Lord of the Abyss wrote:KlavoHunter wrote:Reinhard is on Geiersburg in its original position; Reuental is on Odin.
At least in between very large fixed installations, there is FTL comms so fast as to have a live conversation.
For a comparison, late-generation Manticoran FTl comms allows conversations with visuals and also works fine between ships, not just large installations. However, they aren't fast enough to eliminate delay, and they are strictly in-system in range; I've no idea what range LoGH has with its version.
LoGH is communicating between
widely separated star systems here. Assuming we can scale the maps I've seen of the LoGH powers to the Milky Way galaxy, it would probably take decades if not centuries for an Honorverse grav-pulse comm message to cross the distance between Geiersburg and Odin.
Said pulses travel at 64c, FTL but slow enough to cause noticeable transmission delays even in-system- fire one up in Earth orbit to talk to someone on Mars and you can expect at least a few seconds' signal lag.
Connor MacLeod wrote:Xon wrote:Those fields are good for 2 metric tons @ 0.6c which is ~10gt of relativistic KE. It's going to take a lot of really fast particles to match that.
Weber also flat out noted that as the velocity increases the mass goes down and vice versa, which presumably also factors in relativity (if Weber didn't go all "Doc Smith' in his universe, that is. And inasmuch as an Impeller wedge can obey relativity) It seems like particle shields are more concerned with the sheer force/momentum of the impact rather than the KE, because the KE of different masses striking at different speeds will be quite considerable.
My impression is that the effectiveness of Honorverse defenses against high-velocity particles
of any kind starts to drop off as particles become highly relativistic. I can imagine reasons for this to be true, ones no more contrived than sidewalls and wedges are in the first place (say, because "particle shielding" is built around static electric fields that can only absorb so much momentum from an incoming particle before it punches through the zone the field occupies and hits you on the nose).
The radiation shielding covering a warship's bow is considered "safe" at, say, 0.7c, but not at 0.9c. Now, we can say this is because of the risk of solid impactors being in the ship's path... but on the one hand the risk of encountering such an impactor is small, and on the other hand there's a question of relative mass. Getting hit by a two-gram chunk of space gravel at 0.7c hurts more than getting hit by a one-gram chunk of space gravel at 0.9c... but Honorverse shielding is considered in-universe to be adequate protection against the former and not the latter.
Ah, well, wouldn't be the first kind of shielding in SF whose performance is velocity-dependent.
Of course, I repeat, this is
not a test of sidewall performance. But sidewalls are explicitly described as using a force which does not distinguish between charged and uncharged particles- and ultrarelativistic charged particles aren't
that much more strongly deflected by gravity than photons are.
I'm also skeptical that "particle shielding" actually would affect particle beams rather than the anti-radiation shields (Because there are forms of stellar radiation that aren't photons, after all.) Especailly given that particle beams and kinetic impactors, despite havng mass and having KE, will have different damage mechanisms.
In the extreme limiting case, there isn't much difference between a
relativistic impactor and a particle beam: the kinetic energy of individual atoms is much greater than the potential energy binding the atoms together, and more to the point, the kinetic energy of individual
subatomic particles is much greater than the potential energy binding the particles together.
So the difference between a solid hunk of iron traveling at 0.5c and a tight bundle of very cold* iron plasma traveling at 0.5c really isn't going to be all that noticeable. Sort of like how the difference between falling head-first into water from 10000 feet and falling head-first onto concrete from 10000 feet isn't all that noticeable.
*"Cold" plasma means plasma where the individual particles have low thermal velocity and thus do not disperse much. This is the one noticeable difference- while a blob of iron plasma will be spreading out in three dimensions at some calculable rate, a chunk of solid iron is not. But at equal density and velocity, the difference just isn't going to matter much.
Connor MacLeod wrote:Well you have a point inasmuch the sidewalls shouldn't be just an either/or sort of thing. However, teh only "mechanism" I could think of that might work would be something along the lines of
this without the "down the hill" part. (Mentally I tend to visualize the target ship being on the top of a metaphorical hill, and the weapons ifre has to crawl up that hill to reach it.)
Very possible; I think there's a secondary belt which generates dispersion of shot which
does pass through- a relatively tight, coherent beam (of any kind) which passes through the sidewall comes out more spread out than it went in. This may reduce the effect of a direct hit, hopefully reducing the
intensity of the beam weapon to something the ship's armor scheme can survive with minimal permanent damage.
Pardon my ignorance but if I am reading you right, you are basically saying that any highly relativistic particle beam would dump out a shitload of photons even against the magical sidewall (Aplogies for dumbing it down, but I want to be sure I have the gist of things.)
Nope. It would just travel
very fast.
A proton travelling at 0.9c carries more kinetic energy than it does rest-energy: the E=mc
2 component is smaller than the extra boost to its energy from how fast it's going. Granted, not a lot smaller... but you can
get it a lot smaller. As you start tacking on extra nines to that 0.9, the kinetic energy of the particle approaches infinity... and the particle starts behaving more and more like a (very energetic) photon for practical purposes.
