Escape Velocity Problem Returns in T5!

[Vladika]

No. That's the point that you are missing. Technically you never completely leave the atmosphere, you just drop down to a point where the atmosphere is so low that for all practical purposes we treat it as 0. Even in interstellar space there is a weak 'atmospheric' pressure caused by those 20-50 atoms per cm³. Those scattered atoms will provide lift just like they will at more normal atmospheric pressures, the only thing is that the lift they provide is incredibly minute.

Fortunately the air resistance is also incredibly minute so a ship that maintains the same amount of thrust as what it needs to ascend in the normal atmosphere will end up travelling so mindbogglingly fast that that minute amount will turn into real lift.

The formula for lift is F_L = (1/2) d v² s C_L with d being the density of the medium, s being the surface area of the wing and C_L being the coefficient of lift.

The formula for drag (using the same symbology and similar sequence) is F_D = (1/2) d v² a C_D where a is the area of the object and C_D is the coefficient of drag.

This means that as d decreases v will increase in order to keep F_D the same (since the thrust of the engine remains constant), and because of how the math works it increases at exactly the rate it has to in order to maintain F_L.

The reason jet aircraft have maximum ceilings is because they are still air-breathing engines. Take one out to the interplanetary medium and it won't even ignite. As the plane moves higher and higher above the engine's optimal altitude (I presume that most jet engines are probably not tuned to be at their most optimal at sea level) their output decreases. This means that F_D also decreases as they gain altitude and so while v might increase for a while as the plane goes higher it won't increase fast enough to maintain F_L. Long before the engine simply cuts out from lack of atmosphere the plane will reach an equilibrium where it will be unable to gain altitude. (This is in reference to a powered ascent. It is entirely possible that some jets may be able to make ballistic ascents that allow their momentum to carry them past the equilibrium point to the point where their engines cut out, but that's not what is being talked about).

Long before you reach interplanetary medium, however, you will cross the Karman line. This is the point in which the velocity of the plane must be so high to maintain lift that the plane is already travelling at orbital velocity and so no longer needs any lift to continue to ascend. It simply needs to increase velocity like any other orbital body.

The primary reason we need the big Saturn V rockets in the real world is because of what is known as specific impulse and the ideal rocket equation. Basically it says that because the amount of thrust produced in relation to the amount of mass expelled (the specific impulse) is relatively low (in relation to theoretical propulsion sources, not in relation to something like a modern car or jet) you have to carry enormous amounts of fuel in order to reach escape velocity. Ships in Traveller have either effectively infinity specific impulse or extremely high specific impulse depending on how you view it (you could arguably create a specific impulse from the amount of fuel required to run the powerplant and maneuver drive of the ship). If you could effectively put an engine with a similar specific impulse and that did not lose efficiency as it gained altitude on a jet then it could simply fly into space, even if the engine's power output was no greater than that produced by the conventional jet engine (i.e. it only has to be a fraction of a G since these don't have to be the jet engines on a fighter. They could be the jet engines on a 747).

All of your arguments are well though out. I do believe, for the foreseeable future, that there are other insurmountable problems. An example might be heat. What is the difference between an object burning up on reentry or burning up on exit? (Other than torching off on exit do we assume they are coming back down? The Shuttle was damnably slow compared to what you're proposing.)

The SR-71 elongates 9 inches due to heat at it's designed altitude and velocity. That's a lot, therefore expansion is also an issue. (It has fuel leak issues too due to this expansion.)

Then there's the "noise pollution" crowd that stops current aircraft from being allowed to break the sound barrier. Admittedly that's a legalistic rather than physical law. I do wonder what the effect would be with hundreds, or more, craft daily transiting to space would be.

Hopefully, one day, it will work out. I, for one, hope so and think it would be nice to live long enough to see it happen.

 

[esampson]

Yeah, I'm sure there are some technical problems, especially when the vehicle has to go through the sound barrier. I shouldn't have made it sound like 'replace the engines on a 747 and you're good to go'. However none of those problems are caused by the basic math of lifting bodies and velocity.

Interestingly, I'm not entirely sure if friction heat is one of them. I know that the SR-71 heats and expands (another interesting factoid I read was that the skin is sort of a micro-honeycomb shape in order to allow for expansion and that on the tarmac the SR-71 would 'sweat' fuel until the skin warmed up enough to close up those cells) but I think that has more to do with the incredibly high thrust to drag ratio of the plane. Basically the engines were ramming it through the air so fast that you could produce that same heating effect even at the lower speeds of the lower altitude.

