Detecting Weapons' Fire

[Terry Mixon]

That is changing the characteristics of emissions rather than reducing them. That might be good for pretending to be another type of ship but by definition that means you have been detected.

Read it more closely. It can either change the characteristics or reduce emissions.

"Emission Masking mode imposes DM-2 on attempts to detect, identify or track the vessel at Medium range or greater."

 

[Sigtrygg]

But they are only emitting IR radiation since there is no conduction or convection.

That is sufficient. If you don't want to cook the contents of your ship you have to cool it down, which needs radiators or a magic heat sink.

Those radiators need quite a surface area, which broadcasts thermal radiation like a beacon.

I can block IR radiation with fairly mundane materials.

Sure you can, on earh, in an atmosphere. In scape the object you put between your radiator and the observer heats up, and radiates...

They will be reflected back at me or off to the side, but critically they can be reflected away from a particular receiver.

You would need a perfect reflector, sadly there is no such thing. You can certainly direct the radiated heat in certain directions, you just need to hop no one has had the sense to put sensors in that direction too.

If I wish to block my signature to the main world I just need to put the reflector in front of me.

The reflector gets hot on its backside, and you are now reflecting the heat back at your ship, which starts to cook.

If it is a short distance from the ship or has a vacuum between the "hot" ship and the reflector then it needn't pickup any significant heat from convection or conduction.

There is no convection or conduction in space, only radiation.

I cannot block IR in every direction, but I could collimate it and push it out in a beam (possibly quite a divergent beam) in the direction where detection is least likely (say behind me).

That requires you to do work, which generates yet more waste heat.

I could also have a cooling jacket around the whole ship with a heat pump to bring the exterior of the ship down close to background levels. I would need to sink that heat, but there is nothing thermodynamically prohibited. If my fuel source is liquid hydrogen then I have a ready thermal sink.

Then the hydrogen becomes a gas and the pressure increase blows your ship up.

It isn't perfect, but it doesn't have to be.

It has to obey the laws of thermodynamics unless you invoke space magic.

 

[MasterGwydion]

Read it more closely. It can either change the characteristics or reduce emissions.

"Emission Masking mode imposes DM-2 on attempts to detect, identify or track the vessel at Medium range or greater."

But wouldn't this only apply to the emissions from the M-Drive? Not from the Power Plant. Also, wouldn't this only effect passive sensors? Since radar/lidar wouldn't be effected?

I can get Minimal Detail for a densometer at Medium Range and get a complete outline of the target. This is a passive scan that has nothing to do with the M-Drive, so why would it give me a penalty? I can get shape and structure from just visual optics (passive) at Medium Range. Since the Power Plant is a power source, I can also detect it (passive EM) at Medium Range as well. None of this has anything to do with the M-Drive.

Or is this just another case of bad writing?

 

[Terry Mixon]

But wouldn't this only apply to the emissions from the M-Drive? Not from the Power Plant. Also, wouldn't this only effect passive sensors? Since radar/lidar wouldn't be effected?

I can get Minimal Detail for a densometer at Medium Range and get a complete outline of the target. This is a passive scan that has nothing to do with the M-Drive, so why would it give me a penalty? I can get shape and structure from just visual optics (passive) at Medium Range. Since the Power Plant is a power source, I can also detect it (passive EM) at Medium Range as well. None of this has anything to do with the M-Drive.

Or is this just another case of bad writing?

I was answering for the maneuver drive. Power plants add a DM+1 at minimal power and above. This just means you are less detectable under thrust (DM+1 to detection per Thrust). Two additional points of Thrust with no worse detection odds or stealthier at a slower speed.

 

[MasterGwydion]

I was answering for the maneuver drive. Power plants add a DM+1 at minimal power and above. This just means you are less detectable under thrust (DM+1 to detection per Thrust). Two additional points of Thrust with no worse detection odds or stealthier at a slower speed.

Okay. This makes sense. What still gets me is when would this be applicable? How often are you given the order to "scan for M-Drives"? Or do you just say, "Active scans on all sensors"? Do you make a separate roll for each type of sensor? Do the modifiers only apply to one sensor type or to all of them? I am starting to think I should not have jumped down the rabbit hole of reading Mongoose sensor rules.

