penny wrote:Actually I don’t know how a ship finds its own ass from a hole in the ground, much less a waypoint. Especially with a very long trip of many light years. If the hyperlog is precise, then there should not be a problem. If the hyperlog is not precise then there should be a problem. Intuitively.
How does a ship account for the imprecision? On the one hand it all makes a little sense if you think about it. OTOH certain aspects of it does not make sense. If there is drift while waiting in hyper, it appears the drift cannot be too great if CLACs are ordered to fallback into hyper in the heat of battle waiting to be recalled. Even if the drift isn’t that great it should be bad enough that the CLAC cannot reappear in the battle at a bearing / location that is precise enough to be of tactical assistance. And the CLAC cannot transit down into n-space in the midst of battle if there is a chance it would be needed, because it takes too much tactical time to recharge the hyper generator. Therefore, a CLAC remains in hyper for at least 45 minutes. That time would have been much longer before MDMs when energy weapons win the battle. There were no CLACs before MDMs but there still would have been a need for even longer loiter times in hyper to execute a mouse trap in the age of battles that culminated with energy weapons.
First, let’s try to account for the imprecision of the hyperlogs.
The only way that I could ever make sense of it is to compare hyper space to a raging rapid and the fact that the mechanics of travel acts as it does in the age of sail. Mostly. Attempting to come to a complete stop in a wet navy by lowering the sails of a ship in a raging rapids is still going to result in ship movement unless the ship deploys some sort of an anchor. Sails cannot be lowered while in hyper. So it would seem that ships are like most real life sharks; they must keep moving or they will die.
Which brings me to my first question.
1. How does a ship drop anchor in hyperspace?
If I am not mistaken, wedges do not work in hyper. I suppose reaction thrusters could maintain station if there was some way to know how much thrust needs to be maintained to counteract movement relative to n-space; i.e., thrust / duration. If ships can wait in hyper for a short time then there does not seem to be a lot of drift. I would estimate loiter times in text to be equal to at least thirty to forty five minutes.
If we count the longest wait in hyper to spring a mouse trap it could be a few hours if we allow for the time it takes an enemy to cross the hyper limit after hypering in. Thirty to forty five minutes to a few hours is a significant amount of time for a fleet to loiter in hyper for a destroyer waiting to transit up to summon that fleet.
It is true that that amount of time pales in comparison to the wait times that would occur if a fleet tries to drop anchor for days or weeks waiting for orders to attack. But for short wait times the drift is allegedly manageable. Probably because, as you all say, a destroyer calculates the probable drift of the “currents.” The analogy in real life is determining the location of a body or object that has been dumped or dropped in the ocean by the ocean’s currents.
2. If the amount of drift can be calculated in the HV for short durations, then why can’t it be calculated for long durations?
I think the use of hyperlogs is precise if a warship follows the logs to the letter which implies that there must be a specific waypoint listed. For instance for the sake of argument, I don’t think the logs can say, “from the MBS to Gryphon via hyper is going to take 3 hrs." I would think it has to list a specific beginning waypoint inside or relative to the MBS. Navigation buoys?
The system is large. Is the beginning waypoint that is associated with the MBS in the middle of the system? My point is it would appear that long distance hyper travel should require a ship to drop out of hyper in the closest system to reset the hyperlogs. Like a bus trip that does not go straight through to your destination. It would seem that the longer the trip in hyper the more imprecise the logs would be. But that is not the case that we are presented with in the books. Trips are straight through, direct connections. So I think the problem in navigation is the laziness of the navigator and / or the impracticality of following the logs to the letter. Plus, travel along any route varies. During a track meet, each runner's position is staggered to account for the longer distance that must be run when entering turns. Curves. Is hyperspace a straight line between two waypoints? Ships don't travel the same lanes even on well traveled routes.
I can’t believe ships do not constantly drop out of hyper near a known system just to reset the hyperlogs. Annoying the heck out of systems like the MBS. “We’re just passing through!”
Therefore, how does a ship like a CLAC drop anchor to prevent drift? If there is SOME drift then it should be impractical for a CLAC to return to the battle in the correct tactical position. Mousetraps should be impossible. Refueling should be impossible, etc.
Unless there is a way to drop anchor. But wedges don’t work in hyper.
3. But what about a spider drive? Does a spider drive work in hyper? If it does, then a spider drive might be able to drop anchor and halt movement in relation to n-space. Can the tractors of an LD attach itself to the nearest wall as an anchor?
Note: The problem with drift should be greater in the highest bands.
You might find it interesting to read how intertidal navigation works here on Earth (
https://en.wikipedia.org/wiki/Inertial_ ... ion_system)
wikipedia wrote:nertial navigation is a self-contained navigation technique in which measurements provided by accelerometers and gyroscopes are used to track the position and orientation of an object relative to a known starting point, orientation and velocity. Inertial measurement units (IMUs) typically contain three orthogonal rate-gyroscopes and three orthogonal accelerometers, measuring angular velocity and linear acceleration respectively. By processing signals from these devices it is possible to track the position and orientation of a device.
The honorverse hyperlog presumably can't use quite the same mechanism because the inertial compensator would prevent accelerometers from feeling the acceleration; but it appears to work in an analogous manner - where it takes a vast number of small measurements of change in heading or acceleration and integrates them (in the literal calculous sense) to work out current location and velocity.
The reason that INUs have drift is several-fold.
One is mechanical, the gyros aren't perfect and so don't perfectly hold a reference position. So the more time that passes without the ability to realign them to a known position the more off they're going to be (though ring laser gyros are better about holding their reference than mechanical ones); but also hard maneuvers or vibration will cause further disruption to the gyros can cause them to report ever growing (but still fairly small) errors in their data.
