The Question thread

Blackwing
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Re: The Question thread

Post by Blackwing »

Erhm... Nooooooooooo.

Why not?

Because the equal reaction of momentum of the 'launcher' is reflected back on the magnetic field, not the gun that generates it. Essentially, the magnetic field 'cushions' the momentum for the gun.

The only way you'd get recoil is if you were stupid enough to build the non-magnet parts of the gun out of steel or some other ferromagnetic material. And even then the recoil wouldn't be that large (only the effect of the now magnetized bullet pulling on the gun).

Your example references a permanent magnet, but a copper or super-conductor electro-magnet is only magnetic as long as it's got electricity running through it.

Essentially, a Coilgun has no or very little recoil for the same reason a recoilless rifle has no recoil: The projectile is propelled by forces that do not act directly upon the barrel itself, the barrel is only there to guide the projectile.

Hell the only reason why an 'electro-slide' coilgun (that's my personal description of a coilgun that suspends the bullet in electromagnetic fields) even needs a genuine barrel is to protect the electromagnets from the bullet if one of them malfunctions (thus sending the bullet off course).

Recoil in a gunpowder weapon comes not from the force of the bullet leaving the gun, but from the force of the exploding gunpowder pushing in all directions, the barrel keeps it from going in all directions except on: the direction of the bullet.
It's the explosion of the gunpoweder and subsequently expelled gasses, not the movement of the bullet, that is the 'action' that causes the opposite and equal reaction.
That's why recoilless rifles are (nearly) recoilless: the rocket-propellant is able to leave the barrel without hindrance.
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Re: The Question thread

Post by Artemis »

Okay, can we all agree that a coilgun can be fired by a person? If the answer is yes, then let's nip this argument in the bud, or at least continue it elsewhere.
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Re: The Question thread

Post by Booted Vulture »

Blackwing, just where to think the momentum is going to go? It's not acting on the barrel, it'd act on the coils but the gun as a whole would still kick.
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Re: The Question thread

Post by Artemis »

Regarding laser protection, what about some sort of armor device that absorbs the heat from the laser and then instantly radiates it into the air? Obviously this couldn't be worn against skin, so what if it were a kind of plating worn over your basic combat gear? I have no idea how something like that might work, but if we can't reflect lasers, this is really the only way to protect against them, it seems.
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Re: The Question thread

Post by Siege »

Blackwing wrote:Because the equal reaction of momentum of the 'launcher' is reflected back on the magnetic field, not the gun that generates it. Essentially, the magnetic field 'cushions' the momentum for the gun.
No it doesn't. Any momentum imparted to the magnetic field will be transferred from the field into whatever is generating it, just like the successive fields impart momentum onto any ferrogmagnetic projectile passing through them. It's a two way street and there's no way around the Third Law. The momentum has to go somewhere, it can't simply disappear. Sooner or later the equal and opposite force is going to act on whatever platform is generating it.
Artemis wrote:Okay, can we all agree that a coilgun can be fired by a person? If the answer is yes, then let's nip this argument in the bud, or at least continue it elsewhere.
That would depend entirely on the size of the projectile and the velocity generated by the magnetic field. The greater those two factors, the less likely it will be for any person to be able to wield the coilgun without risk of serious injury.
I have no idea how something like that might work, but if we can't reflect lasers, this is really the only way to protect against them, it seems.
A suit with a layer of gel that is extremely good at absorbing heat might be a good idea. That way the energy imparted by the laser will be absorbed rather than deflected. I still think however that lasers will do a pretty nasty number on most people that get hit with them.

(Then again they have drawbacks on the battlefield too- like the massive heat signature generated by them, or the batteries you'd have to carry around, or the cooling issues you'd be faced with.)
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Re: The Question thread

Post by Destructionator »

Artemis wrote:Okay, can we all agree that a coilgun can be fired by a person? If the answer is yes, then let's nip this argument in the bud, or at least continue it elsewhere.
Yes, it can be. I just edited in a few more calculations, based on the M16, in my previous post if you are interested in the math. The calculations and thus the numbers would be exactly the same for a coilgun firing a similar bullet.

The coilgun might be slightly heavier, but not so much to be unusable (WW2 era US Army rifles weighed 25% more than the M16 and were obviously handled by soldiers. The coilgun shouldn't weigh much more than that.)
Artemis wrote:Regarding laser protection, what about some sort of armor device that absorbs the heat from the laser and then instantly radiates it into the air?
Medieval plate armor!