 

[Terry Mixon]

Okay. This makes sense. What still gets me is when would this be applicable? How often are you given the order to "scan for M-Drives"? Or do you just say, "Active scans on all sensors"? Do you make a separate roll for each type of sensor? Do the modifiers only apply to one sensor type or to all of them? I am starting to think I should not have jumped down the rabbit hole of reading Mongoose sensor rules.

It's not separate. All the things are considered together to detect a vessel. If you have a guy racing an out-of-control bicycle down a steep hill while it is on fire, he is screaming his fool head off, and fireworks are going off from the rear like the 4th of July, you aren't just looking at a single element. Each of them combine to make him more detectable.

 

[Sigtrygg]

The sensor rules need a complete re-write.

 

[Terry Mixon]

The sensor rules need a complete re-write.

How would you recommend it change? It doesn't need to be far more convoluted, though the range bands kind of leave something to be desired.

 

[MasterGwydion]

It's not separate. All the things are considered together to detect a vessel. If you have a guy racing an out-of-control bicycle down a steep hill while it is on fire, he is screaming his fool head off, and fireworks are going off from the rear like the 4th of July, you aren't just looking at a single element. Each of them combine to make him more detectable.

View attachment 6604View attachment 6605

That makes no sense. If the disturbance is gravimetric and you don't have a densometer, how do you detect it? Only TL-12 Improved Sensors and above have those. Having every other sensor except the densometer won't help you at all. So, it can't be all taken together. Also, each sensor has different outcomes (Full, Limited, Minimal, and None) at different range bands. How can you take them all together?

 

[Sigtrygg]

How would you recommend it change? It doesn't need to be far more convoluted, though the range bands kind of leave something to be desired.

Three previous editions of Traveller have better rules, then there is T:2300/AD and Star Cruiser (not the Mongoose version)

The range band system of MgT is an aberration that should be excised

 

[Terry Mixon]

That makes no sense. If the disturbance is gravimetric and you don't have a densometer, how do you detect it? Only TL-12 Improved Sensors and above have those. Having every other sensor except the densometer won't help you at all. So, it can't be all taken together. Also, each sensor has different outcomes (Full, Limited, Minimal, and None) at different range bands. How can you take them all together?

It absolutely makes sense when we're talking about maneuver drives, which is what we were talking about. If you're working with a special case that only a certain brand of sensor can detect, then you have to use the rules for that sensor alone.

 

[swordtart]

That is sufficient. If you don't want to cook the contents of your ship you have to cool it down, which needs radiators or a magic heat sink.

Radiators.

Those radiators need quite a surface area, which broadcasts thermal radiation like a beacon.

But not necessarily in all directions.

Sure you can, on earh, in an atmosphere. In scape the object you put between your radiator and the observer heats up, and radiates...

I am not sure what difference being on earth will make. Reflectors get hot on earth as well. The heat generate is just the proportion you could not reflect.

You would need a perfect reflector, sadly there is no such thing.

A really efficient reflector is just better science, not space magic. Gold reflectors are 95% efficient and polished aluminium 98%. If I can reduce emission to 2% then I am going to be harder to detect.

You can certainly direct the radiated heat in certain directions, you just need to hop no one has had the sense to put sensors in that direction too.

Agreed. "He's behind you!"

The reflector gets hot on its backside, and you are now reflecting the heat back at your ship, which starts to cook.

It need not be focussed on the ship it can be deflected to either side but still broadly rearward.

There is no convection or conduction in space, only radiation.

Yes, that was my point, however that reflector would presumably need to be attached somehow and that introduces the chance of conduction.

That requires you to do work, which generates yet more waste heat.

Are you saying that a parabolic reflector (for example) is doing work? I am not sure that is thermodynamically true.

Then the hydrogen becomes a gas and the pressure increase blows your ship up.

