Abandoned Routes: X-boats in wartime

[Whipsnade]

A nice chat with Grav Moped over in the Ghost Ship thread helped me dredge up some old ideas regarding the x-boat network.

Because the routes the 'boats fly aren't physical objects like rails or roads, they can be adjusted, created, or abandoned with relative ease by shifting tenders or calculating different jump courses. Why the system flies the routes we're shown is a long standing and, in my opinion, insolvable problem. However, this isn't about "explaining" why sub-optimal routes exist or why the Imperium won't change them. This is about all the shenanigans that can happen when the Imperium is forced to change routes and the adventuring possibilities which can arise.

Many events can cause the Imperium to shift routes, but wars and rebellions can force a lot of shifts in a short period of time. A rumor in A:1 Kinunir mentions unrest on Feri in threatening "imperial communications" between Regina and Efate but the fleet position maps for the 5th Frontier War found in SMC suggest all sorts of other possibilities and locations. Most of the routes in Jewell and coreward half of Regina subsector should have been significantly disrupted given the paths of the Zhodani and Vargr fleets and the systems they seized. So many stations and routes should have been disrupted there that I'm not going to use the Jewell/Regina region as an example. Instead, let's look at how the Vilis/Lanth region was effected by the Gram Fleet's offensive and the Consulate's Abyss Campaign.

 

[Whipsnade]

Two x-boat routes cross the Lanth/Vilis region where those two campaigns took place. One runs along the border following an Extolay - Denotam - Frenzie - Garda Vilis route. The other a runs few parsecs to trailing on a Dinomn - Ghandi - Lanth - D'Ganzio - Ivendo route. Just prior to the 5FW, the systems along coreward end of the Extolay to Garda Vilis route are defended by the Imperial 1st Fleet while the 23rd Fleet defends that route's rimward systems. The Dinomn to Ivendo route is defended at distance by the 212th round Rhylanor and the 213th in the Lunion region.

When the war starts on 187-1107, the Dinomn to Ivendo route is quickly lost. The Gram Fleet slips past the 213th's right flank and advances into the 23rd's rear. Lanth is under attack by 204-1107, by 001-1108 Lanth and 5 nearby systems are occupied, and by 180-1108 D'Ganzio is also occupied. Lanth will remain occupied until 096-1109 and, according to SMC's position maps, D'Ganzio is occupied until as late as 001-1109.

Along the border, the Extolay to Garda Vilis route remains in operation until the Consulate's 40th Fleet takes Denotam sometime between 180-1108 and 001-1109. A later date seems probable because Ghandi is under attack by the same fleet on 021-1109. (The dates in SMC are muddled a bit with some of the text not quite agreeing with both other parts of the text and the maps. I went with the "worst case" analysis for this example.) Denotam is reoccupied by the 23rd Fleet by 180-1109, but Ghandi remains occupied as late as 001-1110.

Our Extolay to Garda Vilis x-boat route is disrupted at most for a year; 180-1108 to the same date in 1109. The Dinomn to Ivendo route is disrupted for much longer from 204-1107 when Lanth is under attack until when Ghandi is reoccupied sometime between 001 and 120-1110. What's going to happen when those disruptions occur?

 

[Whipsnade]

When the invaders arrive, it's bugout time. Depending on the size of the invading force, the local Imperial commanders may order the stations to keep "last message out" 'boat on hand or request space to evacuate personnel. Apart from that, the tenders and other assets working each link in the system are going to prep and dispatch every 'boat they can as quickly as they can. The usual one boat per day per link schedule is out the window. 'Boats will jump as soon as they can be refueled and resupplied. They're going to send out as much data, personnel, and equipment aboard those 'boats as possible too.

Fuel stocks will be the controlling factor. We've often talked about how the canonical tender's small fuel tankage means it needs almost daily refueling itself to support the one boat per day operational tempo. There are good arguments to suggest that each link station usually has a tank farm of sorts on hand. The capacity and number of those tank farms may even be increased in time of war. Whatever fuel is on hand, however, will determine how many 'boats the station can save.

