Relative size of combatants

I would like to point out to those discussing travelling the cliff that trains don't really like switchbacks very much (heck, I don't care for them all that much!), At the Kicking Horse pass, the railway line was originally built on the slope of the mountain which lead to many trains exceeding the speed limit and some of them crashing. They eventually built a couple of spiral tunnels to reduce the grade from 1 in 23 to 1 in 46.

The original route of the CPR between the summit of the pass near Wapta Lake and Field was known as "The Big Hill"; with a ruling gradient of 4.5 percent (1 in 23), it was the steepest stretch of main-line railroad in North America.

Due to frequent accidents and expensive helper engines associated with railroading in the pass, the CPR opened a pair of Spiral Tunnels in 1909 that replaced the direct route. Although these tunnels add several kilometres to the route, the ruling grade was reduced to a more manageable 2.2 percent (1 in 46).

The Trans-Canada Highway was constructed through the pass in 1962 following essentially the original CPR route. It reaches its highest point at the Kicking Horse Pass with an elevation of 1,643 metres (5,390 ft).

https://en.wikipedia.org/wiki/Kicking_Horse_Pass

I see from this --

As it is from the prolog we know that ground level on the Karys side is about 700 ft above sea level (14.33 PSI stp). And mountains on the Traisum had peaks around 4,6000 feet -- but 3,000+ feet of cliff are exposed. So the "ground level" of the portal is 4,600 - 3,000 = about 1,600 feet above sea level (13.87 PSI stp). We're only talking about 0.46 PSI difference (or a 31 millibar drop). That seems a very long way from creating hurricane force winds.


Would there be some erosion and fallen rock? Sure. But I don't think it's going to be significant parts of the cliff-side.

You are having a "several orders of magnitude problem."

You are talking in terms of pressure per SQUARE INCH.

I am talking about the 1/2 of the mass that 0.46 PSI of pressure represents, MULTIPLIED BY THE ENTIRE SURFACE AREA OF THE PLANET EARTH.

We are talking the mass of 800 feet of the entire planet Earth's atmosphere going through a 4.5 mile wide by however high hole.

Plus all the water and solid dust like material that mass of fast moving gas can pick up and pull through that hole into a lower pressure area.

Condensation from the pressure drop alone would have delivered _megatons_ worth of water in the cliff face area, and _a lot_ more behind it.

However smooth and high the cliff was when first cut, it would be much less so, and much farther away from the edge of the portal, especially at its cliff top after the pressure equalized, from the wind and water erosion.

The kinetic energy from that much gas equalizing between two planets is, conservatively, several times the humanity's peak nuclear weapon yield in the Mid-1970's.

And about 30% to 40% of that kinetic energy would have been hitting the cliffs directly.

Sorry, but wind speed is a function of pressure differential, and that only. The amount of air to be transferred will affect the _duration_ of the flow, not the speed. AAMOF, flow speed decreases exponentially as the pressure equalises. Or, to be more accurate, as mean pressure equalises, since the pressure on each side of the portal will never be the same unless met conditions are identical - which is bound to happen occasionally, but wouldn't be a normal condition.

Mind you, 31mb is a big enough drop to drive something closer to gale-force winds than not.

Mil-tech bard wrote:I see from this --

As it is from the prolog we know that ground level on the Karys side is about 700 ft above sea level (14.33 PSI stp). And mountains on the Traisum had peaks around 4,6000 feet -- but 3,000+ feet of cliff are exposed. So the "ground level" of the portal is 4,600 - 3,000 = about 1,600 feet above sea level (13.87 PSI stp). We're only talking about 0.46 PSI difference (or a 31 millibar drop). That seems a very long way from creating hurricane force winds.


Would there be some erosion and fallen rock? Sure. But I don't think it's going to be significant parts of the cliff-side.

You are having a "several orders of magnitude problem."

You are talking in terms of pressure per SQUARE INCH.

I am talking about the 1/2 of the mass that 0.46 PSI of pressure represents, MULTIPLIED BY THE ENTIRE SURFACE AREA OF THE PLANET EARTH.

