and fancy things like "radar" dont exist?

Cornflakes_91 wrote:and fancy things like "radar" dont exist?

To be fair, we're not talking about a couple kilometres of ocean, we're talking about thousands of kilometres of EMPTY space, which would be substantially harder to use a RADAR like system in.

Black--Snow wrote: To be fair, we're not talking about a couple kilometres of ocean, we're talking about thousands of kilometres of EMPTY space, which would be substantially harder to use a RADAR like system in.

errr, EMPTY doesnt change the effectivity of RADAR, thousands of kilometres neither

Cornflakes_91 wrote:

Black--Snow wrote: To be fair, we're not talking about a couple kilometres of ocean, we're talking about thousands of kilometres of EMPTY space, which would be substantially harder to use a RADAR like system in.

errr, EMPTY doesnt change the effectivity of RADAR, thousands of kilometres neither

While being fully incompetent, I would guess that distance matters.
I assume the "ping" response is proportional to the proportion of the solid angle where an object reflects the radar. So if the object is far away, it will have a (inverse square?) smaller response.
So assuming that the scale of operation increases quicker than the square root of vessel sizes, the use of radar is indeed made more difficult with distance.
Very much so.

As the reflected signal will itself spread over a whole sphere (and be partially adsorbed as well) the energy needed is much higher to allow a signal/noise sufficient compred to an active transponder from the "target" ship.

Unless I would happen to be wrong?

CSE wrote:

Cornflakes_91 wrote:

Black--Snow wrote: To be fair, we're not talking about a couple kilometres of ocean, we're talking about thousands of kilometres of EMPTY space, which would be substantially harder to use a RADAR like system in.

errr, EMPTY doesnt change the effectivity of RADAR, thousands of kilometres neither

While being fully incompetent, I would guess that distance matters.
I assume the "ping" response is proportional to the proportion of the solid angle where an object reflects the radar. So if the object is far away, it will have a (inverse square?) smaller response.
So assuming that the scale of operation increases quicker than the square root of vessel sizes, the use of radar is indeed made more difficult with distance.
Very much so.

As the reflected signal will itself spread over a whole sphere (and be partially adsorbed as well) the energy needed is much higher to allow a signal/noise sufficient compred to an active transponder from the "target" ship.

Unless I would happen to be wrong?

Luckily we have toolsets that deal with RADAR already deployed in ships.

Yes, ping response would be lower when the ship is further away, but you know the inverse square law, and apply it to the response.
Empty space doesn't respond at all, so thats a feature.
So even the tiniest response at all means SOMETHING, with a cross section larger than the wavelength of the frequency used, is at a distance of (t*c)/2, where c is lightspeed, and t is the time of the response from the initial ping.

However modern radar is designed to work in 2D, so it swings around in a circle, slow enough that 2*(distance to horizon)/c = (angle of sweep);
Basically keeping the receiver in position to "listen" to the responses from the transmitter, while the transmitter is slightly ahead, this way you know the current angle of the transmitter, and receiver and can work out how long the ping took.
Without moving the receiver around you start getting ghosting from the return ping that hits something on the other side of your ship, then bounces back.
But with a slowly (usually in the order of a few seconds) revolving receiver/transmitter array, you can be sure of the direction, and can then ignore ghosting.

However in 3D space, you require another axis of rotation to be able to "see" the entire sphere of space you are looking at. Which is equivalent to t=(4πr^2) where r is the scanning radius in seconds. While on a circle it is simply t=(2πr), which is an increase of (2r) times the circular value.
You also need to take into account the angle you can scan at once, this is dependant upon the size of the wavelength, and is approximately equivalent to θ=sin(r / λ);

These two values taken together will then provide the approximate length of time to scan the skies around you!
And in space, this'll be 2r TIMES the time it takes on the ocean. (so taking on order of a hundred seconds for one !!short range!! sweep)




TL;DR?

Space is fecking massive, RADAR is slow as crap in space, you can detect anything larger than the wavelength of the radar, but smaller wavelengths create proportionally larger times to scan!

RADAR is best used to passively determine direction of enemy sweeps, then actively scan the direction the enemy is in.
LADAR is just RADAR with VERY small wavelengths

Distance doesn't just matter, it's a multiplier for the scanning time!

