A Farewell to Traveller

[rust]

Can you send radio signals through water at all?

Yes, but high frequencies have an extremely short range, and low
frequencies require huge antenna arrays and have an extremely
low data transfer rate. So, for almost all practical purposes, radio
signals are useless under water.

The message torpedo is a good idea, but how does it find its way back to the right ship?

The ship would have to remain stationary or on a specific course
to enable the torpedo (actually a torpedo shaped robot) to return
to the ship. Of course a disadvantage, but depending on the ship's
depth still better than having to dive all the way to the surface and
back down again.

You don't need the networked commsat to sink in the event of a storm, unless you want it to be unavailable to the players once in a while... a long enough cable that allowed a degree of drift would be enough to compensate for tides and wave amplitude.

Thinking of my setting, there are quite often hypercanes with a wind
speed of up to 500 km/h and waves 30 m high, so this could be a bit
much for buoy and cable, diving until the worst weather is over seems
reasonable.

I do wonder if something like carbon fibre weave wouldn't be suitable for the cable "chain", to be honest...

Yes, probably, it would only have to be protected against "squatters"
like coral, which could otherwise make a cleaning schedule necessary
to remove their additional weight from the cable.

 

[BFalcon]

Can you send radio signals through water at all?

Yes, but high frequencies have an extremely short range, and low
frequencies require huge antenna arrays and have an extremely
low data transfer rate. So, for almost all practical purposes, radio
signals are useless under water.

The message torpedo is a good idea, but how does it find its way back to the right ship?

The ship would have to remain stationary or on a specific course
to enable the torpedo (actually a torpedo shaped robot) to return
to the ship. Of course a disadvantage, but depending on the ship's
depth still better than having to dive all the way to the surface and
back down again.

You don't need the networked commsat to sink in the event of a storm, unless you want it to be unavailable to the players once in a while... a long enough cable that allowed a degree of drift would be enough to compensate for tides and wave amplitude.

Thinking of my setting, there are quite often hypercanes with a wind
speed of up to 500 km/h and waves 30 m high, so this could be a bit
much for buoy and cable, diving until the worst weather is over seems
reasonable.

I do wonder if something like carbon fibre weave wouldn't be suitable for the cable "chain", to be honest...

Yes, probably, it would only have to be protected against "squatters"
like coral, which could otherwise make a cleaning schedule necessary
to remove their additional weight from the cable.

Re: Radio - I was just thinking about whether you could use a radio uplink to connect to the seabed network from a reasonable distance, that's all I was thinking.

Such large waves might be a problem - remember, though, that the uplink would only need to be small unit, so a seabed-based winch might be sufficient to retract it. With 30m waves, you'd need to extract it some 50m + to avoid the turbulance that takes place below the surface - more if the tides are low at the same time.

Cleaning the cable could be done partly by the winching - just fed it through a narrow tube and it should knock off the hitchhikers - a similar approach could be done either through having a fixed mast, through which the cable runs or through a robot that just travels up and down the cable, so would probably have a disk-like structure built around the cable itself (making strong currents less of a risk, since it can't be detached from the cable).

Having a mast, incidently, would probably be wise if you have deep water and want to eliminate excessive drift on the surface. The mast could also have a radio uplink itself to the network and so provide a service in itself. Height wouldn't be a problem and it would probably include sonar, visual, radio and (possibly) a thermal beacon to make crashing into it practically impossible (although I'd not bet against a PC party managing it somehow).

Somebody: Well, considering that we have satellite uplinks that can be built into a mobile phone, high-bandwidth uplinks at a decent TL, would probably be around the size of a briefcase, I'd say... so the cable would be the most weight. If, as I suggested, you could build in air bladders to make it neutrally buoyant, the weight of the buoy would be the main weight, so you could make it very buoyant indeed, if you wanted - however, if you want to eliminate excessive strain on the cable, full retraction (to the mast if used) would be the wisest choice, so you'd either need some means of using a ballast tank or only as much buoyancy as needed.

A full-retraction cable and buoy would also be the wisest choice for anyone wishing to maintain secrecy (a bit like a towed array on a sub, it would only be deployed as needed) or on a submersible machine (like a sub), especially military, where 2-way communications are needed. Such buoys would not have much of a navigational beacon (although might have one that can be detected at short range (a few hundred metres) to prevent loss through accidental collision. Such systems would probably have a means of cutting the cable in case of such an entanglement.

 

[rust]

As for the buoys: What must be "above the waves" for the unit to function? Would an antenna be enough, maybe keeping the rest "deeper under water"?

The way I handle it in my setting, it is about the equivalent of a
modern satellite phone. However, an antenna alone at the sur-
face and the other components farther down should indeed work,
too. The only disadvantage would be that it would no longer be
narrow beam, and would therefore require more power to reach
the receivers.