So dramatic

You know how refrigerators work. You have latent heat of vaporisation to get through before it even changes phase. Then you get expansion, but that can be in an expansion vessel. The only stage missing is the condensation stage where that heat is released. So as long as I keep that cold front toward the sensor I am good. We know we can do that because the sensor detecting me also has to be cooled and insulated from the ship carrying it or it won't work properly. We do this presently with high fidelity thermal seekers. we just tend to do it sacrificially by venting gas to atmosphere (we could do that with a plume to the rear).

There are other methods of reducing heat to manageable levels. You can lock heat in chemically (endothermic reactions), use to to melt supercooled ice and vaporise water (which can also be the fuel of the fusion plant), you could even lock it into a solid with high thermal capacity and let it out the back of the ship (creating a decoy signature).

It has to obey the laws of thermodynamics unless you invoke space magic.

What laws are being broken. You reflect most of the heat going forward to change the direction of radiation. You cool the reflector with phase change hydrogen. You pump that heated hydrogen to the rear of the ship and allow it to cool by radiating to space or you feed it preheated into your fusion reactor (not sure what phase the reactor uses, plasma?).

You are not eliminating heat magically you are just sending it in your direction of choice (where hopefully there is no sensor).

Without some actual metrics it will be hard to know if this is enough.
How sensitive are thermal sensors in Traveller. Can they detect a single degree above background from a 20 Dton launch 50,000 km away?
How much heat is the ship generating?
Can it dump any of that heat when it is already flaring during emergence (or can it dump some whilst in jump).
How efficient is the power usage of the ship? Running circuits close to the hull will reduce their temperature to near zero permitting super conduction with very little waste heat.
How much heat deficit can it accumulate before emergence (e.g. if the fuel is stored as super cooled ice).
What is 1 power anyway.

I am mostly concerned with the first few hours after emergence. After that you are moving at such speed that interception is realistically impossible. I think being able to present some percentage of the ship as having close to ambient temperature is entirely possible with current science let alone future science. The percentage of the ship that can be "behind" the shield would need to be determined, and your aspect to any possible detector would be critical to determining whether you got the benefit. If you present the wrong aspect you would be radiating more than an unshielded ship.

Even if all the heat is radiated in a 360 degrees aspect, only waves that are moving in the direction of the sensor will be detectable. Any that are even 1 degree off boresight will whizz past unless your sensors are hundreds of km in radius or you have extensive sensor nets. I saw a giga watt* bandied around previously. Now disperse all of that gigawatt as waste heat over the surface of a sphere 10,000 km in radius. The power per square metre is under 1 millionth of a watt. For a 50,000 km sphere it is under 35 billionths of a watt.

I don't think a 20 DTon launch generates a gigawatt of waste heat. I think it would take months to even generate that level of energy. I am not sure how big the ship needs to be, but currently the rules don't address that at all. I don't think you would be able to detect that launch at 50,000 km by passive sensors unless you already had an idea of where it was (or where you were checking if you were just looking to confirm an absence of a threat).

Absolute statements have to be true in all circumstances.

* 1Dton of liquid hydrogen can can optimally generate 120,000 MJ of energy. A free trader is burning 1Dton per month for the power plant and that can be the only real source of heat. That's less than 180 MJ per hour or 50 Kilo Watts (plus 100 Watts per crew member) with everything running (if we limit ourselves to minimal life support we be on a third of that).

 

[MasterGwydion]

It absolutely makes sense when we're talking about maneuver drives, which is what we were talking about. If you're working with a special case that only a certain brand of sensor can detect, then you have to use the rules for that sensor alone.

Maybe I am explaining it wrong. Your post says Medium Range or greater, but different sensors give different detail at Medium Range. Plus, with things like the Extension Net which increase the level of detail you can gain from sensors by one range band. Does that mean against a ship with the stealth m-drive they still get the penalty at medium range or is it now at long range? Or does it not apply at all since the m-drive rules doesn't specify what level of detail you are getting at medium range?

Also,

Read it more closely. It can either change the characteristics or reduce emissions.

"Emission Masking mode imposes DM-2 on attempts to detect, identify or track the vessel at Medium range or greater."

