Solving the IR problem in Traveller

[phavoc]

An interesting article on Physics.org for a paint that can convert heat into electricity. It's a potential way of having spaceships convert the heat they generate internally into electricity, which if you add in say x-ray lasers, you'd be able to safely dispose of excess heat in a way that is not easily detectable (assuming your heat to power ratio was in excess of your internal needs). You could even use it externally to abssorb some of the heat from the star to lower your hull temp, making you invisible to passive IR detectors.

Anyways, it's a possibility to solve the issue of being detected at range using passive IR sensors. I'm not sure it will resolve "you can't hide in space" issue, but hey, another data point to argue over.

http://phys.org/news/2016-11-thermoelectric-enables-walls-electricity.html

 

[Condottiere]

I'd try to convert it to propulsion.

 

[Solomani666]

.

Reading the title I was half expecting to see a #ZLM hashtag for the "Zhodhani Lives Matter" movement.


.

 

[AnotherDilbert]

Anyways, it's a possibility to solve the issue of being detected at range using passive IR sensors. I'm not sure it will resolve "you can't hide in space" issue, but hey, another data point to argue over.

It's difficult to get around entropy. If we convert heat to electricity, where do we increase entropy?

I guess we still end up spilling heat somewhere?

 

[phavoc]

Anyways, it's a possibility to solve the issue of being detected at range using passive IR sensors. I'm not sure it will resolve "you can't hide in space" issue, but hey, another data point to argue over.

It's difficult to get around entropy. If we convert heat to electricity, where do we increase entropy?

I guess we still end up spilling heat somewhere?

In theory, since you are converting heat to energy, you are just changing states. I'd think (as a physics layman) that by the state change would mean you don't have to worry about those pesky laws of thermodynamics. If I'm remembering my physics, the Carnot (sp?) issue about reversing the state of energy is solved here, because you are converting heat to energy, which is one of the principles of entropy (again, I may be mis-remembering this... it's been a Loooonngg time!).

 

[Galadrion]

.

Reading the title I was half expecting to see a #ZLM hashtag for the "Zhodhani Lives Matter" movement.


.

*Snort* #ZLM, no doubt, is being driven and manipulated by some Hiver think tank, for who knows what devious ends...

 

[AnotherDilbert]

In theory, since you are converting heat to energy, you are just changing states. I'd think (as a physics layman) that by the state change would mean you don't have to worry about those pesky laws of thermodynamics.

Heat is disorganised energy (so with a lot of entropy), electrical power is organised energy (so with little entropy). In a closed system we cannot decrease entropy. Thermodynamics is a cruel mistress.

It's been quite some time for me to, but as far as I remember transforming high entropy energy (heat) into low entropy energy (electrical power) without losses is a complete no-no. We have to dump the entropy somewhere.

Carnot talks about transforming heat into heat, not really applicable here?

 

[phavoc]

In theory, since you are converting heat to energy, you are just changing states. I'd think (as a physics layman) that by the state change would mean you don't have to worry about those pesky laws of thermodynamics.

Heat is disorganised energy (so with a lot of entropy), electrical power is organised energy (so with little entropy). In a closed system we cannot decrease entropy. Thermodynamics is a cruel mistress.

It's been quite some time for me to, but as far as I remember transforming high entropy energy (heat) into low entropy energy (electrical power) without losses is a complete no-no. We have to dump the entropy somewhere.

Carnot talks about transforming heat into heat, not really applicable here?

Hrm... well, if you could get the majority, say 90-95% of the heat being converted into energy you could, for a while at least I guess, dump the heat into your Lhyd tanks. Just how long you could do that before you run out of excess places to store the heat internally is one question. And the efficiency of your conversion governs the process as well.

Re - Carnot... well, I told you it was a long time ago... in a classroom far, far away!

 

[AnotherDilbert]

Hrm... well, if you could get the majority, say 90-95% of the heat being converted into energy you could, for a while at least I guess, dump the heat into your Lhyd tanks. Just how long you could do that before you run out of excess places to store the heat internally is one question. And the efficiency of your conversion governs the process as well.

I really doubt we could get anything like 90% efficiency.

LHyd seems to have a specific heat of 10 J/gK so to heat a tonne of LHyd (≈14 m³) 1° would take 10 × 1000000 × 1 = 10000000 J or 10 MJ. That is about 1 Power for 1 second. Your LHyd fuel would boil away in a few seconds if you tried to dump any significant amount of heat into it. Instead you would need use energy to keep it cold.

What you can do is radiate the waste heat in a specified direction away from any likely enemy.

 

[Condottiere]

If you could vent it in a narrow beam out system.

 

[phavoc]

Hrm... well, if you could get the majority, say 90-95% of the heat being converted into energy you could, for a while at least I guess, dump the heat into your Lhyd tanks. Just how long you could do that before you run out of excess places to store the heat internally is one question. And the efficiency of your conversion governs the process as well.

I really doubt we could get anything like 90% efficiency.

LHyd seems to have a specific heat of 10 J/gK so to heat a tonne of LHyd (≈14 m³) 1° would take 10 × 1000000 × 1 = 10000000 J or 10 MJ. That is about 1 Power for 1 second. Your LHyd fuel would boil away in a few seconds if you tried to dump any significant amount of heat into it. Instead you would need use energy to keep it cold.

