Stealth in Space

[GypsyComet]

The one factor I'm not sure I've ever seen mentioned on the potential emissions side is L-Hyd. Traveller's ships have no energy budget for keeping many tons of hydrogen as liquid, but manage for weeks or months at a time anyway...

 

[Wil Mireu]

The one factor I'm not sure I've ever seen mentioned on the potential emissions side is L-Hyd. Traveller's ships have no energy budget for keeping many tons of hydrogen as liquid, but manage for weeks or months at a time anyway...

Do they need an energy budget if it's just stored at (very) high pressure? Though that would require a lot of energy to actually compress down to that form when refining it in the field.

Though if it's stored at such high pressure then any hit on those fuel tanks around the outside of the ship is going to be ridiculously explosive... (and also strangely ignored)

 

[phavoc]

The one factor I'm not sure I've ever seen mentioned on the potential emissions side is L-Hyd. Traveller's ships have no energy budget for keeping many tons of hydrogen as liquid, but manage for weeks or months at a time anyway...

The fusion plants should be putting out quite a bit of energy. Plus I'm assuming they would have conquered super-conductors by then, as well as other breakthroughs in materials sciences. It may be quite easy for them to keep it liquified.

I also ran across this info, where some chemists have come up with a way to safely store hydrogen in a solid format, called hydrogen borane. It's being developed for fuel cells. It's a couple of years old, but it's the first I've heard of them being able to store it in a stable solid form.

http://phys.org/news/2011-08-breakthrough-hydrogen-fuel-cells-chemists.html

 

[Condottiere]

1. Exactly how compact is solid hydrogen in relation to the stuff we usually pack in the tanks?

2. Stealth is the elimination or minimization of one or various of your ship's radiation signatures.

3. You could have a facade constructed that creates a visual outline of a different class with the associated energy signatures that routine sweeps would verify as such, which is spoofing, rather than stealthing.

4. You could hide inside the shadows of natural phenomenon, assuming that such things happen in deep space, rather like submarine skippers look for in thermal layers, or in the shadows of other signatures such as large freighters or a planet.

 

[simonh]

Here is a little experiment.

On a really dark, cloudless winter night you and a friend go out to a field a few miles from the nearest street light.

Your friend walks into the field in a random direction while you face the other way so you have no idea where they are.

After 10 minutes they have to strike a match and you have to find them.

Sorry, but your sense of scale is seriously deceiving you.

Try this. Instead of a field do this in the Australian outback. Give your friend a week and a jeep. Then try your nighttime match spotting from an aircraft at 10,000ft. It's still a little easy, the scale is probably still a bit low by a few orders of magnitude, maybe we should be doing this over the pacific ocean with you in a satelite, but now we're beginning to get a little closer to the relative scale of the solar system.

There is no stealth in space for a multi-gigawatt fusion reactor maintaining a room temperature environment - basic thermodynamics and black body radiation physics. If you do not understand this either take a course or just admit you haven't a clue about real science.
or read this:

http://www.projectrho.com/public_html/rocket/spacewardetect.php

That article makes all the same mistakes that have already been roundly debunked in this discussion, and also makes assumptions that just don't apply to Traveller.

Carefully filtering out the known characteristics of the signal from Voyager from the background noise, in a signal picked up using our very best highly directional instruments, trained at exactly the correct position, to detect a signal directionally beamed straight at us is in absolutely no way even vaguely similar to attempting the same feat against a Voyager type probe positioned at a completely random point in the solar system, pointing it's transmissions in a random direction. I can see how the way that article poses the issues might appear on the face of it to be persuasive to the uncritical reader, but for the author of that article to try and pass off listening to Voyager as a general example of full-sky detection of arbitrary targets is either a deliberate ploy to deceive, or willfully obtuse.

The other factor is that the base assumptions that article makes about what it is you're trying to detect - fusion torch rocket engines, simple don't apply to Traveller. Ship's in Traveller don't spew out thousands of kilometre long plumes of super-heated fusing hydrogen. They're basically room-temperature objects with no particular energetic particle emissions. Stick a 10m thick insulating foam screen across it, and it shouldn't be any easier to detect that a similarly sized rock, and we already know how hard it is to detect rocks. Our planet is routinely hit by rocks we had absolutely no idea were coming at us, until thy literally explode over one of our cities.

So yes, if your fish is in a barrel, shooting it is easy. However the solar system, including it's off-ecliptic volume, is an ocean. Shooting an arbitrary fish at an unknown location in an ocean is a lot harder. i.e. if you miss-scale your analogy to a ridiculous degree, you will come up with completely unrealistic conclusions.

