Comm Range

[Supplement Four]

Originally posted by far-trader:
I still don't like the idea of ship's zooming around at those velocities though

Another quickie comments before I re-read yours and Hal's comments...

That was just using the Traveller travel formula. If those velocities are not obtained, then all jumps into systems have to be doggone close to destination points. Otherwise, travelling at speed far less than the travel formula suggests, in-system time is going to be much more than a week. Ships will run out of supplies, fuel, life support, etc.

Also, a quick note on sensors: I take the ranges listed in CT for sensors to be the combat range of the sensors. I'm sure they've got spectral analysis and other types of sensors for long range (it probably helps them for plotting jump courses, too--especially in seeing/predicting the postion of nearby stars, etc).

 

[Supplement Four]

Originally posted by far-trader:
I still don't like the idea of ship's zooming around at those velocities though

Another quickie comments before I re-read yours and Hal's comments...

That was just using the Traveller travel formula. If those velocities are not obtained, then all jumps into systems have to be doggone close to destination points. Otherwise, travelling at speed far less than the travel formula suggests, in-system time is going to be much more than a week. Ships will run out of supplies, fuel, life support, etc.

Also, a quick note on sensors: I take the ranges listed in CT for sensors to be the combat range of the sensors. I'm sure they've got spectral analysis and other types of sensors for long range (it probably helps them for plotting jump courses, too--especially in seeing/predicting the postion of nearby stars, etc).

 

[Supplement Four]

I've modified Dan's thoughts above, coming up with a rule I'm going to use in my game.

Consider this....


=================================================
COMMUNICATION RANGE
=================================================


Range - A starship comm's range is measured in range bands of one-half light second, and the base range for any starship is a number of these range bands equal to the ship's computer model number.


Comm Range = Computer Model Number x 150,000 km


Thus, a ship with a Model/1 computer has a comm range of 150,000 km. A ship with a Model-3 computer has a comm range of 450,000 km.

Typically, in a Traveller game, this base range can be used to determine if a ship is within comm distance of another vessel/planet/station/whatever.


A skilled comm operator, though, can coax more gain out of the ship's receivers if he is successful on a task:


Communications/EDU or Ship's TL/+2


This is a ROUTINE UGM task roll (in normal CT terms, this roll is: Roll 6+ on 2D using Communications skill as a DM).

If this task fails, comm range is restricted to the comm's base range.

If this task succeeds, comm range is increased by one-half light second (add 150,000 km to range).

For every two points rolled over the task target number, add another one-half light second range band to the comm's range.

Situational modifiers may apply to this roll. Comm Relays, Comm Beacons, and Comm Buoys all may add a positive DM to the roll. Some starports are responsible for powerful transmission signals, or aid may be had by communication satellites. Sunspots, or a planet's atmosphere may provide comm interference, etc.








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Example

The ADROIT PURSUIT is engaged with a pirate vessel in the Patinir asteroid belt. The ship's navigator sends out a Signal GK.

The PURSUIT has a Model/1 computer, therefore, base comm range is 150,000 km. But, the PURSUIT's captain, wants the SOS to be as strong and as "loud" as possible, increasing the chance their cry for help will be heard by a passing vessel.

The navigator makes the roll:

Communications/EDU or Ship's TL/+2

Since the "corridor" (the standard approach pattern for Patinir's Station "C") is lined with comm relays attached some some of the asteroids, the GM allows a positive DM on this roll equal to 1D. He rolls and gets a "6", meaning that a +6 DM situational modifier is used on this roll.

The Navigator rolls the task, and when all DMs are applied, the total of the throw is 15.

This means that comm range is extended 3 range bands (due, mainly, to the relay comm repeaters).

The ship's SOS can be picked up out to 600,000 km (two light seconds).

 

[Supplement Four]

I've modified Dan's thoughts above, coming up with a rule I'm going to use in my game.

Consider this....