We are talking the mass of 800 feet of the entire planet Earth's atmosphere going through a 4.5 mile wide by however high hole.

Plus all the water and solid dust like material that mass of fast moving gas can pick up and pull through that hole into a lower pressure area.

Condensation from the pressure drop alone would have delivered _megatons_ worth of water in the cliff face area, and _a lot_ more behind it.

However smooth and high the cliff was when first cut, it would be much less so, and much farther away from the edge of the portal, especially at its cliff top after the pressure equalized, from the wind and water erosion.

The kinetic energy from that much gas equalizing between two planets is, conservatively, several times the humanity's peak nuclear weapon yield in the Mid-1970's.

And about 30% to 40% of that kinetic energy would have been hitting the cliffs directly.

Mil-tech bard wrote:And the cliff bottom debris field from the protracted hurricane (+++) winds pulling material through the portal and collapsing material from the cliff top to the bottom is very much on the Arcanian side.

The wind would be traveling into Traisum, since the Traisum portal aspect is at a higher altitude than the Karys aspect. No debris would have been pulled into Karys be the wind, although some (maybe even large amounts) may have fallen there after being loosened, or as part of natural crumbling of the cliff.

Mil-tech bard wrote:The beach at the cliffs of Dover is not at the edge of the cliff top.

The cliffs of Dover were naturally formed, probably were never completely vertical, and erosion has had millions of years to work on them. Comparatively the cliff caused by the portal has been there for very little time, was at creation perfectly flat, and without much chance for erosion (aside from the wind at the beginning) to work on it. Even a thousand years of powerful winds moving through the portal won't compare to millions of years of natural erosion.

When you post something like this --

Sorry, but wind speed is a function of pressure differential, and that only. The amount of air to be transferred will affect the _duration_ of the flow, not the speed. AAMOF, flow speed decreases exponentially as the pressure equalizes. Or, to be more accurate, as mean pressure equalizes, since the pressure on each side of the portal will never be the same unless met conditions are identical - which is bound to happen occasionally, but wouldn't be a normal condition.

Mind you, 31mb is a big enough drop to drive something closer to gale-force winds than not.

You are missing the implications of the momentum equation.

Kinetic energy = M * V^^2

Your concern is "V" velocity of the mass through the portal.

I am talking "M" for mass.

To determine that you would have to take the sphere equation for the diameter of the Earth plus ~1600 feet and subtract the diameter of the earth plus 800 feet.

Then you would have to determine the average density for the column of air that represents and figure out things like the water/humidity and the mass of the dust percentage in that density average.

Then you would have to compute the portal area-- both sides -- and figure how long it would take that mass of air to transit given the pressure difference curve.

NB: This feels like the set up of a rocket equation to figure out the area under the curve to determine the total mass/energy budget.

My gut says were are looking several tens of "Nixon-Brezhnev's", AKA Humanities combined nuclear arsenal at 1975-79 worth of kinetic energy transiting the portal. And that is at the low end.

This energy would be expressed in several ways, starting with the most intense low pressure area in the history of the planet up chain from Ft Salby causing a continent sized standing hurricane system centered on the portal while atmospheres equalize.

And there would be no "eye" at the center of this hurricane, as the rotating atmosphere would be going down the portal "drain".

My gut sees something on the order of the pre-diversion Aral Sea's worth of water coming through the portal in that mass of atmospheric gas, with most of it condensing out in the immediate vicinity of the Ft Salby portal.

Living through May 2015 in Dallas, where we had the 3rd rainiest month in recorded human history (about 110 years, or 1320 months, worth of weather records), and on mostly flat land, gives me some minor idea of what flood water can do.

In that 30 day period really intense 1 to six inch an hour rains fell fell at most 5% of the time. Several spot areas in the DFW metroplex got six inches in three hours and 12 inches total in a day and they were all flash flooded.

What does precipitation at a rate of 1 to 6 inches an hour, pushed at gale force winds, for tens of weeks to tens of months on end, do to a mountain topography?