Simon Hibbs

 

[dragoner]

Given the timeline of trav being 3500 years in the future - basically from the bronze age again to now, it is impossible to really think of how different the tech will be. Ships are basically magic carpets rules-wise, and that isn't even touching upon stealth; though given the time, it isn't that unbelievable.

Stealth, I would throw down a few rules:

1. It costs extra.

2. Stealth does not mean invisible.

3. There is a time limit, meaning eventually you will be picked up by sensors.

Addendum to this is that big fleets do not have stealth, and most commercial craft either; so that a stealth equipped or using craft will draw extra attention when detected.

 

[Strithe]

The other factor is that the base assumptions that article makes about what it is you're trying to detect - fusion torch rocket engines, simple don't apply to Traveller. Ship's in Traveller don't spew out thousands of kilometre long plumes of super-heated fusing hydrogen. They're basically room-temperature objects with no particular energetic particle emissions. Stick a 10m thick insulating foam screen across it, and it shouldn't be any easier to detect that a similarly sized rock, and we already know how hard it is to detect rocks. Our planet is routinely hit by rocks we had absolutely no idea were coming at us, until thy literally explode over one of our cities.

They may not have huge fusion-torch drives, but as I recall they also don't have direct matter to energy conversion either. This means that some percentage of that energy becomes heat or other emissions.

There don't seem to be some sort of obvious radiators on any canon illustrations or deck plans, so we'll assume they radiate that heat through portions of the hull (or perhaps that explains why the ships with reactionless thrusters have what appear to be rocket-nozzles on them).

Megatraveller (because that's the source I have most readily available) lists the Type S Scout/Courier as having an 864 mw fusion plant (of which 350 mw is needed to give it 2g of thrust from the maneuver drive).

The Subsidized Merchant has a 1,476 mw plant (and needs 400 mw for maneuvering).

Just running the ship's systems alone requires massive amounts of energy, and even though the maneuver drives aren't fusion plumes they by definition have to be emitting SOMETHING that could be detected.

My point is starships are likely to be quite a bit hotter than room temperature, especially if they're operating under acceleration.

You could of course, just coast at some point and power down to minimize the radiated signature. But even at "room temperature" you're going to be quite a bit hotter than the background unless you're in the inner solar system.

Coating the ship in insulation is going to cause other problems. That heat is now trapped and the ship's interior gets hotter & hotter: "You evade the patrol's sensors, now make endurance rolls to avoid dying of heat exhaustion."

 

[simonh]

They may not have huge fusion-torch drives, but as I recall they also don't have direct matter to energy conversion either. This means that some percentage of that energy becomes heat or other emissions. ...

You make a lot of reasonable point, but I'd argue a few mitigating factors. That power plant rating is for maximum power draw, I.e. Engines at full throttle, energy weapons blazing away and jump drive powering up. Traveller does a particularly bad job at modelling power plant endurance in an even vaguely realistic manner, it just doesn't even try. That power plant draw appears to be basically assuming that all that energy is being blasted out in the form of manoeuvre drive output or weapons fire and jump bubble formation. IMHO the only sensible conclusion is that in practice the power plant usually idles at very low output.

How much residual heat is left over is a matter of conjecture, but as you say the absence of enormous heat sinks argues for moderate waste heat output. Even if those 'exhaust ports' are venting heat, they argue for narrow directionality, which would favour a stealthy design.

I do agree it wouldn't be possible to mask a heat signature in all directions at the same time, that could never work, but if you can effectively mask even two thirds of your vehicle's surface area that could be pretty useful tactically.

Simon Hibbs

 

[Prime_Evil]

Don't forget that FTL communication does not exist in the Traveller universe. And sensor signals do not propagate instantaneously over interplanetary distances. A starship that emerges from jump at the edge of a system might not be detected by ground-based sensors on the mainworld for 2-3 hours due to this time lag - sensor images of the incoming starship will be a couple of hours old by the time the observers detect them. The time-lag caused by distance means that observers do not see events as they happen - it also ensures that information about the movements of incoming ships will be out of date. To put this into perspective, the average distance from Earth to Jupiter is approximately 47 Light-Minutes, which means that starships near Jupiter will be undetectable from Earth for at least 47 minutes after they arrive. The vast distances within a typical star system provide some effective stealth capabilities, making it possible for ships to hide their true intentions and movements for some time.

