Jonathan_S wrote:Fair. They'd be coming in slower than the ballistic strikes Honor was worried about the Masadans/Peeps pulling off against Grayson if she didn't left Thunder of God uncontested access to the outer system. Those might come in so fast she didn't expect to have much luck getting point defense solutions against them.
Several important differences there. Starting with the simplest, which is that Honor had much older technology herself to work with. Her interception ratios and ranges were much smaller than what we're used to today, and especially the throw weight of CMs.
But the more important thing to consider is that a planet can't dodge and has no wedges. Any un-intercepted missile from Thunder of God would be able to fire on the planet or a target of opportunity and would definitely not miss it. Honor would have needed to acheve a 100% interception ratio from well outside the range of those missiles... which is considerably high too because of the lack of wedges or sidewall.
That all such missiles would have been flying ballistic would be small consolation.
A 4 drive system defense missile salvo might be launch from so far away that the FTL sensors of it's first 3 drives are unlikely to give you particularly actionable data -- the signals from the salvo's drives will just be a cacophony of "noise" leaving you unsure of even its size, much less the precise vector of each missile as it went ballistic. (After all, with Mycroft you could trivially shoot at enemies as they crossed the hyperlimit using pods in Manticore's orbit -- at minimum a 6.4 light minute ballistic phase)
But if you've got 8 minutes to gather passive IR data on those 0.81c targets you might well have a solid track to hit them as they cross your defensive perimeter.
Indeed and because they were already at 0.81c before the third stage shut off, the vector should be good enough. The missiles have negligible delta-v in ballistic stage. I imagine they could have some cold gas thrusters to avoid a completely ballistic flight, but against a base velocity of 0.81c, their effect will not be apparent. So the sensors might not have been able to track just how many missiles were in space, but there will be no mistaking that it was "a whole lot" and "they're coming right for us!"
But it's probably irrelevant - you're coasting outwards so quickly (0.81c) that you'll basically always have to bring up your terminal maneuvering drive long before reaching their defensive CM envelope just to have time to build the lateral velocity you need to achieve intercept. (Because enemies rarely maintain perfectly ruler straight courses, especially when they know they've been fired upon)
* Over the 180 second max of a normal half-power drive's endurance it can deflect the missile sideways by up to 7.3 million km, but over that same time it'll also coast nearly 44 million km further downrange.
Very good point. So there's a limit on how long your ballistic course can be, because in the intervening time the target ships could have moved away from the interception zone for when the missiles do light up their drives, which is a sphere 7.3 million km in radius from where they'd be if they themselves kept ballistic. At 600 gravities, ships can shift their positions by that much in 26.25 minutes.
That in turn sets an upper limit on a 4DM interception range at 10 minutes[1] accelerating at 46000 gravities and 26.25 minutes coasting at 0.81c = 463.7 million km = 25.77 light-minutes. That's more than the radius of most inhabitable systems' hyperlimits, but less than the diameter. In the Manticore-A system, the RMN could for example place their 4DM on Salamander and would have complete coverage of the hyperlimit volume.
[1] 10 minutes because that brings up their speed to 0.9c using the usual calculations, and that is the upper limit. The last 2 minutes of the last stage can't be used for accelerating in the same direction.
This series is ~over.