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The Honorverse is pretty good at telling us how long voyages take for "the universe at large" versus people on the ship. Their ships are limited to a speed of .8c, or slower in hyper-space. This limitation is imposed by the ability of their particle screens, and should, theoretically, affect missiles too.

In some of the more recent Honorverse books (specifically Storm From the Shadows) missiles are described as going at velocities up to (and possibly above) .7c.

This doesn't pose a problem for most missile, as they are programmed with targets, activation times, ECCM tactics, etc at launch, with little update capability.

But with the advent of

Apollo and its near-real-time link to the missiles

this no longer hold strictly true. How do the missiles handle communication with people and ships that are traveling at significantly different velocities? Wouldn't time dilation make that difficult or impossible?

2 Answers 2

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I don't see this as a huge technical problem - time dilation would just act as a frequency shift in the message, which could be accounted for in the mechanism for decoding such messages.

Presumably they would already be doing that for voice messages from ships to base.

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  • Good point about ships to planetary/stationary objects, I hadn't even thought about that.
    – Jeff
    Commented Mar 5, 2014 at 14:10
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I, on the other hand, see huge technical problems. But not in connection to Apollo. Or: not mostly.

First the time dilation is easy to compensate in transmissions. As noted by @Oldcat - can do that with frequency shift. But this is a piece of cake. Also, ship fleet itself travel at high-fraction C, so this is even less of an issue. However, Apollo is gravitic, so no time dilation stuff. Easy-peasy. But, there is a lag in grav comms, which barely allows for decent missile control while in the initial attack phase (countermeasures, assigned targets reacquisition and so on) at extreme ranges. And comms being grav-based, it makes it more difficult to avoid interference from multiple grav-sources. IIRC it means that Apollo caused decrease in number of links to missiles.

On the other hand, the time dilation at .7C affects onboard equipment tremendously. Time will flow over 40% slower. Thus, for example, missile travelling at that speed will cross the outer defense zone (anti-missile envelope) in 5 seconds real time, but only 3 seconds onboard time. Then after it it takes 1s realtime/0.6s onboard to reach stand-off range and explode. Which said explosion is not instantaneous - laser needs to be spun up to power, grav lensing has to be formed, rods need to be deployed and targeted, thermonuclear explosion has to occur... Rod deployment is worst, because missile cannot maneuver after that, so it's necessarily done at the last possible moment. Also, during that 0.6s missile's computer and sensor suites need to do quite a lot of calculations, which themselves take time.. even with molecular circuitry this will be noticeable (and basically, molycircs aren't faster; just smaller. unless they are photon based. Or quantum based, but then all bets are off. But that's completely different story.) Let's assume computer needs some nanoseconds to do each thing. Even with such incredible calculation speed we're talking about, say... 10 nanoseconds onboard, which means 14 nanoseconds realtime (during that time light itself travels 4.2 m), and there's still the whole mechanical part stuff (which cannot be done simultaneously). IF target ship itself is moving at any noticeable speed, during that whole attack sequence it will be several ship-lengths (or beams) away from the position when the attack was initiated. And if it's maneuvering, computer has to basically guess. And possibilities increase with every nanosecond literally exponentially. Because the problem is that anything computer receives as sensor input is already outdated (more or less if suite is EM or grav). And what if there are - sigh! - electronics on board as well? Electron travels at approx. 60% of C itself (depending on medium). So, 40% of 60% is what? Presumably this may hold true for molycircs as well (if electron-based), but let's not go there... SO basically to recap: say 0.1 sec to deploy lasing rods and warhead, 10ns for comp to do it's stuff (which is beyond amazing), 10ns to target lasing rods, 10ns to initiate reaction (laser can be spun way earlier), 10ns for said thermonuclear reaction to reach "usable" state, 0.1-0.2 seconds for the resulting laser to reach target. And voila - time dilation is a bitch.

Fortunately, author conveniently ignores all that.

EDIT: Non-Apollo missiles are still controlled via EM comms. Distance means time lag, time dilation means freq. shift. Again: this shift is non-problem, but time lag means that only with follow on-salvos missiles will noticeably increase in effectiveness (ECM/ECCM gets updated with new info). With initial salvos all you can do is update tracking and target identification (which in itself is huge: if you know what kind of ship you face, you can use that data to program for known EM emissions, equipment quirks. I.e. Second Yeltsin, when missiles were programmed to recognize "canned" tactical procedures and home in on target with contact nukes. Or Later, after analyzing SLN's captured ships, RMN could use it to practically ignore ECM/ECCM of those ships later. But in contrast to Apollo, you could control more missiles (since the communication is mostly one-way to the missile, just trickle (telemetry) on the other way to the ship). If I remember correctly. Bottom line: it is incorrect to assume that with Apollo there was change in doctrine. New technology simplified things and increased effectiveness, but didn't change doctrine. And, of course, missile itself has same issues onboard with or without Apollo.

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