The closest idea I have is the Channeled Scablands of eastern Washington state, See:

https://en.wikipedia.org/wiki/Channeled_Scablands


See also:

https://en.wikipedia.org/wiki/Glacial_l ... urst_flood

and:

https://en.wikipedia.org/wiki/Missoula_Floods


Which means, whatever else happened at the portal after its formation, the cliffs -- and especially the cliff tops -- are now set back a significant distance from the portal wall, with all that implies for Arcanian magic based weapons.

And the low point where the Sharonan's began cutting their railway was the bottom of a glacial flash flood class "notch" in those cliffs.

I have been doing some thinking about what happens during portal formation. Our problem is that we are trying to use standard earth atmospheric pressure to gauge what airflow would look like when the portal forms. Normally that wouldn't be a problem, but with portals opening on the worlds in question, and with the resulting airflow, we can't really know what atmospheric conditions apply. Air pressure could have been lower or higher than normal on either world. We haven't been given enough detail to make worthwhile guesses.

Just going be evidence in the text, there does not appear to be significant erosion of the cliff face, and no mention of erosion effects have been made (like in Thermyn, around Fort Ghartoun). Erosion effects may have been left out because it did not impact the story, but the description of the cliff seems pretty definitive.

Your arguments sound logical, though I don't have the meteorological knowledge to know for sure, but they don't match what the books say.

HHNF Prologue wrote:That was what created the spectacular scenery. Zaithag was barely seven hundred feet above sea level; the mountains west of Narshalla reached heights of over forty-six hundred feet… and the portal’s Traisum nexus was located smack in the middle of one of those mountains.

Most people who saw it from the Karys side for the first time felt a peculiar sense of disorientation. It was something the human eye and the human mind weren’t trained to expect: an absolutely vertical, glassy-smooth cliff over a half-mile high at its shortest point and four and a half miles wide.

The good news was that Karys was outbound from Sharona. That had allowed the Trans-Temporal Express’ construction crews to come at it from the slopes of Mount Karek rather than straight out of the mountain’s heart. The portal was actually located east of the mountain’s crest, which made the impossible cliff several hundred feet shorter...

The implication is that the top of the portal is at approximately the same altitude on both worlds (maximum mountain height 3900 ft higher, but the difference only over 2640 ft at the short point, which is hundreds of feet below the top), with the only difference being the mountain. It should certainly make itself felt in weather patterns, especially in interrupting air moving on the lower side, but there aren't great air pressure differentials where the atmosphere can actually go through, and since (I think) both sides are desert, there probably isn't much moisture either. Dust, sure, but moisture is usually much more important than dust for erosion.

So if there isn't much mass of air moving or at great speed, and it isn't dropping any water along the way, that might account for the lack of erosion. The age of the portal might contribute, if it's fairly new. Maybe the authors decided they didn't want this cliff eroded for whatever reason and deliberately set up the conditions so it wouldn't be. As Astalon said, they included altitude differential erosion at another portal, so they can't have simply overlooked it here.

Not incidentally, since Voices can't speak through a portal, the only way anyone at Fort Salby could continue the Voicenet down-chain is either going to the bottom of the cliff or poking his head through the portal, probably through some kind of platform sticking over at the top. Having a vertical cliff butting up against the portal would sure make communications easier and faster than having to descend the mountain or post a Voice down there for the through-portal relay.

And Kinlafia is seeing it from the Hell's Gate side on that prologue. The Sharonians started at the top and cut down, not from the bottom and working up.

Mil-tech bard wrote:When you post something like this --

Sorry, but wind speed is a function of pressure differential, and that only. The amount of air to be transferred will affect the _duration_ of the flow, not the speed. AAMOF, flow speed decreases exponentially as the pressure equalizes. Or, to be more accurate, as mean pressure equalizes, since the pressure on each side of the portal will never be the same unless met conditions are identical - which is bound to happen occasionally, but wouldn't be a normal condition.

Mind you, 31mb is a big enough drop to drive something closer to gale-force winds than not.

You are missing the implications of the momentum equation.

Kinetic energy = M * V^^2

Your concern is "V" velocity of the mass through the portal.

I am talking "M" for mass.