I'm also fairly certain that de-orbiting objects are travelling far in excess of what they would be traveling if they were using a more conventional 'flying' path. It has to do with the fact that aerobraking like that is a more fuel-efficient way to bring the object down, but since that's not a real issue in Traveller they can use easier powered flight landings.

I am nowhere near as certain on either of those points, however, as I was about the lift/velocity issue and I could quite definitely be wrong about them. I should probably play around with the configuration of the Delta Glider in Orbiter to test those theories.

 

[Supplement Four]

I'm sorry, I see that I skipped a couple of steps in the chain of logic:

I definitely see your side of the argument, but what you're saying is not canon. It's something that you've worked out logically.

Canon is that major trade routes generally follow the X-Boat lanes.

Your logic forms an argument to the contrary.

With your argument, flawless logic or not, it's still not canon. Canon is what is stipulated in the book.





Now, I will say this: I think taking your logic and applying it to a game would be a good move for your game.

As a similar example, I look at the Career Choices in CT as basic examples. I think that they should be changed to reflect the world that they are associated with.

Tech Level limits should be enforced. Maybe some skills should be traded out or not allowed. Maybe a default skill added. Take the base career and customize it to fit the world.

I feel the same about the CT weapons chart. Those are baseline, basic weapons. I think that different models from different worlds will sometimes have slightly different stats. Or, maybe a TL increase or decerease will also cause a variation from the base line stats.

I think that's good CT play.

But, what I suggest is not necessarily canon.

 

[rancke]

I definitely see your side of the argument, but what you're saying is not canon. It's something that you've worked out logically.

But what is the logic based on? Canon, that's what. So if the logic is sound, the conclusion is just as much canon as the bit of text you quoted.

Canon is that major trade routes generally follow the X-Boat lanes.

One part of canon is that major trade routes generally follow the X-boat lanes. A different part of canon (to wit, the ship design rules) implies that they don't. And as is always the case with a canon conflict, you have to choose. I choose the bit that makes sense over the bit that doesn't.

With your argument, flawless logic or not, it's still not canon.

Yes it is, because it is based on canon. It's not something I'm pulling out of thin air.

The thing is that fictional facts don't come with built-in self-consistency, the way Real Life facts does. So we can't just accept everything that canon says uncritically. It also has to make sense.

Canon is what is stipulated in the book.

That's true. What the book with the ship design rules says is canon.

Mind you, I usually prefer setting material over rules. However, in this particular case, I don't think it would be possible to come up with simple alternate rules that would make J4 traffic cheaper than J2 and J3 traffic. I think one would have to make arbitrary changes to the costs of different jump drives. I could be wrong, but I would have to be shown. in any case, I don't think there's any chance of convincing Marc Miller to convert to any such rules. Which leaves adapting the setting to fit the rules, something I abhor, but needs must...

My suggestion would be to consider the statement folk wisdom rather than authorial voice material. It's one of those things that "everybody knows" that actually ain't so.


Hans

 

[aramis]

But what is the logic based on? Canon, that's what. So if the logic is sound, the conclusion is just as much canon as the bit of text you quoted.

doesn't work that way, Hans.

Canon is only what is explicitly listed.

Derived from canon, yes, but not canonical, since other logical extrapolations exist that are equally derived from canon.

 

[rancke]

doesn't work that way, Hans.

Why not, Wil? I'm afraid I can't agree with your opinion. Any fact that can be logically deduced from canon facts must likewise be canon facts. That's how logic works.

Derived from canon, yes, but not canonical, since other logical extrapolations exist that are equally derived from canon.

Oh, if you're talking about deductions that can logically turn out more than one way, I agree that one can't always know which one applies to the OTU. In which case the one that agrees with other parts of canon obviously has the advantage. If you can come up with an interpretation of the various ship design systems that makes J4 cheaper (per parsec) than J2 and J3, I'll cheerfully retract and recant.

Can you?


Hans

 

[Supplement Four]

Why not, Wil? I'm afraid I can't agree with your opinion. Any fact that can be logically deduced from canon facts must likewise be canon facts. That's how logic works.

Not putting words in Wil's mouth, but I would answer by saying that one person's logic is another person's opinion. Like statistics, logic can be used to support a variety of opinions, not all of which agree with the other.

In other words, what you see as fact derived from logical means is not necessarily a shared point of agreement among other Traveller enthusiasts.