=================================================
COMMUNICATION RANGE
=================================================


Range - A starship comm's range is measured in range bands of one-half light second, and the base range for any starship is a number of these range bands equal to the ship's computer model number.


Comm Range = Computer Model Number x 150,000 km


Thus, a ship with a Model/1 computer has a comm range of 150,000 km. A ship with a Model-3 computer has a comm range of 450,000 km.

Typically, in a Traveller game, this base range can be used to determine if a ship is within comm distance of another vessel/planet/station/whatever.


A skilled comm operator, though, can coax more gain out of the ship's receivers if he is successful on a task:


Communications/EDU or Ship's TL/+2


This is a ROUTINE UGM task roll (in normal CT terms, this roll is: Roll 6+ on 2D using Communications skill as a DM).

If this task fails, comm range is restricted to the comm's base range.

If this task succeeds, comm range is increased by one-half light second (add 150,000 km to range).

For every two points rolled over the task target number, add another one-half light second range band to the comm's range.

Situational modifiers may apply to this roll. Comm Relays, Comm Beacons, and Comm Buoys all may add a positive DM to the roll. Some starports are responsible for powerful transmission signals, or aid may be had by communication satellites. Sunspots, or a planet's atmosphere may provide comm interference, etc.








-------------------------------------------------
Example

The ADROIT PURSUIT is engaged with a pirate vessel in the Patinir asteroid belt. The ship's navigator sends out a Signal GK.

The PURSUIT has a Model/1 computer, therefore, base comm range is 150,000 km. But, the PURSUIT's captain, wants the SOS to be as strong and as "loud" as possible, increasing the chance their cry for help will be heard by a passing vessel.

The navigator makes the roll:

Communications/EDU or Ship's TL/+2

Since the "corridor" (the standard approach pattern for Patinir's Station "C") is lined with comm relays attached some some of the asteroids, the GM allows a positive DM on this roll equal to 1D. He rolls and gets a "6", meaning that a +6 DM situational modifier is used on this roll.

The Navigator rolls the task, and when all DMs are applied, the total of the throw is 15.

This means that comm range is extended 3 range bands (due, mainly, to the relay comm repeaters).

The ship's SOS can be picked up out to 600,000 km (two light seconds).

 

[Golan2072]

On a related note, how effective are RL comm systems in these regards? I know that relatively small (but expensive) probes such as Voyager I and 2 and Pioneer 10 (IIRC) could be communicated with from Earth when they are in the fringes of our solar system, but doesn't that require the ground-station to track them and listen specifically to their frequency?

Oh, and I like the use of the ship's TL as a substitute for EDU on comm rolls and ship's computer as an indicator of comm range.

 

[Golan2072]

On a related note, how effective are RL comm systems in these regards? I know that relatively small (but expensive) probes such as Voyager I and 2 and Pioneer 10 (IIRC) could be communicated with from Earth when they are in the fringes of our solar system, but doesn't that require the ground-station to track them and listen specifically to their frequency?

Oh, and I like the use of the ship's TL as a substitute for EDU on comm rolls and ship's computer as an indicator of comm range.

 

[atpollard]

Originally posted by Hal:
Some thoughts on excessive speed...

Lets say that you're travelling at 2% the speed of light. Further suppose that you can see things out to 1 light second...

An object that is 1 light second away takes two seconds to notice, because the signal hits it, and then bounces back (active sensors that is). That's just 2 seconds for one "ping" of a signal here.