Just where to send the 'boats is another decision to make. Because they have no maneuver drive, sending a 'boat to system where no one is waiting for it is gambling with the lives of those aboard. 'Boats are going to be sent to other systems where x-boat stations are already in place. Failing that, they're going to be sent to systems with enough ship traffic or other assets to make a rescue likely. Failing that, they're not going to sent at all. Fuel is part of this destination decsion too. Look at Lanth for example.

Ghandi is 4 parsecs away while D'Ganzio is only two. Lanth can send two 'boats to D'Ganzio for the fuel "price" of sending one 'boat to Ghandi. In the event of an evacuation, the tender and assets working the Lanth-Ghandi link aren't going to send 'boats back to Ghandi when they can use the same fuel to send more boats to D'Ganzio. The tenders working off Lanth are lucky however. The tenders working off Denotam also have two destinations, but each are 4 parsecs away.

Time is another part of the equation. How long will the tenders working each link station have? How quickly can or will the invaders move against them? Can the defenders spare assets to protect them? With a 'boat arriving every day, will the station be able to keep operating long enough to save one, two, three, or more? The answer to all those questions will depend on the specific details associated with the specific invasion of each specific system. The Gram Fleet assaulting Lanth and it's naval base might decide not to divert any assets to "sweep up" the system's link stations until after the main battles off the mainworld have been decided while the over-strength Consulate 40th Fleet making it's sickle stroke towards Rhylanor to win the war might have enough assets to target Ghandi's link stations immediately.

The position of each link station within their host system will also play a role. Each station is well beyond any 100D stellar jump limit and away from any potential jump shadows. That means each station is "close" to jump space. Tenders have minimal weapons, scout/couriers boast one turret, and the 'boats have no weapons at all. An enemy warship needn't be very big to drop out of jump 3,000km away and order a link station to cease operations.

 

[Whipsnade]

Finally, with existing routes lost, the Imperium is going to setup new and, hopefully, temporary ones. The disrupted Dinomn to Ivendo route is, allegedly, Regina's only link to the Imperial core. The Big Boys have their own jump6 courier flying their own routes, but the Hoi Polloi still need to send their mail. Setting up temporary routes could be as easy as positioning the tenders and other assets needed to refuel and resupply 'boats flying those routes.

Resupplying those tenders then becomes the issue. In A:3 Twilight's Peak, we're told the IISS is building a base on Echiste to support x-boat operations along a new Risek - Echiste - Yori - Regina route which suggests much of a station's supply requirements are normally met by the host system. While that might be the Imperium's preference in peacetime, supplying dozens of link stations by ship in wartime would be a trivial effort compared to the logistical effort necessary to supply entire fleets in the "field".

 

[mike wightman]

Interesting stuff, consider it borrowed

Take a look at these quotes:
Any world which is the source of a printed jump-route and is not otherwise marked as holding a base will have a rudimentary scout base for the purposes of support of xboat operations... (S:3 Spinward marches)
it [the x-boat) jumps, relays its messages to the station on arrival, and then waits to be picked up by a tender, to be refuelled and sent on its way with a new load of messages. The local station, meanwhile, accepts messages, encodes them, and transmits them to a tender at the edges of the stellar system. (S:7 Traders and Gunboats)

One of the final MgT1e supplements Space Stations had details of a 10,000t scout station.

So to shift an x-boat route you need to relocate or build a new central hub, this can be a station or a ground installation.

One IN tender could easily move a 10,000t stations, a dozen tenders and a couple of dozen x-boats to a new system, but I can't stop thinking of using a scout service AHL to do the job.

If it can not be saved the compromised station can be evacuated and powered down or destroyed.

 

[Whipsnade]

Interesting stuff, consider it borrowed

You're welcome to it. As always, please fold, spindle, and mutilate to your heart's content.

Take a look at these quotes...

Eagerly.

Any world which is the source of a printed jump-route and is not otherwise marked as holding a base will have a rudimentary scout base for the purposes of support of xboat operations...

That's CT right? It folds neatly into the A:3 rumor regarding Echiste. The IISS has some sort of facility in system producing/procuring fungibles for x-boat/tender operations.

it [the x-boat) jumps, relays its messages to the station on arrival...

My bad. I should have provided definitions for some of my descriptions.