For example, I clearly see your argument, but I don't agree that it's canon.

 

[Supplement Four]

Mind you, I usually prefer setting material over rules. However, in this particular case, I don't think it would be possible to come up with simple alternate rules that would make J4 traffic cheaper than J2 and J3 traffic.

It's easy, I think. Canon says that "most commercial starships routinely carry cargos as common carriers, charging a flat rate of Cr1,000 per ton."

So, the canon amount is Cr1,000 per ton.

But, it also says "most", meaning that there may be some variant. Logic dictates that somewhere in Known Space, the price must vary if "most" of them use that fee but not "all" of them. Logic also says, as you've said, that a MegaCorp wouldn't run a J-4 route if it lost money when it did so.

So...raise the prices on certain legs of the route.

Or...create a governmental subsidy to promote trade so that shippers still pay the Cr1,000 per ton price but shipping companies collect a guaranteed profit on these runs via the subsidy--so that the shipping companies make about the same regardless of the jump.



Here's two logical outcomes (and maybe both and more exist--it's a big universe), both different from each other, but both also supporting canon.

 

[Supplement Four]

RE: Canon

Canon exists to give us a baseline. Canon is what is stipulated in the game.

But, I don't think canon was ever intended to make us adhere to it 100%.

Some Canon is more "unbreakable" that other types. One week in jump regardless of distance traveled is a stronger piece of canon than enforcing the Imperial monetary unit as the Credit. Changing the name of the monetary unit to, say, "spacers", is less of a departure from canon than declaring that time spent in jump is variable based on 1 hour times Jump number.

I like using as much canon as I can, but I don't feel hemmed in by it. If I want to bend or break canon, typically, it's for a good reason. And, my game is better for it.

Canon is there to help us, not to fence us in.

 

[Vladika]

Digression

Has this thread digressed enough from the original topic for everyone's satisfaction?

Perhaps it could be split?

 

[rancke]

Not putting words in Wil's mouth, but I would answer by saying that one person's logic is another person's opinion.

Only if the other person doesn't know what logic is.

Like statistics, logic can be used to support a variety of opinions, not all of which agree with the other.

In other words, what you see as fact derived from logical means is not necessarily a shared point of agreement among other Traveller enthusiasts.

This is where the nature of logic makes things so simple (some times, anyway). If those other enthusiasts can show where my axioms are not canonical or the deductions are wrong, then the deductions are not canon. If, on the other hand, the assumptions are canonical and the deductions are sound, then they are canon, no matter what the other enthusiasts would like to think.

So which of my axioms are not canonical and/or which of my deductions are flawed? Is J4 traffic cheaper per parsec than J2 and J3? Will most merchants prefer a more expensive means of transport for cargo than a cheaper one? Or what?

For example, I clearly see your argument, but I don't agree that it's canon.

I can only repeat that if a fact can be deduced from a canonical fact then that fact is itself canonical. To give a simple example, if we have a canonical statement to the effect that Norris was born in 1063, then it's a canonical fact that he had his 40th birthday in 1103, even if we don't have a canonical statement to that effect.

It's easy, I think. Canon says that "most commercial starships routinely carry cargos as common carriers, charging a flat rate of Cr1,000 per ton."

So, the canon amount is Cr1,000 per ton.

That's another bit of canon that doesn't make sense.

But, it also says "most", meaning that there may be some variant. Logic dictates that somewhere in Known Space, the price must vary if "most" of them use that fee but not "all" of them.

Actually, it either says "all" (if the rules apply in all cases) or it doesn't say anything at all on the subject (if the rules are merely a game artifact to make is easier to referee a PC-run free trader without having to spend endless time on role-playing negotiations over freight and passenger rates).

Logic also says, as you've said, that a MegaCorp wouldn't run a J-4 route if it lost money when it did so.

So...raise the prices on certain legs of the route.

Sorry. Canon says the price is Cr1000. With no option for varying the price, so that must mean everywhere and always with no exceptions.

You can, of course, declare that this particular bit of canon is inconsistent and ignore it, but then I have to ask you, why can you ignore an inconsistent bit of canon and I can't?

Or...create a governmental subsidy to promote trade so that shippers still pay the Cr1,000 per ton price but shipping companies collect a guaranteed profit on these runs via the subsidy--so that the shipping companies make about the same regardless of the jump.

:nonono:

That would be introducing a new and worse improbability into the setting to shore up a lesser improbability.

