The physics of space battle

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Re: The physics of space battle

Post by Kackling Kobold on Mon Oct 29, 2012 1:11 pm

where did everyone else go?

did i scare them off?
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Re: The physics of space battle

Post by Loki on Mon Oct 29, 2012 3:21 pm

At the ranges we are discussing, even beam weapons still have travel time measured in seconds (or minutes if you start shooting from sizable fractions of AUs).

I've read many books (fiction or otherwise) which suggest that until you reach a distance of 2 or 3c to your target, much of the tactical maneuvering is erratic lateral shifts while advancing and attempting to predict the enemy movements enough to land hits with your own weapons. It's almost a turn-based strategy game at this point; you set your lateral movement, read your opponent as best you can to guess where to fire your cannon (of whatever type) and hope your opponent guessed wrong.

Once close enough, you more or less circle (a la Eve Online) and blast away until someone overheats (and bakes the crew) or is a frozen cloud of metallic vapour.

Any tactical frigates or fighters/bombers are much too small and maneuverable to hit with the long range weaponry and must be dealt with using point defense weaponry or your own screening ships. Missiles, l/masers, plasma projectiles, and even plain old bullets become variously viable at these ranges. This is where all the exciting stuff happens and is where most games/stories like to place the players/characters.

If someone were to come up with a faster-than-light weapon, that would be an extremely powerful advantage.

Alternately, refusing to engage on the above terms is also advantageous; sneaking in behind a large enough comet/asteroid/moon that is supposed to be there, cloaking devices, faster than light propulsion, wormholes, sabotage, etc, all improve your ability to catch the opposition unprepared (while their guns are not pointed at you).

A good example is Star Wars; the generations-old technology of the hyperdrive obviates the need for long-term sublight travel and extremely long-range weaponry, which is why we never see any in the books/movies/etc. (whether George L had come up with this-because-of-that for these specific reasons or not is a different topic that could fill a thread with a thousand comments...)
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Re: The physics of space battle

Post by Abstractness on Mon Oct 29, 2012 4:32 pm

Abstractness wrote:A hard Xaser still hits at r²/λ = 25 Gm < 1 AU. Where diameter=1m
Strange, if I look up the German Wikipedia, X-rays can have shorter wavelengths: one pikometer.
This means a hard Xaser hits at 250 Gm = 1.7 AU.
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Re: The physics of space battle

Post by DrunkenMonkey on Mon Oct 29, 2012 6:05 pm

Yes, hitting with any weapon at the AU scale is like a carrier turret versus a boosting F3X.

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Re: The physics of space battle

Post by Nightwing on Mon Oct 29, 2012 7:45 pm

DrunkenMonkey wrote:Yes, hitting with any weapon at the AU scale is like a carrier turret versus a boosting F3X.

Or a turret vs. a corkscrewing mamba under 100% boost...
I pwn those turrets...
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Re: The physics of space battle

Post by the-anger on Mon Oct 29, 2012 8:53 pm

DrunkenMonkey wrote:Yes, hitting with any weapon at the AU scale is like a carrier turret versus a boosting F3X.
well, more like hitting a fly on earth with a rifle from the moon.
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Re: The physics of space battle

Post by the-anger on Mon Oct 29, 2012 8:59 pm

Loki wrote:If someone were to come up with a faster-than-light weapon, that would be an extremely powerful advantage.

Alternately, refusing to engage on the above terms is also advantageous; sneaking in behind a large enough comet/asteroid/moon that is supposed to be there, cloaking devices, faster than light propulsion, wormholes, sabotage, etc, all improve your ability to catch the opposition unprepared (while their guns are not pointed at you).

A good example is Star Wars; the generations-old technology of the hyperdrive obviates the need for long-term sublight travel and extremely long-range weaponry, which is why we never see any in the books/movies/etc. (whether George L had come up with this-because-of-that for these specific reasons or not is a different topic that could fill a thread with a thousand comments...)
you mentioned eve, and FTL weapon... they did have that for one or two releases, and then removed the ability for obvious reasons... titans could fire their doomsday weapon (very large self-centered AoE, single-type 50k damage) through their wormhole to the other side. wormholes could span something like 5-10ly depending on class (i cant and dont want to remember).

what would be interesting is continuing the trend of self-propelling weapons - torpedoes, tomahawk missiles, ICBM's... why not strap a FTL drive to an ICBM to make it an ISBM? sounds fun...
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Re: The physics of space battle

Post by Kackling Kobold on Mon Oct 29, 2012 9:35 pm

DrunkenMonkey wrote:Yes, hitting with any weapon at the AU scale is like a carrier turret versus a boosting F3X.

no, its more like carriers shooting their own torpedos at each other, intervening fighter's be damned.

why don't we see more of this in game?
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Re: The physics of space battle

Post by Kackling Kobold on Mon Oct 29, 2012 9:57 pm

Loki wrote:If someone were to come up with a faster-than-light weapon, that would be an extremely powerful advantage.
the-anger wrote:
what would be interesting is continuing the trend of self-propelling weapons - torpedoes, tomahawk missiles, ICBM's... why not strap a FTL drive to an ICBM to make it an ISBM? sounds fun...

faster than light travel is purely theoretical if not fictional. Sure it's fun to postulate weapons based on these techs, but it's hard to know where to start from.

