Emergency Beacon Detection Range

[Arkathan]

A transponder gives a plus six to detection. I’m willing to grant an emergency beacon the same effect. Unlimited detection? No.

A transponder wants people local to it (weapons range) to know what level of threat they do not present. Distant range is mostly irrelevant to a transponder.
An emergency beacon wants people to hear it. It is made to scream for help.
The only case in which an emergency beacon would be as quiet as a transponder is if it was trying to conserve power, because it has been screaming for a long while.

Only the people who want to hear a Voyager probe are going to look for that signal. One on the emergency frequency or with an emergency prefix is going to be pushed into anyone's face.

So, Oort cloud, maybe not. Near Kuiper Belt, It will be annoying anyone with a space craft built to any interstellar standard.

An independent non-interstellar world or barely interplanetary: that is where you start having trouble.

Edit: Naturally Plot McGuffins will nerf detectability.

 

[MasterGwydion]

To a dedicated, massive receiver array that knows precisely where to look.

A transponder gives a plus six to detection. I’m willing to grant an emergency beacon the same effect. Unlimited detection? No.

Why does the Emergency Beacon have to be an EM tranmitter? Why not a gravitic beacon? All it does is make gravity pulses, of the same type as when you exit jumpspace, in a repeating Signal GK. Then you could use the jump detection rules.

 

[Terry Mixon]

Why does the Emergency Beacon have to be an EM tranmitter? Why not a gravitic beacon? All it does is make gravity pulses, of the same type as when you exit jumpspace, in a repeating Signal GK. Then you could use the jump detection rules.

The broken rules that let you detect a jump flash from other galaxies with unlimited range? Hard pass.

 

[Terry Mixon]

A transponder wants people local to it (weapons range) to know what level of threat they do not present. Distant range is mostly irrelevant to a transponder.
An emergency beacon wants people to hear it. It is made to scream for help.
The only case in which an emergency beacon would be as quiet as a transponder is if it was trying to conserve power, because it has been screaming for a long while.

Only the people who want to hear a Voyager probe are going to look for that signal. One on the emergency frequency or with an emergency prefix is going to be pushed into anyone's face.

So, Oort cloud, maybe not. Near Kuiper Belt, It will be annoying anyone with a space craft built to any interstellar standard.

An independent non-interstellar world or barely interplanetary: that is where you start having trouble.

Edit: Naturally Plot McGuffins will nerf detectability.

A transponder also wants to be detected. I don't see much reason they would be less powerful, After all, a Signal GK is transmitted by something. It might as well be the transponder. In fact, that makes the most sense. All ships need to be able to scream for help and the transponder is the most likely medium. I just don't buy the argument of virtually unlimited in-system detection.

Being pushed into one's face is still ineffective if the signal doesn't have the power. That will be the limiting factor. We have Interplanetary transmitters that can have viable communications out to 500,000 km. After that, the signal will be detectable, but not forever. Not even close. Cube law. If we knew what the base strength and frequency was, that would help. A starport will likely have bigger receivers, too.

 

[Arkathan]

A transponder also wants to be detected. I don't see much reason they would be less powerful, After all, a Signal GK is transmitted by something. It might as well be the transponder. In fact, that makes the most sense. All ships need to be able to scream for help and the transponder is the most likely medium. I just don't buy the argument of virtually unlimited in-system detection.

Being pushed into one's face is still ineffective if the signal doesn't have the power. That will be the limiting factor. We have Interplanetary transmitters that can have viable communications out to 500,000 km. After that, the signal will be detectable, but not forever. Not even close. Cube law. If we knew what the base strength and frequency was, that would help. A starport will likely have bigger receivers, too.

I strongly suspect that the transmitter will be more powerful than the one on Voyager, with the 220 watts of the entire spacecraft barely scratching the surface. The signal will be detectable and decipherable out to the heliopause. Because the weaker signal is.
Much like your phone is set up to respond to an emergency broadcast, Ship's sensors and starport sensors are going to be triggered by any detected emergency broadcast.
Unless your plot requires that the signal be weak or masked.