Canon exists to give us a baseline. Canon is what is stipulated in the game.

But, I don't think canon was ever intended to make us adhere to it 100%.

Some Canon is more "unbreakable" that other types. One week in jump regardless of distance traveled is a stronger piece of canon than enforcing the Imperial monetary unit as the Credit. Changing the name of the monetary unit to, say, "spacers", is less of a departure from canon than declaring that time spent in jump is variable based on 1 hour times Jump number.

I like using as much canon as I can, but I don't feel hemmed in by it. If I want to bend or break canon, typically, it's for a good reason. And, my game is better for it.

Canon is there to help us, not to fence us in.

You do realize that every one of these words of wisdom support my position just as much as they support your position, right?

Just as a matter of curiosity, what is it about the concept that trade follows the X-boat routes that makes you defend it so fiercely? Is it nothing but good, oldfashioned joy in holding your own in a vigorous discussion[*] or is there something about the concept that you consider worth preserving? Is it "my canon right or wrong" or is it "I'm not giving up X-boats as the creators of trade without a fight"?

[*] Please note that I do not think there would be anything odious in that; I enjoy the occasional argument for argument's sake myself.​

Hans

 

[Supplement Four]

Actually, it either says "all" (if the rules apply in all cases) or it doesn't say anything at all on the subject (if the rules are merely a game artifact to make is easier to referee a PC-run free trader without having to spend endless time on role-playing negotiations over freight and passenger rates).

It says "most". I quoted it correctly.

Just as a matter of curiosity, what is it about the concept that trade follows the X-boat routes that makes you defend it so fiercely?

You began this fork of the discussion by saying that major trade routes do not follow the X-Boat lanes. I'm simply reporting that what you say is false as canon says otherwise.

 

[Supplement Four]

You do realize that every one of these words of wisdom support my position just as much as they support your position, right?

I wasn't trying to support my side or your side of the discussion. I simply meant to say that Canon is a baseline, but the Ref shouldn't always chain himself to canon.

It's OK to wander away from canon, change, disregard it, use your logic to take it to a new place--whatever.

But, if you do, don't call it "canon".

 

[rancke]

As per Vladika's request I've started a new thread here.

Hans

 

[djwildstar]

One part of canon is that major trade routes generally follow the X-boat lanes. A different part of canon (to wit, the ship design rules) implies that they don't.

Not quite. Canon explicitly states that major trade routes generally follow the X-boat lanes. Canon (in the form of the ship design rules) does NOT explicitly contravene that. The rules say that shipping freight or cargo costs more per ton-parsec in J-4 ships than it does in J-2 or J-3 ships. A slight difference, but not the same as stating that shipping freight and cargo in J-4 ships is impossible.

It's not something I'm pulling out of thin air. The thing is that fictional facts don't come with built-in self-consistency, the way Real Life facts does. So we can't just accept everything that canon says uncritically. It also has to make sense.

You are correct that canon puts J-4 and higher ships at an economic disadvantage compared to shorter-ranged ships. But what you are pulling out of thin air is that such ships cannot compete because they operate at a higher cost per ton-parsec.

Transportation in the Real World and in Traveller are both subject to multiple factors, and the cost to move a unit of goods a unit of distance is only one of those factors. To give a Real World example, on a strictly cost per ton-mile or cost per passenger-mile basis, air transport should not exist in competition with surface transport, since costs are several times higher for air transport. Yet air passenger and air freight routes link major world economic centers and generally follow major trade routes.

Similarly, there are multiple canon sources that indicate that large successful companies do operate over the X-boat routes in the OTU. The Traveller Adventure indicates that Tukera does so, and The Spinward Marches Campaign clearly shows Al Morai operating along trade routes that match the X-boat network.

This is a lot of canon to invalidate. Therefore, instead of implying that some canon material is wrong, I suggest that the facts together imply that there are other reasons than cost per ton-parsec driving the design of the ships that ply major trade routes. This is the same as in the real world, where cost per ton-mile and cost per passenger-mile are not the only factors that drive transportation choices, vehicle design, or vehicle usage.

I usually prefer setting material over rules. However, in this particular case, I don't think it would be possible to come up with simple alternate rules that would make J4 traffic cheaper than J2 and J3 traffic.

I think you're ignoring many important factors by focussing on just one consequence of the ship design rules. While it is true that, all other things being equal, a J-2 or J-3 ship will be more profitable than a J-4 ship, things aren't always equal.

