Energy from heat - The argument against stealth in space

[Reynard]

Found examples images and descriptions for reducing exhaust signatures on stealth craft such as the Nighthawk. The exhaust flow is kept tight and pointed away out the back keeping dissipation minimal ninety degrees to the back. These jets also have flexible cowls around the exhaust to direct and control the flow. By the time the heated exhaust begins to fan out, it's cooling and dissipating.

A similar technique could be used for spacecraft exhaust using reaction drives but would only apply to gravitic (spacecraft) and maneuver (starships) drives to collect non-IR waste energy and direct it away in a tight beam. Notice again the Stealth rules only cover radar, lidar and heat emissions which seems to more refer to overall IR bleed rather than engine emission.

 

[phavoc]

Assuming the heat stays focused and in a perfect shape without dissatisfied g. It's still going to be seen. Satellites or other scanners would be liking in a 360 degree view from multiple elevations. So it would still be spotted in that sense.

 

[Reynard]

If it works for 20th century aircraft, why so impossible for more advanced tech levels in the context of a game system?

I swear people summon Reality here when it suits them but deny it when it refutes their argument.

 

[Anonymous]

Because we have no idea whatsoever what the reality of life in space ships in the 57th century is.

We have our current knowledge.

We have a collective wish to play a science fiction role playing game.

Joining the last two means acknowledging the first and accepting that no one is right.

But when the thread starts to drift and people talk stuff that they are calling science but is really not then we have silly arguments.

http://txchnologist.com/post/61492589701/did-you-know-we-can-still-spot-voyager-1

Now, it's transmitting so go ahead and tell me that it doesn't count. But if we can "see" 22 watts from that far away with current technology (and yes, I agree it is a large telescope, but who knows what we'll be able to do in the 57th century, see the first line of this post)

Likewise, we may be able to hide stuff really well in the 57th century. I can't see that tramp ships like your average A2 will have that tech but in your TU, they can.

The point of the thread is to discuss how an emerging technology may give us what Traveller presupposes to be true in the 57th century.

 

[Anonymous]

And can we please stop talking about hiding the heat of the exhaust when we already stated that Traveller is using a gravitic drive and there's nothing written (cos you know, if you read it on the internet it must be true, mustn't it?) that implies there's an exhaust of any kind cos it ain't a reaction drive cos it uses no fuel, the power for the M drive coming from the ships fusion reactor...

Now, if you want to join me in my lovely 2350 setting that does not have gravitic drives or anti grav plates or whatever you want to call them and we will be using drives pushing stuff out the back then please, lets talk heat in space. Briefly, cos, you will see it from a long long way away.

 

[Condottiere]

Grav drives is either thrust or field, and I don't think you can hide a field.

On the other hand, ping pong balls gravitationally accelerated to hit the back of the space ship to provide thrust might be stealthy.

 

[phavoc]

If it works for 20th century aircraft, why so impossible for more advanced tech levels in the context of a game system?

I swear people summon Reality here when it suits them but deny it when it refutes their argument.

Maybe because spacecraft and aircraft displace heat in different ways?

Stealth aircraft don't magically dissipate heat. They use bypass air flow to blend cooler air with hotter exhaust air, thus trying to lower their thermal signature. They also use ducts of sorts to hide the exhaust point direct observation. The F-22 and the B-2 bomber have exhausts over the wing edge to hide it from ground-based sensors. Look at an F-18 or F-22 for comparison.

Space is a far different environment because you cannot use the same techniques. I'm sorry to burst your bubble with reality of 20th century aerodynamics and physics. In the far future, as it was discussed up-thread, it may be possible to completely convert the heat generated from within a starship to energy, thus making it more stealthy against the coldness of space. Unless that occurs the heat generated from within the ship must be vented somewhere. Only military ships or pirates give a damn about hiding their signature. Merchants want to be seen (unless they are smuggling) because it's safer that way.

