So, why are lasers missing?

[AnotherDilbert]

We have some data points:

Firstly we should say that a bright, high-contrast feature such as a star can be seen however small (in angular terms) it appears. In these cases the star would just appear as a dot. So, if there were a very shiny surface on the Moon that caught the Sun, it might be seen from Earth with quite a small telescope.

...

Then, in an extreme case, such as the Moon, where there is lots of light (a high signal/noise ratio), it’s possible to do image processing (image restoration) and retrieve roughly a factor of two better resolution at the expense of some artefacts. So for Hubble, we conclude that the best resolution we are likely to manage is about 0.024 arcseconds (in the ultraviolet). On the Moon, at its closest distance to the Earth [Perigee: ~363 000 km], this would give a linear resolution of:
363 000 000 ｘ R /206 000 = 43 metres

https://www.spacetelescope.org/about/faq/#21
Thanks, Aramis.
This is the best possible case, a large bright non-manoeuvring target that shines at a shorter wavelength than ships. A ship would be much more difficult to detect, hence much less resolution. So even with something ten times better than Hubble we would struggle to pinpoint a small ship.


LBB22'81, p32 "Detection"

Ordinary or commercial starships can detect other ships out to a range of about one-half light-second; about 1,500 millimeters. Military and scout starships have detection ranges out to two light-seconds; 6,000 mm or 6 meters.
Ships which are maintaining complete silence cannot be detected at distances of greater than half detection range; ships in orbit around a world and also maintaining complete silence cannot be detected at distances greater than one-eighth detection range.

So, even small military ships can barely detect ships at 1 ls = 300 000 km (under emission control) or 0.5 ls with confounding noise. It would suggest that we can hardly track them perfectly.

 

[AnotherDilbert]

Except that we're not dealing with human vision. We're dealing with technology.

Even ideal, perfect sensors have the same problem, albeit with much better resolution. All sensors have limited resolution leading to an uncertainty in measurement.

All sensor data is uncertain to some degree.

Hubble might have a resolution of 0.05 arcsec under ideal conditions, but we need something like 0.0005 arcsec to accurately resolve the position of ships at 1 ls. And the same precision in the weapon mounts. That is very far from possible currently.

 

[mike wightman]

The rest of the CT sensor and detection rules are worth remembering too:

Tracking: Once a vessel has been detected, it can be tracked by anyone up to
three light-seconds (about 9,000 mm, or 9 meters).

This would be a much more narrow field of view tracking system IMHO.
So the 'wide angle' stuff has a range of 1-2 ls (for military sensors) and 0.25-0.5 ls for civilian sensors, while the narrow angle firing solution sensor can go out to 3 ls.

 

[AnotherDilbert]

The rest of the CT sensor and detection rules are worth remembering too:

Tracking: Once a vessel has been detected, it can be tracked by anyone up to three light-seconds (about 9,000 mm, or 9 meters).

This would be a much more narrow field of view tracking system IMHO.
So the 'wide angle' stuff has a range of 1-2 ls (for military sensors) and 0.25-0.5 ls for civilian sensors, while the narrow angle firing solution sensor can go out to 3 ls.

Quite, but there is a large difference between barely be able to detect and extremely accurately pinpoint.

If we can barely see a target at 3 ls, we hardly have a detailed picture of it at 1 ls.

 

[mike wightman]

Tracked and fired upon.
Laser range DMs:
2500mm+....-2 (0.83 ls)
5000mm+....-5 (1.67 ls)

Everything else being equal (computer programs and crew skills) 8+ to hit at 0 to 0.82 ls, 10+ to hit at 0.83 to 1.66 ls, and 13+ to hit at 1.67 to 3 ls.

I may consider introducing some +DMs to hit if the target is close:
1250mm+... no DM (0.42 ls)
625mm+....+2 (0.21 ls)
312mm+....+5 (0.1 ls)
Anything closer than 0.1 ls is an autohit.

As to what the hit actually is I agree that it represents holding the laser in place long enough to cause damage rather than superficial paint removal and hull heating.

 

[Carlobrand]

Even ideal, perfect sensors have the same problem, albeit with much better resolution. All sensors have limited resolution leading to an uncertainty in measurement.

All sensor data is uncertain to some degree.

Hubble might have a resolution of 0.05 arcsec under ideal conditions, but we need something like 0.0005 arcsec to accurately resolve the position of ships at 1 ls. And the same precision in the weapon mounts. That is very far from possible currently.

Now tell me the state of affairs at tech level 14, instead of resting our assumptions on tech level 7-8 technology.

 

[aramis]

Quite, but there is a large difference between barely be able to detect and extremely accurately pinpoint.

If we can barely see a target at 3 ls, we hardly have a detailed picture of it at 1 ls.

Actually, the issue of detection is more about noise. A ship is a blip at about 280° Kelvin; it stands out. So do stars. The issue is determining if what you're seeing is a star, a planet, or a ship...

And, at 3 LS, 1' of arc is 4.8481e-6 radians, 3 x 2.998e+8 = 8.994e+8 m radius, for 4360.38114 m resolution, so at 0.05, that's 1/20 that, or 218m.

The thing is, detections are best done via parallax. Something moving strait across the field is easier to detect than one moving towards or away from the observer.

 

[kilemall]

Synthetic Aperture Radar would feed into that parallax probability point, you would have more comparative looks to build a picture.

However, if I am understanding the technique properly, a SAR equipped ship would be getting the large aperture effect through its' motion relative to the target, even if the target is not moving.


http://www.radartutorial.eu/20.airborne/ab07.en.html
https://en.wikipedia.org/wiki/Synthetic_aperture_radar

 

[aramis]

Synthetic Aperture Radar would feed into that parallax probability point, you would have more comparative looks to build a picture.

