The physics of space battle

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The physics of space battle

Post by Zhaky on Sun Oct 14, 2012 7:00 am

I overheard (read) someone the other day on this forum mention something about how the reality of space battles would be, which led me to a informations search on the matter, and I found this article on The Physics of Space Battle. I found it to be interesting reading, and thought I might as well share it with you folks, maybe get some discussion going on the matter. Like Xron mentioned:

Xron wrote:Huh... explosions don't do shite in space... we better tell WJ to drop nukes and give bombers railguns.

JK!

As it is explained in the article. Explosion is a fast expansion of gas, which in a gas-filled environment, can do tremendous damage, but in the vacuum of space it won't be more than a big fart that if strong enough might knock you out of your course, but do no real damage to you.

In the article he mentions that deflector shield isn't a reality yet, which got me to do small search on that, and the closest we get to that these days is a radiation shield made by a sort of particle-bubble. It's not quite a reality yet, as they still need to find the best way to make it work with design and power. One option mentioned wires on the outside of the ship, but I won't get more into that as I didn't quite understand it.

What are your thoughts on the matter? Do you happen to know stuff about this or know someone who do? Let's discuss the reality of space battles pirat

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Re: The physics of space battle

Post by Abstractness on Sun Oct 14, 2012 10:45 am

Instead of a cannon, I'd use a huge sling weapon powered by an electric motor, to accelerate projectiles to whatever speed I need. While accelerating, the projectile is held by a rope, flying in a spiral shaped trajectory around the ship, until it has the correct speed and direction, to be released. the rope has to be uncoiled while accelerating, so the sling can have always its optimal length. To achieve huge speed, you need a very long rope and a long time of accelerating. I think it's the most energy efficient and cheapest way to do it.
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Re: The physics of space battle

Post by Abstractness on Sun Oct 14, 2012 8:39 pm

But if I'd have enough money, I'd shoot antimatter at my enemy, its the most explosive thing there is.
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Re: The physics of space battle

Post by the-anger on Sun Oct 14, 2012 10:12 pm

in space you dont (shouldnt) have noticeable air resistance (or equivalent, space does have dust which would contribute a small amount) so virtually any form of propulsion relying on fluid dynamics and matter pressure gradients will be at best inefficient compared to electromagnetic or exotic means (alcubiere drive?).

ion drives are an existing technology, we just cant yet power the damn things in space. they are slow to accelerate but run very efficiently. they are different to the rocket only in that they expel charged particles rather than expanding gas for propulsion.

traditional firearms and autocannons should still work (expanding gas in a barrel still will provide thrust to the projectile even in a vacuum) though the combustive reaction needs to be altered to work at 4-5K and 0 pressure. this is currently in the domain of research called ultra-cold chemistry.

in a vacuum, energy weapons and the electromagnetic forces are king since particles are far less likely to interact unintentionally. lasers obviously... but then you can introduce particle blasters & cannons - these work usually on the same principle, create a magnetically sealed off containment area (think tokemack reactor or similar) that builds up charged particles (commonly a plasma) then alter the field in a way that releases the particles in a specific direction. the topology of the magnetic field for this is complex but i don't think its outside our current technology...

railguns - we haven't yet perfected the technology to make it useable in space necessarily. the biggest problem railguns will run into is wear - a railgun generates so much friction that the rails have a low fire count and ones in use today have to be regularly maintained. what is a railgun? take 2 conductive rods and place them parallel with a small distance between them, place a projectile on the 'rails' that is also conductive, then power the rails to fire the projectile. at the moment of firing, the current passing through the projectile exhibits a force that accelerates the projectile away from the power source. this also results in a very powerful magnetic pulse on the rails that acts to drive the rails apart. the force generated is relative to the energy pumped through the weapon, so railguns have an energy rating which caliber for caliber also means effective range and muzzle velocity. the magnitude of energy going into this contraption also results in a LOT of friction and heat, and all railguns in use today have to have their rails regularly maintained and replaced (from memory the service lifetime of a warship-sized railgun is about 100 firings before replacement of rails or something on that scale).