 

[GypsyComet]

Megatraveller (because that's the source I have most readily available) lists the Type S Scout/Courier as having an 864 mw fusion plant (of which 350 mw is needed to give it 2g of thrust from the maneuver drive).

The Subsidized Merchant has a 1,476 mw plant (and needs 400 mw for maneuvering).

MegaTraveller's power numbers are patently ridiculous, though of course M-Drive requirements are backside-extracted in *any* case other than low-tech rocketry. M-Drives are magic, after all.

MegaTraveller's laser turrets pull in enough power over a ten minute turn to liquify the turret, the hull around it, and the curiously not mentioned 3 meter thick busbars required to transmit that much power from the power plant to the turret. We won't even get into the plasma turrets...

So yes, MegaTraveller ships glow visibly if any real level of physics is applied. They also fire small-diameter lasers at targets tens of light seconds away expecting to inflict damage, but don't have tame black holes collimating those lasers.

Even TNE, which stepped MegaTraveller's power numbers down by a factor of 20 or so, is still using a lot of juice.

 

[darue]

first we've broached the topic of thermal management, now we're getting to electrical distribution.

thermal management I've always handwaved as being built into the hull: both for general heat issues and fuel maintenance, handled by advanced thermoelectric materials. with supplemental cooling of the M-drive via a trickle (negligible volume) of hydrogen plasmafied out the 'apparent' thrusters on the back end. This gives an excuse for glowy trails occasionally out the back of ships and the exhaust is 'safe' unlike a fusion rocket's.

electrical distribution, well, we can agree it's not copper wire after TL8 right? I lean toward superconducting flexible 'plasma conduits' though I'd prefer a term that didn't collide with ST, and a solid-state woven superconductor would also be an option, electromesh cabling? It's probably all superconducting at TL9 and up?

 

[simonh]

To put this into perspective, the average distance from Earth to Jupiter is approximately 47 Light-Minutes, which means that starships near Jupiter will be undetectable from Earth for at least 47 minutes after they arrive. The vast distances within a typical star system provide some effective stealth capabilities, making it possible for ships to hide their true intentions and movements for some time.

True but even at 6G, compared to the scale of the solar system the target can't actually go very far during those 47 minutes. It's not like it could flit across to Mars before we know what had happened. I suppose it could manoeuvre about the Jovian moons a bit, but at that range it's not like we could have done anything about it anyway. I mean you're not wrong, but I don't think it make much difference in practice.

Simon Hibbs

 

[simonh]

Megatraveller (because that's the source I have most readily available) lists the Type S Scout/Courier as having an 864 mw fusion plant (of which 350 mw is needed to give it 2g of thrust from the maneuver drive).

The Subsidized Merchant has a 1,476 mw plant (and needs 400 mw for maneuvering).

MegaTraveller's power numbers are patently ridiculous, though of course M-Drive requirements are backside-extracted in *any* case other than low-tech rocketry. M-Drives are magic, after all.

They're in the right ballpark. Assuming perfect conversion, accelerating a 1kg mass by 10m/s takes 50 Joules of energy, or 50 watts for continuous acceleration. If the Type S is 1000 metric tonnes (which I think it roughly is in Mega Traveller) then that's a power requirement of 100 mw for 2G acceleration, with no losses.

Edit: This is why practical propulsion systems are generally also power generators. There are huge inefficiencies in using one technology to generate power, another to convert that to electricity, transferring that electricity to your propulsion system, then another technology to convert the electricity into a form of propulsion. You're generally much better off finding a power generation system that by it's nature can be used to directly develop thrust, or as directly as possible, cutting out the intermediate steps. So in principle you'd be better off using that fusion power plant as a fusion rocket. What Thruster Plates do is get rid of the need to carry around a consumable form of reaction mass and the awkwardness of having a highly weaponisable superheated exhaust plume, which leads to useful simplifications for game purposes, but the cost is that from a physics or engineering perspective they're silly.

Simon Hibbs

 

[Reynard]

I realize there are no Romulan cloaking devices in Traveller. At best, the Stealth coat is the equivalent to 21st century stealth fighters and bombers making a vehicle more difficult but not inherently impossible to find. The vast majority of ships do not have stealth coat and those that do are either known for roles involving stealth or are highly suspect. Really, how do you explain your merchant ship having stealth coat?

The rules, however, do allow sensor detection. Deep space should be a straight unmodified roll unless the ship tries cruising by inertia and powers low for a slight modifier. A failed sensor roll should represent the operator really effed up. Ideally, a new Sensor Check should be made at each new range band. Also remember, if there's more than one sensor array able to scan, there's that many more chances to be spotted, stealth coat or not. The best stealth is terrain. That's why SDBs hide in oceans, asteroid belts and gas giant atmosphere to surprise targets at effective range.

