Invisibility in Space

[rust]

In the end it all depends on the expectations and wishes of the players.
In our group the players prefer characters who solve their problems with
science and technology, so science and technology have to be a little mo-
re detailed and need more precise and consistent rules than in other sty-
les of play. At the same time none of us is very interested in combat and
weaponry, so we only use a minimal number of weapon types and a very
simplified version of the combat rules (hardly above the "Bang - you are
dead" level), and no space combat rules at all.

 

[atpollard]

[1] Why doesn't the fusion reactor melt?
Where are the fragile radiators that dwarf the rest of the ship?
Whatever magic allows fusion to function, could render stealth either possible or even trivially easy.
The 'thermodynamic magic' is already there.

[2] Same with my players. They tend to be science educated and will pounce if they see something like no 2nd Law. They will then apply the rules of the game "world" universally.

[3] No, nothing that isn't REQUIRED for the game world (Jump, power source, interplanetary travel). I don't know how many times I can say it before you understand...

Forgive my apparent confusion, but you state that the power source handwave is REQUIRED for the setting [3] and that we should apply the rules of the game "world" universally [2] yet when I apply the magic thermodynamic coating that lines the inside of the power plant [1] to the inside of the hull in order to reduce heat signature to a level necessary to support the detection ranges given in the rules, then my “universal” application is “unnecessary”.

It is not that I do not understand, it is that I dislike the double standard.

 

[DFW]

Forgive my apparent confusion, but you state that the power source handwave is REQUIRED for the setting [3] and that we should apply the rules of the game "world" universally [2] yet when I apply the magic thermodynamic coating that lines the inside of the power plant

You are confused because you don't understand how fusion reactors ARE being researched ....

 

[atpollard]

Conversion of thermal energy to electric energy at less than 100% efficiency?

 

[rust]

Looking at the incredible amount of fusion power plant fuel required by
the Mongoose Traveller rules, which would normally be sufficient to run
a fusion power plant for centuries instead of weeks*, I suspect that most
of that hydrogen is part of a waste heat disposal system, probably one
which heats hydrogen and then dumps it into space.

A high tech system of that kind could use a plasma which is heated and
released into space, where it travels along magnetic field lines while ra-
diating heat into space, and then returned into the ship for reuse once it
has cooled down - at least this is a system engineers are currently wor-
king on, I do not know whether they can really make it work.

* In GURPS Traveller the internal fuel supply of a new fusion power plant
is sufficient for 200 years of operation, the entire lifetime of the reactor.
This is a lot more realistic than Mongoose Traveller's ridiculous reactor
fuel requirements.

 

[Solomani666]

Since the question of remaining unseen in space has come up in some
recent threads, here are a few suggestions how a starship could avoid
detection:

- do not move in front of any background planets or stars, because
even someone using a simple visual sensor can become suspicious if
stars suddenly disappear and reappear

There is a suit that can do this (in scoundrel I think) so there is no reason that a small ship could not do it too.

- reduce the temperature of your ship to 2.725 Kelvin, because other-
wise a sensor could detect the difference between the ship's tempera-
ture and the cosmic microwave background radiation,

Or you could just broadcast the same white noise as stellar background radiation.

- avoid the use of all nuclear power plants which emit neutrinos, becau-
se otherwise any advanced neutrino detector will be able to locate your
ship,

If you have a surefire way of detecting a neutrinos with sensors that fit into a 100 dton starship, (as opposed to using a massive sphere of water with thousands optical detectors like we use today) then it's a sure bet that you can also shield against them.

- reduce the mass of your ship to zero, or at least almost zero, because
otherwise any densitometer will be able to locate your ship.

If you can manipulate gravity, then you could probably fool a densitometer too.

As you see, remaining unseen in space is not difficult at all ... :twisted:

A special purpose ship could be built with all of the above, but it would be very expensive with the price increasing greatly with the size of the ship.

All of the above could be introduced at TL14 and be practical by TL15. By TL16 it could be standard on certain special purpose destroyers and intelligence ships.

To remain undetected from a free trader with basic sensors should be easy. To remain undetected from a large military ship with dedicated computers and officers for each sensor, a bit more difficult but doable.


.

 

[Solomani666]

and stealth coatings are made of snake-oil

Real world stealth coatings at least include a considerable percentage of
snake oil, just remember the stealth plane shot down by a missile over
former Yugoslavia ... :wink:

Not snake-oil at all.

If the "hopeless diamond" was wide enough to accommodate a bomb bay and if a bomb bay, hatches, eject-able canopy, air in/out-takes etc. were not needed then the F-117 would have as invisible to radar as you can get. It is also susceptible to radar tracking while the bomb doors are open.

It may also have been tracked by and AA gunner visually, hit by 'random' fire, or by a missile detecting it's IR signature. Same applies to the B2.

Un-manned versions will be much stealthier to radar.

.