interesting note on railguns: the game Oni (look it up, retro but awesome for its time) called it a 'mercury bow'. because mercury is liquid at room temperature and still (supposedly) conductive, you could fire it out of a railgun with far less friction than a metal slug but with the same effective energy per round and force on impact. in space this may be a hard quality to come by, but hell, if you have the means to charge a capacitor bank that huge, surely you could melt down a conductive metal (that remains conductive as a liquid) and fire the molten metal along tungsten rails (tungsten has a very very high melting point, its why it is used in light bulbs as filament)?

antimatter... well, supposing you could find a way to hurl antimatter at your foes, i don't know if you could call it an explosion. matter - antimatter reactions are anihilative in nature, the only resultants are energetic photons (often gamma rays) carrying away all of the energy of the reactants. whether this will appear as a pika (an actual term) or just look like light dissolving your target i dont know, either way the result is assured - nothing will remain.
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Re: The physics of space battle

Post by Abstractness on Sun Oct 14, 2012 11:31 pm

Let's see what one gram of antimatter does when it anihilates with one gram of matter:
E=mc²= 0.002 kg*(300'000'000 m/s)² = 180 Terajoule
This means one gram of antimatter destroys two Nagasakis.

If you want to shoot naked antimatter, make sure there's not too much gas or dust in front of your ship, or else you'll blow yourself up.


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Re: The physics of space battle

Post by the-anger on Mon Oct 15, 2012 12:59 am

it would also depend on what antimatter you are producing - having a gram of positrons interact with a gram of electrons is one thing, real anti-matter (anti-hydrogen for example) is more difficult to fully annihilate with its matter-equivalent.

now im curious... supposing you are using pure anti-hydrogen-1 and are able to amass 1 gram of it, there are roughly 1.007825 grams per mole (as with regular H1). 1 gram will contain 6.022 * 1023 / 1.007825 = 5.975 * 1023 anti-H1 atoms (approx 597,538,440,701,510,678,937,316 atoms). each atom-antiatom annihilation event ought to produce 3.012 * 10-7 (0.0000003012) Joules, most of it coming from the proton-antiproton event.

for an atomic event that is actually rather energetic (about as energetic as you can get just on particle interactions) when you consider our food intake is counted in calories and kilojoules (average daily intake is approx 7000-9000 KJ) - 1 gram of antimatter reacting, on average, could 'power' the population of Australia for a day... a decent PC will nowdays soak up 1000 W easily. 1000 W = 1000 Joules / second. 180 TJ is enough to power such a PC for run for 180 Billion seconds, or roughly the time it takes for half of a chunk of carbon-12 to decay (~5,700 years). crazy stuff...
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Re: The physics of space battle

Post by Zhaky on Mon Oct 15, 2012 10:58 am

Now you're talking. I just wish I understood all that. I just see a bunch of numbers.

So guys how would this antimatter projectile work? I mean let's just pretend it was easy enough to produce, so that it would actually make sense to equip a spaceship with the technology. What amount of power would the ship need to fly with such technology, what would it need to keep it safe and not just be a flying timebomb? Other than that would there be any theoretical way to protect one self in case the enemy had the same weapon? And how would it actually affect a ship once it hits?

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Re: The physics of space battle

Post by Loki on Mon Oct 15, 2012 1:21 pm

the-anger wrote:our food intake is counted in calories and kilojoules (average daily intake is approx 7000-9000 KJ)

Off topic, but had to post; I laughed when I saw this number; the US is almost 15800 KJ on average vs 8100 KJ in Ethiopia. Global average is just under 11500 KJ (2700 calories). Many low-order life forms died to bring us this information...

We now return to your regularly scheduled thread.
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Re: The physics of space battle

Post by the-anger on Mon Oct 15, 2012 7:17 pm

Zhaky wrote:Now you're talking. I just wish I understood all that. I just see a bunch of numbers.