Rather seriously, metal plates, with some insulation on the inside to keep from burning the wearer, should do fairly well. Some kind of wet suit probably would too: use a little layer of water to absorb the heat and let it evaporate and fly off before it gets to you.

A high tech ceramic or maybe a fabric might do even better.
Obviously this couldn't be worn against skin, so what if it were a kind of plating worn over your basic combat gear?
Aye.

In Stargate SG-1, they added a plate of some sort inside the team's vests (between the fabric layers) which was a heat conductor to spread out a staff weapon blast over the whole back, where it might burn the skin (and surely hurt like hell if the insulation isn't good enough) but not kill. You'd want to do something similar to defend against lasers.
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Re: The Question thread

Post by Siege »

Hrmm, wouldn't that stuff they use for ceramic tiles on the Space Shuttle make a rather good heat deflection material? Obviously it can take quite a bit of stress and heat without disintegrating...
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Re: The Question thread

Post by Destructionator »

SiegeTank wrote:Hrmm, wouldn't that stuff they use for ceramic tiles on the Space Shuttle make a rather good heat deflection material? Obviously it can take quite a bit of stress and heat without disintegrating...
Probably. I'm not sure though. They are designed to work against hot gases outside, which is a slightly different beast than intense light hitting it - the hot atmosphere would be spread out all over it and doesn't necessarily conduct the heat super well, whereas the laser's danger is in its concentration and directness.

Here's a fun anecdote: a former science teacher of mine has one of those tiles. There was one time he took a blowtorch in one hand and held that tile in his other hand and roasted it. He says he couldn't even feel the heat through that tile. Really cool.

But yeah, they do definitely survive getting very hot without hurting the stuff inside, so there is certainly promise in that direction even if that specific design doesn't work out perfectly.
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Re: The Question thread

Post by Destructionator »

Who wants to get started on some story stuff? With my new alien species I have a wee bit more worldbuilding I can (and soon will) do, but I think its about time to move on to the story lines. It looks like most of us have an idea of what we want to do.

Do we want to do a single collaborative story thread rpg style (surely with side and back stories of course, perhaps in their own threads?) or just single authors writing their own stories that will form the greater whole?

I have a basic plotline for my guys ready to run either way; if someone else is my 'invaders', cool, and if not, I'll invent a new little polity for them (a minor member power of one of the big alliances) and write it myself. The latter might just be easier (I can accelerate the timeline a lot), well, easier for me anyway - you poor readers will have to suffer through twice as much of my shitty writing! :P

Seriously, I say anyone with a story in mind, either internal to their own polity or interacting with someone else, should feel free to start a thread and go.

If a story starts out single author and someone wants to jump in and write a chapter of international fun, I think we ought to go for it. This should of course be at the discresion of the authors involved, but think how much fun it would be if any random short story could turn into a side rpg!
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Re: The Question thread

Post by Blackwing »

*Bashes head against wall*

Everything I know about physics tells me that a non-contact coilgun (i.e. a coilgun that does not make contact with the bullet) should not have any noticeable recoil, because as far as I know Newton's Third Law doesn't enter into it, specifically because the law of Conservation of Energy does.

The reason for this being that it is a fact that in a gunpowder weapon, neither the bullet nor the gun enact any force upon each other (besides friction), you can test this if you like: put a bullet minus the nitrocellulose in a gun, pull the trigger... does the bullet fly off?

All the energy in the firing of a bullet comes from the gunpowder. The bullet leaving the gun with momentum n and the gun having a recoil with a momentum of n in the opposite direction are both equal and opposite reactions to the gunpowder transferring energy to both the bullet and the gun.

Now in physics as I understand it, in a coil gun that doesn't make contact with the bullet, the only transfer of energy SHOULD be between the magnetic field and the bullet. The conservation of Energy then dictates that energy cannot spontaneously come into existence. If there is no physical way of transferring kinetic energy (back) from the bullet to the weapon and the electromagnet only works on the bullet, not on the gun (and it shouldn't) then there simply is no energy for there to be recoil.

