Being all technical and science-like in sci fi

[Ray McCarthy]

I bet that could hurt

Don't try this at home:
Magyver ... short the terminals as you throw, it might explode, in the interests of science I exploded a box of CR2032 single use lithium coin cells by stacking them and shorting them. Some of the metal (-) terminal disc flung 10m / 30' or more. Much popping and flames*. A single one shorted gets a little warm. There were single use Lithium PP3 style 9V cells on the market for a while. I thought most equipment taking PP3 would be unsafe. Also many toys are unsafe with NiMH rechargables. Though by weight less capacity than Lithium, they are MUCH lower resistance, very robust and similar capacity by volume. A shorted wire across 2 x C cells glows very bright orange, sets plastic on fire and eventually melts (a lithium cell would explode or go on fire rather than burning out the wire). Don't put Rechargeable cells in anything not designed to take them. Certainly not toys!

I love chemistry.

[* I have photos, taken from a safe distance, though no video]

 

[Nick B]

Now I'm going to be all paranoid and get rid of all rechargable battaries in my kids stuff :-(

 

[Piousflea84]

No-one is talking relativistic speeds. Hypersonic isn't that fast.
A "pulse rifle" (railgun or gaussgun) will need more than 2000J to be like an AK-47 if an AK-47 exit energy is 2KJ. You lose energy in the barrel. The electronics is also losing energy.

Yes, that's what was discussed. No current battery system or back pack generator can compete with a back pack of chemically powered shots. That's why Hafnium "batteries" were discussed. Forget capacitors except to allow continuous battery discharge to be delivered in peaks (battery internal resistance issues), they actually waste some energy.

Good luck on getting even one rifle power equivalent shot from a phone battery.


The accuracy of a conventional weapon isn't issues with the charge, an electrically powered weapon isn't any better. It's the slug, length of barrel, rifling of it and manufacturing tolerances.

You greatly underestimate the specific energy of electrochemical systems, and you greatly overestimate the specific energy of gunpowder arms.

Gunpowder and other explosives have a *MUCH* lower specific energy than fuels such as gasoline or methane. Compared to combustion, detonation is millions of times faster but doesn't release nearly as much total energy. We're talking about an order-of-magnitude difference, 3-5 MJ/kg for explosives versus 26-55 MJ/kg for petroleum products. (source: Energy density - Wikipedia, the free encyclopedia)

Modern-day nonrechargable lithium batteries are already in the same specific energy range as gunpowder, 1.8 MJ/kg according to Wikipedia and increasing all the time. However, batteries are not of primary importance for weapons because they can't discharge their energy instantaneously. For that you need a capacitor.

Modern-day capacitors have an -extremely- low energy density when compared to batteries; Wikipedia lists supercapacitors as 0.023 MJ/kg based on the product specification sheet for a commercial mass produced capacitor. However, graphene-based electrical devices have not yet reached the production phase, and they have an enormous potential for improvement over "low tech" materials such as activated carbon.

A 2013 research paper from Korea demonstrated a graphene supercapacitor with a specific energy of 0.23 MJ/kg, which is a full order of magnitude higher than existing capacitors. (link: Graphene Supercapacitors Ready for Electric Vehicle Energy Storage, Say Korean Engineers | MIT Technology Review). That's a 10-fold improvement in a very short time, and graphene technology is only in its infancy. No one knows the theoretical max of graphene, it could very well be in the gunpowder range.

Even if ultracapacitor specific energy maxes out well short of the 3-5MJ/kg gunpowder area, capacitors only need to store enough charge to fire one shot (or a few shots if you're burst firing). An electrochemical battery can be used to recharge the capacitor in between shots. Given the several-fold improvement in lithium battery technology over the past decade, it's entirely plausible for a future-tech electrochemical battery to have *equal or better* specific energy to smokeless gunpowder. Pair this with a capacitor that is only one order of magnitude inferior, and your total power-system weight is not going to be that much more than gunpowder. By getting rid of powder you'd do away with cartridge casings and make your ammunition feed simpler / lighter / more reliable.