The Alien example was picked up several light years away, and relayed to the crew of the Nostromo. They knew exactly what they were getting that sleeping crew into. Then there is Ripley's lifeboat, which would not have put her alive in the future and available for Aliens and Alien III had it been detected early.

 

[Terry Mixon]

I strongly suspect that the transmitter will be more powerful than the one on Voyager, with the 220 watts of the entire spacecraft barely scratching the surface. The signal will be detectable and decipherable out to the heliopause. Because the weaker signal is.
Much like your phone is set up to respond to an emergency broadcast, Ship's sensors and starport sensors are going to be triggered by any detected emergency broadcast.
Unless your plot requires that the signal be weak or masked.

The Alien example was picked up several light years away, and relayed to the crew of the Nostromo. They knew exactly what they were getting that sleeping crew into. Then there is Ripley's lifeboat, which would not have put her alive in the future and available for Aliens and Alien III had it been detected early.

I'll bring up again that the signal is picked up by a massive receiver array focused on the target. That is the key fact the seems to be overlooked. Space degrades radio signals--even strong ones--and a general receiver will need to be a lot closer than a dedicated, big, and potentially targeted one.

Let's say that a class A or B starport has a dedicated large array. It will be able to detect an emergency beacon at much greater range and even focus the receivers on it to enhance the signal. They could then dispatch rescue ships that don't get the signal on their own until much closer. That takes into account the scale of the equipment and at least makes this more believable. I do not buy a general sophant created signal is going to be detectable or even coherent at several light years distance. Cube law again.

 

[MasterGwydion]

I'll bring up again that the signal is picked up by a massive receiver array focused on the target. That is the key fact the seems to be overlooked. Space degrades radio signals--even strong ones--and a general receiver will need to be a lot closer than a dedicated, big, and potentially targeted one.

Let's say that a class A or B starport has a dedicated large array. It will be able to detect an emergency beacon at much greater range and even focus the receivers on it to enhance the signal. They could then dispatch rescue ships that don't get the signal on their own until much closer. That takes into account the scale of the equipment and at least makes this more believable. I do not buy a general sophant created signal is going to be detectable or even coherent at several light years distance. Cube law again.

How far away was the Star Trigger Event detectable from? Somehow Project Longbow was looking hundreds of parsecs away. All I am saying is that if you can detect things with focused detection at hundreds of parsecs, then, with general detection and a filter algorithm, you should be able to detect an Emergency Beacon in the same system. There are many in-Canon examples of extremely long-range detection.

 

[Terry Mixon]

As Voyager keeps being mentioned, here is some data on the systems used to transmit and receive the signals.

The two Voyage spacecraft certainly have had an amazing track record. They were sent to photograph planets like Jupiter, Saturn and Neptune and have just kept on going past the outer edge of the solar system. Voyager 1 is currently over 7 billion miles (about 11 billion kilometers) away from Earth and is still transmitting -- it takes about 10 hours for the signal to travel from the spacecraft to Earth!

The Voyager spacecraft use 23-watt radios. This is higher than the 3 watts a typical cell phone uses, but in the grand scheme of things it is still a low-power transmitter. Big radio stations on Earth transmit at tens of thousands of watts and they still fade out fairly quickly.

The key to receiving the signals is therefore not the power of the radio, but a combination of three other things:

• Very large antenna dishes
• Directional antennas that point right at each other
• Radio frequencies without a lot of man-made interference on them

The antenna dishes that the Voyager spacecraft use are big. You may have seen people who have large satellite dishes in their yards. These are typically 2 or 3 meters (6 to 10 feet) in diameter. The Voyager spacecraft has an antenna dish that is 3.7 meters (14 feet) in diameter, and it transmits to a 34 meter (100 feet or so) dish on Earth. The Voyager dish and the Earth dish are pointed right at each other. When you compare your phone's stubby, little omni-directional antenna to a 34 meter directional antenna, you can see the main thing that makes a difference!