And all over the net there's plenty of claims that coilguns supposedly have 'massive' recoil, but at the same time, youtube has plenty of movies of coilguns and in only two is there any recoil. In both cases the poster of that video was actively trying to prove that coilguns have recoil and in both cases the supposed recoil of the gun was a result of the bullet hitting the coilgun itself and knocking it around.

Anyway, I'm at a loss. I simply do not have enough data to determine what's correct in this case.
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Re: The Question thread

Post by Destructionator »

Both conservation of energy and conservation of momentum (Newton's third law) are universal. Both always apply in all cases - satisfying just one isn't good enough.

What happens in the coilgun is very simple. The electricity moving through the coils magnetizes the coil, which attracts the bullet to them (or repels it away, in some designs). The coil right in front of the bullet is turned on, pulling it forward, then it turns off as soon as the bullet passes to avoid bulling it back, thus the bullet flies forward.

And while the magnet is turned on, the bullet attracts the coils right back to it - they are attracted to each other, just like the permanent magnet and piece of steel you can hold in your hand.

The attraction goes both ways, so it accelerates the bullet forward and the coil backward. The coil, being attached to the gun by straps or screws or whatever, also tugs the gun backward.

That's really all it comes down to.

The kinetic energy of both the gun and the bullet comes from the electricity running through the coils, just like how the kinetic energy of the gun and bullet in the M16 comes from the gunpowder inside.

Now in physics as I understand it, in a coil gun that doesn't make contact with the bullet, the only transfer of energy SHOULD be between the magnetic field and the bullet.
The magnetic field doesn't physically exist. It is just a mathematical representation of the attractive and repulsive force between two magnetic objects at various distances.

The attraction is always between the two physical objects, and it is always mutual. The field just "carries" the force between them.
And all over the net there's plenty of claims that coilguns supposedly have 'massive' recoil, but at the same time, youtube has plenty of movies of coilguns and in only two is there any recoil.
All of them would have the recoil, you just might not be able to see it. There is no reason for it to always be 'massive' - if it is firing a little bullet at a slow speed, the recoil wouldn't be very great. If the coilgun is strapped to something massive (like a table) or held by a strong person, the acceleration simply wouldn't be noticeable in the video.

You can try it at home with a refrigerator magnet and a metal object. You'll feel the force in both hands. True, if you turned off the magnet, you wouldn't feel the pull anymore, but of course, neither would the metal object / bullet - it would sit still. You wouldn't expect to feel recoil when not firing the weapon!


edit: Also look up electric rockets. You'll notice that using magnets and coilguns to accelerate rockets is a real concept - something that would be impossible if there was no reaction force on the gun.
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Re: The Question thread

Post by Heretic »

I think I asked the question on whether we could make stories or rpg. Anyway, I am making on already on my Duban, alongside making an American-ish polity heavily inspired by Fallout 3 (damn that game is addicting).

Also, what happened to the old United States of America?
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Re: The Question thread

Post by Blackwing »

Yeah, sorry, it seems the mistake I made was assuming that since the magnet is 'larger' than the bullet and therefore has a great deal more attraction on the bullet than vice versa, there shouldn't be any recoil because the bullet only gains energy (momentum), but doesn't impart it.
Which essentially led me to assume (and I still think this is the case) that as long as the 'apparent' mass of the magnet is larger than that of the bullet there should be very little recoil.

Essentially, in a E=M*V type arrangement, the M of the bullet (Mb) is stable. The apparent M of the magnet (Mma) is variable based on the amount of electrical energy going through the elecro-magnet, though the actual mass of the magnet (Mm) is also stable.

So we arrive at the following conclusion:

Em = Mma * Vm
Eb = Mb * V

Now the bullet starts moving when Eb < Em and it leaves the barrel when Eb > Em

So if we take a bullet that weighs '1', we want it to reach a V of 100 and we apply enough energy to the magnet to reach Mma 100, the following will hold (and I'll stop making the little letters after the big letters smaller here for a sec):

Em = Mma * Vm = 100 * Vm
Eb = Mb * Vb = 1 * 100

In this example Vm = 1.

The amount of electricity needed to give the magnet an Mma of 100 is a very complicated calculation based in part on the mass of the magnet and it's conductivity and suchlike, but it doesn't really matter.