As long as the energy efficiency of a electromagnetic system isn't too terrible (and the fact that the US Navy is installing 33MJ railguns in their next-gen ships suggests it isn't completely horrid), I believe that it's entirely real-world plausible to replace gunpowder weapons with electromagnetic projectile weapons.

It's all unlikely to happen immediately - too many rounds of technological advancement are required - but it's absolutely 100% plausible for science fiction. There is no hard scientific rule that prevents electrochemical reactions from holding as much energy as gunpowder. The pulse rifle doesn't have to perform nuclear fusion, it doesn't need relativistic speeds or million-degree temperatures, it just needs to accelerate a bullet with a similar amount of force to a couple grams of smokeless gunpowder.

 

[Mirannan]

Piousflea84 - I'd like to offer a comment on your statement about the energy density of fuels such as gasoline. It could be said that the energy density of gasoline is zero. Sounds stupid, right? But gasoline on its own (and any other fuel, for that matter) doesn't produce any energy unless you mix it with an oxidiser first - which isn't actually all that easy, because at least some of the fuel has to be vaporised (at least with the most common oxidiser, atmospheric oxygen).

This train of thought does lead to the idea, being researched currently, of BLP (binary liquid propellant) projectile weapons. The projectiles are delivered similarly to the cartridges in current weapons, while the propellant (which is similar to hypergolic rocket fuels) is delivered separately.

Further, it turns out that the casings of cartridges have a secondary function that isn't obvious. Caseless rounds for small arms have been tried, but such weapons tend to overheat. And the reason is that the waste heat from the detonation of the propellant has to go into the gun itself, whereas in conventional weapons most of the heat is dumped into the cartridge casing, which is expelled along with the heat it's absorbed. (Try picking up a freshly used spent cartridge!)

 

[Loren]

(Try picking up a freshly used spent cartridge!)

I had spent .223 brass from an adjacent shooter land on the back of my neck while lying prone and sighting my own target.

Normally, you would just slap it off like a red-hot mosquito, but I couldn't with both hands busy engaging my own target, so it just had to sizzle out on its own, which was a bit distracting.

 

[Ursa major]

Sorry to be late to the party....

Plasma is very problematic if it's charged as it will expand rapidly.

Problematic, but not necessarily to the extent of becoming a real problem. Surely it depends on how rapid that expansion is compared to the velocity imparted to the plasma, when considered in combination with how far away the intended target is.

At a handwaving level, I've tended to assume that plasma would be more associated with reaction drives** than weapons, and that the latter would tend towards using something solid as a projectile (thus maximising the kinetic energy hitting the target).


** - Because a plasma stream would naturally disperse (eventually) and so an engine*** using it would be less dangerous in use than what would, without that expansion, resemble the output of a very powerful rail gun.

*** - I'm thinking of big engines on big ships able to deliver significant accelerations, not small engines used for long periods to give, eventually, small probes reasonably high velocities.

 

[Ray McCarthy]

Surely it depends on how rapid that expansion is compared to the velocity imparted to the plasma

There is a science based article that examines this. A plasma weapon is very short range (very rapid expansion due to vacuum if in space and the charge anyway) and damage vs power in compared to anything else. A bit like a flame-thrower.

As you suggest, if the plasma is the exhaust of a multi-terawatt "torch ship" main drive, then obviously that's dangerous.

 

[Loren]

I guess I am lost a little with the way the thread has deviated and turned, but if you look at current military trends in small arms you may get a more realistic view of what works and why.

That trend has a few venues, but all use mass projectiles.

One is called the smart round or bullet. They are designed to work around obstructions where enemy forces hide by either altering the trajectory (within limits) or detonating at a predetermined point in space. For instance, if a combatant is behind a knee wall the round will detonate just above and beyond the wall.

The other advancement is in smart scopes that read distance, movement, and windage. These are tools for snipers.

The bottom line is the conventional firearm still rules and adding explosive charges to the round with the ability to program when and where they detonate.

However, it is unlikely to see the demise of the standard firearm. Electronics in weapon systems are very vulnerable and with the advent of microwave EMP weapons in the theater, there is nothing like the old reliable assault rifle.

