Megatrav sensor question

[Carlobrand]

MegaTraveller's a bit difficult to interpret sometimes. Apologies in advance for my ignorance.

For small craft (<100 dTons) with small power plants (<1000 Mw) and EM Masking, the guidelines (P89, Ref's Manual) state, "means no emissions". Assuming they don't decide to start blasting in radio or radar, does that mean they can't be detected by passive energy sensors?

Also, when discussing Powering Down as a combat maneuver, the rules (P95, Ref's Manual) direct you to the chapter on Travelling. What chapter on Travelling??

[McPerth]

Originally Posted by Carlobrand

MegaTraveller's a bit difficult to interpret sometimes. Apologies in advance for my ignorance.

For small craft (<100 dTons) with small power plants (<1000 Mw) and EM Masking, the guidelines (P89, Ref's Manual) state, "means no emissions". Assuming they don't decide to start blasting in radio or radar, does that mean they can't be detected by passive energy sensors?

Also, when discussing Powering Down as a combat maneuver, the rules (P95, Ref's Manual) direct you to the chapter on Travelling. What chapter on Travelling??

As I apply them, a ship with so low enegy emission could not be detected by neutrino sensors. If it was on deep space, it could by other pasive sensors (mostly IR). If in orbit of a planet, probably not even so, or at least not so easily.

[aramis]

You can detect such "no emissions" targets by reflection, so yes, you can detect them with passives illuminated by the local star.

[Carlobrand]

Originally Posted by aramis

You can detect such "no emissions" targets by reflection, so yes, you can detect them with passives illuminated by the local star.

"(P)assives illuminated by the local star"???

"An EMS Passive Sensor Array combines laser sensor, radar direction finder, radio direction finder, radiation sensor, Passive IR. light amplification, and image enhancement into one integrated and optimized sensor array"

How would that work within the existing rules? There's nothing in the rules about how far out from the local star I am when combat starts, or how much light a given star type's putting out and its relation to sensor function, or my ship's albedo or any of that. Surely I'd expect a difference between, say, my profile from the third planet of a magnitude-A and my profile while approaching a distant gas giant circling a small M-type star. That sounds like we're crafting new rules.

The rules say I drop down an emission class, but then there's no actual description of an emission class less than "under 1000MW", just the statement that there are no emissions. I guess I could invent one, if that's what you're suggesting, just extend it down. However, the logic escapes me: the enemy can't detect the residual heat of my EM Masked 900MW fusion reactor - which, masked, still puts out as much heat as a good-size car engine if I have it figured right - but they can detect the thermal reflection from the magnitude-M star 10 or 20 AU distant?

I'm silent, but I'm not invisible. At high tech, a silent ship is still going to show up on densitometers - they don't have quite the range of the high tech passive EMS array, but they still have excellent range. I'm a headache for the low-tech opponents, but I expect the low tech folk to be using active scanners on expendable scouts and fighters in the first place, because that's the only way the low-techs ever manage a pinpoint roll against even ordinary targets.

[aramis]

Carlo, You're ignoring the LI and image enhancement - both rely upon natural light from the local star. We detect asteroids at 2+ AU routinely based upon reflected light alone.

You don't need to invent a new range - the extant "no signature" range already includes stellar effects (as a simplification, it doesn't increase detectability for aspect, position in system, and a dozen other factors that do matter in real life).

No EM sensor works without a source of EMR. Ever. A laser detector only works when a laser hits it. A Radio DF won't work if there's no signal at or above its squelch threshold. Light Amplification still requires light be bounced off the target; it is just that an LI system doesn't include that light, relying on environmental sources.

If you really want to make it matter, Give a +1 signature level for a target in an orbit less than half the hab zone; give a -1 for more than double... But don't stress over it. The sensor rules are convoluted enough as is.

[Carlobrand]

I'm not precisely ignoring LI/image-enhancement. Asteroids reflect some light. A civilian ship has no reason to hide and every reason to be seen - it will reflect light. A warship does not want to be seen - to be seen is to be targeted for weapon-fire. A matte-black ship is going to reflect essentially nothing - at least, not in its original wavelength. I don't think it can avoid absorbing that radiation and then re-radiating it as heat. Thus, such a craft is likely to be more visible in infrared than in the visible light spectrum, which is why I focus on thermal reflection - well, re-radiation - rather than light.

That is where I face the paradox in the proposition: the craft's own output of heat, even masked, is higher than anything it could absorb and re-radiate from a distant sun. The idea that the game could describe a masked craft as "emissionless" under such circumstances, but that the craft could be spotted by reflection or re-radiation of stellar emissions, seems to be contradictory.

I don't want to "make it matter." I want to know what the game rules themselves say about this situation. If compelled to "make it matter," I'd extend the existing table down a level and treat it as a -2 DM rather than declaring it "invisible", on the argument that the tables show that masking is not absolute.

[aramis]

You can't have a true "Zero reflection" nor a true "zero emission" object with a temperature aboard above 0 Kelvin (-273.3° C).

You're reading way too much into "No Emissions" ... just call it "very low" instead, and ignore it. It's better for gaming, it's better for sanity.

[Carlobrand]

"Very low" works for me. Who proof-read these rules, anyway??

[aramis]

Originally Posted by Carlobrand

"Very low" works for me. Who proof-read these rules, anyway??

Don't know, but it sure is an issue. Love the game, hate the editing.

[McPerth]

How will you handle a solar powered defense satellite drone, with no neutrino emisions (as it has no fusion plant), deployed in relatively close orbit to a planet (so its IR emisions masked against the planet's own)?

IMHO it should be quite difficult to detect without resorting to active sensor measures (and so being sure you are detected).