However, if I am understanding the technique properly, a SAR equipped ship would be getting the large aperture effect through its' motion relative to the target, even if the target is not moving.


http://www.radartutorial.eu/20.airborne/ab07.en.html
https://en.wikipedia.org/wiki/Synthetic_aperture_radar

parallax doesn't matter whether the target or the observer is moving, just so long the view angle changes.

 

[kilemall]

parallax doesn't matter whether the target or the observer is moving, just so long the view angle changes.

My comment was relevant to your second sentence about something moving across the field.

So, all those bits of rules injected into 2300 and I'm gathering TNE about the exposed cross-section of the detected object to the detecting/targeting ship should probably also have a DM for relative bearing effects.

 

[aramis]

My comment was relevant to your second sentence about something moving across the field.

So, all those bits of rules injected into 2300 and I'm gathering TNE about the exposed cross-section of the detected object to the detecting/targeting ship should probably also have a DM for relative bearing effects.

Not bearing, but vector. Not actually synonyms, y'know.

The bearing won't matter nearly as much as the apparent motion, wich is based on the relative vectors.

 

[kilemall]

Not bearing, but vector. Not actually synonyms, y'know.

The bearing won't matter nearly as much as the apparent motion, wich is based on the relative vectors.

And bearing changes.

 

[jcrocker]

Radar has a problem with very long ranges. The reflected signal is proportional to (among other things) Power × Aperture / Range⁴, if I have understood it correctly.

To make a radar that can detect small spacecraft at 300 000 km range would take prodigious amounts of power and/or huge antennas.

I don't know CT power ratings, but to mix systems a bit, a Beowulf can generate 990 MW in MT. If it gets to a point where the ship needs an extra MW or two in order to get a firing solution on the pirate that wants to kill them, in most cases it's available.

Besides, if a ship needs an exact range for a target because they don't want the meson blast to miss, it's a warship that has a lot more generation capacity than that.

To mix systems a bit more, GURPS stats out the Tigress with a 2.9 TJ main battery, plus all of the other bells and whistles, which means that one ship can generate a sizeable fraction of what wikipedia tells me was the total electrical consumption of the USA in 2014.

These ships travel through jumpspace, some have portable black holes for shields, and generate ungodly amounts of power. The biggest violation of physics on these TL-15 ships isn't going to be the rangefinding abilities of a mature TL-5 or TL-6 technology.

 

[kilemall]

I don't know CT power ratings, but to mix systems a bit, a Beowulf can generate 990 MW in MT. If it gets to a point where the ship needs an extra MW or two in order to get a firing solution on the pirate that wants to kill them, in most cases it's available.

Assuming you accept Striker as a CT system, the starship translation bits using the standard of what a laser is, works out to HG 1 EP=250MW.

So a laser is 250 MW, a scout power plant is 500 MW, and a max power T spinal meson is 300 GW.

Now the question is, is that 250 MW constant or 250 MW per 1000-second turn?

You could say that means constant for both power output and weapon input, and it represents constant firing over the course of 1000 seconds, the hit percentage being the miniscule chance of effective hits ala Dilbert's conception of what is happening.

Or you could say it means one shot per 1000 seconds, dealing in the vast distances involved, and the rest of the time the weapons are being charged (or reloaded in the case of missiles).

This is less an academic/theoretical and more a gameplay mechanic taste when approaching this standard like I have been, wanting to create a power distribution/player decision/action game.

Further complicated by the ridiculously low ROF of missile weapons.

I have an answer that works for me for all this, but it does highlight the trouble with stretching game mechanics not designed for a particular game effect/theme beyond their parameters.

 

[jcrocker]

I think a problem with this is that, to the best of my knowledge, none of the original game designers were physicists, so if we look too closely 'under the hood' at some of the underlying assumptions, things start to break down a bit.

That doesn't affect how much fun and enjoyment all these people have gotten from Traveller in all of its forms over all of these decades, but it does mean we're not going to get absolute rock-hard science at the core of every single aspect of the game.

If targeting radar range is an upper limit someone wants in their game, then by all means, battles become knife-fights at closer ranges. Or distant strikes from extreme ranges become the norm - whatever is the most fun for that group of players.

 

[Carlobrand]

...

Now the question is, is that 250 MW constant or 250 MW per 1000-second turn?
...

I understood the watt to be defined as a joule per second, ergo a megawatt is a million joules per second.

 

[boomslang]

I understood the watt to be defined as a joule per second, ergo a megawatt is a million joules per second.

Thus, as (for example) per Striker, we are looking at 250MW/s steady output from those space-combat-rated lasers.

Which is rather a lot of energy and requires a hot fusion power plant to sustain continually.

 

[Carlobrand]

Thus, as (for example) per Striker, we are looking at 250MW/s steady output from those space-combat-rated lasers.

Which is rather a lot of energy and requires a hot fusion power plant to sustain continually.

Still debating the steady output thing, but we do know the ships have fusion plants.

 

[GypsyComet]

Assuming you accept Striker as a CT system, the starship translation bits using the standard of what a laser is, works out to HG 1 EP=250MW.

So a laser is 250 MW...

Every generation must rediscover the basis for MegaTraveller's craft system on its own. Must be a law of Traveller nature or something. Ships using the Striker/MT assumption for power don't just glow in the IR, they glow visibly.

 

[mike wightman]

Which is why I am convinced the missing magic technology of Traveller is the gravitic heat sink - something built into the grav plate and inertial compensation system that keeps the ship cool by removing the waste heat as artificial gravity potential or some such handwave.

A 250MW ship laser, just one, even if it is 99% efficient is going to dump 2.5MW of heat into your ship.
In the 'real world' that would be like having a thousand two bar electric fires scattered throughout your ship and switched on all the time.