For that reason, high tech beam weapons are not likely to rule the battlefield as a standard weapon, but as a specialized weapon. Then again, predicting the future is tricky stuff and the only thing we seem to be good at is getting those predictions wrong.

 

[Piousflea84]

There is a science based article that examines this. A plasma weapon is very short range (very rapid expansion due to vacuum if in space and the charge anyway) and damage vs power in compared to anything else. A bit like a flame-thrower.

As you suggest, if the plasma is the exhaust of a multi-terawatt "torch ship" main drive, then obviously that's dangerous.

A plasma weapon doesn't expand because of its charge, it expands due to its internal pressure and temperature. Any macroscopic-scale plasma stream has to be electrically neutral, with equal numbers of free positive charges and free electrons. If a plasma discharge was non-neutral, whoever was firing the plasma would accumulate a huge negative or positive charge... which would soon become large enough to overwhelm the accelerating potential and cause the plasma to come right back to its source. (not to mention being very harmful to the shooter)

For example, every ion thruster used in real-world spacecraft contains separate accelerating elements for positive ions and negative electrons. The resulting plasma is electrically neutral.
Electrostatic ion thruster - Wikipedia, the free encyclopedia

You're confusing plasma weapons with electron beam weapons. Electron beams are very commonly used for food sterilization and radiation therapy so their physics is well understood. Their mutually repulsive charge spreads them out very widely over a distance of a few meters, and they also create an electrical circuit between the beam and the target.

On the other hand, a plasma weapon would attempt to use some form of confined plasma, usually based on the same plasma technology used to create fusion power. Fusion plasmas are electrically neutral, with magnetic fields that simultaneously confine the positive nuclei and the associated electrons. This also means that a fusion plasma is extremely electrically conductive. Tokamaks only work because the confined fusion plasma carries an extremely strong electrical current; up to 15 megaamperes in ITER according to Wikipedia. (Tokamak - Wikipedia, the free encyclopedia)

I'd imagine that any civilization with a high prevalence of fusion power would have a much better understanding of hot-plasma magnetohydrodynamics than what we have today. It's at least partially plausible that super-advanced plasma physics could produce a free-floating plasmoid that remains stable for milliseconds... If that plasmoid is moving at a substantial percentage of c, that would give a "plasma weapon" an effective range of tens of kilometers.

 

[Tim Murray]

A plasma weapon doesn't expand because of its charge, it expands due to its internal pressure and temperature. Any macroscopic-scale plasma stream has to be electrically neutral, with equal numbers of free positive charges and free electrons. If a plasma discharge was non-neutral, whoever was firing the plasma would accumulate a huge negative or positive charge... which would soon become large enough to overwhelm the accelerating potential and cause the plasma to come right back to its source. (not to mention being very harmful to the shooter)

For example, every ion thruster used in real-world spacecraft contains separate accelerating elements for positive ions and negative electrons. The resulting plasma is electrically neutral.
Electrostatic ion thruster - Wikipedia, the free encyclopedia

You're confusing plasma weapons with electron beam weapons. Electron beams are very commonly used for food sterilization and radiation therapy so their physics is well understood. Their mutually repulsive charge spreads them out very widely over a distance of a few meters, and they also create an electrical circuit between the beam and the target.

On the other hand, a plasma weapon would attempt to use some form of confined plasma, usually based on the same plasma technology used to create fusion power. Fusion plasmas are electrically neutral, with magnetic fields that simultaneously confine the positive nuclei and the associated electrons. This also means that a fusion plasma is extremely electrically conductive. Tokamaks only work because the confined fusion plasma carries an extremely strong electrical current; up to 15 megaamperes in ITER according to Wikipedia. (Tokamak - Wikipedia, the free encyclopedia)

I'd imagine that any civilization with a high prevalence of fusion power would have a much better understanding of hot-plasma magnetohydrodynamics than what we have today. It's at least partially plausible that super-advanced plasma physics could produce a free-floating plasmoid that remains stable for milliseconds... If that plasmoid is moving at a substantial percentage of c, that would give a "plasma weapon" an effective range of tens of kilometers.