What I think should be more common is the Return of the Jedi Endor event. Stealth = bluffing. You've prepared to lie your way in and of course "I don't know, fly casual." Know the system you're going to for security gaps or be ready to pretend you're there for another reason and convince the police cutter crew. This is Hiding in the Open.

 

[Condottiere]

You mean coasting along with the Black Globe generator on?

 

[Reynard]

No. Power down and don't use maneuver drive. Ride on the inertia velocity when you stopped accelerating. Powering down reduces the signature of the power plant. Run silent, run deep.

 

[simonh]

I realize there are no Romulan cloaking devices in Traveller. At best, the Stealth coat is the equivalent to 21st century stealth fighters and bombers making a vehicle more difficult but not inherently impossible to find. The vast majority of ships do not have stealth coat and those that do are either known for roles involving stealth or are highly suspect. Really, how do you explain your merchant ship having stealth coat? ...

I think it's likely to be a lot easier to stealth a spaceship than an aircraft.

Aircraft have to remain aerodynamic and weather proof, which puts massive constraints on how they can be stealthed. In contrast for a space ship it may be that all you need to do is bolt a 10m thick foam screen, with a few layers of radar absorbent and scattering angled platelets, across one side of it. Job done.

Bottom line is, I don't think we can know for sure. There might be a technological leap in detection methods that makes it trivial, or maybe there won't and it'll be practically impossible.

Simon Hibbs

 

[alex_greene]

The best stealth mode is to build your ships out of asteroid hulls.

As long as your vessel doesn't have protruding bits, moves along a parabolic course that doesn't take it near any planets, tumbles gently and runs on battery power with its fusion drive shut off, it should not appear to be anything more than a random asteroid - just another worthless lump of rock drifting through space.

Better than trying to get the other guy's sensors not to see you, why not get them to see you - and think that you are something different?

 

[phavoc]

The best stealth mode is to build your ships out of asteroid hulls.

As long as your vessel doesn't have protruding bits, moves along a parabolic course that doesn't take it near any planets, tumbles gently and runs on battery power with its fusion drive shut off, it should not appear to be anything more than a random asteroid - just another worthless lump of rock drifting through space.

Better than trying to get the other guy's sensors not to see you, why not get them to see you - and think that you are something different?

For the most part, I think that's true. Coming in as an asteroid does have a few flaws though. a) Their path in the system would be known well in advance if it's been settled for a while, b) it's going to be traveling relatively slow compared to a powered spacecraft (hope you stocked up on vids and popcorn!), c) if it's anywhere near a threat to a station, planet or shipping lanes it will get blasted to bits.

It's great for sending in a probe, but I think no to much for a ship - unless it's a special mission you really don't want anyone to know about. But if you have to land it's kind of a dead giveaway when an asteroid hits atmo and doesn't burn up... even a bigger give away when it takes off from a planet.

 

[Bardicheart]

For the most part, I think that's true. Coming in as an asteroid does have a few flaws though. a) Their path in the system would be known well in advance if it's been settled for a while,

Not necessarily, gas giants gravitational effects frequently knock asteroids out of planetary belts and send them off in random directions. There's no way to predict this and its one of the main sources of surprise NOEs.

b) it's going to be traveling relatively slow compared to a powered spacecraft (hope you stocked up on vids and popcorn!),

True, somewhere between 26,000kph to around 60,000 kph for real world NOEs IIRC.

c) if it's anywhere near a threat to a station, planet or shipping lanes it will get blasted to bits.

You wouldn't want to shoot it, that just gets you lots more smaller objects which would actually be more of a threat to orbital facilities and shipping traffic. Unless its on a collision course with something, it'd actually be best to just leave it alone. With the speed and maneuverability of Traveller spacecraft they should be able to avoid such objects, maybe the starport issues a routine warning about space debris "in sector one niner seven, inbound asteroid detected massing 329 dT moving at 29,400 kph... all traffic be advised..."

Expanding on the above idea, doesn't even have to be a custom built small "planetoid" hull, you could just nudge an ordinary asteroid out of the PB in the direction you want to go, grapple to it and ride it in. If its large enough (say 600 to 800 dT) and you're in a 200 dT free trader, would be hard to differentiate your ship from the asteroid unless someone came in close. Course there's always the chance some enterprising mining crew decides to harvest your "stealth rock"... 8)