I'm sure that you can come up with possible factors that would make J-4 ships competitive with or even preferred over J-2 or J-3 ships over routes that include J-4 links. Two that immediately come to mind are shipping fresh food, and passengers - both are time sensitive, and a ship offering a one-week trip would certainly be at a competitive advantage over a ship offering a two-week trip. The route itself may have a large impact: a ship is most efficient when it executes its maximum Jump. Over a single J-4 link, lower-Jump capacity ship would have to have less than half the cost per ton-parsec of a J-4 ship in order to exceed the financial performance of the J-4 ship.

 

[atpollard]

I'm sure that you can come up with possible factors that would make J-4 ships competitive with or even preferred over J-2 or J-3 ships over routes that include J-4 links.

While playing 'accountants in space', I found myself as a broker living on a world using the LBB1-3 trade system to check for speculative cargoes that I could ship to one of several worlds within a few jumps of my location. With 52 weekly rolls per year to check for speculative cargo, you will get multiple chances for each of the listed goods.

There was a natural trading partner to my world located 6 parsecs away that would routinely generate obscene profit margins on the trade of certain very high cost items. The problem was that the very lucrative deal would tie up the majority of my money for 12 weeks as the cargo made its way to the destination world via three J-2 segments and my money made its way back along those same three J-2 segments. The opportunity cost of needing to refuse many speculative cargoes for almost a quarter of a year motivated me to search for an option.

Then I stumbled across one of Aramis posts outlining the cost/profit for operating a ship of J1 to J6 and 'fair' prices for shipping freight. His general conclusion was that the cost of J4+ ships (and especially J6 ships) was prohibitive ... no trader could make a profit even at Cr 1000 per parsec freight costs. Then I thought about the Subsidized Merchant program, and wondered if I could afford to subsidize a J6 ship to make it profitable for the captain on an annual basis and reduce my down time from 12 weeks to 3 or 4 weeks.

Crunching the numbers on a ship design revealed that I could generate enough profit on 1 trade to completely pay off the mortgage on a 200-300 dTon J6 ship. With the reduced turn-around time on my 'deals', I could afford to increase the number of J6 speculative cargoes from 2 per year to 4 per year ... and after the first trip, the ship had no mortgage ... fuel, crew and annual maintenance, that's it. So I only needed to reserve the subsidized ship for 4 trips per year, the rest of the year the crew could carry cargo at a greatly reduced operating cost and keep whatever money they earn. I earned more just buying the ship and using it as needed rather than waiting to ship my goods and get my pay via J2 commercial shipping.

 

[McPerth]

The old debate from CT returns in T5: Can a ship with an M-Drive that produces 1G of thrust make escape velocity from a Size 8+ world (where surface gravity is 1+Gs)?

NOTE: Not sure if anyone has said this before. I think I've read about it not long ago, but not sure about where and I didn't find it in this thread now.

IIRC in MT:SOM, when talking exactly about this subject, is told that the ship drives can have its acceleration raised up to 400% in forward acceleration for short times.

Of course, that's MT, not T5, and I'm not sure if it can be extrapolated, as MT design system (and so the standards and assumptions on it) is usually not compatible with other versions...

 

[djwildstar]

[Excellent description of profitably using a J-6 shipping instead of J-2 shipping for certain types of high-profit-margin freight over a 6-parsec route]

Yes; this sort of thing is exactly what I was thinking about. As an additional data point in your favor, it also mirrors present-day economics. While I was researching this topic, I ran across an MIT report from the mid-1990s that pointed out basically the same thing. Consider a shipment of merchandise, purchased on credit and destined for sale in the United States at healthy profit margins. At some point, the interest charges that rack up while it sits on a ship crossing the Pacific start to exceed the cost of air freight. For the present day, the time differential is about 6:1 instead of the 3:1 in your example. This will change the cut-off point for the value of the deal, but I think the economics are solid.

To put this back in a Traveller context, I think that big companies (the megacorporations like Tukera, multi-sector regional lines, and sector-wide lines like Al Morai) will have big ships that are optimized to take advantage of deals like this. High-Jump ships can make trades across 6 to 12 parsec ranges that would be economically impractical in slower ships. The large companies sell any excess capacity at the "standard" rates, while smaller lines and tramp starships compete in the niches left un-filled - worlds that aren't served by the big companies (probably because they don't offer sufficiently-lucrative trades), shipments that are too small for the large players to show much interest in (as an Executive VP told me once, "I'm not interested in contracts that are worth less than my credit card balance"), or situations where the need temporarily exceeds the capacity of the big players.