And can we please stop talking about hiding the heat of the exhaust when we already stated that Traveller is using a gravitic drive and there's nothing written (cos you know, if you read it on the internet it must be true, mustn't it?) that implies there's an exhaust of any kind cos it ain't a reaction drive cos it uses no fuel, the power for the M drive coming from the ships fusion reactor...

The original issue was not heat generated by drives, or whether it does or does not. It was about the heat generated internally within a ship from electronics, people, etc, etc. That's very real and the intent behind the thread. Normally the heat would simply be radiated away into space, but that causes an IR flare easily seen. So unless you can store or convert that heat you'll have real-world problems with it. The F-35 stores some heat in the fuel, which they have learned has an upper effective limit temperature wise while it's stored prior to fueling. Especially in hotter climates. Their temporary fix is repainting fuel trucks to reflect sunlight and heat and to park them in the shade. Low tech fixes for an unforseen problem.

As to the Voyager issue, it's not as challenging as make it out to be. The Deep Space Network knows pretty much exactly where to listen for Voyager's signal. They know where it is at all times, so it's not very hard rocket science once they worked out the math. If all of a sudden it moved way of course then yes, it would be a formidable effort to detect the signal.

 

[wbnc]

Wile discussing hiding a space ship I once compared finding a hostile starship to playing hide and go seek in the Super Dome, with nothing but your ears,eyes, a flashlight, and a loaded .45 pistol....it's a very loose, and not so accurate comparison but it does give you the general gist of the process.

Yes you can hear the sounds a person makes as they stumble around in the dark( equivalent to heat and EM radiation) You might hear the sound of their feet on a metal stair, or the sound of them tripping over a stray bottle on the floor, and that will give you a very good idea that there is someone nearby, and that they aint you....
But in reality space is a very noisy place. there's a good bit of trash noise that might confuse you. That noise might have been the other guy with the gun, or it could have been the sound of fans, some stray dog, a couple of cats fighting over something, and the occasional sound of a truck driving by outside.

so unless you have very good ears, and a good knowledge of the ambient sounds of a major sports arena committed to memory, you are going t spend half the time jumping at random noises and going..."oh crap what was that."

the scenario gets even more confusing, and nerve racking, when there are other people randomly strolling though the area. and you have to determine is that the guy with the gun, or some poor schmuck trying to avoid getting blown away by two guys with guns, or a friendly
player" looking for the same guy you are..

 

[Condottiere]

Gravitationally compress the heat, and emit it in the other direction from likely observers occasionally.

 

[Reynard]

"Normally the heat would simply be radiated away into space, but that causes an IR flare easily seen."

What insane spacecraft design has so little insulation that it readily dumps internal heat into space to glow like you describe? That would mean the ship must generate tremendous amounts of life support heat to keep the crew from freezing as it's lost so easily. Must explain why Mongoose Traveller doesn't bother mentioning passive sensors with every ship a firefly in the night sky. Don't they ever invent effective insulation along with meson weapons and jump drives?

 

[phavoc]

What insane spacecraft design has so little insulation that it readily dumps internal heat into space to glow like you describe? That would mean the ship must generate tremendous amounts of life support heat to keep the crew from freezing as it's lost so easily. Must explain why Mongoose Traveller doesn't bother mentioning passive sensors with every ship a firefly in the night sky. Don't they ever invent effective insulation along with meson weapons and jump drives?

Well, sane spacecraft designers from the US and Russia are well aware of the issue of heat buildup in the space stations they design. And you are getting the issue backwards. It's not a question of too LITTLE insulation. Using that assumption the heat would bleed out though the hull on it's own. But you don't want that. The designs are meant to be controlled so that you can dump the heat out in the manner of your choosing. The ISS (American side) uses an ammonium-based heat transfer system to collect excess ambient heat from inside the station and the solar panels and radiates it away via a radiator. The Russian modules use a different system, but it also dumps into the primary heat transfer system.