By "link station" I meant the collection of tender(s), scout/couriers, small craft, and tank farms tasked with supporting operations for each of a system's x-boat links. Much like how one 'boat per day per link is the generally accepted canonical operational tempo, having each link serviced by it's own group in-system assets is also generally accepted. The reasons for this have to do with the different jump shadows and relative velocities the different systems will have.

Thus Lanth will have two "link stations". One for the Lanth-Ghandi link and one for the Lanth-D'Ganzio link. Similarly, Ivendo will have three stations; once each for it's links to D'Ganzio, Equus, and Icetina.

These "link stations" will transmit 'boat messages to "central" station as needed.

So to shift an x-boat route you need to relocate or build a new central hub, this can be a station or a ground installation.

More accurately, perhaps, is that a system on a permanent x-boat route will have a central station; i.e. the building project on Echiste. A temporary or "hostilities only" will make do with tenders only and those will be supplied from other systems.

If it can not be saved the compromised station can be evacuated and powered down or destroyed.

Agreed. Depending on the amount of time the invaders "allow" between arriving in the system and detaching assets to "occupy" the station, the link stations I wrote about could be fully or partially evacuated, see their ships "scuttled", and take other measures.

Imagine the Gram Fleet invading Lanth. The entire force chooses to concentrate on the mainworld and the Imperial assets nearby. Located in outer system, the two "link stations" use the reprieve to begin saving as much as they can. First, every 'boat on hand is fueled to jump away. Most will go to D'Ganzio because that 2 parsec distance use less of the fuel the stations have on hand while one 'boat will be sent to Ghandi to "turn off" the flow of 'boats from that system. Any scout/couriers on hand will be fueled to leave too.

Both stations will ship off all but a skeleton crew aboard the departing 'boats and couriers plus whatever stores, equipment, parts, and supplies aren't absolutely needed. The station's collection of small craft will made inoperable and the tank farm(s) readied to either "spill" or be self destruct.

Both Ghandi and D'Ganzio will keep sending daily 'boats to Lanth for the week it takes news of the invasion to reach them. Each day another 'boat will arrive and, if the Gram Fleet still hasn't taken steps to "occupy" the stations, it will be refueled and resupplied as quickly as possible so it can escape. Again, D'Ganzio will be the preferred destination because fueling the 'boat for that trip will only take half the time needed to fuel a 'boat for Ghandi. It's even possible that each station may keep a prepped 'boat on hand as a "getaway car" to be used when enemy assets finally arrive.

The skeleton staff at the station is going to keep refueling newly arrived boats and sending them off to D'Ganzio until assets from the Gram Fleet arrive with weapons range. When that happens, they're going to slag data banks, wreck computers, and otherwise render the tender inoperable while waiting to taken prisoner.

Of course all of this is made moot if the invading force details a few escorts to "sweep up" the link stations from the start. The stations are "close" to jump space and an enemy can appear as close as 3000km from their known positions. Given the weapons aboard a tender, it wouldn't take much a warship to "capture" a link station. Then again, the defenders may have some of their own warships providing cover.

 

[BRJN]

IMTU, I've been re-writing some of the Solomani efforts in The Rebellion.

A well-thought-out invasion plan of the Solomani Rim sector is going to rip up Coreward-bound communications. This is frighteningly easy when you analyze the marked X-boat routes. The Imperium must have "backup plans" in the event of invasion. (I send some Deep Strike Squadrons to where those "backup plans" might build new infrastructure, with instructions to look around for it.)

 

[Whipsnade]

A well-thought-out invasion plan of the Solomani Rim sector is going to rip up Coreward-bound communications. This is frighteningly easy when you analyze the marked X-boat routes. The Imperium must have "backup plans" in the event of invasion.

We know the "important" people and organizations don't use or need the X-boat system. The navy, the nobility, the megacorps, none of them bother with the X-boat system. They have their own jump6 couriers and other assets instead. Their system is one "backup" system and it is working alongside the everyday system all the time.

That being said, there must be plans to reroute and restore links within the system because of all the other people and organizations which use it. There must be plans to "bugout" whatever kit can be saved when the war arrives too.