The Voyager satellites are also transmitting in the 8 GHz range, and there is not a lot of interference at this frequency. Therefore the antenna on Earth can use an extremely sensitive amplifier and still make sense of the faint signals it receives. Then when the Earth antenna transmits back to the spacecraft, it uses extremely high power (tens of thousands of watts) to make sure the spacecraft gets the message.

Note the strength of the signal to transmit to Voyager. Tens of thousands of watts and using a powerful amplifier. Note the sizes of the dishes and the fact they are focused at one another. These are why this is not the same as would be used for what we are talking about.

 

[Arkathan]

I'll bring up again that the signal is picked up by a massive receiver array focused on the target. That is the key fact the seems to be overlooked. Space degrades radio signals--even strong ones--and a general receiver will need to be a lot closer than a dedicated, big, and potentially targeted one.

Let's say that a class A or B starport has a dedicated large array. It will be able to detect an emergency beacon at much greater range and even focus the receivers on it to enhance the signal. They could then dispatch rescue ships that don't get the signal on their own until much closer. That takes into account the scale of the equipment and at least makes this more believable. I do not buy a general sophant created signal is going to be detectable or even coherent at several light years distance. Cube law again.

A massive TL 6 radio receiver should be a standard TL 12 receiver (actually, the TL 12 should be much smaller and better). I would expect any up port to be a communications array. It only makes sense to distribute the sensors across the hull and any satellites to take advantage of virtual dish sizes, in the same manner that telescopes on Earth share data to form planet sized mirrors.
A pulsar sends EM signals across billions of light years via concentrated spinning/wobbling jets. Design the beacon to similarly rotate a tightband communication along the plane of the ecliptic.
Casini also used a 20 watt transmitter. The ones used to talk back are more on the order of 18 kW. There is no reason that the beacon would be any weaker, unless your plot requires it.

 

[Terry Mixon]

How far away was the Star Trigger Event detectable from? Somehow Project Longbow was looking hundreds of parsecs away. All I am saying is that if you can detect things with focused detection at hundreds of parsecs, then, with general detection and a filter algorithm, you should be able to detect an Emergency Beacon in the same system. There are many in-Canon examples of extremely long-range detection.

Project Longbow is a very, very large array. The collector plane is a disk of billions of linked receiver elements 42,000,000 kilometers in diameter. Once again, not the same thing as being used in this case.

Dragging in examples that have nothing in common with the situation of what an escape pod of only a few tons could manage and what might be in the system listening does not bolster your case. Ships in distress will not have monstrous dishes to focus the signals. The ships that receive them will not have big dishes pointed at where they need to be to pick up the signal.

 

[Terry Mixon]

A massive TL 6 radio receiver should be a standard TL 12 receiver. I would expect any up port to be a communications array. It only makes sense to distribute the sensors across the hull and any satellites to take advantage of virtual dish sizes, in the same manner that telescopes on Earth share data to form planet sized lenses.
A pulsar sends EM signals across billions of light years via concentrated spinning/wobbling jets. Design the beacon to similarly rotate a tightband communication along the plane of the ecliptic.
Casini also used a 20 watt transmitter. The ones used to talk back are more on the order of 18 kW. There is no reason that the beacon would be any weaker, unless your plot requires it.

Again, these signals are sent from dedicated transmitters and receivers that use large dishes aimed at one another precisely. A general signal is not the same. A rotating transmitter will boost the signal some, I'm sure. The receivers will not have the resolution to make sense of them when the signal degrades. Pesky cube law again. Sadly, an emergency beacon is not a pulsar and the comparison is not the same as reality.

 

[MasterGwydion]

The most powerful transmitter on Earth currently, that is smaller than 1m3 is 2,500,000 watts. TL-7, less than 1/14 of a Dton, 2,500,000 watts.

 

[MasterGwydion]

You want a distress beacon that can be seen across the system? Harden the Life Pod. Drop an EMP. Boom! A-bomb-sized EMP without the explosion. Easily seen across the system and what looks like a nuke going off? Yeah, someone will come running.

