Jonathan_S wrote:By the time a Mk23E could see the grasrehead detonating (well it doesn't detonate, but does slag down after 3 seconds) the graser would already be hitting at least its first target -- as both the visual of the detonation and the graser would be traveling at the speed of light.
This is assuming that the warhead detonating is near instantaneous to the graser beam. I made an (unspoken) assumption that there are telltale signs that the missile is about to detonate its warhead and fire. The process is fast, but not instantaneous, so there's a delay between seeing the signs of detonation and the graser beam arriving. The question is how long that is, how quickly the Mk23E can determine to be a threat, how quickly its signal reaches the other missiles (since they cluster, I assume they're within 3000 km of each other, so within 10ms lightspeed command) and how quickly the missiles can pitch.
Given that they can target a ship that has pitched wedge, we know they can rotate really quickly, in the order of milliseconds (20 rotations per second means it can turn 45° in 6.25 ms and it wouldn't need 45° to protect itself). A 10 ms command delay implies the Mk23E is up to 10 light-milliseconds behind the other ones too, so that means the worst reaction time is 26.25 ms. Does a 300-ms graser take more than this to ramp up to firing power?
And that's only for the first, targeted missiles. The other clusters of Apollo would have more advance notice because the graser beam isn't directed at them. They'd have the additional time of the beam swinging towards them. Admittedly, this will be shorter than the reactor ramping up to full power, but every millisecond counts.
If the Mk23E carries forward looking grav sensors it might well see the graserhead starting to spin in preperation of this 'deathblosson' -- that'd give it warning time to order its brood to take defensive action -- but otherwise I don't think it'd see anything until the graser hit something. (But I still agree this is pretty much, at best, a "use one" tactic. If absolutely nothing else it can be countered by preemptively spreading salvos out more so no more than one missile is within graser range of each other during their ballistic phase - over a 65+ million km flight even very small divergence in heading will add up to a ton of lateral seperation by the time the 2nd drive goes down)
Or just applying plain evasive manoeuvres. Constantly pitch up and down and constantly roll too. The missiles have acceleration to spare.
You're talking about targeting them during the ballistic phase. Indeed, that would be a tactic the MAN would want to have, because they won't have Apollo-quality missiles for a while. That means that even with a true 3-stage MDM, their accuracy is going to suck at 50+ million km, while the GA would fire from well over 80 million to stay outside of any powered range. Somehow negating that advantage would be foremost on their minds.
During the ballistic phase, a missile spinning and firing a curtain of graser as a disc makes sense... except that it's still highly unlikely to hit anything. A missile is 10 m in length and if the graser beam had a 2 m aperture (which is highly unlikely for a missile beam), a missile enters and departs the disc in 75 nanoseconds. If the graserhead-spinning-CM wanted to complete a rotation in 75 ns, its angular velocity is 84.8 million rad/s and the linear velocity of a 30-metre missile - assuming it rotates around its centre point - would be 1.27 million km/s... or 4.2c.
That's physically impossible. If we reduce the rotation to something a wedge could produce, you have the problem of there's a wedge pitched up right in front of you and the missiles are not going to mistake that. If there's one thing Apollo missiles are programmed for besides their primary mission is evading a wedge that isn't their target. And you can bet that Harkness' barricade stunt was programmed into the ACM. Besides, if you had the wedge right there, why not do the barricade?
If you remove the wedge, then you have to rotate using either the spider or rocket Physics, both of which should reduce the rotation rate so much that nearly all of missiles would pass through the disc while the CM isn't pointing at them.