 

[Ishmael]

Or you could just broadcast the same white noise as stellar background radiation.

You have to radiate the waste heat that you generate. The thing is, you can radiate it in the direction you like. So to radiate only background in one direction, you have to radiate the difference in another direction. In other words, to make yourself hidden to someone in front of you, you're going to make yourself ridiculously easy to be seen by someone behind you.
You'll have to know or make good guesses as to where the enemy's sensors are.
Sounds like a job for the senors ops guy.

But this requires its own handwave too.
How do you go about transferring heat around, regardless of the temperature differential, without generating more heat?

an alternative is to severely reduce the size of powerplants in use and having more of them that can be brought online ( or be capable of running them at low power levels ). Just because a plant can provide 100MW doesn't mean that its running at 100% capacity all the time. ... lower power levels means less waste heat to radiate away.

Capacitors are already over 99% efficient, so at Trav tech levels just assume 100% efficiency for simplicity; run the ship off batteries/capacitors. Have a small powerplant keeping them charged and have extra caps to provide headroom for extra power usage until more powerplants can be brought on-line. The only waste heat will be from powered-up systems such as life support ( zero-g, to save power ), sensors ( passive only, to save power ) and the computer.

Use separate, heavy-duty powerplants for drives which are brought on-line only when needed. Use a separate powerplant for weapons and defenses which are brought on-line only when running in general quarters. If you need them, you've been seen already, so you might as well power up ( unless you need to look harmless... think Q-ship )

The less power you are actively using, the cooler you can run.
why keep big PP's running at red-line ALL the time? ( huge waste heat generated )

Drifting, with non-essential systems turned off is quiet....
Run silent, run deep


btw, the F-117 is not invisible to radar from all aspects. A lot depends on where the sensor is looking from. I'm certain that the F-117 is really bright from a couple of narrow angles, but that goes back to the point I made above; if you're hard to see from this direction, you're easy to see from another direction.

You can't be invisible, but you can make it harder for that guy over there to see you.

 

[DFW]

Or you could just broadcast the same white noise as stellar background radiation.

Sure but, it doesn't change your ships actual temp and IR sig. Therefore, not useful against passive IR sensors.

 

[rust]

You can't be invisible, but you can make it harder for that guy over there to see you.

Yes, and to actually recognize what he sees.

For example, you could probably make a 1,000 dton ship with a low IR
signature look like a 200 dton ship of another configuration with a high
IR signature, by cooling certain parts of the hull and transferring the
heat to radiators on other parts of the hull - a camouflage pattern, pro-
bably not perfect, but able to fool any sensor operator who does not
expect something like this and trusts what his IR sensor shows him.

Or you can hide a ship (or many ships, if you can pay for it) behind the
equivalent of a huge solar sail. The enemy's sensor operators can assu-
me that there is something "behind the veil", but they cannot be certain,
and they cannot know what exactly it is - a battleship, a flight of fighters,
only a decoy ?

These are just two of the ideas the players of one of our campaigns ca-
me up with, there are certainly lots of other possibilities to make space
combat tactics more interesting than just "I have it in sensor range and
fire at it".

 

[DFW]

For example, you could probably make a 1,000 dton ship with a low IR
signature look like a 200 dton ship of another configuration with a high
IR signature, by cooling certain parts of the hull and transferring the
heat to radiators on other parts of the hull - a camouflage pattern, pro-
bably not perfect, but able to fool any sensor operator who does not
expect something like this and trusts what his IR sensor shows him.

I would expect pirates to make liberal use of such a ruse. You average free trader Master isn't going to fire 1st. By the time the pirate gets close enough, its too late... Give up the cargo and live to see another day.

 

[Iron Warrior.]

I wonder if the old ww1 trick of diving out of a sun would work in space?

In ww1 german pilots had planes with higher ceilings than their enemies, leading them to practice the tactic od diving at the enemy in such a way as to put the sun at their backs and in the enemies eyes.

Hence the old saying "Beware the hun in the sun." which british pilots used.

In traveller if you were approaching objective x with a star at your back would it give you a stealth approach based on the enemy being blinded by the sun's emissions? You heat sig would likely be drowned out all the way to hell and back for one thing.

 

[GypsyComet]

If you are close in that might work, but once you get very far from the sun you run the risk of occluding it. Unlike a random star somewhere else in their sensor arc, they WILL notice the sun blinking.

 

[Iron Warrior.]

If you are close in that might work, but once you get very far from the sun you run the risk of occluding it. Unlike a random star somewhere else in their sensor arc, they WILL notice the sun blinking.

I'd imagine if the star was close enough to show a disk you'd be close enough for it to work.

 

[Jeraa]

In traveller if you were approaching objective x with a star at your back would it give you a stealth approach based on the enemy being blinded by the sun's emissions? You heat sig would likely be drowned out all the way to hell and back for one thing.