Travelling at 2% the speed of light, is going to give you 1/.02 seconds to react to the problem your sensor just noted. Remember that 2 second spread for sensor. Out of 50 seconds reaction time, you've spent 2, leaving you 48. Lets say for the sake of argument, that you have an automated system that is authorized to change course by as much as 30 seconds with 1 G acceleration in any direction. So the computer flashes a warning message to the navigator "Warning,immenient collision, abort course?". If nothing is done, it automatically upon reaching 18 seconds after detecting a possible collision, begins to nudge your ship slightly off course. 32.17 feet per second per second, or 9.8 meters per second per second, will be what 1 G accelleration will provide. Distance travelled is 1/2 acceleration x Time squared. So how much displacement will our ship have if it only has 30 seconds at 1 G? Roughly 14476.5 ft, or roughly 4,410 meters. That should be ample enough time to avoid hitting something. At 5 seconds, the displacement would be 400 ft or 122 meters. At 10 seconds, the displacement is 1608 ft or 490 meters. Unless the object you are responding to is moving eratically (such as a ship or missile) *AND* It is directly on a collision course, moving at high speeds is not all that bad of an issue. The problem here is that each "Turn" is roughly 1000 seconds (CT) or 1,200 (High Guard) - and people forget to look at it as a real-time issue.

All things considered - it is those pesky sand grains that give you the major headaches, but Traveller ignores them, so I shall too

HAL,
A very good analysis.

I too was guilty of thinking in terms of "you are travelling farther than your sensor range in a turn, so you cannot avoid objects". When you look at it from a reaction time perspective, everything changes.

All of the other comments on this post still apply, but the maximum safe speed just got a lot faster.

 

[atpollard]

Originally posted by Hal:
Some thoughts on excessive speed...

Lets say that you're travelling at 2% the speed of light. Further suppose that you can see things out to 1 light second...

An object that is 1 light second away takes two seconds to notice, because the signal hits it, and then bounces back (active sensors that is). That's just 2 seconds for one "ping" of a signal here.

Travelling at 2% the speed of light, is going to give you 1/.02 seconds to react to the problem your sensor just noted. Remember that 2 second spread for sensor. Out of 50 seconds reaction time, you've spent 2, leaving you 48. Lets say for the sake of argument, that you have an automated system that is authorized to change course by as much as 30 seconds with 1 G acceleration in any direction. So the computer flashes a warning message to the navigator "Warning,immenient collision, abort course?". If nothing is done, it automatically upon reaching 18 seconds after detecting a possible collision, begins to nudge your ship slightly off course. 32.17 feet per second per second, or 9.8 meters per second per second, will be what 1 G accelleration will provide. Distance travelled is 1/2 acceleration x Time squared. So how much displacement will our ship have if it only has 30 seconds at 1 G? Roughly 14476.5 ft, or roughly 4,410 meters. That should be ample enough time to avoid hitting something. At 5 seconds, the displacement would be 400 ft or 122 meters. At 10 seconds, the displacement is 1608 ft or 490 meters. Unless the object you are responding to is moving eratically (such as a ship or missile) *AND* It is directly on a collision course, moving at high speeds is not all that bad of an issue. The problem here is that each "Turn" is roughly 1000 seconds (CT) or 1,200 (High Guard) - and people forget to look at it as a real-time issue.

All things considered - it is those pesky sand grains that give you the major headaches, but Traveller ignores them, so I shall too

HAL,
A very good analysis.

I too was guilty of thinking in terms of "you are travelling farther than your sensor range in a turn, so you cannot avoid objects". When you look at it from a reaction time perspective, everything changes.

All of the other comments on this post still apply, but the maximum safe speed just got a lot faster.

 

[Ptah]

Originally posted by Supplement Four:
...

The speed of light travels at 299,792 km per second, so that tells me that the communications delay, in speaking with the station, is something just under 6 minutes.

...I guess my question is this: Should it be very easy for a ship, 2.38 days from its destination, to communicate with the colony?

What factors (besides military jamming) would make communication with the colony difficult?

I like Dan's rules but have always had a problem with the CT comm ranges. Small TL 7 probes, e.g., Voyager, have no problem communicating with Earth using very low power and low volume communicators. And we can send signals to this little thing. Okay maybe not anymore, but I think is was going pretty good for at least 20AU maybe more.