So guys how would this antimatter projectile work? I mean let's just pretend it was easy enough to produce, so that it would actually make sense to equip a spaceship with the technology. What amount of power would the ship need to fly with such technology, what would it need to keep it safe and not just be a flying timebomb? Other than that would there be any theoretical way to protect one self in case the enemy had the same weapon? And how would it actually affect a ship once it hits?

how to power it - i honestly dont know. until we create cold fusion i think this one is best left open ended. on that note, the amount of energy it takes to create antimatter (even one gram of it) is so excessive that as a planet we would currently need to pool resources to generate that much... but then a lot of sci-fi depicts battleships having lasers that instead could have powered planets for days at a time, go figure...

the rest of the questions are best explained by explaining just how volatile anti-matter is - it will react in contact with any normal matter. any. at all. gone. when matter comes in contact with antimatter, BOTH are annihilated and converted into pure energy (often in the form of gamma rays). the only way to shield or contain it is to physically separate it from normal matter using some kind of 'trap'. so either a force field of some kind has to be invented, or possibly a sufficiently powerful light-well (walls made of photons). the light-wall containment / shielding would work on the principle that if you could construct a quantum object sufficiently energy-dense enough and thick enough, you could prevent any tunneling through it. due to the bosonic nature of photons you could even have them moving about from all directions to ensure that no excess momentum is transferred to/from the shielding and its contents (via interacting with the field - photons moving all in one direction would cause a net acceleration).

so yeah - antimatter storage has to be powered, it reacts violently with normal matter (its too soft a word to describe it) and you shield yourself from it on principles similar to how you would store it.

as for launching it, there is a good chance you cannot easily do so (with charge-neutral AM). in that case, you could create bombs / torpedoes that carry an AM payload - detonation is as simple as turning off power to the containment field.
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Re: The physics of space battle

Post by Loki on Mon Oct 15, 2012 9:00 pm

So...here's a thought on an energy source. Helium 3, perhaps?
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Re: The physics of space battle

Post by Zhaky on Tue Oct 16, 2012 2:55 am

Thanks Anger. I guess you could make a sort of counter- flare/projectile against anitmatter?

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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 16, 2012 3:06 pm

granted explosions would have little effect in space, but you would still hear them because of the gas wave. Nukes would still... well, nuke. The emp effect alone would be enough to overload your engine shielding and *pop* no more fighter.

As for wings; apart from being a viscerally human invention, they'd be useful for descending into atmo, and more importantly, wing like structures make very efficient heat sinks, even/ especially in a void, while maintaining a low forward profile.

Aerodynamic profiles ensure minimal turbulence while crossing a dust could or gas front, such as would be present just after breaking a big rock. And by minimal i mean "might not destroy your ship," so absolutely necessary, as those gas fronts would be largely invisible. I'm not saying the gas fronts would have pressure, I'm saying that going from no particles to some particles, even in a vaccum, would hurt anything given enough speed.

About the only valid arguement that this is a remotely gas filled environment is the explosion animation when a ship is destroyed, which is very much a fluid mechanical dust billow... but oh well.

And granted Ion engines currently are only used to keep satelites in position, a certain level of advancement/ enhancement has to be allowed even for the most realistic science fiction, hence the term fiction.

Actually speed is another factor here. The speed at which these fighters move is PATHETIC. just fast enough to make a fun game, but slow enough that you could totally chalk it up to something compact & efficient, like a souped up ion engine (they're actually quite small already). Modern atmospheric fighters would cross these maps in the blink of an eye, but a) wheres the fun in that b) these fighters DO NOT have atmo to propell themselves with, hence higher speeds are just not efficient; strategic movement is what the carrier is for.

if you really do want to portray this as a air/ fluid environment, you demean our fighters into some of the most pathetic examples of "aircraft" that have ever seen warfare.

As for gun range... traditional firearmes are impossibly impractical in space, range should be limited. its a game. for one thing; our ships don't have to worry about deceleration everytime we shoot the damn things. I feel lucky.