That being said, what about a plasma energy sword contained in a force field. Star war-ish type, without the cosmic mind connection?

 

[Ray McCarthy]

it expands due to its internal pressure and temperature.

Yes, of course even if neutral it expands rapidly.

Any macroscopic-scale plasma stream has to be electrically neutral, with equal numbers of free positive charges and free electrons.
If a plasma discharge was non-neutral, whoever was firing the plasma would accumulate a huge negative or positive charge...

Or you can have a separate electron beam. Certainly you accelerate the positive ions and negative electrons separately. It otherwise doesn't work!
Either the Electrons are added back at the exhaust or form a separate beam. They have to go somewhere. Adding them to the plasma works best.

In any case you can't have a laser like Plasma beam.

what about a plasma energy sword contained in a force field. Star war-ish type

Star Wars Light Sabres are magic. There is no known physical mechanism. If it was light or plasma, the "swords" would indeed cut, but would ALSO pass through each other.
Any "force field" not relying on a physical container is also pretty much magic.

 

[Nick B]

Something to keep in mind though, is that readers of sf generaly want to see advanced weaponry - even if a modicum of handwavery must take place. I certainly dont want to read about soldiers still using todays basic chemical fired hand weapons as being the height of military ingenuity, however realistic that may be. However, nor do many like totally made up stuff that has seemingly no science to back it up.

 

[psikeyhackr]

Hey everyone,

I was just wondering, concerning sci-fi flicks especially, how much do you value that a given sci-fi novel has its scientific elements founded in something plausible, or perceivable at least?

Do you think, for example, Star Trek's teleportative beams are silly? Would you grumble and shake your fist at an author who suddenly introduces a wormhole portaldevice and explains its existance with little reference to, I don't know, Einstein's theories, or makes some vague explanation of using dark matter energy, taking full advantage of our limited knowledge on the subject?

I ask because I could see myself doing all the above things. And I realize that many of my favorite franchises in the genre are also, at best, very flimsy on the scientific details. How do portals work in Portal?... Something about moonstones, right?

The transporters were not some arbitrary sci-fi device. They were a brilliant solution to a theatrical problem that Roddenberry had with the cost of producing the show. They were not just an arbitrary fantasy like light sabers.

According to The Making of Star Trek, Star Trek creator Gene Roddenberry's original plan did not include transporters, instead calling for characters to land the starship itself. However, this would have required unfeasible and unaffordable sets and model filming, as well as episode running time spent while landing, taking off, etc. The shuttlecraft was the next idea, but when filming began, the full-sized shooting model was not ready. Transporters were devised as a less expensive alternative, achieved by a simple fade-out/fade-in of the subject. Transporters first appear in the original pilot episode "The Cage". The transporter special effect, before being done using computer animation, was created by turning a slow-motion camera upside down and photographing some backlit shiny grains of aluminium powder that were dropped between the camera and a black background.[1]

Transporter (Star Trek) - Wikipedia, the free encyclopedia

If an author puts some phenomenon or technology into a story claiming to be science fiction I think the author should treat it scientifically within the context of her fictional reality. In my opinion Lois Bujold does this very well with wormholes in her story Komarr, but as far as I can tell most reviewers and readers ignore that and talk about literary and social aspects like characterization and the bad marriage.

Since the transporter technology is in the fictional universe of Star Trek then realism dictates that is has the properties of all technology like maintenance and malfunctions. So there are episodes where the transporter becomes a plot device though sometimes used stupidly. Like the TNG episode with two Rikers. Where did the energy come from to make a second body?

psik

 

[ZombieWife]

Entirely up to you - there's a whole genre to play with from soft to hard. Me, I like my sf fast and escapist.....

Excuse me, I need a quiet "alone" moment after reading this....

(grins evilly)

 

[Wanderlog]

I realize that many of my favorite franchises in the genre are also, at best, very flimsy on the scientific details.

Welcome to the club. It's obvious that authors of most impressively-looking movies never studied physics, math, astronomy, chemistry, IT sciences and so on. Their "inventions" look extremely stupid and are subjects to multiple mocking analyses that can be easily found on the Internet.