Every space station we have built, going back to Skylab, had radiators. During launch the micrometeorite shield was torn off, taking with it a solar panel and jamming the other. Temperature inside the station was too high (130 degrees F) to work. To address the heat problem they basically put up a solar 'sheet' of sorts to reflect sunlight off the station. This reflected enough heat to allow the onboard cooling system to function properly and for the station to be used.

I am assuming that Traveller starship hulls, with their ability to shrug off micrometeorites also makes for some damn good insulation. So the heat generated from people, machinery, the power plant, etc, is kept within the hull. Without a way to get rid of it it will continue to increase. And people like a comfortable shirt-sleeve environment work in. If you want to see how it works on a planetary scale, you can compare the planets of Earth and Venus. Venus has a cloudy atmosphere that traps in heat, Earth does not because it's able to radiate heat (there's more to this obviously, but the inability to radiate heat is what makes Venus so hellish). Notice how the temperature can change with the presence of absence of clouds. The idea remains the same - if you trap heat inside it just continues to build up or reaches a plateau and remains constant.

As for what Traveller doesn't mention, well, that's a very long list of things. IR detection in the military started accelerating after WW2, but it wasn't till the late 60s, early 70s it started really taking off. I have no idea how much exposure and knowledge Miller had with it back then. And every version since then has more or less kept the same structure and systems since then.

And, for the record, none of the discussions in the thread (at least by me) have been about changing the rules. What started off here was simply a note that converting heat to electricity is becoming more potentially possible. In the past the argument has always been there was no effective way to get rid of internal heat except by radiating it away, thus making your vessel visible to IR detectors (i.e. there's no hiding in space). My argument has always been that maybe in the future they'll have figured out to get rid of the heat in some other way, thus still providing stealth in space. And, with this breakthrough they are at least getting closer than they were before.

 

[wbnc]

"Normally the heat would simply be radiated away into space, but that causes an IR flare easily seen."

What insane spacecraft design has so little insulation that it readily dumps internal heat into space to glow like you describe?

Venting heat is not a design flaw, it's a design requirement

It's counter intuitive...but being too well insulated is a major problem with any mechanical/electrical system. if you seal in all the heat generated by a system the interior spaces become unlivable. think about your desktop. if your cooling fan craps out...you will soon start having performance issues when the chips get too hot.

which is where a stealth hull comes in as an option. this hull has equipment and devices which hide, or shunt that heat into some sort of storage device, or radiate it in a way that greatly complicates detection and lock ons.

The hull doesn't make the ship invisible to sensors it just slaps a hefty penalty onto the check to detect and gather useful information from your sensors. since there is a big leap from detecting a heat/electromagnetic signature, and figuring out it's an artificial signal/emission, the system just makes the job of the sensor operator harder.

A few simple bits of "fluff" text can handle the basics of how and why both sensors, and sensor deception/spoofing systems, work. Well maybe not few, and simple precisely..but it wouldn't take a text book on electronic warfare and countermeasures....Note to self, consider this as a project....

 

[Condottiere]

How much heat is there really?

The next step would be to feed it to a steam turbine.

 

[Reynard]

Steam turbine? Traveller steampunk? I don't believe a Traveller fusion drive is steam but converts heat to electricity directly. I would assume there is little waste as the generator can be adjusted to optimal output. As we keep mentioning yet seem to keep forgetting, these life support systems in Traveller as well as the power plant should have the capacity to collect waste heat that can't be reused and use sinks to remove it using a particular part of the hull and that may well be what we see on most Traveller ship illustrations. Those are not drive exhausts but radiator sinks sending the energy away from a forward moving vessel. The *majority* of that energy is projected in a straight line dispersing by the inverse-square law as radiation. This means it doesn't shout Here I am like a rocket reaction engine unless your sensors face directly at the 'exhaust'. It doesn't spread out without a medium such as air or a fluid to convey it. All that is taken as part of the transparency of sensor abilities in the game.

There will always be some multi-spectrum energy bleed from a ship especially neutrinos from the power plant and imperfect insulation but not for automatic detection. That's why we have sensor rolls. As was mentioned again above the Stealth coating roll doesn't make a ship perfectly invisible but more unnoticeable. A good electronics system and/or a good sensor operator can find even a stealthed ship or maybe just a lucky roll. It's about less passive IR and active radar/lidar detection made less effective plus distance. Stealth is possible.