Another is that each measurement of turn or acceleration contains some inherent error, maybe you turned 20.005 degrees but it measured 20.007. Seems tiny - but if you then proceed down that heading for 300 km and suddenly you're meters away from where you think you are. And the same thing is happening with the accelerometers. You actually accelerated for a while at 1.007 mps^2 but the accelerometer reported 1.004 mps^2 and every second you hold that acceleration its calculation of your velocity (which its deriving from acceleration and time) gets that much further off from reality (And the accelerometers are also getting hit with vibration so they aren't really measuring just intended acceleration but also the tiny back and forth accelerations from vibration -- all of which have tiny measurement errors which sometimes cancel out and sometimes compound on each other). Then you cease acceleration and hold a steady velocity; well it used the mathematical integration of all those measurements of acceleration to work out what it thinks your velocity is - but because they have inherent errors so does the calculated velocity. So again the longer you hold that velocity the larger the error grows because it thinks you're moving at 987.84 kph but you're actually moving at 987.83 - so every hour you traveled 20 meters less than it thought.
And since your position is always slightly off then when you try to account for the next change you're taking that (slightly) incorrect position and then added another (very very slightly) incorrect input to it resulting in a new position that is likely slightly more off than before.
Also the mathematical integration in our computers isn't infinitely precise and so you get some accumulated rounding/representational errors which, because you're integrating many times a second for the entire trip also slowly accumulate and show up as further tiny errors in position.
And finally inertial navigation systems have trouble directly measuring drift from wind or current and so in the absence of external reference points to correct themselves have to kind of guess that effect.
And, like in the deep sea, there's no way for a ship to anchor in hyperspace (except, maybe, for a spider ship). They just have to use their wedge or sails to slow down to zero speed and drift, or to point their nose into the known prevailing current and hold a vector that should be exactly counter to it. But without landmarks to measure against you're relying on that same inertially calculated heading and velocity to judge when you've slowed to zero, or that you're countering any known local current. And so you'll actually be somewhat off so you won't be stopped or won't be perfectly countering the current and so will continue to move slowly away from where you think you are.
And then for hyper specifically it appears that the hyper generator itself add some positional error each time you cross the alpha wall (and presumably the other walls). Now that error won't really compound over time; but does make precision emergence from hyper a mater of a bit of luck rather than 100% skill.
But the good news is that based on how long you've been in hyper and the amount of vector and acceleration changes you've made, you'll have a good idea of your maximum possible positional error. So, for example, you're not totally lost - you might know you're within, say, 2 light-hours or 1 light-day of your calculated position and thus can add adequate safety margin before exiting hyper.
As for disbelieving that ships would drop out of hyper near the system to take bearings -- we've seen them do so (though not necessarily within range the system could see them do so). When the Citizen Rear Admiral Darlington tried to surprise attack the Basilisk terminus in EoH his "TG 12.4.2 had dropped back into n-space less than two light-months out to allow him to recalibrate and recalculate" (and still missed its exit by "one-point-three light-minutes" "Call it twenty-three-point-seven million klicks". And even around Manticore it wasn't considered unusual for a freighter to drop out light hours or more beyond the hyper limit then make a micro-jump in closer. That's exactly the flight profile that the freighters which snuck the Ghosts into the MBS were mimicking -- they dropped the ghosts way out at what would look to the system sensors like a navigation check stop.
That kind of stop (whether light hours, light months, or even a couple light years) away would let them get their bearings restart a hyperlog from this new much closer position; so it has less time to accumulate error; allowing htem to safely get much closer to the hyper limit and thus limit their total trip time.
Also, none of these sources of inertial positioning error are large enough to be a problem over a few hours. Your change in positional error over that time is probably no more than a few km; even after a long voyage without ever stopping to take bearing. (And if you'd taken a recent fix in n-space and then reentered hyper to wait the positional error of a few hours is more likely meters than kilometers)
And of course having even one ship come back from n-space with new bearings will let an entire convoy or fleet waiting in hyper recalibrate their hyperlog to that newly known position.
Higher hyper bands
would likely end up with more effective error than lower ones, for any given time duration, for a couple of reasons. One, I think any time you cross a hyper wall it adds a bit of uncertainty to your position; so having to cross more walls to get that high will add a bit of error -- though that shouldn't compound over time. Then location within the band shouldn't be any worse than in a lower band, but the effect of the error would presumably be magnified by the higher spatial compression. In both cases you might know where you are to +/- 20 km within the band. But from the Alpha band to n-space that translates to a 20*62= 1,240 km error; while from the Delta bands that translates into a 20*2178 = 43,560 km error.
But in a normal trip the reduced transit time from the higher bands should result in a lower overall error despite those.
But if you need to wait days or weeks for disparate fleet elements to rendezvous... then staying in hyper becomes a problem. If the other force misses you due to your mutual inertial navigation errors then it's very hard to find each other because of the very short sensor ranges in hyper. We saw from the simulation Warfarer was running in Silesia that without grav sensors you can even see 5 million km in hyper, and according to MtH even grav sensors are incapable of picking up anything beyond about 17.6 LM (316,580,880 km.) to 22.4 LM (or 402,921,120 km.); depending on local hyperspace conditions. If a fleet missing by more than that they might be searching around for a really long time trying to find the rendezvous.
But if you pick a nearby unclaimed star system you can set a rendezvous around a given planet and in n-space that's more that close enough to let each arriving force to find the others. Their nav error over any conceivable hyper journey is still more than small enough to find the star
. And from the star finding the planet is easy -- given the vastly longer sensor ranges in normal space.
And since everyone will know whether they're in the right spot the forces already there will know if another hasn't shown up its because they're running late or plans changed, and not because they're wandering around lost in the dark.
