Where are the interplanetary laser comms? CSC64

[Yenaldlooshi]

CSC64 talks about laser comms with interplanetary distances and reaching outer planets yet all the ones listed are 500Km. Where are these comms? Am I misreading something?

 

[swordtart]

Those ranges are planetary and include curvature of the planet and atmospheric interference effects. Pushing out in space you would not suffer these effects. Transceivers of this sort would tend to be part of a ships communication equipment rather than something in the CSC due to the inability to aim accurately enough with hand held equipment, but Travellers are ingenious

This is mentioned in the first Laser Transceiver paragraph on P64 above the table.

 

[Yenaldlooshi]

Those ranges are planetary and include curvature of the planet and atmospheric interference effects. Pushing out in space you would not suffer these effects. Transceivers of this sort would tend to be part of a ships communication equipment rather than something in the CSC due to the inability to aim accurately enough with hand held equipment, but Travellers are ingenious

This is mentioned in the first Laser Transceiver paragraph on P64 above the table.

Thank you! I think I understand it now. So, if I am on a world surface, that is the effective range. If I am in a ship in orbit, my range is effectively the whole entire system, but, I must have positional information with my other laser transceiver.
So, I have two ships that often travel adjacent to each other. When they are together, they can link via laser transceivers, then as they move apart, updating position information as they go, they can then achieve effectively full systemwide, un-jammable, un-interceptable, undetectable comms except when totally blocked line of sight. Is that how you might read that first paragraph?
Are laser comms standard on ships or military ships?

 

[swordtart]

Thank you! I think I understand it now. So, if I am on a world surface, that is the effective range. If I am in a ship in orbit, my range is effectively the whole entire system, but, I must have positional information with my other laser transceiver.
So, I have two ships that often travel adjacent to each other. When they are together, they can link via laser transceivers, then as they move apart, updating position information as they go, they can then achieve effectively full systemwide, un-jammable, un-interceptable, undetectable comms except when totally blocked line of sight. Is that how you might read that first paragraph?
Are laser comms standard on ships or military ships?

The sensors on your ship will probably be the deciding factor (since comms are not explicitly covered). LIDAR is probably the closest equivalent (since it is based on pinging put a laser beam and detecting the reflection) and the table tells us that this works well out to short range (1,250km), is limited out to long range(25,000km) and minimal out to distant range(beyond 50,000km).

Given your ships are both wanting to conduct communication and I would say you could manage to remain in comms out beyond 50,000km as you can at the very least double the range compared to LIDAR and your coded transmissions can have error correction as you know the format the communication will take.

I haven't seen anything specific about Laser Communications on ships, but I would say that since even the Basic Sensor Suite has LIDAR then LASER Communications should be part of it.

Whether LASER communication is undetectable to ships sensors systems is a matter for the referee. Logic would indicate that unless a detector was in direct line of the beam they wouldn't see it over short distances. However the further it goes the greater the chance of cosmic dust scattering it a little and when that beam hits the other ship it is likely to scatter a lot and be detectable in a broad area. Sensor checks to find a ship using active LIDAR are at +2. Of course you wouldn't necessarily know it was communication, you might think it was just a LIDAR scan.

 

[Yenaldlooshi]

The sensors on your ship will probably be the deciding factor (since comms are not explicitly covered). LIDAR is probably the closest equivalent (since it is based on pinging put a laser beam and detecting the reflection) and the table tells us that this works well out to short range (1,250km), is limited out to long range(25,000km) and minimal out to distant range(beyond 50,000km).

Given your ships are both wanting to conduct communication and I would say you could manage to remain in comms out beyond 50,000km as you can at the very least double the range compared to LIDAR and your coded transmissions can have error correction as you know the format the communication will take.

I haven't seen anything specific about Laser Communications on ships, but I would say that since even the Basic Sensor Suite has LIDAR then LASER Communications should be part of it.

Whether LASER communication is undetectable to ships sensors systems is a matter for the referee. Logic would indicate that unless a detector was in direct line of the beam they wouldn't see it over short distances. However the further it goes the greater the chance of cosmic dust scattering it a little and when that beam hits the other ship it is likely to scatter a lot and be detectable in a broad area. Sensor checks to find a ship using active LIDAR are at +2. Of course you wouldn't necessarily know it was communication, you might think it was just a LIDAR scan.

"out beyond 50,000km"? I would hope so. That is nothing in space and the CSC still says interplanetary distances are possible for the L-Comms it lists. Looking at the costs and weight and TL of these comms in the CSC, including them as being normal on ships for ship to ship comms in the same group makes sense as these seem negligible. This then creates a big question for piracy. Can your target simply send a laser communication distress call to the starport anytime they are under an attack in a system and the starport will automatically receive it and can respond?