What kind of FTL are we talking about and what are it's limitations?
Rift drive (time/space bending that effects teleportation)
Warp drive (purely fictional suspension of physics)
Worm Hole Generators?
Jump Gates (pre-stabilized worm holes)
Hyperdrive (shift into 4th+ dimension & again, change how physics apply)

Speaking of limitations, one of the most important to consider is whether or not your FTL remains stable/ funtional in the proximity of a gravity well, & if not just how far away do you first have to travel? If you had to reach the orbit of neptune before jumping (30+ AU), for instance, strategic (long range) weapons and/ or deep orbit defense platforms become the rule. If not, they might still be plausible as "artillery"; even with ranges like those seen in star wars, a 3 AU range ICPM or mass driver fired from a mining base in the asteroid field or the moons of mars, could be a critical game changer.

Another three things that greatly define a conflict are
A) communications. Limited to the speed of light, space conflict harkens back to the wild west. If on the other hand you have ansibles or some other means of FTL comms, why not have entire fleets largely unmanned. For that matter, does your FTL even allow for transportation of organic materials?
B) Sensors. (or cloaking) just how far away can you actually detect an enemy ship? If I can't see your carrier from 1 AU, then those IPCM's I've been suggesting are relegated to planetoid bombardment; still useful, but mostly as a tool for breaking footholds on other bodies, mars or titan, for instance.
C) Symmetry. Are the enemies human? Are they relying on the same technologies? It is fairly common for sci-fi to surmise asymmetrical conflict with aliens, which seems pretty likely if conflict were to occur soon after contact.

I think limitations really are the defining factors that make a technology interesting. Often because that's what the next gen of that technology will strain against or work around.

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Re: The physics of space battle

Post by the-anger on Mon Oct 29, 2012 10:05 pm

re FTL, ive seen only one plausible method - a specific space-time metric that effectively results in FTL.

the principle is not too different from what star trek imagines...

the basic description of the metric is a very strong curvature of space-time that creates a forward gradient, accelerating the local region of space-time itself with the ship in it. there is nothing to say that space-time cannot move FTL, only that particles / matter cannot locally exceed c.

ref: http://en.wikipedia.org/wiki/Alcubierre_drive

edit - its as close to FTL as we get... current theories on this require either silly materials (negative mass matter) or don't look too useful (travel sub-light or die from hawking radiation as you approach c)
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Re: The physics of space battle

Post by Nightwing on Mon Oct 29, 2012 10:28 pm

What if we figured out a way to project a field that negates friction with surrounding celestial bodies?
Even in space, a supposed "vacuum", there are all manner of obstacles to contend with, from micrometeoroids to radiation to atomic structures.
If we could create a field that repels these particles, it is entirely possible that we could go FTL even with current rocket-based technology. Of course, barring a mechanism that negates the friction displacement field, reaction drives would be next to useless.
A workaround could be "inertial drives", which might consist of massive tubes running through the length of the ship. The tubes would have huge weights sliding through them that work by being shot or pulled to the nose of the ship before hitting a special bumper that would then transfer the momentum to the ship.
The only limitation that I can see for inertia drive would be that it wouldn't be very good at maneuvering, limiting application in fighters, but it would be great for capital ships like carriers and battle ships, which are already fairly cumbersome to maneuver.
Just a thought.
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Re: The physics of space battle

Post by the-anger on Mon Oct 29, 2012 10:46 pm

wouldnt work. inertial drive violates newtons 3rd and 1st laws.

the system as a whole (ship + all moving parts inside it) cannot accelerate without expelling energy in some way out of the system; simply sliding things around doesn't expel energy in a meaningful way.

even then, there are arguments why a rocket cannot reach c even accelerating forever... as you accelerate, your mass increases relative to the 'stationary' frame you started in. accelerating at the same rate requires more energy the faster you go, and though you will approach c in speed, your speed will asymptotically approach c very very slowly (at about 1/5 c this is very noticeable), but never reach it.

the warp-drive direction of FTL is actually less than frictionless, if there could be such a thing - the frictional force is negative, resulting in an acceleration of sorts upon contact with the 'outside' of the warp rather than a 'sticking' / 'dampening' effect.
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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 30, 2012 12:57 pm

and here I thought the notion of warp drives were silly.

so, if I understand you right, an Alcubierre drive simulates a gravity well in motion, much like the gravity well of a star moving through space. You may not be moving at all relative to the gravity well, but the gravity well itself moves as fast as you can make it?