The large shippers can set their standard rates largely without regard for the actual cost of providing the transportation: the high-value deals underlying the trade route subsidizes the investment in the ship and crew. The result is that any fees they collect to fill empty staterooms and cargo hold are largely profit. The practice of low flat-rate prices has the additional advantage that it places small "tramp" shipping operations at a competitive disadvantage.

So we get the situation portrayed in the canonical Traveller rules, but with a reasonable economic backstory to support them.

 

[djwildstar]

To get back to the original topic of the thread:

IIRC in MT:SOM, when talking exactly about this subject, is told that the ship drives can have its acceleration raised up to 400% in forward acceleration for short times.

Yes, your recollection is correct - that was the MT solution the problem.

It seems that T5 explicitly disavows this interpretation, by requiring that ships acceleration equal or exceed local gravity. My personal solution is the following:

For worlds with no atmosphere or a trace atmosphere, any ship that is designed for landing and has acceleration greater than surface gravity can land and take off. Other ships may not land, and will automatically crash if they attempt it.

For worlds with an atmosphere, any ship that is designed for landing and has acceleration greater than the surface gravity can land and take off. In addition, any ship with an airframe or lifting body hull can land and take off, regardless of main drive acceleration, provided that the world has a Class D or better starport, or equivalent spaceport, or an airport to provide a suitable runway. Other ships may not land, and will automatically crash if they attempt it.

I assume that any streamlined, airframe, or living-body hull is designed for landing unless specifically stated otherwise in the ship description. Similarly, any un-streamlined or semi-streamlined hull is not designed for landing unless explicitly stated otherwise in the ship description, and will automatically crash if a landing is attempted. The pilot may attempt a skill roll to lessen the severity of the damage.

Even if they are designed to permit landing, semi-streamlined and un-streamlined ships are a liability in atmospheric operations. To prevent aerodynamic forces from damaging the ship or its surface fittings, the ship must be operated slowly within an atmosphere. Multiply the time required for landing or take-off by the world's atmospheric density class (very thin = 2, thin = 3, standard = 4, dense = 5, etc).

Semi-streamlined, streamlined, airframe, and lifting body ships may skim gas giants for fuel. Unstreamlined ships may not.

 

[rancke]

Not quite. Canon explicitly states that major trade routes generally follow the X-boat lanes. Canon (in the form of the ship design rules) does NOT explicitly contravene that. The rules say that shipping freight or cargo costs more per ton-parsec in J-4 ships than it does in J-2 or J-3 ships. A slight difference, but not the same as stating that shipping freight and cargo in J-4 ships is impossible.

Which is, of course, why I say that the ship construction rules implies and not explicitly states. Nor do I say that shipping by J4 is impossible. I'm saying that unless special circumstances apply, J4 is less profitable than J2 or J3. Which, in turn, implies that in many cases J4 won't be the optimum shipping option. Which, in turn, means that trade routes will mostly be defined by J2 and J3 rather than J4.

You are correct that canon puts J-4 and higher ships at an economic disadvantage compared to shorter-ranged ships. But what you are pulling out of thin air is that such ships cannot compete because they operate at a higher cost per ton-parsec.

Um... having a higher cost per ton-parsec is a pretty serious handicap. I'd say that a claim to that effect is very far from coming out of thin air.

Transportation in the Real World and in Traveller are both subject to multiple factors, and the cost to move a unit of goods a unit of distance is only one of those factors. To give a Real World example, on a strictly cost per ton-mile or cost per passenger-mile basis, air transport should not exist in competition with surface transport, since costs are several times higher for air transport. Yet air passenger and air freight routes link major world economic centers and generally follow major trade routes.

To dispose of passengers first of all, I've never claimed that passenger traffic is subject to the same dynamics as cargo transport. I will claim that passengers do not a trade route make. To make a trade route, you need trade.

As for air traffic, some goods do move by airplane, but even without having checked the figures, I'm quite confident that the majority of goods (by bulk) go by ship.

Similarly, there are multiple canon sources that indicate that large successful companies do operate over the X-boat routes in the OTU. The Traveller Adventure indicates that Tukera does so, and The Spinward Marches Campaign clearly shows Al Morai operating along trade routes that match the X-boat network.