Assuming we're going to take a one-line, eye-rolling comment seriously, there are two points that could be made.

1. The points about about how real-world physics work are good. Distance does matter for active scans of objects because space is feckin' enormous. Audio from the Earth to the Moon takes 1.2 seconds at the speed of light; a little under 3 seconds for a round trip (as a scan "ping" and data response would require). Light from the Sun takes 8 minutes to reach the Earth.

So active scans of objects outside extreme visual range, if something like real-world physics is modeled, would probably take too long to come back to be fun as gameplay.

(Note that energy sources, like stars, can show up just fine on passive sensors at great distances as they're continuously radiating across many spectral frequencies.)

2. LT is a game, so you certainly could just ignore this and say "sensors are magic and can see anything anywhere." That would probably be fun.

Sensors for passive data collection and scanners (sending a short-range signal that gets bounced back) for active data collection could be fun, too.

Problem?

Flatfingers wrote:[What if "sensors" are generally passive and always-running detectors of long-range energy sources, while "scans" are an active interrogation of relatively nearby objects and energy sources through a deliberately-activated ping?

Suppose that "running a scan" has the following effects:

• Depending on distance to target, research level of the scanner, and the power used, a scan can reveal:
  • target ship's true size
  • target ship's general maximum possible power generation
  • average research level of target ship's major components
  • identification of a random number of items in the target ship's cargo hold (poss. incl. contraband)
• target ship is notified that they're being scanned
• scanning ship is clearly highlighted in the target ship's sensors
• running a scan disables the scanning ship's shields for several seconds

There might be more features, but a design similar to this would seem to me to offer some interesting gameplay choices between sticking with sensors (mostly passive) and firing off a deep scan (very definitely active).

Just a small comment to say that Rebel Galaxy had a very similar mechanic, whereby a user-initiated scan would reveal additional items in the vicinity of your ship. To be honest I didn't find it a particularly worthwhile addition - the items could simply have been shown on the map/radar with little impact on gameplay.

Flatfingers wrote:Assuming we're going to take a one-line, eye-rolling comment seriously, there are two points that could be made.

1. The points about about how real-world physics work are good. Distance does matter for active scans of objects because space is feckin' enormous. Audio from the Earth to the Moon takes 1.2 seconds at the speed of light; a little under 3 seconds for a round trip (as a scan "ping" and data response would require). Light from the Sun takes 8 minutes to reach the Earth.

So active scans of objects outside extreme visual range, if something like real-world physics is modeled, would probably take too long to come back to be fun as gameplay.

(Note that energy sources, like stars, can show up just fine on passive sensors at great distances as they're continuously radiating across many spectral frequencies.)

2. LT is a game, so you certainly could just ignore this and say "sensors are magic and can see anything anywhere." That would probably be fun.

Sensors for passive data collection and scanners (sending a short-range signal that gets bounced back) for active data collection could be fun, too.

Problem?

See I would just use sensors range as the limit for simulating ships in reasonable levels of accuracy, outside that they can be quite fuzzy. :V
It's an obvious sphere, that increases with tech level and power, and can be gathered from a reverse calculation of time to cover the sphere.
(say you want to cover the sphere in 5-10 seconds, then you just need to calculate for that radius, and everything inside gets a icon, and you only check to see if items enter that sphere once every 5-10 seconds. )

The real-world physics can give rise to gameplay mechanics this way

First: sorry flat if that came across disrespectful or anything, just didnt have more to say at that point which i didnt already outline somewhere else.

Flatfingers wrote: So active scans of objects outside extreme visual range, if something like real-world physics is modeled, would probably take too long to come back to be fun as gameplay.

+1 for ignoring light speed delay.

Flatfingers wrote: (Note that energy sources, like stars, can show up just fine on passive sensors at great distances as they're continuously radiating across many spectral frequencies.)

You forgot the important point, enormous power output

Flatfingers wrote: Sensors for passive data collection and scanners (sending a short-range signal that gets bounced back) for active data collection could be fun, too.

Problem?