What you can do is radiate the waste heat in a specified direction away from any likely enemy.

There are a number of variables here, but essentially if you are lying doggo in space and making like you aren't really there (i.e. stealth) your power requirements should be minimal. So your power plant would be dialed back to near zero. Though Traveller rules don't really cover this and never have. But the issue with heat is that while you sit there your crew are generating heat, your machinery, etc. And all that heat is trapped in your craft. Without radiators your crew would overheat and die. That's where the radiators come in, but when you do that you become a heat source to be detected via IR sensors. That's the crux of there is no stealth in space argument.

Here, if you could convert the heat, or most of it, to energy, you could potentially use this to provide basic power to lifesupport and passive sensors. Anything outside of that could be dumped to your fuel, at least temporarily. Just how long that would work is variable (distance to the sun, amount of heat, etc).

 

[dragoner]

In theory, since you are converting heat to energy, you are just changing states. I'd think (as a physics layman) that by the state change would mean you don't have to worry about those pesky laws of thermodynamics.

Heat is disorganised energy (so with a lot of entropy), electrical power is organised energy (so with little entropy). In a closed system we cannot decrease entropy. Thermodynamics is a cruel mistress.

It's been quite some time for me to, but as far as I remember transforming high entropy energy (heat) into low entropy energy (electrical power) without losses is a complete no-no. We have to dump the entropy somewhere.

Some new news: http://phys.org/news/2016-10-posit-locally-circumvent-law-thermodynamics.html

Entropy of a system might be able to be moved.

 

[alex_greene]

.Reading the title I was half expecting to see a #ZLM hashtag for the "Zhodhani Lives Matter" movement.
*Snort* #ZLM, no doubt, is being driven and manipulated by some Hiver think tank, for who knows what devious ends...

Not a Hiver think tank ...

 

[alex_greene]

In theory, since you are converting heat to energy, you are just changing states. I'd think (as a physics layman) that by the state change would mean you don't have to worry about those pesky laws of thermodynamics.

Heat is disorganised energy (so with a lot of entropy), electrical power is organised energy (so with little entropy). In a closed system we cannot decrease entropy. Thermodynamics is a cruel mistress.

It's been quite some time for me to, but as far as I remember transforming high entropy energy (heat) into low entropy energy (electrical power) without losses is a complete no-no. We have to dump the entropy somewhere.

Some new news: http://phys.org/news/2016-10-posit-locally-circumvent-law-thermodynamics.html

Entropy of a system might be able to be moved.

It'll probably end up going into the Jump capacitors or something.

 

[phavoc]

"It'll probably end up going into the Jump capacitors or something"

Except MGT doesn't use jump capacitors. They pump Lhyd and do the exotic particles.

Though battery storage is possible. Ships should have some battery capability.

 

[Condottiere]

We do at forty and sixty energy density per tonne.

Somehow collect the heat in one tank to turn water to steam and turn a turbine.

 

[AnotherDilbert]

Capacitors or batteries solves nothing. Heat (high entropy) cannot be stored as electrical power (low entropy) in batteries.

Quantum "Maxwell's Demons" cannot get rid of entropy, only move it around in a closed system. To cool the system, the craft, and dump entropy we still have to e.g. radiate heat, I think. But it might provide a one-way filter for heat and hence entropy allowing us to shape our radiated heat into specified directions or shapes.

If we heat water it has to be cooled again, e.g. by radiating heat...

Radiating heat is a very convenient way of dumping entropy, I do not see any way around it.

 

[locarno24]

Exactly.

Yes, heat can be used to generate electricity.
Yes, electricity can be used for something useful, but anything you do with it will still cause a thermal 'bloom'.

But you can never get 100% efficiency (or, frankly, close to it), and any system within the ship will 'leak' heat, which warms the hull of the ship, IR detectors go "beep" and suddenly there's five capital ship bay's worth of incoming Heavy Missiles and it's that afternoon near Theev all over again.


In order for a 'stealth system' to work for a starship:

~ It has to allow for the power plant and systems to work or the ship can't do anything useful
~ It has to not broil the crew alive (tends to increase your recruitment overheads)
~ It can dump some of the heat into the LHYD tanks, but that's only good for so much, and the heat will still conduct out through the tanks. It's not a long-term fix.

In order to 'hide', it's not enough to just redirect heat away, you'll need to actively cool the respective facing - because it's got to compensate for every heat source on the ship you can't predict, plus absorbed solar radiation.

You can't cool the whole skin of the ship (because a cooling system really just moves the heat, in addition to generating some extra), but you can cool one facing. Provided the actively cooled facing is slightly more than 180' by 180' (i.e. more than a hemisphere) and you can radiate the heat from the other side, you get one bloody hot side consisting mostly of heat sinks and radiators, and an essentially-at-space-background-temperature (I think it's about 3 kelvin?) "this side towards enemy" which won't meaningfully show up on a thermal camera.

So stealth is possible. Just not all-aspect stealth. Meaning a certain amount of cunning route-planning and piloting is important to plan an approach whilst not flashing your arse at enemy warships or orbital scansats.

 

[alex_greene]

And yet, despite that, the bumblebee still flies.

 

[Condottiere]

Hide behind some planetoid, and occasionally launch the heatsink onto the surface.

Which means it would need to be disposable.