OTU Only: Speaking At The Speed of Light

[Supplement Four]

In reading CJ Cherryh's Downbelow Station, I am impressed with how communications are handled at long distances. There is a delay for distance.

In my Traveller games, I have sometimes implemented this, but not often. It was usually easier to roleplay instant-time communications. When I did think of time delay, I just used the speed of light to figure the delay.

There's a nifty quick cheat sheet in T5 (see page 41) that would be useful in a CT game. It basically says this...

Range < 250,000 km use no time delay. Instant communications.

Range 250,000+ km use 1 second delay.

Range 500,000+ km use 2 second delay.

Range 2,500,000+ km use 8 second delay.

Range 5,000,000+ km use 16 second delay.

Range 50,000,000+ km use 3 minute delay.

Range 150,000,000+ km use 8 minute delay. This is also 1 AU.

Range 500,000,000+ km use 30 minute delay.

Range 1,500,000,000+ km use 81 minutes delay.



This can be helpful to Refs for roleplaying communications at long distances.





COMMUNICATIONS BETWEEN STAR SYSTEMS

I would guess that communications between starports of different star systems would be extremely unreliable. Solar flares, magnetic fields, hydrogen clouds, massive stellar bodies, and all sorts of things would disrupt the signal.

But, we're talking about Traveller. The Far Future. The tech might be available to make this idea possible. Maybe signal repeaters are used in deep space between systems.

Time would still be very slow. Let's call it 3.26 years--the time it would take for a signal to reach a system one parsec away.

Can you think of any reason at all why a star system would maintain such a slow and inefficient system for communications when Jump ships are available?

 

[BlackBat242]

There's a nifty quick cheat sheet in T5 (see page 41) that would be useful in a CT game. It basically says this...

Range 250,000+ km use 1 second delay.

Range 500,000+ km use 2 second delay.

Range 2,500,000+ km use 8 second delay.

Range 5,000,000+ km use 16 second delay.

Range 50,000,000+ km use 3 minute delay.

Range 150,000,000+ km use 8 minute delay. This is also 1 AU.

Range 500,000,000+ km use 30 minute delay.

Range 1,500,000,000+ km use 81 minutes delay.

Sorry - someone failed math.

250Kkm to 2.5Mkm is a factor of 10 - but they only increase transmission delay by a factor of 8. This should be a factor of 10.

The same error is carried out throughout the chart.


Here is the corrected chart:

Range 250,000+ km use 1 second delay.

Range 500,000+ km use 2 second delay.

Range 2,500,000+ km use 10 second delay.

Range 5,000,000+ km use 20 second delay.

Range 50,000,000+ km use 3 minute 20 second (200 second) delay.

Range 150,000,000+ km use 10 minute delay. This is also 1 AU.

Range 500,000,000+ km use 33 minute 20 second (2,000 second) delay.

Range 1,500,000,000+ km use 100 minutes delay.

 

[boomslang]

Can you think of any reason at all why a star system would maintain such a slow and inefficient system for communications when Jump ships are available?

Not on an interstellar scale, no. But as you note, it is still useful at sub-lightyear distances.

IMTU, this type of communication -- laser- or maser-based for beamcasting, RF-based for broadcasting -- is relevant to communication "in-system" for very large values of "in".

To whit: Kuiper Belt (and Oort Cloud) Prospecting and Mining often take place under geometries where there can be light-hour distances between parties (especially when those parties might find themselves on opposite sides of the primary). Surveillance/Monitoring and System Defense Activities are also likely to occur in "The Outer System" (as HG and TCS call it, and even provide for an abstracted commo delay in their rules).

I have a few nomadic cultures IMTU that prefer to settle on KBOs, shunning Terrestrial planets and only venturing inside the Snow Line to mine worlds in Torch orbits. They have need to talk among themselves regularly.

Another possibility -- raised by the relatively large Jump Shadows around dwarf stars in comparison to their close-in Habitable Zones -- are open-space construct or repositioned-planetoid farports set up well outside the primary's Jump Shadow to serve as way-stations for refueling and cargo & passenger transfer in support of scheduled commercial traffic. Some farports might be quite distant from the system mainworld, especially during those times their orbits put them in, or close to, opposition to it. These things could be many light-minutes away from the mainworld most of the time, depending.

But chatting over the wireless at interstellar ranges? Only post-Maghiz, perhaps.

 

[kilemall]

Assuming most systems have Oort clouds, that's a band of ice approximately 1-1.5 LYs out, 2-3 LYs across.

In most cases I would presume timely communications would be just like interstellar comms- jump followed by X AUs radio/laser distance. However, my assumption is that Oort cloud denizens are the most private/irrational/illegal of all of sophontkind, and so they may have need of cheap communications between radical organizations.

The other scenario for interstellar comms I can think of is Long Night ones, losing jump support capability but staying in touch with systems 3 parsecs or less.

 

[infojunky]

Thinking about it a 1 second delay probably should kick in at 150,000 km+

In that at half a second it is a noticeable lag. And well also Rounding....

 

[Straybow]

Yes, your delay is only half as long as it needs to be.

Communication is two way. If your only concern is transmitting data from one party to another the listed delay is good. But more often you need an answer, and you'll have to wait twice as long.

 

[ian54]

For perspective the closest Earth and Mars get is 50 Mkm, this is probably the best interplanetary distance you would get, I would think that any TL 12+ system would have heliostationary communications satellites.

 

[Kilgs]

Thanks for the chart! A good handy reference for GMs.

 

[aramis]

For perspective the closest Earth and Mars get is 50 Mkm, this is probably the best interplanetary distance you would get, I would think that any TL 12+ system would have heliostationary communications satellites.

There are systems where the maximum separation is under 600 kkm for a group of multiple worlds. See also Trappist 1.

The Sol system is turning out to be a fairly non-representative system.

 

[kilemall]

There are systems where the maximum separation is under 600 kkm for a group of multiple worlds. See also Trappist 1.

The Sol system is turning out to be a fairly non-representative system.

More Ancients manipulation? Contra-terrene traces at the asteroid belt?

 

[Spartan159]

More Ancients manipulation? Contra-terrene traces at the asteroid belt?

I keep trying to say, but everyone is all like wind sheer this and swamp gas that :rofl:

 

[aramis]

More Ancients manipulation? Contra-terrene traces at the asteroid belt?

Simplest explanation: Traveller's physics aren't the real world's physics in ways far more fundamental than just "FTL works and doesn't violate causality" and "Fusion is cheap and easy."

 

[Carlobrand]

There are systems where the maximum separation is under 600 kkm for a group of multiple worlds. See also Trappist 1.

The Sol system is turning out to be a fairly non-representative system.

Well, in some ways we always were. G2V's are not the most common things out there.

 

[aramis]

Well, in some ways we always were. G2V's are not the most common things out there.

Traveller generates pretty systems way too similar to ours... for the time Bk6 was written, it was bleeding edge...

 

[kilemall]

Well, in some ways we always were. G2V's are not the most common things out there.

I did local space around Terra using the Imperium map, and matching up the systems to their real world counterparts.

Then, used RTT Worldgen to do the system.

Since most of the stars are various K & M red dwarfs, most are very cold and not very terran. The populations are low, as it's frontier only 40 years or less old, most people don't want to move out there and there isn't much industry developed.

One system is even entirely unoccupied. Another was population in the 100s but a religious location (hence the ice monastery).

The moment something like Hop gets discovered, most systems people will concern themselves with will be G stars, and a LOT of things could be lurking out there under the dim ancient red stars no one visits.