Given that gravity wells have so much influence on one another, that might be one of those drives that functions better and better the further from other gravity wells it gets (including further from galactic center or even other ships).

Actually I think "rift drives" are based on a similar theory, just bend space time a bit further.

Worm holes may still be hypothetical, but they are theories based on the current understanding of physics. They're a "missing math" phenomena. At best they'd by problematic to use and fraught with severe pitfalls, never the less they may actually remain our best bet for FTL travel.

FTL communication on the other hand is disturbingly close to reality already, with the research I've read about positive/ negative electron spin.
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Re: The physics of space battle

Post by Abstractness on Tue Oct 30, 2012 1:03 pm

How to make a shield against masers, lasers and xasers:
If the radiation hits a smooth surface at a very flat angle, almost all radiation gets reflected. Hence a very long metal cone pointing towards the incoming radiation, reflects most of it.
Such tricks don't work anymore, if there are incoming beams from from three directions.
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Re: The physics of space battle

Post by Kackling Kobold on Tue Oct 30, 2012 1:55 pm

Interesting.

That may be the most effective way, but it's certainly not the only way to shield against them, mircowaves in particular. It also requires precognition of a precice angle of fire, but from very long ranges that may be less difficult.

That type of shielding might also leave a problem of where that radiation is going after it bounces off your point deflector, but at least it's not focused anymore, which makes less effective shielding more viable.

Aerodynamic shapes and reflective hulls would actually work admirably well as a first layer of defense against lasers as well, or maybe that's what you meant in the first place.

As an unrelated side note; Greek Mythology is annoying!
I'm having second thoughts about In Nomine.
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Re: The physics of space battle

Post by Abstractness on Tue Oct 30, 2012 7:59 pm

The cone shield has the same radius as the ship hiding behind it. The cone shield has to be much longer than its radius, so the x rays touch it in a very flat angle and get reflected instead of penetrating the shield. This only works if the surface is very smooth.
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Re: The physics of space battle

Post by Abstractness on Tue Oct 30, 2012 8:12 pm

If you send something FTL from A to B, depending on my speed, I can observe the message going infinitely fast, or going from B to A instead of going from A to B. I can not imagine how FTL communication would work, because it would be possible to send messages to your own past.
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Re: The physics of space battle

Post by the-anger on Tue Oct 30, 2012 8:33 pm

Kackling Kobold wrote:and here I thought the notion of warp drives were silly.

so, if I understand you right, an Alcubierre drive simulates a gravity well in motion, much like the gravity well of a star moving through space. You may not be moving at all relative to the gravity well, but the gravity well itself moves as fast as you can make it?

Given that gravity wells have so much influence on one another, that might be one of those drives that functions better and better the further from other gravity wells it gets (including further from galactic center or even other ships).

Actually I think "rift drives" are based on a similar theory, just bend space time a bit further.

Worm holes may still be hypothetical, but they are theories based on the current understanding of physics. They're a "missing math" phenomena. At best they'd by problematic to use and fraught with severe pitfalls, never the less they may actually remain our best bet for FTL travel.

FTL communication on the other hand is disturbingly close to reality already, with the research I've read about positive/ negative electron spin.
i havent looked into rift drives.

the Alcubierre Drive is much easier to understand using fluid dynamics as an example...

imagine space as being filled with a fluid / universal solvent. the density of this fluid is affected by gravity. lets not worry about the volume of this fluid or how it is destroyed or created, it's not relevant and will just confuse. this fluid has flow following density gradients - between a region of density X and density Y, on average, there will be a flow from X to Y proportional to how much less dense Y is than X (assuming all in the same frame of motion). flow and density gradient are virtually interchangeable in this context for this reason.

matter will obey this fluid and follow its flow without inertial effects (because the fluid represents space-time itself, and any movement caused by space-time curvature is considered free-fall, too lengthy to clarify in detail, i think you will know what i mean). the Alcubierre Drive (well, one interpretation of) works by creating a bubble around the ship within this fluid. the bubble itself is nothing topologically special, but requires exotic materials and silly energy requirements to manipulate the fluid so drastically. now imagine that this bubble is formed such that the density behind the ship, on the bubble, is made absurdly large, and the reverse is done on the front of the ship. the curvature is so extreme that it all but casually isolates the contents from anything outside the bubble.

