[Spaceships] Sneaking up on a Megastructure

[ericthered]

Originally Posted by AlexanderHowl

Since the ghost of the probe would be so primitive compared to the ghosts of the MB, the tertiary systems of the AI gods (which would probably be IQ 30) would likely squish it like a bug and recycle the materials within. Even if they cared enough to communicate, they would find the intelligence within sadly lacking in sophistication. At best, they might give it as a pet to one of the native ghosts.

Ehh, it might be a bug, but its not the equivalent of an ant. Its this bizarre-looking thing the brain has never seen before. My wife ran across a weird bug the other day. Her response was to call me over and show me, and my response was to take pictures and look it up. Made my day. I suspect the M-brain will have a similar response.

[Aldric]

Originally Posted by AlexanderHowl

As for the numbers, you would take the size (+53) and add them to the plain sight and open space modifiers (+34), for a total of +87. 10 AU is -75, so a 10,000 AU (0.15 ly) would be around -87. Since the ghost is likely not operating most of the time, it would go insane, it depends on a quite dumb NAI to operate the sensors, and it would likely not awaken it until it was obvious that the probe was going towards such an anomaly.

Aren't you missing Time Spent, Telescopic Vision and IR signature modifiers ?

[RyanW]

Originally Posted by Aldric

Aren't you missing Time Spent, Telescopic Vision and IR signature modifiers ?

An M-brain should have a significant IR signature, because of the massive fusion reactor (i.e. a star) powering it.

[Anders]

It would emit as much light as an ordinary star, except it would all be in IR and longer wavelengths. That would look suspicious to any astronomer.

[Tyneras]

Originally Posted by Anders

It would emit as much light as an ordinary star, except it would all be in IR and longer wavelengths. That would look suspicious to any astronomer.

We could see an MB today simply due to that difference, it would be extremely obvious. Our little probe should be able to spot the MB from across the galaxy, as long as it actually looks at that specific star and nothing is blocking the view.

Maybe we should be using Long Distance Modifiers for observations instead of combat range modifiers, at 10 AU that's a -20 penalty, and from across the galaxy its -36.

[Anders]

IIRC IR isn't so obscured by dust either, so it would be easier to spot.

[AlexanderHowl]

Well, there are ways to redirect emissions. For example, it is possible to reflect and redirect IR using very thin sheets of aluminum, so the outer shell of an MB could channel the majority of the emissions in a specific direction, if the builders desired. In fact, a sophisticated system could reflect and redirect IR emissions to pump IR lasers for a defense system.

[Fred Brackin]

Originally Posted by DataPacRat

W
Would it be worth my effort to check whether GURPS's numbers track reality for sensor systems that large, such as diffraction limits and signal-to-noise ratios, or might I just as well assume that the MB's AIs came up with piles of tricks to get around those numbers (likely involving stationing sensor clusters all over the place)?

I'm pretty sure detection of the probe at interstellar distances is not physcially possible without indescribable superscience.

I probably can't do the math myself but first you need to put the probe's IR signature into KW or whatever else is appropriate. Then you use simple geometry (but involving very large numbers) to describe how much that radiated energy is diminished over a particular distance.

Over interstellar distances (at least) I believe you will hit numbers that are so small that they will be less than 1 photon of that wavelength per second. I don't think even hypothetical/indescribable AI geniuses can do much with less than 1 photon per second.

[DataPacRat]

Originally Posted by Fred Brackin

I probably can't do the math myself but first you need to put the probe's IR signature into KW or whatever else is appropriate.

I found some rules-of-thumb that a SpaceShips power-point is roughly equivalent to 50 kW per ton of overall spaceship mass; so an undersized SM+0 generator powering an undersized thruster would be producing 5 kW. Of course, that's kW-electricity, not kW-thermal, which complicates matters.

... Plus, during the probe's coast phase, it doesn't even need that generator, so could be pretty close to the background 3.7K temp.

[AlexanderHowl]

We do plenty will less than 1 photon per second, a lot of the deep space photos are long exposure photos that might only gather a few dozen photons. You cannot keep a power planet at 4 K over the course of centuries, it will not reactivate. Even if you did though, it will occasionally occlude a star during its journey, meaning that the structure would be capable of sensing it. Heck, each of the AI gods would be capable of seeing everything SM+2 or larger within 4700 ly of their position, not only the probe, but every piece of debris.