Since the M of the bullet is stable and it's V is equal to the apparent M of the Electromagnet, the V of the electromagnet is always equal to the mass of the bullet. Since the M of the gun in total is even larger than the bullet, the total V of the gun is further reduced by however much heavier the gun is than the bullet. The M of the soldier holding it is, again larger than the M of the gun (or at least let's hope so) so the V is further reduced.

The more power you feed into the magnet, the further up the Mma and subsequent V of the bullet go, but the M of the bullet stays the same, so the recoil stays the same too.

To summarize:
The speed of the bullet should not matter for the recoil of the Coil gun, because speed in a Coil gun is generated by how much harder the electromagnet pulls on the bullet than vice versa. And since the weight of the bullet remains the same, recoil technically shouldn't increase.

Now, if the actual weight of the magnet/gun (Mm) is equal to or smaller than the weight of the bullet then the magnet will be propelled at a V equal to or larger than the M of the bullet (one meter per second if the bullet and magnet are of equal weight). This is what happens in the one genuine example of coilgun recoil on youtube (which you can see from the fact that even though the bullet is heavier than the coil gun, the bullet still has more velocity since it's propelled by the Mma of the magnet, while the coilgun itself is only propelled by the weight difference between Mb and Mm.

So yes, some recoil, but unlike a gunpowder weapon, only related to bullet weight and nearly unrelated to bullet speed.

Unless there's a mistake in my calculations, which possible, in which case please point it out.

Ps. I know that the pull of the magnet isn't technically mass, but in the case of magnetic attraction, it does act like mass.
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Re: The Question thread

Post by Destructionator »

Heretic wrote:I think I asked the question on whether we could make stories or rpg.
Aye, but it looks like it got lost in the other discussion, so I asked again. Though we do have an answer: Artemis is leading by example!
Also, what happened to the old United States of America?
Given how far humanity has spread out, it must be pretty far in the future. Nations we know in the real world right now are all probably long gone.
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Re: The Question thread

Post by Destructionator »

Blackwing wrote:Yeah, sorry, it seems the mistake I made was assuming that since the magnet is 'larger' than the bullet and therefore has a great deal more attraction on the bullet than vice versa, there shouldn't be any recoil because the bullet only gains energy (momentum)
Stop right there - energy and momentum aren't the same thing. Both are conserved, but are very different animals. Momentum is something only an object with mass (or photons, thanks Einstein) can have, whereas energy comes in all kinds of types.

Something important to separate them is momentum has direction. You can create forward momentum as long as you also create backward momentum at the same time. That way, the total still adds up to zero, so you haven't changed the sum in the universe. Can't do that with energy (well, some weird quantum stuff sort of can, but unlike momentum, you can't see this in everyday objects).
Which essentially led me to assume (and I still think this is the case) that as long as the 'apparent' mass of the magnet is larger than that of the bullet there should be very little recoil.
Here, you're again combining two separate concepts into one. The 'apparent mass' you're thinking of is the strength of the magnet. It doesn't act like mass at all. (Unless you are comparing it to gravity, in which case the force formula is similar, but that's the extent of the similarity.) This affects the strength of the magnetic force, but isn't substitutable for regular mass when doing acceleration and velocity calculations.

Regular mass determines how much something accelerates with a given force, and, when combined with velocity, how much momentum it has.

The magnet's strength and its mass are independent. You can have a very strong lightweight magnet or a weak but heavy magnet all the same.
Essentially, in a E=M*V type arrangement
If be E you mean energy, you've got this wrong: kinetic energy is 1/2 * M * V^2. It is momentum that is M*V. Notice the M's here are the mass, which is separate of the magnet's strength.

(The squaring of velocity in energy is why the recoil of a gun doesn't drive into your shoulder with the same energy of the bullet leaving the barrel. The M16's bullet has about 1/1000 the mass of the gun. So by conservation of momentum, we know it will have about 1000x the speed. Energy of the gun and the bullet is half their mass * their speed squared. The squaring is a big deal: 1000x the speed with equal mass means 1000000x the energy. Here, since the bullet has 1/1000 the mass of the gun, we divide 1000000 by 1000 and know it will get about 1000x the energy of the gun. The bullet has almost 2 kilojoules of kinetic energy. The gun gets only about two joules from the recoil.)

To determine velocity (V), you'll use the magnetic force divided by the object's mass, multiplied by the exposure time to the force. The magnetic force is determined by the strength of the two magnets together, their distance apart, and some other factors (the actual calculation is pretty complex for real world magnets).