 

[Terry Mixon]

"out beyond 50,000km"? I would hope so. That is nothing in space and the CSC still says interplanetary distances are possible for the L-Comms it lists. Looking at the costs and weight and TL of these comms in the CSC, including them as being normal on ships for ship to ship comms in the same group makes sense as these seem negligible. This then creates a big question for piracy. Can your target simply send a laser communication distress call to the starport anytime they are under an attack in a system and the starport will automatically receive it and can respond?

Good point.

 

[swordtart]

Again the issue would be are you in LOS of the star port. If so how long does it take your message to get there. Even the speed of light starts to become an inconvenience at astronomical distances. It might take only 2-3 seconds to get there at the 100D limit, but if you are out at a gas giant 600 Million km away you are talking more like half an hour. The combat will likely have already been decided by that point.

LASERs are nothing special if you are just trying to send a MAYDAY, conventional radio is just as fast and doesn't need to be as tightly directed. It can be jammed, but that level of jamming would be indicative of hostile action anyway and would also paint the jammer.

Getting the SOS message to the authorities isn't really the issue. The issue is the authority getting the message to a response craft and the craft to the site of the attack before it changes from a rescue to a recovery mission. If the response craft is close enough to you for it to be able to make a difference then it is also as far from the star port as you, doubling the communication time.

 

[agentwigggles]

And you probably wouldnt use it laser comms to often. The thing that laser comms do is a point to point connection. Cant be intercepted or even detected. Though for everyday use you'd just use a radio of some frequency.

 

[NOLATrav]

A bit off topic but man, the laser/energy ranges in Traveller have always been crazy IMO.

 

[swordtart]

It is ignored in game but even LASERs diverge over large distances. The larger the wavelength, the greater the diversion and the wider the area the LASER energy is distributed over. We don't notice usually as the distances but over interplanetary distances it would be huge.

 

[Yenaldlooshi]

Again the issue would be are you in LOS of the star port. If so how long does it take your message to get there. Even the speed of light starts to become an inconvenience at astronomical distances. It might take only 2-3 seconds to get there at the 100D limit, but if you are out at a gas giant 600 Million km away you are talking more like half an hour. The combat will likely have already been decided by that point.

LASERs are nothing special if you are just trying to send a MAYDAY, conventional radio is just as fast and doesn't need to be as tightly directed. It can be jammed, but that level of jamming would be indicative of hostile action anyway and would also paint the jammer.

Getting the SOS message to the authorities isn't really the issue. The issue is the authority getting the message to a response craft and the craft to the site of the attack before it changes from a rescue to a recovery mission. If the response craft is close enough to you for it to be able to make a difference then it is also as far from the star port as you, doubling the communication time.

LOS= Probably not an issue. Would only matter in the case of being on the darkside of an orbit either for the receiver or the sender. Any Starport with a Highport would probably have an number of CommSats they could relay laser comms traffic off of. Same at sensitive and strategically valuable parts of the system, obvious example; gas giants.

Response Craft= I take your point about that but again that is a simple fix. A Trader craft using a laser transponder inline with the High Port heading to a gas giant for refueling could hand off their ping to a waiting response patrol craft on station at the gas giant placed their to protect from pirates, if the system has that security.

Jamming= Are we talking jamming comms or jamming sensors? These two different things seem to get confused all the time. Jamming comms is only mentioned in Core67 as an opposed check of Difficult (12+) with lasers... ---Which raises the question about many of these opposed checks listed with a difficulty raised, if the check is opposed and you set it to "difficult" for both parties, how is that any different than any other difficulty since the winner is the one with "best effect", be they both positive, both negative or one each? Should it not be "difficult" for you but average for the defender, depending on who is doing what?
Regardless, if your comms are being jammed, but not sensors, are you automatically detected? Does this mean a starport 30 light minutes away will also be warned? What info is given away if sensors/comms are jammed? Location and bearing or just that there is a hostile somewhere in that direction?

 

[Yenaldlooshi]

And you probably wouldnt use it laser comms to often. The thing that laser comms do is a point to point connection. Cant be intercepted or even detected. Though for everyday use you'd just use a radio of some frequency.

and why is that? We are talking TL's above us here on Terra in the 21st Century after all. I understand your point about can't be intercepted and "maybe" detected, and yet in core they talk about jamming lasers on page67. I am not sure if I agree with that one, though tbh.