To determine that you would have to take the sphere equation for the diameter of the Earth plus ~1600 feet and subtract the diameter of the earth plus 800 feet.

Then you would have to determine the average density for the column of air that represents and figure out things like the water/humidity and the mass of the dust percentage in that density average.

Then you would have to compute the portal area-- both sides -- and figure how long it would take that mass of air to transit given the pressure difference curve.

NB: This feels like the set up of a rocket equation to figure out the area under the curve to determine the total mass/energy budget.

My gut says were are looking several tens of "Nixon-Brezhnev's", AKA Humanities combined nuclear arsenal at 1975-79 worth of kinetic energy transiting the portal. And that is at the low end.

This energy would be expressed in several ways, starting with the most intense low pressure area in the history of the planet up chain from Ft Salby causing a continent sized standing hurricane system centered on the portal while atmospheres equalize.

And there would be no "eye" at the center of this hurricane, as the rotating atmosphere would be going down the portal "drain".

My gut sees something on the order of the pre-diversion Aral Sea's worth of water coming through the portal in that mass of atmospheric gas, with most of it condensing out in the immediate vicinity of the Ft Salby portal.

Living through May 2015 in Dallas, where we had the 3rd rainiest month in recorded human history (about 110 years, or 1320 months, worth of weather records), and on mostly flat land, gives me some minor idea of what flood water can do.

In that 30 day period really intense 1 to six inch an hour rains fell fell at most 5% of the time. Several spot areas in the DFW metroplex got six inches in three hours and 12 inches total in a day and they were all flash flooded.

What does precipitation at a rate of 1 to 6 inches an hour, pushed at gale force winds, for tens of weeks to tens of months on end, do to a mountain topography?

The closest idea I have is the Channeled Scablands of eastern Washington state, See:

https://en.wikipedia.org/wiki/Channeled_Scablands


See also:

https://en.wikipedia.org/wiki/Glacial_l ... urst_flood

and:

https://en.wikipedia.org/wiki/Missoula_Floods


Which means, whatever else happened at the portal after its formation, the cliffs -- and especially the cliff tops -- are now set back a significant distance from the portal wall, with all that implies for Arcanian magic based weapons.

And the low point where the Sharonan's began cutting their railway was the bottom of a glacial flash flood class "notch" in those cliffs.

As for this --

So if there isn't much mass of air moving or at great speed, and it isn't dropping any water along the way, that might account for the lack of erosion. The age of the portal might contribute, if it's fairly new. Maybe the authors decided they didn't want this cliff eroded for whatever reason and deliberately set up the conditions so it wouldn't be. As Astalon said, they included altitude differential erosion at another portal, so they can't have simply overlooked it here.

What looks like "a glass-like cliff" at a distance isn't necessarily so close up.

For reasons I stated, I don't see the cliff face being -at the portal- and especially so -at the cliff tops- near the cut.

Whether there is water there for weathering currently has nothing to bear regards what was caused by the portal formation.

NB: There isn't much water in the Scablands now. Which is why we see it today in almost the same dried out state as post glacial lake flood plus a year.

There were also author comments in the text about how extreme the weather was from pressure differences immediately after the portal was being formed.

Pressure difference equals a huge exchange of planetary atmosphere through the portal, AKA huge amounts of atmosphere with a lot of it bearing water.

Pressure difference equals sustained -- as in weeks or months -- of gale force winds.

Pressure difference also equals huge biblical flash flood amounts of condensation from that planetary atmosphere exchange fraction in the immediate area behind the lower pressure aspects of the portal.

Even if the Portal formation left the mountain face with a water impermeable glass-like coating, the tops of the cliffs were not.

The water would soak in behind the glass like coating and the structural stresses form all that water turning desert mountain side to mud would crack the glass-like coating for gale force winds and water erosion.

And there would be a lot of dust and small rocks thrown against the cliffs by the gale force wind to repeat the process of crack-breaching of said impermeable glass-like coating for condensation to scab off large chunks of the coating.

Parts of the desert cliffs would come down from that weather like Southern California mud slides on methamphetamine's.

The author dropped a slight hint about there being a low point from which the train route was cut.

