I make it a habit of not bringing personal identities into internet arguments for a couple reasons, mainly because anyone can claim to be anything on the internet, and also because I don't like appeals to authority. I think that reasoned arguments (and lots of math) are the best way to go about things. However at this point we are really talking about more nebulous claims than can easily be demonstrated, and you've said "trust me" twice, so I suppose I'll return with the "I do this (examination and implementation of force and environment models to accurately propagate space craft and other heavenly bodies) for a living." I'm a software developer for the company I've linked to twice now, and the main developer of one of their propagation products.
I don't question your math, so much as the ability to actually implement it. Without the giving of names and creds I worked for the government as a physicist in this field and still colaborate on several projects. I resigned my formal government possition and accepted civilian support status and signed far too many forms to count that made it abundantly clear that if I was to share any of my work that I would get to spend a loooong time in a small cell with a big man named Bubba (my apologies to anyone named Bubba...) who will think I am really cute.
The simple fact that you have argued as intelligently as you have indicates that you also have an abundance of experience in this field. I do not question that. But as you are likely well familiar with, those of us in this field have very different ideas of what is possible when you actually get off this planet.
Calculating Sedna's orbit parameters from Earth is a much harder problem than getting a firing solution on Earth (from, say, Neptune). One of those involves propagating the position of an object 12750 km across a few (say 4) weeks forward in time from measurements taken 4.6E9 km away.
I am not saying that calculating it is that difficult. It would be giving adequate time to collect the necessary data. Collecting the data will take time. How long it would take for a race with this level of tech, I don't know. I do leave that to Steve. I would base a kinetic projectile's maximum range/accuracy on the level you have surveyed a system. (perhaps a mod of some sort? to prevent the jump in and blast the pop from extreme range). The problem is like laying any type of non-guided weapon system. The math is easy. Getting the darned thing to go where the numbers say it will is nearly impossible and has more to do with luck than anything. Ballistic calculators can tell us EXACTLY where a bullet should go with a given sectional density/ballistic coefficient/velocity/air temp and pressure/crossing influences/movement of the earth under it/etc. etc. ad nauseum. Problem is those bullets/shells/ etc
always spread out unpredictably. Otherwise we would never miss a target. Like I said, the math can be exact but it never describes reality when it does.
I'm also not sure how you got that I was trying to shoot at Earth from out past Sedna
You implied you were shooting from beyond Neptune, as I understood it. If that was not your intention then I am sorry for the misunderstanding. But even from Neptune, it would require something other than more advanced ways of making a projectile go fast. Somehow you have to keep it from interacting with the interplanetary medium. Jupiter would be considerably easier, but keeping an unguided projectile from deviating to the small degree that is necessary to deflect it would be almost impossible without some form of 'handwavium' that somehow repelled the particles without imparting any deflection.
You also somehow need to keep the launcher and projectile from interacting in any way. Which would be inconducive to firing.
I also assume that in Aurora their algorithms and computers will be no less effective than ours, and will probably be at least an order of magnitude better.
I hope so. Ours are getting better faster than I can keep up. (Ok, I quit trying to over a decade ago. I really haven't moved much past the point when I was happy to program one to generate a number between one and six in school.)
The crux is getting the data. It takes time to measure movements, densities, etc. And I doubt a dedicated warship is going to pack a large number of astrophysics types in its crew just to analyse reams of data so they can figure out how to shoot at a planet. Especially when mass has such a big impact on a ship and its ability to get from point a to b. I know what my superiors would have told me. 'Just get closer.' Which is why when we shoot those asteroids or comets, we get REALLY close. It is a lot easier to do than packing all the gear into a vehicle so that it can do it from a loong ways off.
Which is why I would beleive that most of those distant 'planet killers' would most likely be a missile launched from a long ways out that can follow the planet. The firing solution is so much simpler and chance to hit is immeasurably higher if the vehicle can adjust to its target. By the time it reaches the planet a kinetic kill missile will likely be going a lot faster than the rail gun. This is why we shoot Tomahawks at targets instead of 16" shells. The shells are way cheaper. Just hard to know if you will actually hit anything.