Except when it interacts with an electromagnetic field where its status as a charged particle matters.
Now, that exception makes a major difference when it comes to the effect on a solid target, where a primary mechanism by which energy transfers from the moving particle to the target is electromagnetic. But it doesn't make much difference to the particle's ability to pass through an intense gravitational field. Gravity does not care about electric charge; the protons and neutrons of a falling rock are treated alike.
For this reason, I would argue that a
gravity-based sidewall which fails to stop a beam of X-rays should not be able to reliably stop a beam of highly relativistic particles of comparable intensity.
It is also completely irrelevant to my point- which is that there is no coherent reason why a sidewall should be gloriously effective at stopping megaton-range proton beams travelling at .9c or higher when it cannot stop X-rays in the same or lesser energy ranges. Certainly there is no reason why the anti-rad field should be able to do so, since it can't even stop a far smaller flux of cosmic rays from harming the ship if said ship were to accelerate to .9c or higher.
One problem: if you got a CPB in space, it's range is short because of mutual repulsion IIRC. I think thats why they favored neutral PBs for space warfare.
Well, if you really want to you can cheat- again, the higher the particle velocity the higher the effective range. There are a number of ways to describe what happens, but perhaps the easiest goes like this:
Imagine a bunch of charged particles. They repel each other, and spread outward... but it takes time to spread.
Now, take those same particles and throw them at .9, or .99, or .999c (for reference, the LHC beam takes this out to about five or six nines). Time dilation becomes
really really really important, because you are looking at a
relativistic gamma of five, ten, a hundred, a thousand... (the LHC runs at gamma ~= 3500).
Time dilation increases the perceived lifetime of the beam from the perspective of an outside observer, because the beam only experiences some fraction of a second per second observed from outside.
Get it going fast enough, and it will hit the target before it has, in its own frame of reference, enough time to disperse very far.* The value of "enough" depends on more parameters than I'm at all inclined to sit down and do a calculation on, though it's something you could in principle solve analytically given... hm.
1) Type of particle,
2) particle velocity,
3) current density of the beam (how many particles fly through a given unit area per second),
4) range to target...
And note that given either (2) or (3) and a figure for beam power in watts, you can calculate the other one of that pair.
Yeah. It's doable. The answers will not be especially encouraging unless you go to
really high particle velocities though, with correspondingly high relativistic gamma.
The other way to explain this involves invoking the effect of a Lorentz transform on electromagnetic fields, which is something I'm not entirely sure I trust myself to explain.
*The same effect can also increase the observed lifetime of unstable particles such as muons
as measured in the laboratory frame. A muon has a half-life of 2.2 microseconds... but time dilation can easily stretch this from the point of view of a guy sitting in the lab and watching the muons roar past.
____________
Now, all this being the case, there are
still damn good arguments for a neutral particle beam if you can make one. This is one argument in favor of relativistic mass drivers- you get a large amount of mass moving very fast without having to worry about internal repulsion pushing the round apart. A neutron beam would be very helpful too; I know of no way to generate one that isn't painfully cost-ineffective and prone to irradiate the hell out of your ship, but that's why this is soft-SF territory.
[Notably, a neutron beam would tend to be very effective at penetrating solid materials, and almost immune to any type of shielding which relies on electromagnetism- though it would react to a sidewall exactly as a proton beam would, because again, sidewalls shouldn't give a damn whether the particles striking them are charged or not]
I already pointed out lots of "non gravitic" bits about sidewalls and wedges, so you have no argument from me in that regard. Perhaps particle beams CAN penetrate, but they are attenuated/disrupted by the sidewall. This happen lasers (one reason they have to fire so many, and why range plays a factor in sidewall penetration) Coupled with the radiation/particle shielding, it might be enough to blunt any HV particle beam. For all we know HV particle beams have a limit to how close to lightspeed they get, which impacts their ability to penetrate sidewalls.
Out of curiosity, you did mention that a highly relativistic particle beam is not much different from a laser.. just HOW relativistic are we talking?
Relativistic gamma high enough that the particle's relativistic kinetic energy is much larger than its rest-mass energy. There's no hard limit, but by the time you get around a gamma of about 10 or so, it's safe to say that a charged particle trajectory in a gravitational field is going to be pretty
This is far from unachievable- impractical for a rocket engine, but much more practical for a proton beam. Almost trivial for electron beams.
Now, I will not speculate on why this is not used in the Honorverse- I don't know how they generate high-intensity lasers (including gamma ray lasers). But it will be a relevant concern if Honorverse ships are being shot at by people who
do use effectively-lightspeed particle beam weapons. I would argue that their sidewalls and wedges should be expected to perform about as well against such beams as they do against equivalent Honorverse laser weapons of equal power and intensity.
Though as I said, the ones near the bottom (you can run the page through google translate, sub-headings work well enough) in both instances are historical ships from decades prior to the main series.