Yes, the hard cut is my problem

I'd rather have a flowing scale between "completely passive" and "highly invasive scan".

on the low power end you have the fully passive listener.
Finds things when they are hot enough without needing much (any?) power. But doesnt give you any info over anything thats not radiating, so you wont detect inert objects and deactivated equipment.

Then theres the wide intermediate band of "radar", active emitters that put power out in space and illuminate objects around you, making them easier to detect for your passive sensors while also increasing the diversity of information as you can detect more than actively radiating objects.
You detect 'roids and inert ships from much further out, maybe even at all, and get some composition and inactive equipment/cargo data.
But a general "long range" radar wont give you detailed data because they use coarse emission with fuzzily defined spectra, but they give you the power output to get some range out of them.
This will of course light up your ship, but if you are lucky and have a good receiver compared to the other ships, they may not detect you.

On the "intrusive" end of active emitters is the equivalent of your scanner, flat.
A comparatively low power emitter, but with high spatial and spectral resolution to extract all the info out of an object.
At the range where its useful the scanner will shine brightly and may result in some reaction of the scanned object.


so theres still specialised scanners without the hard border, and everyone can at least attempt to get some data out of something when he finds something interesting
like an ore transport finding some strangely colored 'roid, or a freelancer stumbling over some wrecks are still able to get some data out of their objects of interest without being forced to mount speciality equipment for edge cases.
and the ones with special needs get their speciality sensors can have them without any special cases in game mechanics.

a pirate goes "dark" by turning off the active part of his sensor suite,
a miner has his medium range, medium precision scanners for glancing at rocks,
a police ship will have something similar to generally check on ships plus a high precision scanner for concrete suspects
a surveillance station has a big, coarse, high power array to see every ship (to be controlled by mobile forces)

all in one system without extra cases for scanners or passive sensors or anything.

Silverware wrote: The real-world physics can give rise to gameplay mechanics this way

to be honest, what would give us that delay mechanic? it doesnt add anything to play with, why bother?

Thanks Silverware, for the explanations. I guess I got intuitively the "further away = less sharp" ok (I agree you can correct the signal to account for distance using the delay. But this won't help discriminate against "noise"). But I completely missed the sweep time.

Cornflakes_91 wrote:This will of course light up your ship, but if you are lucky and have a good receiver compared to the other ships, they may not detect you.

This part still is fuzzy for me.

First without sweep:
let's assume I get a power of 1 GW out (as "point light", so evenly distributed among the whole sphere). Let's further assume that the other ship I "see" with my ping has a cross section of 100m2 (which is already a nice ship! Bigger than a fighter) and is 1000km away.
Then this cross section is less than 8.10^12% of the area of my sphere, thus it recieves ca 80 microW. That's obviously lost in the noise.

OK, then obviously I understand why we need a sweep :
So in my sweep, let's assume I have a 1° spread. The power is now round 4000x more concentrated, so I get 0.3 W on the target. Perhaps enough to be spotted by my target. But if I get (due to absorption, and reflections in several direction as the ship is not a mirror wall exactly perpendicular to my ping), I will get only a fraction of this power in return and I will not be able to see it against noise.
Even if I focus my sweep better, the target will always have several order of magnitudes more power than I get. So It is unliekly that any modern ship (of course, if it has no sensors....) will miss a ping large enough to convey the message back to the emitter.

unless.... I missed something again

Sorry for derailing the thread with irrelevant details, it is just interessant

Your numbers sound about right, yeah.

but realistic detection in a space game is no fun from the very beginning as you only need infrared cameras to detect pretty much anything that has life support or a drive system

CF is entirely correct.
The best method of detecting incoming enemy forces is infrared cameras covering the hull pointing in each direction.
This is a passive sensor with massive range in space, as even the coldest spaceship is lit up like a nuclear bomb going off (fission not fusion)

Then you can just sweep that direction with some active RADAR pings, or LADAR pings for more resolution, and boom instant detection of hot objects.

However most of what is in space is not spaceships, it's rocks, and dust, and screws, and bullets that were fired a hundred years ago orbiting in the wrong direction. :V

These require active LADAR/RADAR to detect, or correct positioning in regards to the star(s).
You should be able to scan only a tiny sector of space for these though, a thousand kilometers is more than enough.