Does the user of the stealth ship have to decide which he wants to give the penalty on? It says "Detect, indentify, or track" not "and"

If so, how long does it take to change between settings?

 

[Terry Mixon]

Maybe I am explaining it wrong. Your post says Medium Range or greater, but different sensors give different detail at Medium Range. Plus, with things like the Extension Net which increase the level of detail you can gain from sensors by one range band. Does that mean against a ship with the stealth m-drive they still get the penalty at medium range or is it now at long range? Or does it not apply at all since the m-drive rules doesn't specify what level of detail you are getting at medium range?

Your guess is as good as mine. Talk to a manager.

Also,

Does the user of the stealth ship have to decide which he wants to give the penalty on? It says "Detect, indentify, or track" not "and"

If so, how long does it take to change between settings?

I'd say the penalty applies to all three even with the use of or.

 

[MasterGwydion]

Your guess is as good as mine. Talk to a manager.

lolz. Fair enough.

I'd say the penalty applies to all three even with the use of or.

Isn't that kind of the opposite of what "or" means?

 

[Sigtrygg]

Radiators.

Which broadcast your location.

But not necessarily in all directions.

You can make them directional and hope there are no sensors in that direction.

I am not sure what difference being on earth will make. Reflectors get hot on earth as well. The heat generate is just the proportion you could not reflect.

Because you are using the environment as a heat sink, in space that is not possible.

A really efficient reflector is just better science, not space magic. Gold reflectors are 95% efficient and polished aluminium 98%. If I can reduce emission to 2% then I am going to be harder to detect.

The heat has to go somewhere, and 2% of a terra watt is pretty easy to detect.

Agreed. "He's behind you!"

It need not be focussed on the ship it can be deflected to either side but still broadly rearward.

Again you are hoping that the system does not have sensors throughout the system, which is unlikely by the 57th century

Yes, that was my point, however that reflector would presumably need to be attached somehow and that introduces the chance of conduction.

In which case it radiates the heat.

Are you saying that a parabolic reflector (for example) is doing work? I am not sure that is thermodynamically true.

The parabolic reflector gets hot, so radiates heat.

So dramatic

You know how refrigerators work. You have latent heat of vaporisation to get through before it even changes phase. Then you get expansion, but that can be in an expansion vessel. The only stage missing is the condensation stage where that heat is released. So as long as I keep that cold front toward the sensor I am good. We know we can do that because the sensor detecting me also has to be cooled and insulated from the ship carrying it or it won't work properly. We do this presently with high fidelity thermal seekers. we just tend to do it sacrificially by venting gas to atmosphere (we could do that with a plume to the rear).

Ever put your hand round the back of a fridge? The heat has to go somewhere. Your are missing the fact that your ship is a closed system.

There are other methods of reducing heat to manageable levels. You can lock heat in chemically (endothermic reactions), use to to melt supercooled ice and vaporise water (which can also be the fuel of the fusion plant), you could even lock it into a solid with high thermal capacity and let it out the back of the ship (creating a decoy signature).

All of which requires significat mass of the ship given over to whatever internal heat sink you use, eventually your ship melts or you have to eject the heat sink or radiate the heat to space.

What laws are being broken. You reflect most of the heat going forward to change the direction of radiation. You cool the reflector with phase change hydrogen. You pump that heated hydrogen to the rear of the ship and allow it to cool by radiating to space or you feed it preheated into your fusion reactor (not sure what phase the reactor uses, plasma?).

Reflecting heat will heat up the reflector, phase changes involve heat transfer, cooling the reflector means you are ejecting hot hydrogen into space, you can't transfer heat from cold to hot.

You are not eliminating heat magically you are just sending it in your direction of choice (where hopefully there is no sensor).

That is possible, but in the 57th century every system with a starport will have system wide sensors.

Without some actual metrics it will be hard to know if this is enough.

Agreed.

How sensitive are thermal sensors in Traveller. Can they detect a single degree above background from a 20 Dton launch 50,000 km away?

it is not a single degree, space is ~3K a ship is ~300K.