Remember what I said about fictional reality not coming with built-in self-consistency? TTA indicates that Tukera follows the X-boats from Nasemin to Towers to Junidy and from L'oul d'Dieu to Aramis to Natoko. Except for Junidy, all of these worlds have population levels of 4 or 5 (Natoko has 2). Whatever trade their populations can muster is not going to amount to that of a major trade route.

Aramis is admittedly going to be functioning out of its weight class[*], being the transshipment point for Vargr trade goods brought from the border along routes that do not follow X-boat routes (J1 routes if we believe what TTA tells us, J2 routes if we believe in rational company managers, but under no circumstance following the X-boat routes from Junidy to Marz to Ash to Pretoria to Teh to Natoko to Aramis).

[*] Something none of the canonical trade rules are able to account for, incidentally.​

So from Aramis there will be considerable trade into Rhylanor subsector (probably mostly to Rhylanor). But it won't be following the X-boat route from Aramis to L'oul d'Dieu to Celepina, it will be going from Aramis to Nutema to Celepina (because that's cheaper)[**]. From Celepina to Rhylanor the trade will indeed overlap the (sub-optimal) X-boat route, but it will do so because the X-boats make two-parsec jumps from Celepina to Jae Telona to Rhylanor instead of jumping directly from Celepina to Rhylanor.

[**] An X-boat route designed for rapid information transfer would be going directly from Aramis to Celepina and from Celepina to Rhylanor, incidentally.​

As for Al Morai, I'll leave aside the fact that a trade scheme that has J4 ships routinely employed on J1 routes is not overly supplied with self-consistency and just flat out contradict you. No, the Al Morai routes do not follow the X-boat routes as such (that is, follow them because they are there), at least not according to the text: they "maintain interstellar service to the capitals of Imperial subsectors in the Spinward Marches, and to Imperial worlds along the trade routes which connect them".

It's true that the map shows them following X-boats routes regardless of the actual trade to be found between the worlds they service, but I don't see that as improving plausibility any. But be that as it may, the actual trade carried by Al Morai ships amount to 1200T per month (I would have said 1200T per month each way, but the text claims each world is only visited by a ship once every four weeks with a 50/50 chance it is going in a specific direction (don't ask about the worlds with three connections :devil). 1200T per month do not a major trade route make.

This is a lot of canon to invalidate.

But is it good canon? The description of Al Morai's trade fleet and standard operations is IMO a complete pig's breakfast and in dire need of a retcon (I have a suggestion for one that would preserve the trade route map[***] ).

[***] Well, mostly. ​

As for TTA, I submit that it does not actually show any trade following J4 X-boat routes.

Therefore, instead of implying that some canon material is wrong, I suggest that the facts together imply that there are other reasons than cost per ton-parsec driving the design of the ships that ply major trade routes.

See, that's where I see the prime disconnect. Ships plying J4 routes would indeed be driven by other considerations than cost per ton-parsec. And those other concerns would result in such routes not being major. I'm not saying they'd be non-existent. But they wouldn't be major, because they'd be restricted to special cargoes -- "China tea" goods and other time-sensitive stuff.

Meanwhile, except for places where astrography makes them more expensive than J4, the major share of goods will be transported by J2 and J3 ships.

I think you're ignoring many important factors by focussing on just one consequence of the ship design rules. While it is true that, all other things being equal, a J-2 or J-3 ship will be more profitable than a J-4 ship, things aren't always equal.

I'm not ignoring them, I'm assigning less importance to them. Things aren't always equal, but often they are.

The route itself may have a large impact: a ship is most efficient when it executes its maximum Jump.

All the calculations assume that the ships perform maximum jumps.

Over a single J-4 link, lower-Jump capacity ship would have to have less than half the cost per ton-parsec of a J-4 ship in order to exceed the financial performance of the J-4 ship.

That is already factored into the calculations. A J4 ship can deliver two loads of cargo across four parsecs every time a J2 ship delivers one. But the extra cost and lesser cargo capacity of a J4 ship makes the per ton-parsec cost of J4 shipping about 25% higher than J2. The only time a J4 ship is cheaper than J2 is if there's no intermediate star system for the J2 ship to refuel. Which is certainly the case with some X-boat link. But it isn't the case with a lot of other X-boat links. And in some of the examples, like the trade route from Ivendo to D'Ganzio to Lanth to Ghandi to Dinomn, there's not going to be enough trade to make it a major route even without competition from J2 ships.


Hans