Since the M of the gun in total is even larger than the bullet, the total V of the gun is further reduced by however much heavier the gun is than the bullet. The M of the soldier holding it is, again larger than the M of the gun (or at least let's hope so) so the V is further reduced.
This here is accurate, with M meaning mass. The bullet flies forward very quickly. The gun and soldier have the same momentum (which you were really looking at with your E = equations), but much much more mass, and thus don't go flying backward at the same speed the bullet is flying forward.
To summarize:
The speed of the bullet should not matter for the recoil of the Coil gun, because speed in a Coil gun is generated by how much harder the electromagnet pulls on the bullet than vice versa. And since the weight of the bullet remains the same, recoil technically shouldn't increase.
Nay.

speed of the gun (moving backward) * mass of the gun = speed of the bullet (moving forward) * mass of the bullet.

How you got it up to speed doesn't matter. It can be magnets, gunpowder, or rubber bands. In all cases, the above will hold true.

In coilguns:

Magnet strength alone (practically) determines force.
Force, combined with the bullet's mass, determines muzzle velocity.
This same force (equal and opposite), combined with the gun's mass, determines recoil velocity.



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Re: The Question thread

Post by Blackwing »

If you want to read a simple summary of the conclusion of this post, just scroll down to the end.

The problem with that is that recoil is a result of what is essentially a simulated 'Elastic collision' (the formula for which is 1/2M*V^2, as you pointed out), this a result of a gunpowder (cordite) charge exploding right in between the bullet and the weapon.

In an Elastic collision, the 'first' object collides with a 'second' object, imparting part it's kinetic energy to the second object, based on the angle of impact, which then proceeds to move in a direction based on the angle at which the first object hit it and the second object proceeds at an angle which is the angle of the second object mirrored over an axis with a 90 degrees rotation from the 'before impact' path of the first object (in other words: if a pool ball hits another pool ball of the same material and size dead centre, the other pool ball will continue along the original trajectory at half the original's speed, while the original ball travels 'back' along it's original path at the same speed, theoretically).

In a gunpowder (or other 'explosive propellant') weapon, a similar 'dead on' collision is simulated by the explosion in the centre between the bullet and the weapon. This imparts half the kinetic energy of the explosion on the bullet and the other half on the weapon.

In a coilgun, however, what happens is not a simulated collision, but a gravity-esque attraction between two objects. Electro-magnetic attraction IS mass-based.
In fact the only difference in attraction between gravity and electro-magnetism (and the Strong Nuclear Force and the Weak Nuclear Force) is that gravity is many times weaker than electro-magnetism (while the SNF and WNF are both of similar strength to Electro-magnetism).

The earlier assumption that the bullet in a coilgun pulls on a magnet just as hard as the magnet pulls on it is also false.
While it is true that when you hold a magnet in one hand and a piece of iron in the other you can feel a pull between them, not just a pull from the magnet, this does not prove an equal and opposite reaction as far as pull is concerned.

This can, in turn, be proven with a practical experiment:

Take a 1cm^3 cube of pure iron (for the purpose of optional calculations you may want to do) and a 10 cm^3 cube of magnetized iron with a field strength you know (again for optional calculations).
Put the magnetic cube in some kind of suspending rig made of a non-magnetic material (for the purpose of eliminating it as a potential factor in the experiment). Now use a non-magnetic ruler and some appropriately non-magnetic weight measuring equipment to determine the point at which the pull of the magnetic force overcomes the pull of gravity. Note this down and then put the iron cube against the magnet. It should stick and be held up, because the pull of the magnet is stronger than the gravitational pull of the entire planet earth.

Now, perform the same experiment, except this time put the 1cm^3 iron cube in the rig and test when the pull of gravity is overcome by the pull of the magnetic field.
You will find that while the 'weight' of the magnet decreases a bit it never, at any point, does unless you're so far away from the earth's gravity that you've pretty much already left the lower atmosphere. The natural magnet is also unable to be suspended from the iron cube.

What have we just proven here?

We've proven that while the iron cube does pull on the natural magnet, the natural magnet always pulls harder and more over how much it pulls is based largely on mass.