 

[Terry Mixon]

The most powerful transmitter on Earth currently, that is smaller than 1m3 is 2,500,000 watts. TL-7, less than 1/14 of a Dton, 2,500,000 watts.

While the transmitter is that size, the antenna are much larger. As I said, it's the transmission medium that gets you. Here is an image of the antennas for you.

 

[Terry Mixon]

You want a distress beacon that can be seen across the system? Harden the Life Pod. Drop an EMP. Boom! A-bomb-sized EMP without the explosion. Easily seen across the system and what looks like a nuke going off? Yeah, someone will come running.

How would you know how far an EMP is detectable? Why would it not be the same as a transmission. Cube law.

 

[Arkathan]

Again, these signals are sent from dedicated transmitters and receivers that use large dishes aimed at one another precisely. A general signal is not the same. A rotating transmitter will boost the signal some, I'm sure. The receivers will not have the resolution to make sense of them when the signal degrades. Pesky cube law again. Sadly, an emergency beacon is not a pulsar and the comparison is not the same as reality.

I wasn't suggesting the beacon was a pulsar, I was suggesting a directed, concentrated signal that changes directions to maximize range and coverage.
I guarantee that 3I sensors will have a filter on them to weed out a GK from stellar background. It will be on a specific frequency range with a standardized waveform.
Dust will attenuate the signal.
Intervening bodies will completely block the signal
Proximity to a gas giant will dilute the signal.
Same with crossing stellar coronas.
Barring that, if you can get to it with an M-Drive under current 1000D Mongoose rules, the beacon should be powerful enough, focused enough and designed to be detected anywhere you are. If a transponder is +6, a beacon should be at least an additional d6.

 

[Vormaerin]

This is practically the definition of in irreconcilable argument. We have no idea what the technology is like. It's like someone arguing about what size a radio receiver antennae has to be who doesn't have the technology for virtual aperture arrays and computer signal analysis or to even conceive of them.

TL 12 has ftl travel, gravity drives, anti gravity, and the ability to fire damaging lasers tens of thousands of kilometers without needing a focusing array. Who knows what the heck they'll have for communications technology?

If you want people to detect days' old emergency beacons, its easy to imagine technology improving enough to do that. If you don't like that, its easy to imagine that this one of the bits of modern physics that doesn't get exponentially improved.

 

[MasterGwydion]

How would you know how far an EMP is detectable? Why would it not be the same as a transmission. Cube law.

Right, but now you have increased the transmitter power exponentially. We can see a distant sun with about a 1" MkI Eyeball at night. With that same eyeball, we'd be able to see a nuclear explosion on the Earth-facing side of the moon. Detecting the non-visible light portions of the explosion is possible much further away due to the difference in wavelengths being transmitted. That is why We look in different wavelengths in our telescopes.

I am not sure that it matters though, since, as far as I can find, the size of the antenna doesn't really matter in Traveller. 5,000-ton ship and a 500,000-ton ship and the 15,000,000,000-ton highport all have the same size antenna. One does not have any bonuses over the others as far as detecting other objects. Or am I wrong?

 

[Arkathan]

This is practically the definition of in irreconcilable argument. We have no idea what the technology is like.

But it is reasonable to assume that if you are selling something as an emergency beacon for interplanetary craft, that the beacon SHOULD be easily detectable in-system, and far more effective than a TL 6 probe.

 

[Arkathan]

Right, but now you have increased the transmitter power exponentially. We can see a distant sun with about a 1" MkI Eyeball at night. With that same eyeball, we'd be able to see a nuclear explosion on the Earth-facing side of the moon. Detecting the non-visible light portions of the explosion is possible much further away due to the difference in wavelengths being transmitted. That is why We look in different wavelengths in our telescopes.

I am not sure that it matters though, since, as far as I can find, the size of the antenna doesn't really matter in Traveller. 5,000-ton ship and a 500,000-ton ship and the 15,000,000,000-ton highport all have the same size antenna. One does not have any bonuses over the others as far as detecting other objects. Or am I wrong?

Distributed Arrays, Extended Arrays and Probe Drone Nets.