 

[Rikki Tikki Traveller]

Even a steam engine produces waste heat. Thermodynamics says there is ALWAYS waste heat. That is what you have to radiate away. No matter how much heat you can use, there is always going to be waste heat created in that process.

Even a direct Heat to Electricity system (piezoelectric or whatever) will have some waste heat that cannot be converted, not might not be converted CANNOT be converted.

 

[phavoc]

The fact of the matter is objects in space will generate heat, either through their own methods or by absorbing heat from the sun. The farther you get away from a star the less you have to worry about the latter. As has been pointed out lots of things generate heat. Perfect insulation just means you have to deal more specifically with waste heat.

The Space shuttle uses fuel cells for power. It has (had) radiators onboard to get rid of excess heat. And that's even with them pointing their belly towards the two sources of heat - the sun and the Earth. That heat gets radiated out from the radiators into the darkness of space. If you look at the shuttle in IR mode you'll see hotter and cooler parts. You can't "hide" the heat, even by diffusing it through multiple radiators. The same amount of heat in a vessel gets vented and the entire thing would radiate as a single object, especially if the detector is a long way away.

So in addition to the stealthy coatings a ship would need to somehow to control how the heat escapes. Converting it to electricity and either consuming it onboard, or simply beaming it off into space as a microwave or x-ray laser is one method. In a temporary mode you might be able to use your super-cooled hydrogen to store some of the heat. But one way or another it's got to be taken care of in order for the ship to stay stealthy. Hull coatings won't work.

Nobody has said stealthy space ships aren't possible. The entire point of this discussion was about how that might be possible (i.e. converting internal heat directly into electricity).

 

[Reynard]

Then the subject line should not be "The argument against stealth in space" but "Breakthrough may suggest stealth in space possible". I see it as I read it.

 

[phavoc]

Then the subject line should not be "The argument against stealth in space" but "Breakthrough may suggest stealth in space possible". I see it as I read it.

If you'd drop your snarkiness you'd understand exactly why it is titled the way it is. Or do you forget the other threads that discussed stealth that you participated in?

Previous discussions danced around the inability of a ship to be stealthy in the cold depth of space because it was going to generate heat. The title "energy from heat - the argument against stealth in space" is a direct reference to this and why it COULD work.

 

[atpollard]

Three points to make in contribution to this topic:

First, Insulation in spacecraft is kind of an odd concept because space is a vacuum ... you already have the worlds best insulation (you are a giant thermos bottle).

Second, If you posit the existence of a material that will efficiently reflect or refract heat (EM energy in the IR spectrum - or other spectrum), then it is possible to construct a Fresnel lens (like on a lighthouse) for the 'radiator' and direct your waste heat in a narrow cone. This makes your ship very bright from one specific direction and very dim from all other directions.

Third, There was some anti-radar research that involved compounds that could absorb energy in specific EM wavelengths and radiate it off in a different wavelength. In the real world, this is used for anti-radar coatings on military vehicles. If the Far Future has materials/coatings that operate on a similar principle except across a broader range of EM wavelengths, it may be possible to tune what wavelength your ship glows in. Enemy scanning for IR signatures, too bad you radiate all your waste energy in the x-ray wavelengths.

Just tossing in my 2 cents.
Use or ignore as appropriate.

 

[Sigtrygg]

Second, If you posit the existence of a material that will efficiently reflect or refract heat (EM energy in the IR spectrum - or other spectrum), then it is possible to construct a Fresnel lens (like on a lighthouse) for the 'radiator' and direct your waste heat in a narrow cone. This makes your ship very bright from one specific direction and very dim from all other directions.

Perhaps that's what the exhaust ports on the back of ships are - they are not part of the maneuver drive they are part of the heat management system bleeding off excess energy in a cone behind the ship.