Railguns? Railguns would have either an unmanagable kick, or a lot less damage than you think. Additionally, there are at least four different types of "railguns" not counting mass drivers; your jacob's ladder type is one of most crude & least functional, & is not the type currently in military consideration. Youre right about the low fire count, but it's not friction with the projectile that causes the wear & tear; it's the thunder of the magnetically levitated projectile parting air at relativistic speeds. If you slow down the projectile, or eliminate air, wear and tear becomes almost a non-issue.


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Re: The physics of space battle

Post by Zhaky on Tue Oct 16, 2012 3:30 pm

We're not discussing the game opposed to real life, we are discussing what it would be like in a real life space battle. As the article says, kinetic projectiles will first of all damage the other ship, and wouldn't have the same range penalty as there's no friction in space to stop it once it has been given the energy needed to push it onwards, however accelerating the projectile will also leave energy going the opposite direction (can't remember the technical term for this), which you somehow need to make up for as well, say accelerate the ship as well as the projectile to make sure the counter energy doesn't knock you back either.

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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 16, 2012 3:38 pm

the discussion started that way... at least in my other thread. Sorry for the misunderstanding.

the range problem for solid projectiles is not about them continuing on forever, it's about targeting. They go straight, but not perfectly straight out of the barrel; at speeds similar to the speed of sound, & at ranges that space battles generally should take place this actually becomes a problem pretty quickly. Your point about leaving energy going in the opposite direction was pretty much my point as well. If my engines can handle that kick, why don't i just move faster?

The main thing I can think of traditional firearms being good for in space would be shooting down traditional missiles.



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Re: The physics of space battle

Post by Zhaky on Tue Oct 16, 2012 3:49 pm

I agree on the range and direction of solid projectiles, and I mentioned ealier the use for it as a sort of counter measure towards /rockets, as you just need to breach the capsule containing the anitmatter, at a safe distance, and you're safe. If not you're pretty dead pirat

They also mentioned lasers in the article being of different power and purpose. That I found quite interesting. Say you could overheat and enemy ship in a short time resulting them in being disabled. You could blind their sensors (windows weak point in a combat space vessel, thus the need for cameras and the like), or you could slice them up with a big, energy-consuming laser.

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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 16, 2012 3:59 pm

mass drivers are one of my favorite weapons. They assume that you have some form of artificial gravity, and are limited by whatever limitations are imposed on that technology. There are always ways though.

So... a mass driver is basically just a compact gravity well, as high as you can safely muster (say 1000Gs) & then you drop what ever you want into it. A shard of metal, a brick, a piece of pummice... whatever. Effects on the target may vary considerably based on the material used... consider the tunguska incident (which was determined to be a pumice-like asteroid splashing into the atmosphere at relativistic speeds). If you have accuracy problems; load the damn thing up with a few million needles.

Projectile aside, just sweeping the muzzle of such a weapon across an enemy at short range would likely have tidal influences that would tear a ship in half, spewing guts, crew & air out the other side at about 1000Gs, barring some exotic, very high powered shielding. That shielding is actually considerably more preposterous than the weapon itself, which is part of what makes it so awesomely scary.

Say you could only muster 3 G's safely; there is no terminal velocity in space. The longer you can project this field, the higher your muzzle velocity, the closer your projectile gets to the speed of light. Even at 3G's, a muzzle sweep would flatten the crew of an unshielded enemy ship, & at the very least stress vital components however well mounted they may be.
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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 16, 2012 4:01 pm

I've also heard whacky ideas of using lasers to create a curtain of light to deflect some of the light from the local star, cutting a solar powered enemy off from solar winds.
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Re: The physics of space battle

Post by Abstractness on Wed Oct 17, 2012 3:21 pm

Kackling Kobold wrote:mass drivers are one of my favorite weapons. They assume that you have some form of artificial gravity, and are limited by whatever limitations are imposed on that technology. There are always ways though.