In general you will see that a natural magnet will be able to suspend a ferric object of the same material as long as said object is of equal or lower mass than the magnet and likewise a natural magnet can be suspended from a ferric object of the same material as long as the magnet is of equal or lower mass than the ferric object. Suspension, in this case, is to be taken as the ability to defeat the pull of gravity completely when the objects are in direct contact. If gravity is not defeated then neither of the ferric objects used is a natural magnet.

Electro-magnets, however, act differently and you can both suspend something from an electro-magnet and suspend an electro-magnet from and object with far greater mass than that of the electro-magnet.

Why is this?

This is because the maximum possible potency of a natural magnet is determined by it's mass and the material it is made of. This in turn also means that no matter how powerful a magnet is, 1 gram of iron can never pull on that magnet more than the maximum magnetic potential of 1 gram of iron, however that magnet CAN pull harder than that on 1 gram of iron.

This in turn ultimately means that an electro-magnet, for the purpose of electro-magnetic attraction (which is similar to, if much stronger than, gravitational attraction) can have much greater 'apparent mass' that it's actual mass.

Conservation of momentum and the third law of movement work (near) perfectly for objects colliding with each other, but in the case of a coil gun, it's Classical Electrodynamics, not Conservation of momentum, that's at work.

A regular gunpowder weapon works by using an explosion that collides with both the bullet and the weapon, simulating an elastic collision between the weapon and the projectile. A gunpowder weapon actually uses the conservation of momentum to convert chemical energy into kinetic energy and transfer it to the bullet. Because the bullet is lighter than the weapon, the third law of movement dictates it should have more velocity than the weapon and it is thus fired.
To propel the bullet faster, you need more energy to be divided between the bullet and the gun, which you achieve by increasing the chemical energy of the explosive which acts on both the bullet and the gun and thus greater speed increases recoil. A smaller bullet but a similar explosive charge creates more speed, but equal recoil.

A coil gun however uses electro-magnetic attraction to convert electrical energy into magnetic attraction, which in turn is converted into kinetic energy in the bullet, because the attraction of the magnet on the bullet is greater than that of the attraction of the bullet on the magnet.
To propel the bullet faster, you need more energy to be imparted on the bullet, which you achieve by increasing the electrical energy that the electromagnet converts for magnetic attraction on the bullet and this greater speed does not increase recoil. A smaller bullet but a similar electric charge increases speed (by decreasing the amount of kinetic energy required for the bullet to gain velocity and increasing relative attraction on it), but decreases recoil (because less bullet mass = less maximum potential field strength).

Or, summarized, gunpowder weapons rely on conservation of momentum and the third law of movement by creating a three way elastic collision between the gas cloud of the explosion and the bullet and weapon to divide energy between the bullet and the gun. This is similar to an inverted Newton's Cradle with the explosion taking the place of the middle balls (inverted in the sense that if you take the two outer balls of a Newton's Cradle and extend them to the same relative distances and then release them, the opposite momentums of the two balls cancel each other out. In a gunpowder weapon, the energy instead originates from the middle and is transferred outwards).

In a coilgun, there is no (intentional) collision at all and any interaction between bullet and weapon is instead an electromagnetic attraction, which uses Electrodynamics, rather than the laws of movement to determine 'action-reaction'.
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Re: The Question thread

Post by Blackwing »

On other notes (and I'm doing this in a separate post from the above since if that discussion continues it's probably better to split the thread from this one at this point):

I don't see any reason why a permeating electro-magnetic field would be harmful to organic life, at least not on a space ship.

The main potential harm of most electro-magnetic equipment (like MRI scanners) is not the electro-magnetic field itself, if that were the case then being in a college computer room or near a large server is liable to kill you eventually. Instead the harm comes from the fact that an MRI scanner relies on rapidly switching said super-powerful magnet on and off in order to get the protons of the water in your body to resonate, which it then detects. The effect is essentially the same as putting a person into a sort of micro-wave oven (with the main difference being that a micro-wave oven tends to have a much higher frequency. MRI rarely heats you up more than a few tenths of a degree).

MRI exposure, if incidental, is not proven to be harmful, but caution is advised in case it turns out to be, to avoid that happened when X-rays were first discovered ("Hey look, I can see my bones!" followed by "How the hell did I get cancer all of a sudden?").