(By the way, private conversations with other anons pointed out there was some confusion over the terms I used. "Link station" refers to those assets working at the region in a system where x-boats flying a route between two systems arrive and depart. A "link station" is made up of a revolving cast of tenders, small craft, scout/couriers, x-boats, tank farms, stations like Mr. Pearce's wonderful 300dTon variant, and other assets. It doesn't refer to a single physical object. Descriptions of the system also refer to a "station" on or in orbit around the mainworld which handles messages traffic between the mainworld and tenders.)

Because link station operate well outside any local 100D jump limits and because their locations are going to remain relatively fixed, the link stations are going to be hideously vulnerable to an enemy. Jump drive has an accuracy of 3000km per parsec jumped so an enemy can exit jump space within easy weapons range to shoot up a link station. Station locations within a system are going to chosen on the basis of two criteria. First, clearing any jump shadows which exist on a jump course between the two systems in question. Second, limiting comm lag between the link station and the mainworld. While those criteria are going to be paramount in peacetime, keeping the system operating will be the sole priority in wartime.

Apart from tank farms, the assets making up link station are mobile. They can displace within systems and there's a lot of room within a system. Clearing jump shadows will still be necessary; limiting comm times between link stations and the mainworld will not. Link stations could "bugout" to other locations within the system on a war warning. The station at the other end of their link just needs to know where to send the 'boats and when to start sending them there. Multiple "bugouts" within a system could also occur on a schedule; i.e. Location A during weeks 1 thru 5, Location B during weeks 6 thru 10, etc.

The canonical tender's one parsec jump range gives it lousy interstellar "legs". That same range can be an option during a "bugout" within a system. If the distance involved is great enough, a tender can jump ahead to a new link station location carrying what fuel and small craft are needed to setup operations there while leaving behind enough assets to maintain operations at the old point for the week or so 'boats continue to use it.

This "location hopping" can help maintain the system's operation much like how frequency hopping does the same thing with cell phones.

 

[Ulsyus]

The Imperium must have "backup plans" in the event of invasion. (I send some Deep Strike Squadrons to where those "backup plans" might build new infrastructure, with instructions to look around for it.)

That's always good risk management

We know the "important" people and organizations don't use or need the X-boat system. The navy, the nobility, the megacorps, none of them bother with the X-boat system. They have their own jump6 couriers and other assets instead. Their system is one "backup" system and it is working alongside the everyday system all the time.

That being said, there must be plans to reroute and restore links within the system because of all the other people and organizations which use it. There must be plans to "bugout" whatever kit can be saved when the war arrives too.

The network is extensive and well tested over time, but how great is the investment in infrastructure compared with a subsector or greater naval force? If it's not that much in comparison but contributes significantly to the connectedness of the worlds of the Imperium then how likely is it that there would be contingency and redundancy and replacement plans in place? How many X-boats exist per link in the route? Four per leg, or more? Would there be a store of X-boats mothballed away in each sub-sector to jump along the network to replace losses along it, or would there be dispersed spare vessels at each node where the tenders work?

I have my own ideas about all of that, but am keen to hear other thoughts...

 

[Whipsnade]

The network is extensive and well tested over time, but how great is the investment in infrastructure compared with a subsector or greater naval force?

You'd be surprised at how much the system costs.

How many X-boats exist per link in the route? Four per leg, or more?

Four? Try fourteen at the very least. A system on an x-boat receives one 'boat per day per link. That's seven boats flying each link in one direction at any given moment. To that number, you'll need to add a 'boat prepped and waiting to depart as soon as the incoming 'boat's data load can be transferred plus another which can be swapped for an outgoing or incoming 'boat requiring maintenance. You're up to eighteen 'boats per each link now and you haven't even begun to count the tenders, scout/couriers, tankers, and small craft servicing each link in each system.

Would there be a store of X-boats mothballed away in each sub-sector to jump along the network to replace losses along it, or would there be dispersed spare vessels at each node where the tenders work?

Yes, if only to make up for 'boats undergoing annual maintenance. With annual maintenance requiring two weeks out of every 52, you're going to need 54 boats at the very least to keep 52 available. Don't forget to factor in annual and unforeseen maintenance for all your tenders, scout/couriers, tankers, and small craft too.