I expect that the "notch" or "low point" was not there before the portal.

From 3900 ft to only over 2640 ft (1260 feet difference) is about right for a catastrophic flood cut into the cliff face starting from a relative depression in the terrain.

bkwormlisa wrote:Your arguments sound logical, though I don't have the meteorological knowledge to know for sure, but they don't match what the books say.

HHNF Prologue wrote:That was what created the spectacular scenery. Zaithag was barely seven hundred feet above sea level; the mountains west of Narshalla reached heights of over forty-six hundred feet… and the portal’s Traisum nexus was located smack in the middle of one of those mountains.

Most people who saw it from the Karys side for the first time felt a peculiar sense of disorientation. It was something the human eye and the human mind weren’t trained to expect: an absolutely vertical, glassy-smooth cliff over a half-mile high at its shortest point and four and a half miles wide.

The good news was that Karys was outbound from Sharona. That had allowed the Trans-Temporal Express’ construction crews to come at it from the slopes of Mount Karek rather than straight out of the mountain’s heart. The portal was actually located east of the mountain’s crest, which made the impossible cliff several hundred feet shorter...

The implication is that the top of the portal is at approximately the same altitude on both worlds (maximum mountain height 3900 ft higher, but the difference only over 2640 ft at the short point, which is hundreds of feet below the top), with the only difference being the mountain. It should certainly make itself felt in weather patterns, especially in interrupting air moving on the lower side, but there aren't great air pressure differentials where the atmosphere can actually go through, and since (I think) both sides are desert, there probably isn't much moisture either. Dust, sure, but moisture is usually much more important than dust for erosion.

So if there isn't much mass of air moving or at great speed, and it isn't dropping any water along the way, that might account for the lack of erosion. The age of the portal might contribute, if it's fairly new. Maybe the authors decided they didn't want this cliff eroded for whatever reason and deliberately set up the conditions so it wouldn't be. As Astalon said, they included altitude differential erosion at another portal, so they can't have simply overlooked it here.

Not incidentally, since Voices can't speak through a portal, the only way anyone at Fort Salby could continue the Voicenet down-chain is either going to the bottom of the cliff or poking his head through the portal, probably through some kind of platform sticking over at the top. Having a vertical cliff butting up against the portal would sure make communications easier and faster than having to descend the mountain or post a Voice down there for the through-portal relay.

And Kinlafia is seeing it from the Hell's Gate side on that prologue. The Sharonians started at the top and cut down, not from the bottom and working up.

I think I found the textev to prove you right and us wrong:

HHNF Prologue wrote:There was a two-hour time difference between the two sides of the portal, which, fortunately was also one of the older portals which had so far been discovered. It must have been… lively around Fort Salby’s present location for the first century or so after the portal formed, Kinlafia reflected. The altitude differential was less than that of some other portals, but it had still been sufficient to channel a standing, unending, twenty-four-hour-a-day, three-mile-wide hurricane through from Karys until the pressures finally equalized. There was ample evidence of the sort of sandblasting erosion portals at disparate heights tended to produce, although none of it was very recent. And there was still a permanent, moderately stiff breeze blowing through the portal, even now, which made it unfortunate that Zaithag was about as dry (and hot) as Narshalla. Fort Salby could have used a little rain, if Karys had had any to spare.

HHNF second Fort Salby attack wrote:The maneuver wouldn’t have been very practical without dragons. The nature of the portals between universes meant that any traveler from Karys found himself confronting the same sort of enormous cliffs no matter which way he passed through the portal, but the westernmost cliffs were quite a bit higher than those to the east. Wind erosion had softened and grooved the tops of those sheer cliffs until the pressures between the two sides of the portals had equalized, but the palisade of stone remained steeply and starkly unscalable.

Facing east into Traisum, from the opposite side of the portal, the cliffs were much shallower, and the wind screaming down the slopes beyond the cliffs edges had carved deep ravines. The Sharonian construction engineers had taken advantage of that when they cut their road and “railroad” routes. As far as Fahrlo could see, they hadn’t had very much choice about that, but the Expeditionary Force did, and Two Thousand Harshu and Thousand Toralk had decided to take advantage of that fact.