There are studies that suggest that power-line and other magnetic field related cases of cancer are likely to be due to the strong local disruption of the earth's natural magnetic field rather that anything else. This is because the water in the human body is usually aligned nominally with the earth's magnetic field, while power-lines especially can cause that water to lose alignment and move erratically.

It doesn't much matter which way the water in your body is aligned (on the far southern hemisphere, the water is aligned 'upside down' from our perspective and considering where humans are likely to have evolved, the water of people on the northern hemisphere is facing the opposite direction it was when we first evolved and it doesn't seem to have harmed us. The main point seems to be that is has to be aligned in some direction otherwise you're more likely to get cancer and a few other afflictions.

As such having a permanent (strong) magnetic field on your inter-planetary and inter-stellar space-ship is probably a good idea.

And my own question: orbital bombardment as an invasion strategy. Yea or Nay?

Personally, I'm not a fan of the concept.
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Re: The Question thread

Post by Booted Vulture »

How is orbital bombardment an invasion strategy? Its blowing shit up. It not invasion until you get boots on the ground. It could be a useful tool for softening up the enemy before you drop troops but it of course depends entirely upon the situation. for example, I can't imagine it being very precise so there are lots of scenarios where you wouldn't be able to employ it if you say, wanted to take mcguffin x intact, you wouldn't want to be dropping bombs or honking great laser on the surrounding area with out taking out the macguffin with shock waves or a stray blast.

How could would standard missile be at handing re-entry though? Would special re-entry capable missile have to be designed? Or would races just tend to go for a near by object or drop a big ass tungsten rod?
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Re: The Question thread

Post by Destructionator »

Blackwing, virtually everything you said in your first post on this page is incorrect. I'm sick, it's late, and I have work in the morning, so I can't go into detail now, but magnets aren't magic. Forces *always* work the same way.

EDIT: For your experiment, the magnet weighs 1000x more than the non-magnet. It is really surprising that an equal force can hold one up but not the other? /EDIT
Blackwing wrote:There are studies that suggest that power-line and other magnetic field related cases of cancer are likely to be due to the strong local disruption of the earth's natural magnetic field rather that anything else. This is because the water in the human body is usually aligned nominally with the earth's magnetic field, while power-lines especially can cause that water to lose alignment and move erratically.
This sounds like bullshit - how does the water in the body stay aligned as you move around? The Earth's magnetic field really isn't that strong.

Have a link to one of those studies?

And my own question: orbital bombardment as an invasion strategy. Yea or Nay?
It isn't invasion, but can be effectively used prior to invasion. You can use a large number of pin point attacks with a laser to take out just about any exposed target.

IIRC Sikon discussed this possibility somewhere in the essay quoted (and dissected and expanded upon by commentators) here:
http://projectrho.com/rocket/rocket3as.html#overview

(self pimpage: one of my old essays saying how I think warship design will be relatively undiversified is also quoted later on that page. I've gotta send a revision to Mr Chung one of these days though; I've changed my mind of a few specifics in there, but my general conclusion holds: space warships in any given setting will probably all be basically the same.)


Booted Vulture - keep in mind laser's can have their power turned down to avoid collateral damage. I seem to recall Sikon having a detailed analysis about this around the same time he wrote the essay linked above, but I don't have it on hand. I'll find it tomorrow or friday when I have more time.

The short of it: turn your super gun down to tank gun energy levels and send down little drones to give you precise targetting information. Blast exposed stuff with the low power, set to a frequency that mostly goes right through the atmosphere. Collateral damage is to a minimum and since the low power shot is a fraction of what your ship can do, you virtually have infinite ammo and a very high refire rate.


A missile made for reentry should be rather simple. A sleek object doesn't interact with the atmosphere much, so it just flies right down without getting super hot. (The superheat of the space shuttle is primarily caused by it trying to slow down to make a landing. A missile doesn't care about blowing up, so it needn't try to slow down and thus can avoid much of the heat.) Worst case is you put some simple ablative heat shielding on it.

It probably would be a different model than space to space missile for efficiency, but I can imagine a space to space missile being lobbed at the ground and doing the job in a pinch.
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Re: The Question thread

Post by Artemis »

I think this all depends on what you're bombarding and how dead you need it to be, but I agree that bombardment alone is not an invasion - if anything, it's a siege. But I think any successful invasion would have to have constant orbital support, including artillery - orbital bombardment doesn't have to be an extinction event any more than regular bombing or artillery does. A single well-placed missile or cloud of steel pellets could level an enemy base while leaving the civilian population center, not to mention your infantry holding position a klick away, unharmed.