 

[rust]

@ BFalcon:

Yes, the system you describe should work well enough, at least for
the lower depth range (up to perhaps 2.500 m) or so, with greater
depth it would probably require more advanced materials than we
currently have, and the costs would also go up considerably - bui-
ding and anchoring a stable mast several kilometers high, or wor-
king with a cable several kilometers long, would be quite an engi-
neering challenge, I think.

 

[Rick]

@ BFalcon:

Yes, the system you describe should work well enough, at least for
the lower depth range (up to perhaps 2.500 m) or so, with greater
depth it would probably require more advanced materials than we
currently have, and the costs would also go up considerably - bui-
ding and anchoring a stable mast several kilometers high, or wor-
king with a cable several kilometers long, would be quite an engi-
neering challenge, I think.

What you're talking about seems to be something like the beanstalk/skyhook technology for use underwater (almost in reverse, as it were) - I think carbon nanotubes were put forward as a possible way of doing this.
To sidetrack a bit - Peter F Hamilton had a water world in his "Reality Dysfunction" series - they used floating cities on the surface of the water built using a form of bio-engineered coral. There might be different technologies in use on your world: bio-engineering and mechanical engineering solutions to the same problems?

 

[BFalcon]

@ BFalcon:

Yes, the system you describe should work well enough, at least for
the lower depth range (up to perhaps 2.500 m) or so, with greater
depth it would probably require more advanced materials than we
currently have, and the costs would also go up considerably - bui-
ding and anchoring a stable mast several kilometers high, or wor-
king with a cable several kilometers long, would be quite an engi-
neering challenge, I think.

You only need a handful of uplink sites... it's only to link the underwater system with the satellites, after al...

 

[rust]

To sidetrack a bit - Peter F Hamilton had a water world in his "Reality Dysfunction" series - they used floating cities on the surface of the water built using a form of bio-engineered coral. There might be different technologies in use on your world: bio-engineering and mechanical engineering solutions to the same problems?

In my setting the original floating habitat, which served as a base for
all the other construction, was assembled from parts dropped from or-
bit as "dead landers". The sea floor habitat was then grown with gene-
tically engineered coral ("biocrete"), which took a few years, but was
the most cost efficient way, because it would have been very expensi-
ve to buy the parts for the domed habitat's hull and ship them to the
planet. Almost all future habitats, whether floating or on the sea floor,
will also be built from biocrete coral.

 

[Rick]

You Bitek engineering wizard, you! :lol:

 

[BFalcon]

Rust: how many floating cities and how well spaced out?

 

[rust]

Rust: how many floating cities and how well spaced out?

In the setting I am currently working on, Thalassa, there is now only one
floating habitat and one sea floor habitat below it. The campaign will start
very soon after the colony was originally established, and the characters
will influence the future development of the colony through their decisions,
so I decided to begin with an almost "clear slate" and leave as much as pos-
sible of the further development to the characters / players.

Previous water world settings, those using the Traveller technology, were a
lot more developed, but this time I intend to dare to be dumb and start it
as small as possible, which also enables me to slowly get used to the diffe-
rent technology assumptions (e.g. no gravitics, etc.).

 

[BFalcon]

Rust: how many floating cities and how well spaced out?

In the setting I am currently working on, Thalassa, there is now only one
floating habitat and one sea floor habitat below it. The campaign will start
very soon after the colony was originally established, and the characters
will influence the future development of the colony through their decisions,
so I decided to begin with an almost "clear slate" and leave as much as pos-
sible of the further development to the characters / players.

Previous water world settings, those using the Traveller technology, were a
lot more developed, but this time I intend to dare to be dumb and start it
as small as possible, which also enables me to slowly get used to the diffe-
rent technology assumptions (e.g. no gravitics, etc.).

Yeah, good plan. Only reason I asked - if you have enough habitats, spaced out sufficiently, the uplinks could be based on the habitats. Of course - that assumes that the habs are anchored, come to think of it, unless you have a jellyfish-type affair where the whole habs are propelled along the cables on the sea floor and "tentacles" dangle down to make radio contact with them...

What kind of landmasses? There's bound to be at least a few, right? (the tips of underwater mountains if nothing else).

 

[rust]

What kind of landmasses? There's bound to be at least a few, right? (the tips of underwater mountains if nothing else).

No, Thalassa is a pure water world, no part of the sea floor
is closer than ca. 160 m to the ocean surface.

This is more a campaign design decision, because otherwise
the characters would be likely to concentrate on the dry land,
no matter how small, and I want to have them on or under
the water all of the time.

 

[Rick]

Actually - a floating habitat with cables dropping down through several thermal layers?

Couldn't you generate energy that way - by using a similiar method to geothermal? But obviously, in water instead! That and solar panels might help supply some of your energy?

