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In the OTU In the Official Traveller Universe. Any milieux that's been published in any edition. Not for discussion of rules except in reference to how they reflect the OTU

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  #11  
Old September 11th, 2018, 07:29 AM
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Quote:
Originally Posted by Whipsnade View Post
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?
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  #12  
Old September 11th, 2018, 08:14 AM
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Originally Posted by Ulsyus View Post
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.
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Last edited by Whipsnade; September 11th, 2018 at 09:55 AM.. Reason: clarity
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  #13  
Old September 11th, 2018, 11:19 AM
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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.
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Old September 11th, 2018, 01:43 PM
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Quote:
Originally Posted by whartung View Post
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.

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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.

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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.
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Old September 11th, 2018, 07:22 PM
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Quote:
Originally Posted by Whipsnade View Post
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.

Quote:
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.
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Old September 11th, 2018, 08:18 PM
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Quote:
Originally Posted by whartung View Post
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.

Quote:
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.

Quote:
Now, to the velocity part. This is where the fun begins.
Not "fun" as much misunderstanding.

Quote:
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.

Quote:
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.

Quote:
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.
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Old September 11th, 2018, 09:52 PM
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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! the money saved would be huge.
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Old September 11th, 2018, 09:57 PM
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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....
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  #19  
Old September 11th, 2018, 11:03 PM
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Quote:
Originally Posted by Enoki View Post
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.
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Old September 11th, 2018, 11:07 PM
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Originally Posted by aramis View Post
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.

Quote:
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.

Quote:
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.
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Last edited by Whipsnade; September 12th, 2018 at 12:32 AM.. Reason: spelling
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