To an SF writer, the First Commandment is "Never invent specific technical details in the area where you're not a highly skilled professional." The Second Commandment is "Never concentrate on technical details of fictional technologies whether you're a pro or not. Avoid discussing them whenever possible and write about characters instead."

Sorry to be late to the party....Problematic, but not necessarily to the extent of becoming a real problem. Surely it depends on how rapid that expansion is compared to the velocity imparted to the plasma, when considered in combination with how far away the intended target is.

In addition to what has been already said, don't forget that plasma is essentially an overheated charged gas with very little mass. It not only expands rapidly, it also interacts with the environment. For example, it's not possible to shoot a plasma projectile in the atmosphere. The surrounding air would simply stop it in a matter or meters. It's like launching a jet of overheated steam from a pipe: may be effective at a very close range, but no one would seriously deploy such a weapon in a real combat. Another example, plasma can be stopped with an electromagnetic field, so it would be an extremely poor weapon against space ships that can generate such a field easily.

what about a plasma energy sword contained in a force field. Star war-ish type, without the cosmic mind connection?

A fairy tale. I like playing SWTOR, but I still can't see how a beam of light (or an electromagnetic field container, or whatever) can not only stop an incoming object made of an insulator, but to transmit the pressure of that object back to the hand that holds it as well.

Besides, the entire Jedi Universe goes down in flames with only one simple question: where are machine-guns and other rapid-fire gunpowder-based weapons? A single machine-gun can stop an entire Jedi sword-wielding infantry army. So it's no use seriously discussing the elements of its scenery - from light sabers to universal space-and-atmosphere small fighting crafts and Star Destroyers with their command bridges placed in the most vulnerable positions on the "top" of external hulls.

 

[Tim Murray]

Something to keep in mind though, is that readers of sf generaly want to see advanced weaponry - even if a modicum of handwavery must take place. I certainly dont want to read about soldiers still using todays basic chemical fired hand weapons as being the height of military ingenuity, however realistic that may be. However, nor do many like totally made up stuff that has seemingly no science to back it up.

This speaks to one of my biggest grips in modern sci fi movies, Bullets! If you have ships with hyper drives and energy weapons for ships, why are you still shooting bullets in hand held guns?

 

[Ray McCarthy]

why are you still shooting bullets in hand held guns?

Because actually unlike Light Sabres or Star Trek's Phaser, it's quite likely!
We still use tech today invented a long time ago. Sometimes there isn't a better way.

 

[Arawak]

Being technical is something I avoid since I'm horrible at it, however astronomy is important to me regardless since in my mind, when working with space, it's good to know how it's structured. Just like why in a fantasy world, knowing some geography is important. Spec wise I am confident with scaling, but when it comes to all the intricacies of a technology I tend to be as basic as possible. Instead I focus on what the tech does and its implications for society at large since admittedly, my interests always have been more in culture and social structures of future or alien civilizations than the machinations of the tech they use. Yet I care about how technology affects these civilizations, as technology plays such a huge role in how things are ran. Nuclear weapons completely changed the world by creating weapons so deadly that any full-on war with them is something no nation has yet to actually do leading to asymmetrical warfare and proxy warfare as the norm. With sci-fi, i find "what would the implications of interstellar travel be?" a very interesting question because there's just no way a civilization in the future can structure itself like today in a interstellar environment due to information delays and isolation as a result of planets being rather insular systems (when not taking into account gravity).

 

[psikeyhackr]

This speaks to one of my biggest grips in modern sci fi movies, Bullets! If you have ships with hyper drives and energy weapons for ships, why are you still shooting bullets in hand held guns?

It could be a matter of the size and weight of the energy source.

What I think should be possible is a backpack with ammunition and a computer connected to glasses built into the helmet. The gun over the shoulder tracking with the eyes for fast and accurate targeting. Soldiers having to aim with their hands should be obsolete. There should also be mini-tanks about the size of lawn tractors.

psik

 

[Ray McCarthy]

backpack with ammunition and a computer connected to glasses built into the helmet

with steerable bullets.