Kinetic infrastructure attacks
This point was thrashed out at some length some months ago, and I don't recall becoming involved on the front lines. IIRC, Richard waxed fairly vocal about it, and I was content to let him have at it. Nonetheless, most of what he said at the time was based on his discussions (and war games) with myself. I do not intend to recap all of it at this point, but the nub of the matter is that Mr. Maurer is correct when he argues that defenses to cover critical targets are part of any intelligent planner's considerations, and both the SKM and the PRH (within the limits of the latter's tech base) are quite intelligent.
While those like Mr. Green who argue that kinetic attacks are possible have a point, the effectiveness of such attacks is pretty minimal for most of the reasons Richard brought up, plus some that Mr. Maurer has--somewhat to my surprise--put a finger upon, as well. Cee-fractional missile attacks can be deadly, but only under certain circumstances which system defense planners go far out of their way to prevent. In the case of Honor's decision loop in Flag in Exile, the system defense planners had not had sufficient technology/time to eliminate those circumstances. Indeed, the Graysons' orbital farms probably make Grayson--unlike Manticore--a system in which such attacks would have the greatest probability of success, because the farms can't maneuver. Perhaps future farms will be built with maneuver capability, but none of the existing ones have it, which make them the sort of sitting ducks that cee-fractional attacks are best suited to nailing.
Nonetheless, Grayson's fortifications are now very nearly up to SKM standards, and the system now has the same sort of deep space passive arrays as Manticore and Haven, which would detect the hyper footprint of any ship dropping out of hyper close enough for a practical attack of the type(s) which have been described and also have the reach to detect missile impeller drives at truly enormous ranges, giving the defenses plenty of warning against such attack forms.
The lower-velocity, "killer ball-bearing" forms of attack would be even less effective. First, all high-value system infrastructure in the SKM (and now in Yeltsin) modules comes with built in particle-shielding of the sort installed in hyper ships. Unless your ball-bearings come in at a very high fraction of light-speed, the particle shielding can probably handle them. Remember that this shielding is designed to protect ships moving at up to 80% of light-speed, and while the average particle level in deep space is very low, it is also designed to deal with the occasional "Oopsie! Didn't see that coming!" lump of matter too small for a decent radar return. That sounds to me very like the size range in which your ball-bearing would fall, and unless your attack unit spent a lot of time accelerating before launching them, they would be coming in much slower than .8 cee. And if your attack unit spends the time to accelerate before launch, it will be sighted, the probability of an attack will be allowed for even if it hypers back out before interception, and defensive measures will be initiated.
As for what those defensive measures are, Richard alluded to one: the "sweeper" effect of a wall of missiles/drones. If the attack vector is known, it is relatively inexpensive to use counter missiles or even recon drones to interdict the incoming with their wedges. Even less expensive, put a couple of intra-system freighters in front of the incoming, roll them up on their sides, and just leave them there until the threat is past. Their wedges will be impenetrable to the kinetic projectiles, and one or two of them will have wedges wide enough to cover just about any target in a star system.
No defenses can cover all targets. Mr. Green is correct about that. An attack of the sort he envisions would take out communications satellites, any sensor platforms in its direct path, power collectors in its way, etc. Those sorts of targets, however, are relatively low budget items for a tech base like the SKM's (or even the PRH's), and a counter-gravity civilization would find it extremely inexpensive to put the new birds into position once the factories handed them over. The expense in ships, hardware, time away from the battle front, etc., would almost certainly be higher for the attacker than for the defender in both relative and absolute terms.
The reason that Esther McQueen went for a major fleet operation in Echoes of Honor was precisely because the flea-bite attacks proposed for kinetic weapons would be ineffectual. For the most part, given decent sensor reach, they could be defeated by a navy with nothing heavier than a LAC as long as it could get the LACs into position to interpose their wedges, and you may rest assured that navies in shooting wars always have something with a wedge close enough to important targets to get into position In A Real Big Hurry. That being the case, the only really practical way to raid a system important enough to the enemy to make it worth your time to raid is to send in a force sufficient to suppress the local mobile defenses, close to your chosen range of the infrastructure you want to destroy, and then employ weapons (including energy weapons) which are not easily stopped. Which is precisely what Giscard did in Basilisk.
From a post to Baen's Bar BuShips dated January 18, 2002:
That's basically what most inhabited planets do, except that the "orbital defenses" are basically just very powerful impeller nodes which are constantly on standby. They require replacement every year or so, even at standby power levels, but they are ready to bring up overlapping impeller "plates" on any threat bearing as long as they have as little as five minutes of warning. A succession of them will pretty much vaporize any cee-fractional projectile you can hit them with.
In emergency situations, or to protect particular point targets -- like space stations or orbital shipyards -- redundant warships or even freighters can be used for the same purpose. They simply have to be positioned well ahead of time, which requires a fairly large number of them to cover all threat bearings. And, of course, if the Bad Guys are thinking of throwing anything at all large at you, it would be a Good Idea to use automated ships wherever possible Just In Case.