Along with those spares being staged at central points, as I already explained there will also be spare 'boats already in each of the systems along the route to provide availability in the case of an operational 'boat needs to be taken out of service.

While you're trying to tally up all the ships and small craft the system needs, start thinking about all the salaries, supplies, fuel, parts, repairs, training, pensions, rations, fungibles, mainworld stations, bases, and other expenses too.

I have my own ideas about all of that, but am keen to hear other thoughts...

They should be interesting to read.

 

[Ulsyus]

Four? Try fourteen at the very least. A system on an x-boat receives one 'boat per day per link. That's seven boats flying each link in one direction at any given moment. To that number, you'll need to add a 'boat prepped and waiting to depart as soon as the incoming 'boat's data load can be transferred plus another which can be swapped for an outgoing or incoming 'boat requiring maintenance. You're up to eighteen 'boats per each link now and you haven't even begun to count the tenders, scout/couriers, tankers, and small craft servicing each link in each system.

After a day of meetings I'm struggling with the maths.

Eight vessels to travel along one link to the next node, ensuring a rate of one per day for the week. On day (D) 1 vessel (V) 1 leaves location (L) 1. On D8 (planning for reasonable timing variations) V1 arrives at L2. If there's a wait of a week for turnaround, then the eight vessels at L2 transit back to L1 from D8, arriving there no later than D16. Is that something like where you're getting your numbers from?

 

[Whipsnade]

After a day of meetings I'm struggling with the maths.

One x-boat per day per link.

Regina had three x-boat links; Dinomn, Extolay, and Roup. A 'boat arrives from each of those systems every 24 hours and, because each of those three systems are also getting one boat per day per link, Regina sends a 'boat to each of those systems every 24 hours.

A jump lasts 168 hours give or take amounts which vary according to whatever rules you're using. No matter how early or late the daily 'boat from Roup arrives, Regina is still going to dispatch a 'boat to Roup every day.

Day 1: Boat A arrives at Regina from Roup. Boats B, C, D, E, F, and G are still in transit from Roup. Boat H jumps from Roup.
Day 2: Boat B arrives from Roup. Boats C, D, E, F, G, and H are still in transit from Roup. Boat I jumps from Roup.
Day 3: Boats C arrives. Boats D, E, F, G, H, and I are in transit. Boat J is jumps.
Day 4: Rinse, wash, repeat 365 days a year.

While Roup is "pumping" all those 'boats down the link to Regina, Regina is pumping the same number of 'boats on the same schedule down the link to Roup. Extolay and Dinomn are dispatching 'boats to Regina on the same schedule and Regina sending 'boats to them on the same schedule.

And the end points of each link is each system are being service by tenders, tankers, scout/couriers, and small craft. The pace is steady, not frantic. Each link station has to "recover" one 'boat roughly every 24 hours while dispatching one 'boat at a fixed time every 24 hours. 'Boats will jump when they're scheduled to jump. There's no point in waiting for that day's 'boat to arrive as the delays will accumulate down the line. Besides, the next day's 'boat can carry whatever messages the tardy 'boat was carrying.

One 'boat per day per link.

 

[whartung]

There's no reason for an X-Boat to linger around for a week before it can be reused. The "1 week" in system, is designed to cover the gross affects of arriving, landing, fueling, carousing, scumming for trade and passengers, loading, launching, and leaving.

X-Boats don't suffer that. They arrive, beam their messages, are seized by their tenders, serviced, fueled, and ready to go. It may take a day or two, but certainly not a week.

Down time for X-Boats is very costly. There's also nothing to suggest a boat needs be on the same route. The CREWS may have routes, but the boats, not necessarily. Would be interesting to have a story about an X-Boat as it travels from Core to Regina, not that's it's intentionally destined to Regina, rather it simply gets pulled from the pool of available X-Boats and eventually ends up there.

X-Boats are just expensive message envelopes like those vacuum tube transport cylinders.

 

[Whipsnade]

There's no reason for an X-Boat to linger around for a week before it can be reused.

I haven't suggested they do. Ulsyus may think so, but I most certainly don't. 'Boats arrive, get checked out, get refueled, get resupplied, get staged, and are sent back the way they came.

