Information I'd love to know

tlb wrote:

tlb wrote:The gravity wave is the only thing in hyperspace that has the same effect as wind or currents on the old sailing ships

Jonathan_S wrote:Or it was.

But now, with negative grab factor sails, I expect there's no longer any difference between sailing "upwind" or "downwind" -- leaving nothing that seems to still exert a 'wind or current' effect on starships.

I find it difficult to believe that the magnitude of the grab factor can be as great going against the gravity wave as it is going with the wave.

My understanding (which is shaky) is that the grab factor is related to the amount of acceleration it is possible to get. So once the maximum speed is reached (I do not know how travel direction through the gravity wave affects this max value), then a grab factor of zero is fine; the sails are no longer generating acceleration and are just supplying power to the ship. If the bulk of the journey through the wave is at max speed, then the time accelerating does not affect the total travel time all that much. Does this sound at all correct?

Certainly acceleration is normally a small part of an interstellar journey. That that's even truer in a grav wave where acceleration is so much higher, and so you max out so much sooner.

However, if ships accelerated more slowly "into the wind" than with it I'd have still expected that to be listed as a downside. But I'll requote what I see as the key passage from "The Universe of Honor Harrington" in More Than Honor
[quote=]Indeed, it became possible to create a negative grab factor which, in effect, permitted a starship to sail directly "into the wind," although with a marginally greater danger of sail failure.[/quote]In contrast to when ships were slower sailing upwind due to the need to tack, as of 1750 pd (150ish years before the series started) this lists only a downside of that slight increase in sail failure risk when sailing "into the wind"

And keep in mind that the limiting acceleration factor, even in a grav wave, is usually the ship's inertial compensator. The deeper "sump" of a sail in a 'wave gives around a 10x acceleration advantage over a wedge - but I don't see why the size of the "sump" would differ based on your angle of sail relative to the "wind". So even if the sails have to work harder for the same accel (which might account for the higher risk of failure) the max accel is almost certainly still limited by the compensator -- which, as I said, I don't think cares which way you're heading in the 'wave.

Jonathan_S wrote:Certainly acceleration is normally a small part of an interstellar journey. That that's even truer in a grav wave where acceleration is so much higher, and so you max out so much sooner.

However, if ships accelerated more slowly "into the wind" than with it I'd have still expected that to be listed as a downside. But I'll requote what I see as the key passage from "The Universe of Honor Harrington" in More Than Honor

Indeed, it became possible to create a negative grab factor which, in effect, permitted a starship to sail directly "into the wind," although with a marginally greater danger of sail failure.

In contrast to when ships were slower sailing upwind due to the need to tack, as of 1750 pd (150ish years before the series started) this lists only a downside of that slight increase in sail failure risk when sailing "into the wind"

And keep in mind that the limiting acceleration factor, even in a grav wave, is usually the ship's inertial compensator. The deeper "sump" of a sail in a 'wave gives around a 10x acceleration advantage over a wedge - but I don't see why the size of the "sump" would differ based on your angle of sail relative to the "wind". So even if the sails have to work harder for the same accel (which might account for the higher risk of failure) the max accel is almost certainly still limited by the compensator -- which, as I said, I don't think cares which way you're heading in the 'wave.

That still leaves the possibility that the grab factor could be the limit when sailing into the gravity wave, not the compensator sump. It would still be faster than tacking, which involves deceleration and acceleration at every turn; whereas sailing directly into the wave only requires possible acceleration on initial entry. Still you could be right and the major gain is the elimination of all the deceleration and acceleration required by tacking.

If you are switching from wedge to sail upon entry into a gravity wave in hyperspace; then is there even an initial acceleration needed, since you are probably at the maximum velocity already? If no acceleration is needed, then whether the limit is the grab factor or not is moot.

tlb wrote:That still leaves the possibility that the grab factor could be the limit when sailing into the gravity wave, not the compensator sump. It would still be faster than tacking, which involves deceleration and acceleration at every turn; whereas sailing directly into the wave only requires possible acceleration on initial entry. Still you could be right and the major gain is the elimination of all the deceleration and acceleration required by tacking.

If you are switching from wedge to sail upon entry into a gravity wave in hyperspace; then is there even an initial acceleration needed, since you are probably at the maximum velocity already? If no acceleration is needed, then whether the limit is the grab factor or not is moot.

Sure, it's possible that grab factor limits your acceleration "into the wind". I just happen to think that if that was true it would have been mentioned.

However you've got a point about entering the grav wave at full speed. We know that doesn't happen all the time, but it certainly could be the norm.

(The one known, and one logically existing, counterexample would be:
a) The Selker Rift -- were the text explicitly points out that ships cross it "under impeller drive at extremely low velocities—on the order of .16 c—in order to be sure they could dodge if the Selker Shear suddenly appeared on their detectors." [HAE] So even if it's safe to accelerate once the (non-rogue) wave on far side is spotting there's not enough room to work up to full speed before reaching it.

b) A system situated within a grav wave (which we know happens) where some destinations are reached by leaving "into the wind". (We don't know of an explicit example, as outside of that historic reference the books don't talk about the "wind" within a wave, at least not that I can recall. But logically there must be some routes where that's the case. And a ship freshly entering hyper is going slowly and must accelerate; yet its already within the wave.