For some reason, I was thinking that the only portal where such a differential was mentioned was Fort Ghartoun (which also had desert winds rip through at high pressure differentials). But Salby had hurricane force winds for decades and they obviously did a whole lot of damage. It was probably mostly at the top, since that's where the winds were, but I doubt the cliff is actually glassy smooth anywhere anymore.

I don't know if there was any significant flooding (it wasn't mentioned and is still in a desert on both sides) and I'm not certain how far down the erosion is or how much debris there is - the quotes only refers to erosion at the top, and much of it must have been carried into Traisum with the winds rather than fallen into Karys - but you're right; the top of the cliff isn't pressed up against the portal, and probably not even close. Must make communications difficult.

One thing that puzzles me; the books say that serious exploration was bottlenecked until the Traisum Cut was finished. I'd think it would have been impossible. Other than rappelling down and stringing some kind of lines (ski lifts half a mile high?) how could they have explored it at all? Would ski-lift style transport even be doable in that kind of terrain?

Mil-tech bard wrote:As for this --

So if there isn't much mass of air moving or at great speed, and it isn't dropping any water along the way, that might account for the lack of erosion. The age of the portal might contribute, if it's fairly new. Maybe the authors decided they didn't want this cliff eroded for whatever reason and deliberately set up the conditions so it wouldn't be. As Astalon said, they included altitude differential erosion at another portal, so they can't have simply overlooked it here.

What looks like "a glass-like cliff" at a distance isn't necessarily so close up.

For reasons I stated, I don't see the cliff face being -at the portal- and especially so -at the cliff tops- near the cut.

Whether there is water there for weathering currently has nothing to bear regards what was caused by the portal formation.

NB: There isn't much water in the Scablands now. Which is why we see it today in almost the same dried out state as post glacial lake flood plus a year.

There were also author comments in the text about how extreme the weather was from pressure differences immediately after the portal was being formed.

Pressure difference equals a huge exchange of planetary atmosphere through the portal, AKA huge amounts of atmosphere with a lot of it bearing water.

Pressure difference equals sustained -- as in weeks or months -- of gale force winds.

Pressure difference also equals huge biblical flash flood amounts of condensation from that planetary atmosphere exchange fraction in the immediate area behind the lower pressure aspects of the portal.

Even if the Portal formation left the mountain face with a water impermeable glass-like coating, the tops of the cliffs were not.

The water would soak in behind the glass like coating and the structural stresses form all that water turning desert mountain side to mud would crack the glass-like coating for gale force winds and water erosion.

And there would be a lot of dust and small rocks thrown against the cliffs by the gale force wind to repeat the process of crack-breaching of said impermeable glass-like coating for condensation to scab off large chunks of the coating.

Parts of the desert cliffs would come down from that weather like Southern California mud slides on methamphetamine's.

The author dropped a slight hint about there being a low point from which the train route was cut.

I expect that the "notch" or "low point" was not there before the portal.

From 3900 ft to only over 2640 ft (1260 feet difference) is about right for a catastrophic flood cut into the cliff face starting from a relative depression in the terrain.

bkwormlisa wrote:
One thing that puzzles me; the books say that serious exploration was bottlenecked until the Traisum Cut was finished. I'd think it would have been impossible. Other than rappelling down and stringing some kind of lines (ski lifts half a mile high?) how could they have explored it at all? Would ski-lift style transport even be doable in that kind of terrain?

As an arborist I can give some information. The limit on the usefull length that a rope can be is when the weight of the rope and the load being carried is equal to the Working Load Limit. Arborsts consider 10% of breaking strength to be a usefull WLL. Since we use rope with a minimum breaking strength of 5400 LBs, our WLL is generally something over 540LBs. Note that Rope is not light, and while the longest rope I have personal experience with is only 150 feet, most manufacturers largest sale length is 600 feet.

http://www.sherrilltree.com/Blue-Streak ... ZxptkYfCUk

The rope I am familiar with is 15lbs for 200FT Thus would be 7200 ft to be 540lbs of rope.