How much heat is the ship generating?

Until MgT defines its EP I have no idea, but previous editions had numbers, and then there is the conversion of power plant energy to kinetic energy of the shi...

Can it dump any of that heat when it is already flaring during emergence (or can it dump some whilst in jump).

Even if it does what happens to the heat generated after jump emergence?

How efficient is the power usage of the ship? Running circuits close to the hull will reduce their temperature to near zero permitting super conduction with very little waste heat.

Room temperature superconductors are akin to perpetual motion , unlikely to be physically possible, as to running circuits close to the hull to reduce theri temperature - where does the waste heat from the circuit go? It is radiated into space and you are a beacon again

How much heat deficit can it accumulate before emergence (e.g. if the fuel is stored as super cooled ice).

How much ice does a Traveller starship carry as a heat sink? heat sinks are physically possible, but they will take up a significant amount of payload.

What is 1 power anyway.

That is edition specific.

I am mostly concerned with the first few hours after emergence. After that you are moving at such speed that interception is realistically impossible. I think being able to present some percentage of the ship as having close to ambient temperature is entirely possible with current science let alone future science.

It isn't. Unless your crew enjoys an ambient temperature of 3K.

The percentage of the ship that can be "behind" the shield would need to be determined, and your aspect to any possible detector would be critical to determining whether you got the benefit. If you present the wrong aspect you would be radiating more than an unshielded ship.

Traveller ships are not built with these mechanisms in mind, they could be but the deckplans of the type A would have to change

Regardless, in the 57th century I expect a network of sensors throughout any system with an Imperial starport.

Even if all the heat is radiated in a 360 degrees aspect, only waves that are moving in the direction of the sensor will be detectable. Any that are even 1 degree off boresight will whizz past unless your sensors are hundreds of km in radius or you have extensive sensor nets. I saw a giga watt* bandied around previously. Now disperse all of that gigawatt as waste heat over the surface of a sphere 10,000 km in radius. The power per square metre is under 1 millionth of a watt. For a 50,000 km sphere it is under 35 billionths of a watt.

Easily detectable - check the signal strength from Voyager.

I don't think a 20 DTon launch generates a gigawatt of waste heat.

Using CT numbers 1EP is 250MW, I have yet to see a MgT definition.

I think it would take months to even generate that level of energy.

See previous answer. 250MJ per second.

I am not sure how big the ship needs to be, but currently the rules don't address that at all. I don't think you would be able to detect that launch at 50,000 km by passive sensors unless you already had an idea of where it was (or where you were checking if you were just looking to confirm an absence of a threat).

it is a 300K object against a 3K background...

Absolute statements have to be true in all circumstances.

The laws of thermodynamics are yet to be challenged (successfully)

* 1Dton of liquid hydrogen can can optimally generate 120,000 MJ of energy. A free trader is burning 1Dton per month for the power plant and that can be the only real source of heat. That's less than 180 MJ per hour or 50 Kilo Watts (plus 100 Watts per crew member) with everything running (if we limit ourselves to minimal life support we be on a third of that).

We have no idea of how much fusion fuel is being used in a free trader, the mechanisms we know are not modeled in Traveller.

 

[Condottiere]

Other power plants require fuel tankage equal to 10% of their size (rounding up, minimum 1 ton) per month of operation.

 

[MasterGwydion]

Other power plants require fuel tankage equal to 10% of their size (rounding up, minimum 1 ton) per month of operation.

I remember a previous conversation that went something along the lines of power plant fuel not actually being fuel, but being used as coolant, since that high of usage didn't make sense for fusion. Something like that.

 

[Condottiere]

Not a nuclear scientist, so on that I couldn't give enlightenment.

Though in terms of coolant, I always thought you transfer that to the mass used for reactionary rocket propellant, and dump it out the rear.

 

[MasterGwydion]

Not a nuclear scientist, so on that I couldn't give enlightenment.

Though in terms of coolant, I always thought you transfer that to the mass used for reactionary rocket propellant, and dump it out the rear.

Space magic. I have no idea. lol.