think of the deformation as placing 2 magnets in space, fixed from eachother at a distance, with the ship in the middle; the one at the rear repels the front one, and the front one pulls on the rear magnet. in practice that wouln't do anything, but for space-time curvature, the theory goes that the bubble will experience such a drastic acceleration that the region of space-time within it will be capable of exceeding the speed of light. the bubble is considered less than frictionless by virtue that space-time doesn't really have friction against itself that we know of, coupled with the lack of restrictions on the speeds of space-time stretching / distorting.

re FTL communication, you aren't referring to entanglement by any chance are you? if so it can't be used for FTL communication (proven by information theory). i can explain why if you like, but ill have to dive into quantum mechanics, uncertainty theory and particle statistics to give a clear reason lol...
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Re: The physics of space battle

Post by the-anger on Tue Oct 30, 2012 8:43 pm

Abstractness wrote:If you send something FTL from A to B, depending on my speed, I can observe the message going infinitely fast, or going from B to A instead of going from A to B. I can not imagine how FTL communication would work, because it would be possible to send messages to your own past.
http://en.wikipedia.org/wiki/Tachyonic_antitelephone

it gets silly indeed lol...

however, a small mention is warranted here...
one research paper ive read suggests quantum teleportations are capable of backwards time travel. the results were interesting, apparently you can send something back in time if and only if it interferes constructively with itself in the past (no hope for complex objects unless exceptions are found with the use of a macro quantum object, once we can teleport a system that large to try it too). they 'teleported' photons in a way that allowed them to interact with their past selves and noted that they only had observations if both copies of the photons didn't cancel the other out of existence (destructively interfering waves). the time scale we are talking about is irrelevantly small though, but nonetheless an interesting result... if i find it ill link it here
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Re: The physics of space battle

Post by Abstractness on Wed Oct 31, 2012 6:37 am

quantum teleportation will never be used for FTL communication, because you can't control which message is sends. It sends a random message. It doesn't produce silly things like real FTL communication would.
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Re: The physics of space battle

Post by Kackling Kobold on Wed Oct 31, 2012 2:05 pm

im pretty sure i WAS talking about entanglement.

disappointing to hear.

The thing about FTL communication is that is does not involve sending a physical object, just an idea. Abandoning our century old dependence on radio waves, and using physical medium to send messages; communication only requires that we effect a change at the target location instantaneously.

My understanding of entanglement (i think) is that with two paired electrons, if one alters it's spin characteristics, so does the other, regardless of how far apart they are. The difficulty then is manipulating the spin of one of the pair.

I remember reading about advancements made in teleportation (of all things) based on this. (I never understood how they were related).

Supposedly; This teleportation only sent one molecule at a time though.

If you could safely teleport one molecule any distance, you could send fuel. More importantly, you could use the frequency with which you send fuel as a medium for communication, even if that communication is very slow (morse code any one?) it still spans one light year or more instantly without any issues with time distortion, because nothing is actually moving at FTL speeds.
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Re: The physics of space battle

Post by Kackling Kobold on Wed Oct 31, 2012 2:14 pm

On a seperate note; you make the Alcubierre Drive sound more and more like a warp drive... for which wildly different technobabble was invented several times.

I think i mostly followed you.

I had a different thought though; what if you somehow created a small stellar object (ignite jupiter?) and somehow compelled it to hurtle through space at near light speeds, then piggyback a moon (colony ship) into a safe orbit of it for the ride?

I had a question based on that scenario, but now i cant remember it.

NEED MORE COFFEE.
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Re: The physics of space battle

Post by DrunkenMonkey on Wed Oct 31, 2012 3:13 pm

You know what, I had my piece all spelled out with regards to quantum entanglement and FTL communication. But then I realized it's probably better to just show you some information from people much more qualified myself.

In particular, check out section 2.3: http://arxiv.org/ftp/quant-ph/papers/0008/0008036.pdf

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Re: The physics of space battle

Post by the-anger on Wed Oct 31, 2012 6:40 pm

skimmed that briefly, work - coffee = bad reading... delayed choice quantum eraser experiment?

re quantum mechanics, entanglement and so on, this link explains a lot in a way that most should be able to follow even without a good grasp on quantum mechanics - http://www.ipod.org.uk/reality/
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Re: The physics of space battle

Post by DrunkenMonkey on Wed Oct 31, 2012 7:34 pm

The quantum eraser, and its various offshoots, is one of the coolest things we know of, in my opinion.

Hmm, I don't see any reference in that material to the QM interpretation used. It's important to distinguish between say, the Copenhagen interpretation and the Many-Worlds interpretation. More so to someone interested in the philosophy of science, but with real implications regardless. Check them out!

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Re: The physics of space battle

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