There's also nothing to suggest a boat needs be on the same route.

Nothing except concerns about jump shadows/masking and radial velocity. Link stations are going to be placed at a location in a system where the shadows and masking are not a problem with regards to the system on the other end of the link. A location in Regina which is clear with regards to Roup may not be clear with regards to Extolay or Dinomn so the links to those two systems will be serviced by their own link stations.

Radial velocity is a concern because vectors are conserved through jump. Barnard's Star, for example, is moving at vector whose velocity component is ~140km/sec relative to Sol. A 'boat entering jump at rest relative to Barnard's is going to exit jump at Sol on a vector with a velocity component of ~140km/sec. A 'boat leaving Sol at rest will arrive at Barnard's on a reciprocal vector with a velocity component of ~140km/sec. Before jump, a 'boat is going to be "staged" so that it leaves the departure system with a vector which will be helpful in the arrival system. Not a perfect vector, not a vector which will leave it at rest in the arrival system, but helpful a helpful vector. Radial velocity is another reason why each link will usually have it's own link station.

And, again, by "link station" I'm referring to the collection of tenders, scout/couriers, tankers, small craft, and tank farms supporting the operations of the 'boats flying along one link. I am not referring to some stationary space station.

X-Boats are just expensive message envelopes like those vacuum tube transport cylinders.

Which is why they aren't going to hang around.

A 'boat will arrive and begin transmitting it's messages to the tender while the tender intercepts it. Another 'boat which is already fueled, resupplied, and "staged" will jump away once it receives it's final message "load". If the arriving 'boat is "late", the departing 'boat is still going to leave on schedule. There's no need to wait with 'boats leaving every day and 'boats are too expensive not to keep working.

'Boats will be arriving within a sphere with a 12,000km radius. The tender's one gee maneuver drive can cover that volume in trivial amount of time relative to an operational tempo of one arrival and one departure every day. Once a 'boat arrives, the link station has at least 24 hours to prep it for departure. If a 'boat which had earlier been pulled from the queue for repairs or maintenance is ready for use, the newly arrived 'boat could hang around for 48 hours. Only equipment failures and planned maintenance will pull a 'boat out of the operational queue for longer.

 

[whartung]

Nothing except concerns about jump shadows/masking and radial velocity.

By route I meant that there's no reason to expect that an X-Boat from System A would be necessarily sent back to System A.

Radial velocity is a concern because vectors are conserved through jump.

A bunch of little things come in to play here.

First, you have the ~34hr (+/- 16.8hr, +/-10% jump window). Which is interesting. My math but be wrong.

You have 2 X-Boats.

Boat 1 jumps at time 0h from system A.
Boas 2 jumps at time 24h from system A (this is "tomorrows" boat).

Worst case, Boat 1 arrives in System B at: 0 + 168 + 17 = 185 hours
Boat 2, gets the other swing and arrives in System B at: 24 + 168 - 17 = 175 hours.

Boat 2 arrives 10 hours before Boat 1. The math works, but it's not intuitive to me. I'm surprised they overlap. But, I guess not, since there's a 34 hour window, but only a 24 hour day -- of course there's potential overlap.

Anyway, the Jump destination is fixed in space via some absolute space coordinate system. That means, that the arrival is not relative to anything save a "universal 0,0", which means that everything moves around the destination point: stars, moons, planets.

The Tenders know "where" the X-Boat will arrive (give or take a fee 1000 kilometers). And, in fact, they can (and would) station keep relative to the galactic origin so that the tender will be there once they arrive, they just don't know when the boat will arrive. If X-Boats always leave at 00:00hr, the tenders know they're arrive between 151.2 and 184.8 hours later. Which means a tender must be there for that ~34 hour window.

Now, to the velocity part. This is where the fun begins. As soon as the boat arrives, it's going to take off in whatever retained direction it's going to -- X-Boats have no M-Drives, so they can't slow down. At this point, the tender has to give chase. With your 140km/s vector, a 1G tender is going to take some time just to catch the boat and match vectors to facilitate rendezvous. Meanwhile, the X-Boat is chattering away broadcasting any electronic data that it can (packages are going to have to wait).

