flights under UPS Airlines..), except the two pilots.

At 14:53 UTC, UPS Flight 6 departed from Dubai International. At 15:15, the a warning for fire appeared on the plane's EICAS display. The pilots were roughly 138 miles away from Dubai International. The fire had destroyed the connections from the controls to the elevators. Thick smoke rapidly filled the cockpit.

At one point, captain Douglas Lampe's oxygen mask failed. He went to get the emergency reserve oxygen supply (EROS) but fell unconscious before reaching it. This left Matthew Bell to control the plane.

Bell attempted to land at Dubai again, but was too high and passed over the airport. He then attempted to land at Sharjah airport, but turned the plane in the wrong direction.

Finally, just past 15:42 UTC, the plane crashed in an unpopulated.

The culprit? Lithium batteries.

UPS Flight 6 was carrying some 81,000 lithium batteries. The batteries caught fire through autoignition (as stated in the NTSB's final report), burned through the flame-resistant cargo lining, and went on to destroy the plane.

Lithium batteries (and many other lithium compounds) are very flammable. Battery fires have caused numerous fatal or damaging accidents, and are not easily extinguished via conventional methods.

Considering this, batteries that are capable of operating FTL systems would be a massive fire hazard. Once ignited, controlling the fire would be very challenging; this is evidenced by UPS Flight 6, where, despite fire supression systems, the fire still went on to destroy the aircraft.