That TL 10+ ships perform worse is hard to believe. I would use Dan's approach but drastically up the ranges by at least 3 orders of magnitude and probably 4 (i.e. to millions of km, 1AU = about 150,000,000 km IIRC) especially when communicating with a colony that probably has a large radio telescope, or array of same (ole' TL 7 surplus) and plenty of power to send signals. And this is assuming the system has no repeaters/transciever such as our lowly system.

I might keep the lower ranges for ship-to-ship communication but up them at least a power of 10 for communications.

This is all assuming rather serene planetary ionospheric and solar flare conditions. Add in some of the latter, or maybe even jump space emergence interference and this could get harder. That is if you like the idea of being out of comm range.

Sensors are a different matter.

 

[Ptah]

Originally posted by Supplement Four:
...

The speed of light travels at 299,792 km per second, so that tells me that the communications delay, in speaking with the station, is something just under 6 minutes.

...I guess my question is this: Should it be very easy for a ship, 2.38 days from its destination, to communicate with the colony?

What factors (besides military jamming) would make communication with the colony difficult?

I like Dan's rules but have always had a problem with the CT comm ranges. Small TL 7 probes, e.g., Voyager, have no problem communicating with Earth using very low power and low volume communicators. And we can send signals to this little thing. Okay maybe not anymore, but I think is was going pretty good for at least 20AU maybe more.

That TL 10+ ships perform worse is hard to believe. I would use Dan's approach but drastically up the ranges by at least 3 orders of magnitude and probably 4 (i.e. to millions of km, 1AU = about 150,000,000 km IIRC) especially when communicating with a colony that probably has a large radio telescope, or array of same (ole' TL 7 surplus) and plenty of power to send signals. And this is assuming the system has no repeaters/transciever such as our lowly system.

I might keep the lower ranges for ship-to-ship communication but up them at least a power of 10 for communications.

This is all assuming rather serene planetary ionospheric and solar flare conditions. Add in some of the latter, or maybe even jump space emergence interference and this could get harder. That is if you like the idea of being out of comm range.

Sensors are a different matter.

 

[Ptah]

Originally posted by far-trader:
....

As far as being in comms range only briefly anyone who's driven cross country can attest to the reality, albeit on a slower and shorter scale. You drive away from one radio station and the signal fades while another gets stronger and then it too fades.

This effect has to do with a lot of things, one of which is dealing with radio waves bouncing off the atmosphere and destructively interfereing with each oterh as they reflect off objects. Just sayiing, not the best analogy for propagation of radio ways through sapce.

The only real difference between a TL5 radio tranceiver and a TL15 one of the same power is the interface. ....

Not exactly. A friend of mine collects old radios, those TL5 kind, the tubes and other stuff in them makes them larger than a TL 8 radio that uses less power, is far, far smaller, and works much better. This is for radios that don't even have fancy singal processing chips, solid state antennas, etc. Even if TL5 means transitors, current radios beat them hands down as well. So I'd say 10TL makes a huge difference, even if the TL15 set implements TL5 pricipals of operation.

 

[Ptah]

Originally posted by far-trader:
....

As far as being in comms range only briefly anyone who's driven cross country can attest to the reality, albeit on a slower and shorter scale. You drive away from one radio station and the signal fades while another gets stronger and then it too fades.

This effect has to do with a lot of things, one of which is dealing with radio waves bouncing off the atmosphere and destructively interfereing with each oterh as they reflect off objects. Just sayiing, not the best analogy for propagation of radio ways through sapce.

The only real difference between a TL5 radio tranceiver and a TL15 one of the same power is the interface. ....

Not exactly. A friend of mine collects old radios, those TL5 kind, the tubes and other stuff in them makes them larger than a TL 8 radio that uses less power, is far, far smaller, and works much better. This is for radios that don't even have fancy singal processing chips, solid state antennas, etc. Even if TL5 means transitors, current radios beat them hands down as well. So I'd say 10TL makes a huge difference, even if the TL15 set implements TL5 pricipals of operation.