My space slings are much cheaper and do almost the same.
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Re: The physics of space battle

Post by Abstractness on Wed Oct 17, 2012 5:11 pm

If you have accuracy problems, I suggest to put small rocket motors on the projectile, to correct its trajectory.
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Re: The physics of space battle

Post by Abstractness on Thu Oct 18, 2012 12:50 am

Kackling Kobold wrote:I've also heard whacky ideas of using lasers to create a curtain of light to deflect some of the light from the local star, cutting a solar powered enemy off from solar winds.

I didn't know Solar wind is a usefull powersource. Or do you just mean Sunlight ?
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Re: The physics of space battle

Post by Kackling Kobold on Thu Oct 18, 2012 8:56 pm

Light alone is a shadow of the power there to harness. Solar winds carry radiation; & the movement of it can cause a very significant static charge. lots and lots of power to harness, you just collect it a little differently, to say nothing of the heat that radiation carries.


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Re: The physics of space battle

Post by Kackling Kobold on Thu Oct 18, 2012 9:10 pm

Abstractness wrote:Instead of a cannon, I'd use a huge sling weapon powered by an electric motor, to accelerate projectiles to whatever speed I need. While accelerating, the projectile is held by a rope, flying in a spiral shaped trajectory around the ship, until it has the correct speed and direction, to be released. the rope has to be uncoiled while accelerating, so the sling can have always its optimal length. To achieve huge speed, you need a very long rope and a long time of accelerating. I think it's the most energy efficient and cheapest way to do it.

your sling idea is problematic at best. By turning the sling, you also turn the ship in the opposite direction, affecting everything inside. You're giving the sling stone a slight mechanical advantage though, so it will effect the ship more than a closer weight with the same turn. The mechanical advantage might not be enough to make a serious difference, but you also have to consider the effects on the ship of pulling the sling stone back around. The stone and the ship would be spinning around a space somewhere between them, depending on the balance. You could still manage it by having a spinning counterweight on the ship, but the weight & speed of the counterweight would have to be prohibitively huge for a large projectile to reach "muzzle velocities" that would compare even to old fashioned gunpowder, in a time that would be considered combat feasible. At this point you're talking about a huge about of electricity; how are you generating all that?

you could, however, slingshot siege projectiles around a planet's gravity well.

actually, your idea gave me a different one; a self counter balancing double flywheel projectile weapon; but you're still looking at either very very low muzzle velocities, or ridiculous electricity consumption.


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Re: The physics of space battle

Post by Kackling Kobold on Thu Oct 18, 2012 9:18 pm

Abstractness wrote:
Kackling Kobold wrote:mass drivers are one of my favorite weapons. They assume that you have some form of artificial gravity, and are limited by whatever limitations are imposed on that technology. There are always ways though.

My space slings are much cheaper and do almost the same.

well, that really depends on the limitations of your artificial gravity technology. If the best you can generate is .5 Gs, your slings are possibly superior barring the creation of a mind bendingly ginormous gravity track (a muzzle longer than africa). If you can generate 1000 G's or more, the electric motor needed to make your sling come even close to comparing is more ridiculous a stretch than the artificial gravity tech, and the influence of the sling on it's ship would be similarly impossible to deal with, not to mention the electicity consumption, yet again.

It just occured to me though, there's little reason your sling weapon has to be attached to a ship activating it, particularly if it used a laser or microwave relay to power it's motor.
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Re: The physics of space battle

Post by Kackling Kobold on Thu Oct 18, 2012 9:28 pm

oh yes, and theres virtually no way to release a sling projectile that doesn't put spin of the projectile, which bars any possibility of guidance or trajectory adjustment, & makes proximity warheads difficult as well.

A light G mass driver would not have those issues, while a heavy G massdriver would have projectiles significantly close to the speed of light.
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Re: The physics of space battle

Post by Kackling Kobold on Thu Oct 18, 2012 9:29 pm

Ion and plasma weapons are fascinatingly close to being reality, but I'm not quite up to explaining exactly how.
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