Dropping a missile into atmosphere wouldn't be all that hard, really - drop it in a heat-resistant pod that breaks open once you're past the ozone layer, the missile shoots out and its computer takes over, probably guided by the ship it came from or from a position on the ground. Dropping in atmospheric fighter drones (or even manned fighters, should you wish) could probably be done the same way. I'm imagining this is how dropships and landing craft come in, anyway.
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Re: The Question thread

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As pointed out, bombardment is never an invasion strategy. Just like American airstrikes on Iraqi military targets in the No Fly Zones during the '90's didn't constitute an invasion the orbital bombardment of a planet won't either. Having said that, if you want to put boots on the ground on any halfway properly defended planet I don't see how you'll manage without conducting some form of bombardment. It's not like ground-to-space missiles are a particularly problematic technology, and I'd prefer to have any such sites well out of the way before my dropships hit atmo.

There's of course different ways you can conduct an orbital bombardment: it could be precision targeting with KKVs or missiles with tactical nuclear or conventional warheads, or you could go the ta-su way and just drop strategic h-bombs on your enemy.
Booted Vulture wrote:How could would standard missile be at handing re-entry though? Would special re-entry capable missile have to be designed? Or would races just tend to go for a near by object or drop a big ass tungsten rod?
Missiles would probably be useful for stand-off/target-finding capability they provide. Such missiles definitely have to be engineered for atmospheric entry though, because there's some not-insignificant problems associated with getting a high-speed missile from space to a target (the friction of hypersonic passage into the deeper atmosphere; the plasma sheath and how to look through it; getting a really fast missile delivered onto a target, etc.)

EDIT: I have to admit that Artemis' idea of a drop pod containing a missile is an interesting one. I wonder why I never thought of that before... After all, submarines use a similar system, launching missiles encased in a torpedo which breaks open when its near/at the surface...
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Re: The Question thread

Post by Destructionator »

In Mobile Suit Zeta Gundam, their reentry devices were inflatable things of some sort, discarded after one use. This seems plausible; the drop pods needn't necessarily be reusable or expensive.
SiegeTank wrote:EDIT: I have to admit that Artemis' idea of a drop pod containing a missile is an interesting one. I wonder why I never thought of that before... After all, submarines use a similar system, launching missiles encased in a torpedo which breaks open when its near/at the surface...
The best part: that incoming drop pod... is it a dropship or a multiple missile pod??? Or is it just a decoy?

Such trickery I think would be common in space war, especially space to space, but surprise drop pods might work too.

For space to space, there might not be stealth, but there sure can be trickery. A quality episode of nBSG was season one's "The Hand of God" where they hid Vipers in civilian ship's cargo pods to fool the Cylons. I think this kind of thing will be fairly common.
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Re: The Question thread

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Destructionator wrote:The best part: that incoming drop pod... is it a dropship or a multiple missile pod??? Or is it just a decoy?
I doubt you'll fool anyone; any halfway decent anti-air missile can discriminate between decoys and the actual target, that's why ICBMs haven't any decoys aboard these days, and why chaff and flares hardly work against modern missiles anymore.

For this to work, the drop pod has to have the same ballistic properties, size and heat signature as a drop ship. Which it won't, for obvious reasons...
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Re: The Question thread

Post by Destructionator »

Could they tell before it launches though; before the drop pod deploys its payload? If all the pods look the same from the outside and you load them up with the same weight (either of ships or missiles), it seems like it should be difficult to determine which one's which until it actually deploys.

At that point, carrying dummy missiles is a waste of time like you said, but I'm not so sure about before that point.
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Re: The Question thread

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Destructionator wrote:Could they tell before it launches though; before the drop pod deploys its payload? If all the pods look the same from the outside and you load them up with the same weight (either of ships or missiles), it seems like it should be difficult to determine which one's which until it actually deploys.
You wouldn't-- at least as long as missile pods and trooper drop pods in them have exactly the same characteristics (heat signature, size, entry velocity, etc.) However, I see no real reason why they should have the same characteristics. They're quite different in function and purpose after all; troop pods will have to do all kinds of things that missile pods won't, and vice versa.
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