So, what this boils down to, particularly in cases like this kind of differential in velocity, you may well have to have 5 tenders to handle the traffic from a single system, if each one takes much of a day just to retrieve the boat once it pops in to normal space, while you have others waiting for the next boat.

Honestly, for this reason alone I'd put an M-Drive on the X-Boat, at least for those systems that have particularly high deltas. Seems like it would be worth the money in the long run, but I dunno.

Plus maintenance of the boats and tenders. There may be no stationary station, but there's going to be a hive of activity around the agreed upon entry points for X-Boats, and each route will have it's own mini fleet of support vessels.

 

[Whipsnade]

First, you have the ~34hr (+/- 16.8hr, +/-10% jump window). Which is interesting. My math but be wrong.

Your math isn't wrong, but you've forgotten that the amount of variation itself varies between editions, that the amount of variation is controlled by navigation rolls in most editions, and that all the variation results are distributed along a bell curve.

Yes, there's a chance that Monday's 'boat may arrive before Tuesday's 'boat. Given the sheer numbers of 'boats jumping daily in the system, Monday is arriving before Tuesday somewhere in the Imperium all the time. The fact that Monday can occasionally arrive before Tuesday doesn't really matter. All that matters is that one 'boat per link is scheduled to arrive every 24 hours.

Anyway, the Jump destination is fixed in space via some absolute space coordinate system.

No. This has been explained for decades now.

Plotting a jump is best thought of as like the old school plotting of artillery fire. You plot where the shell will land relative to the gun and not relative to the target or some universal coordinate system. Similarly, when jumping from Regina to Roup, you plot your exit point relative to Regina and not relative to Roup. You don't attempt to plot an exit a certain distance from Roup because, thanks to jump's temporal variations, you can't know where Roup will be. You don't know where Roup will be because you don't know when you'll exit jump. Instead, you plot your exit point relative to Regina.

This is why Miller's jump space essay in JTAS #24 makes such a big deal regarding jump drive's physical accuracy.

Now, to the velocity part. This is where the fun begins.

Not "fun" as much misunderstanding.

As soon as the boat arrives, it's going to take off in whatever retained direction it's going to -- X-Boats have no M-Drives, so they can't slow down. At this point, the tender has to give chase. With your 140km/s vector, a 1G tender is going to take some time just to catch the boat and match vectors to facilitate rendezvous.

Which is why I specifically wrote about 'boats jumping with helpful vectors and why I wrote about 'boats being "staged" prior to jump. A 'boat is going to be placed on a helpful vector prior to jump. Not a perfect one mind you because the time variation precludes that, but a helpful one. A 'boat isn't going to jump at rest relative to it's departure system because of the issues you raised in your "example". The tender, or in some cases dedicated small craft, are going to "stage" the 'boat scheduled to depart by placing it on a vector which will be helpful in the arrival system. Again, not perfect but helpful.

Using "real world" Sol as an guide, creating the helpful vectors radial velocity differences between systems require will be well within the capabilities of a canonical tender. The radial velocity of Barnard's, for example, is the largest relative to Sol. For those exceptional systems which have large radial velocity differences - and canon states they exist - dedicated chaser/tug small craft will be used.

Honestly, for this reason alone I'd put an M-Drive on the X-Boat, at least for those systems that have particularly high deltas. Seems like it would be worth the money in the long run, but I dunno.

That's been discussed for decades too and it make no sense from an economic standpoint. There's no need to pay to put m-drives aboard all 'boats which will be used to perform a job for a few hours out of every 168 hours when a single m-drive aboard a tender or small craft "chaser" can be used to perform the same job all the time.

Plus maintenance of the boats and tenders. There may be no stationary station, but there's going to be a hive of activity around the agreed upon entry points for X-Boats, and each route will have it's own mini fleet of support vessels.

Yes. That's what I've meant by "link station". The designated arrival/departure "points" - actually regions - for each link will be a collection of tenders, scout/couriers, and small craft plus visiting tankers and shuttle. Because of jump shadows/masking and radial velocity concerns, each link will have it's own "link station".