 

[rust]

Couldn't you generate energy that way - by using a similiar method to geothermal? But obviously, in water instead! That and solar panels might help supply some of your energy?

Yes, indeed, and both methods will most probably be used for future
floating habitats. The current floating habitat uses a fission reator, be-
cause it contains a lot of the colony's power hungry industry, from ore
processing to submarine shipyard, but floaters which are mostly used
for living space would do well with renewable energies only, from solar
panels through wave energy to geothermal energy.

 

[BFalcon]

Rick: nice idea...

Rust: very unusual not to have some kind of land, even if was a barren rock in the middle of an ocean...

Fully understand why though.

(you didn't answer my question about the floating cities though - anchored or no?)

But you could use the "high points" to set up a commsat uplink there. I would also suggest, having thought about it, that you would (at least initially) be able to get away with only a few uplink sites. The commsats themselves would communicate the signal to the furthest commsats in the orbital net, so if a region didn't have an uplink, it could get the signal ok... assuming it surfaced to communicate.

 

[rust]

(you didn't answer my question about the floating cities though - anchored or no?)

Ah, sorry. Not anchored - since the floater is the colony's downport, it
needs the ability to avoid the worst of the weather, otherwise the colo-
ny's shuttle could be "trapped" in orbit for several days, waiting for a
hurricane to move on so it can land on the floater. Therefore the floa-
ter usually stays above or close to the sea floor habitat, but is able to
move elsewhere with its hydrojet drive at short notice.

 

[Dave Chase]

I remember that setting.

lots of modules used in the initial building of the colony.

Dave Chase

 

[BFalcon]

(you didn't answer my question about the floating cities though - anchored or no?)

Ah, sorry. Not anchored - since the floater is the colony's downport, it
needs the ability to avoid the worst of the weather, otherwise the colo-
ny's shuttle could be "trapped" in orbit for several days, waiting for a
hurricane to move on so it can land on the floater. Therefore the floa-
ter usually stays above or close to the sea floor habitat, but is able to
move elsewhere with its hydrojet drive at short notice.

No problem.

Could still be anchored to save fuel - just un-anchor and reel in the cables when you need to move... and send down the mini-subs to reattach later. Mind you, with thermal, solar, wind and tidal power, let alone cracked hydrogen in a reactor, you're hardly going to worry about power useage that much I'd have thought...

One thought (and it's a strange one, given normal thinking, but) given the huge amount of water, might hydrogen-based combustion turbines not be a reasonable idea for a power source - its only output would be water, which would return to the eco-system, thereby being pretty much neutral. I'm assuming that, with high tech (ie lower power consumption) and the readily available power sources, they'd only be needed for emergency power (ie when moving or when caught in a storm)...?

With 100% water coverage, the tides are going to be a killer... you could harness that and have the seabed habitats use power-farms to harness the tidal strength and crack the water into hydrogen and oxygen... the oxygen being used by the habitat, the hydrogen being shipped up to the floating city for storage in case it needs it. It wouldn't then need to crack its own hydrogen except to top up its own supply in an emergency. That would be one product that would be readily available too for trading, along (presumably) with food from the deeper water (anyone for a Kelpburger? Kelpfries with that? Kelpshake?).

 

[rust]

One thought (and it's a strange one, given normal thinking, but) given the huge amount of water, might hydrogen-based combustion turbines not be a reasonable idea for a power source ...

No strange thought at all, the floater has an electrolysis system,
(there was some surplus power from the reactor ...) and all the
colony's surface watercraft (hydrofoils, fishing boats, etc.) use
hydrogen as fuel for their MHD turbines. Only the long range ex-
ploration submarines use nuclear power, mainly because it needs
less space than hydrogen and oxygen tanks for a closed cycle tur-
bine system would do.

With 100% water coverage, the tides are going to be a killer...

Not really, Thalassa has no moon and is comparatively far from its
star (I promised myself long ago never again to attempt to calcula-
te tide tables for a setting ...), so there are only the weak solar ti-
des to deal with, and the planet's "shallows" (think big flooded is-
lands less than 200 m below the ocean surface) reduce the strength
of these tides somewhat.

That would be one product that would be readily available too for trading, along (presumably) with food from the deeper water (anyone for a Kelpburger? Kelpfries with that? Kelpshake?).

There is not much trade, the characters will have to negotiate a few
good trade deals, or the bank loans will kill the colony project soon.
Right now there are rare earths from the seafloor mining and metals
from the phytomining (genetically engineered algae which accumulate
the metals from the sea water and are then processed) and some sea-
food. Hydrogen would perhaps be another product, but I leave that to
the characters to find out.

 

[rust]

I remember that setting.

lots of modules used in the initial building of the colony.

Yep, it is just a somewhat later version of it.