According to NASA fact sites the Hubble telescope has a Pointing Accuracy of 7/1000th of an arcsecond, so platforms in space can align to a target with a great deal of stability. Now granted it's another ball game entirely to maintain stability on an object accelerating on a huge cloud of plasma. I suppose Steve could model accuracy penalties while accelerating, but I think he could also handwave that requirement away. We have a variety of ways already to mitigate instability and jolts for both turrets on naval vessels and more rudimentary science experiments, and it would seem fairly reasonable (to me anyways) to just say, "eh, they have something like that".
Now as far as how long it takes the platform to regain stability after a shot, that depends on the mass of the platform, the offset of the barrel from the center of mass, the abilities of the control system to torque the craft, and a heck of a lot of other things that Steve is not modelling. Seems reasonable to just say that the spaceship is able to damp out it's orientation by the time the next shot is ready.
Pointing something isn't the huge problem. We can aquire a target with a high degree of precision. It is the act of firing that will mess everything up. When Hubble does this it is being held as 'motionless' (I hate that term, sorry) as possible. Firing a projectile will upset this profoundly. I agree that the next shot will not occur until the platform has stabilized, and that could be assumed under the rate of fire. But the platform and launcher are moving and deforming
during the shot, and this deviation is impossible to predict within certain levels of certainty. If you are firing a projectile at the limit of what your technology is capable of using (and why wouldn't you on a military weapon) you will only be capable of a certain level of accuracy over distance. The platform will deviate and the environment will then act on it. They accuracy a weapon is capable of - I don't know. But if Steve wished to limit it to much shorter distances than what some people are talking about - it is supportable. Shooting from Earth to Mars - yeah. Might not hit a spacestation/ship/habitat, but the planet would be easy. If you really need to hit the little target either shoot alot (artillery barrage) or firs a missile (tomahawk).
Hitting a Callisto from Earth with an unguided weapon. Better shoot a lot. Hitting Earth from Neptune - hope Steve doesn't track ammo because you will need a lot.
For a normal unguided kinetic slug going through a coil gun or railgun you don’t have to worry about the G force destroying the slug since the magnetic forces apply to the entire projectile fairly uniformly.
Not a good arguement. Gravity applies (as far as we know) perfectly uniformly. Check what happens to a bridge if you exceed its bearing strength. Even or not, exceed what it can take and it comes apart. When you apply a quarter million G's plus to an object - even or not - it will deform unpredictably. You can try to argue that it is being 'pulled' as much as it is being pushed, but that defies Newton's Third Law. In the end, the slug is going to go a direction and the launcher won't be. And they are going to act on one another with the slug absorbing a LOT of energy. It will deform. So will the launcher. And just how much at a given point will be impossible to predict beyond a certain degree.
I base this on the entirety of our civilized history, which has shown our weapons becoming longer-ranged, higher powered, and more accurate over time.
Our weapons have better range and accuracy, but it is due to the type of weapon. Guided munitions are a god send when the bullets start flying. But our accuracy and range with unguided munitions hasn't actually changed much at all since WWII. That is the reason we don't have bigger and better cannons (for the most part). We have the ability to factor in more variables (which is why the Germans considered our use of artillery with TOT fire missions a violation of the rules of war in WWII), but the shell is only so accurate. If they had gotten lots better, the battleships wouldn't be parked, and destroyers that are now the size of WWII cruisers would pack more than a single 5" gun. The M1 fires a shell no bigger than those of the large Soviet Tanks of WWII. We have better first hit percentages, but the range hasn't gotten much longer. That was why when I did my time overseas we used the M1's laser designators to light up our targets for the helos Hellfire's that could find the target farther out than the M1 could reliably engage.
Ok, this will likely be my last post on this. I have stated what I feel to be accurate. What the future holds is going to be a lot different that any of us can see. I mostly have pursued this to give support to the fact that if Steve wishes to give max ranges to unguided projectiles - it is realistic. They don't have to be interplanetary weapons if he doesn't want them to be. If he wants to say that 10+km/s projectiles are only accurate over a few light seconds - so be it. If he wants to shut it off at a light minute - that is very realistic (probably optomistic).
Now guided planet killers ( missiles), those could be a problem.
( I will try to find a public reference to the particle densities in interplanetary space. I don't have any on hand but I know I have read several college papers that stated this fact, so it has to be in the public forum somewhere. I will PM you references that I find if you are truly interested. I suspect that it could be googled to come up with results anymore.)