Canon also states that the mainworld or, in the case of planetoid belts, the main "rock" will have a station either on the ground or in orbit to coordinating message traffic not only between the world and the tenders but also between tenders themselves.

 

[Enoki]

What I've never been able to understand is why bother with a pilot / crew on one to begin with? Make it robotic / autopilot. The tender takes it to the jump point and a crewman on the tender gets it into position and it jumps.
At the other end, it has an automatic beacon that tells the tender where to pick it up when it arrives.

That saves the cost and space of thousands, likely tens of thousands of crewmen, increases safety through reduced loss of life, and gives the same boat way more space for cargo CHACHING! :drooling: the money saved would be huge.

 

[aramis]

there's good reason to assume that the "oldest boat" in system takes the next scheduled jump. Given the window (±16.8 h), that's 151.2 to 184.8 hours, or 6d 7:12 to 7d 16:48 ... essentially a 3 day window, fairly heavily centered on 7.
To prevent oddities, a route should have 8.5 or even 9 days per jump for each ship, not 8, to allow a full 4 hours catch time, 4 hours release time, and 12 hours for maintenance check.

this also gives a "weekend" day for the pilot, who, likely as not, stays on a boat for several jumps, until he returns to his start, for the other pilot of the boat. (Crew 1, but 2 staterooms...).

Hans and I got into the math a few years ago, and 9 days is a sustainable liner schedule, too... gives 40 jumps plus 5 days end of year, most places the crew have a day in port (5/6 jumps on average), and up to 1.5 days. 39 jumps a year plus maintenance is a good cycle, and can be a 13 jump cycle 3 times per year.

So, for a single X-boat hop with daily departures... at 9 days per jump...
#1-#6 are definitely in jump
#7 is probably in jump, may be in tender
#8 is probably in the tender
#9 is definitely in the tender.
Same going back.
On a given day, up to 3 boats may come in, or none might.

So each link represents 18 boats, and, since 1/40.5 jumps needs to be sent to maintenance, that's half a spare boat- each 2 links is 39 boats, 72 pilots, and 2 tenders.

Since that all nicely gets bookended by the 3 X-boat bay (which, really, CAN fit 4, just barely, as long as the tender can leave the doors ajar... Checked it in sketchup. The angles are WONKY...)

FIFO is the generally fairest way to handle it. Besides, the scout's only there to prevent claims of salvage, and to make it piracy to board....

 

[Whipsnade]

What I've never been able to understand is why bother with a pilot / crew on one to begin with?

There are several in-game reasons some of which Wil touched on; having a sophont aboard prevents salvage claims or makes any unwanted boarding attempt an act of piracy. Our late friend Hans toyed with the idea that a "living mind" needed to be aboard a vessel in jump much like how the hyperspace mass indicator in Niven's Known Space was psionic on some manner. The implied psionic angle, however, was something which never sat well with him.

IMTU, the crewman is there to perform planned maintenance inflight. The maintenance they do during jump shortens the amount of time needed for maintenance and checks between jumps. They're rated as pilots so the IISS can pay them more for what has to be one of the worst jobs in that service. (Bennies like that are not uncommon. I became an NCO within a month of leaving boot camp so that the Navy could pay me more as a bennie for volunteering for the nuclear propulsion program.)

There are no real metagame reasons for it.

 

[Whipsnade]

there's good reason to assume that the "oldest boat" in system takes the next scheduled jump. Given the window (±16.8 h), that's 151.2 to 184.8 hours, or 6d 7:12 to 7d 16:48 ... essentially a 3 day window, fairly heavily centered on 7.

Yup, the distribution of jump's temporal variation is heavily centered on 7. As you note, 'boats can and will arrive early or late. A healthy majority will arrive close enough to seven days as to make little difference.

To prevent oddities, a route should have 8.5 or even 9 days per jump for each ship, not 8, to allow a full 4 hours catch time, 4 hours release time, and 12 hours for maintenance check.

Again, yes. A 'boat is on a one-jump every 9 day schedule while a link sees one 'boat arriving each day.

So each link represents 18 boats, and, since 1/40.5 jumps needs to be sent to maintenance, that's half a spare boat- each 2 links is 39 boats, 72 pilots, and 2 tenders.

The numbers and the costs add up quick.