The Radar, NAS, and Densitometer sensors on the ship wouldn't be affected. Thermal sensors can detect hot or cold spots on a ship out to 25,000 kilometers (I would count this being a cold spot, at least compared to the sun in the background), so at the least you'll limit thermal sensors effective range. Visual sensors would probably be impaired. I don't know enough about EM sensors to say one way or the other.

So, it would seem that no, having the sun at your back won't really change things. It will mess with visual and thermal sensors, but the rest of the sensors won't have a problem detecting you. Everyone has radar, and I don't think the sun will bother that at all (though I could be wrong).

 

[GypsyComet]

Radar is an active sensor, though, and will allow the predator to pinpoint *you* without cranking up active sensors of his own. As an active emission type sensor, Radar is also severely affected by distance. As a scanning sensor it works reasonably well for collision avoidance, but you have to scream your location very loudly for it to work as a targeting sensor against small targets like ships. As noted already, there are also quite effective signature reduction technologies available versus radar.

Neutrino sensors are also "blinded" by having the star behind you, as stars are the biggest neutrino generators in any system.

NAS shouldn't have that kind of range. If "detect intelligent life from orbit" is standard tech (and 25,000 kilometers qualifies as "from orbit") the whole picture of exploration and first contact is altered beyond recognition. I'm here for the Traveller, not Star Trek.

Densitometers are an odd case. MegaTraveller made them out to be super sensors in the Star Trek mold, while TNE scaled them WAY back. They are like an MRI at range, but are stymied by artificial gravity fields. Some argue that this foible allows them to be used as a scanning sensor, but my impression is that they suffer huge losses in resolution with range, making any target that occupies less than a few arcminutes of a ship's sky effectively invisible. Terra's Moon averages about 32 arcminutes, for comparison.

The question of Thermal sensors is more open, as modern types are not all that good at scanning and work best when you don't point them at the Sun. Sun observation calls for specialized sensors, which a civilian ship may or may not have. Normal Thermal sensors are going to work best looking for reflected heat of fairly low magnitudes instead of staring into an emitter like the Sun.

 

[locarno24]

I would expect pirates to make liberal use of such a ruse. You average free trader Master isn't going to fire 1st. By the time the pirate gets close enough, its too late... Give up the cargo and live to see another day.

See previous comment; looking like something else is far, far easier than looking like nothing at all. Impersonating an SDB with legal stop-and-search powers is another unpleasant trick I've pulled on players before.

Hmm, with a 1 meter TL 7 scope you could see the Space Shuttles maneuver thrusters from Earth if it was at the Asteroid belts.

If you're actually looking at it. How long does such a scope take to sweep an area of the sky? Say a 5 degree x 5 degree sphere surface element? (genuinely don't know)

Well, the idea would be to start off with your fuel as ice, and then as you dumped heat into it, it would thaw and become liquid again. It wouldn't be hard to have a few hundred liters to start off with.

Of course, the easiest way to avoid this would be to ensure your path was coming from some other object that may be generating a heat signature of its own, so you minimize detection possibilities. Space is BIG, and I don't think you could conceivably track every IR signature and run it down.

If you just want to limit your IR signature by sinking heat temporarily, I doubt it'd be too hard with a bit of preparation at a design level. After all, a (fairly common) jump-2 design is carrying 20% of its volume as bloody liquid hydrogen, after all. The point is, sooner or later, any heat sink will reach useful capacity.

 

[rust]

I wonder if the old ww1 trick of diving out of a sun would work in space?

The filter I use for my telescope when looking for sunspots cost me just
a few Euros and enables me to point the telescope right at the sun. Any
advanced visual sensor would certainly include a similar filter, if only to
avoid overload when pointed at any extremely bright object (just think
of a nuke explosion in combat), so "hiding in the sun" would most pro-
bably not work.

 

[rust]

How long does such a scope take to sweep an area of the sky? Say a 5 degree x 5 degree sphere surface element? (genuinely don't know)

With an advanced CCD and a good computer program to evaluate the
data you could do it almost as fast as you can move the telescope.

It would work the same way that is currently used to look for asteroids
or comets, the computer would store the data from the pass and would
compare them to the data of the previous passes, if anything would ha-
ve become brighter or less bright or would have moved and would not
be in the database of known objects (planets, moon, known asteroids)
it would alarm the operator, who would take a closer look at the object
- and this is what actually takes time.

So, you could plant a couple of decoys in a system, and activate them
once a hostile spaceship appears. The sensors of the ship would almost
immediately detect the decoys, but then the sensor operator would ha-
ve to "work through them" to find out whether they really are decoys,
whch could keep him quite busy and give you a chance for some sur-
prise.

 

[DFW]

The question of Thermal sensors is more open, as modern types are not all that good at scanning and work best when you don't point them at the Sun. .

Actually, in space, when looking for "hot" objects" They work EXTREMELY well.