What is the CEP of traveller beam weapons?

[Dragoner]

Space is kinda big and you can't look everywhere at once, and at the distances we are talking about from Trav's combat rules (which I intuit might be a bit whacking too far, but whatever).

I was reading bk2 before I went to sleep and came to the same conclusion about range. Missiles don't work at long range, the detection distances are 600,000 km for warships (150,000 km for civilian) and once detected, 900,000 km to maintain contact. The bk2 turn is a 1000 seconds or 17 minutes roughly, which means a missile incoming at 6g acceleration from 600,000 km would need 8.5 turns to make contact (using the travel times from bk2), more than enough turns to knock it down with multiple laser shots. Lasers traveling at the speed of light would cross this distance in seconds, there could be a miss with a smaller ship, as a few meters off could make a difference, though I wouldn't think it would make a difference with huge ships. This is counter intuitive to what HG says in that missiles are long range and beam weapons short range. I have a feeling though that combat speeds won't equal out to travel times, for example a 6g ship (or missile) will travel 60,000 km in a 1000 second turn which comes to 83 minutes to travel 300,000 km, 10 minutes more than the listed travel time, this isn't taking into account continuous acceleration, which to reach 600,000 km per turn it would still be 5 turns (there is still the missing 10 minutes). The calculations for rate of travel are somewhat different, after 4 turns it would have traveled 420,000 km (120,000 km over the 300,000 km mark) at a velocity of 240,000 km per turn for the distance of the 420,000 km traveled in 67 minutes, 6 less than the stated travel time but with an additional 120,000 km traveled.

With the various sensors (Aramis is right, there should be a luminal sensor), the probability is that there would be a range associated detection distance. Missiles would most likely have a multi-sensor guidance package. I can't help to think though that ships would have ways of casting an echo, or outright jamming to prevent being hit, esp at greater ranges. Ship's sensors would do a 360 degree spherical sweep constantly with anomalous readings getting tagged by the computer for an alert or more focus. The question would be how fast it can sweep an area.

A lot to think about.

 

[HG_B]

Ship's sensors would do a 360 degree spherical sweep constantly with anomalous readings getting tagged by the computer for an alert or more focus. The question would be how fast it can sweep an area.

A lot to think about.

At TL 7, a ship with 4 IR sensors could complete a 360 degree spherical sweep in ~1 hour. Ship would detect something like the shuttle maneuvering thrusters , out to about the Asteroid belt from Earth. At TL 15 I don't know how long it would take and what magnitude object could be seen from what distance.

 

[altasilvapuer]

Depends, you can't have an IR permeable hull if human life is supposed to exist inside it, nor is space one even temp (which is why the hull can't be permeable. This is also not including decoys, flares etc. as physical countermeasures to weapons lock, something which is done now.

You could have a signature of the light of the engine, and IR, but which travels faster? It still is sensor dependent.

One thing I've always wondered about IR radiation in space. Physics heads please correct me if I'm wrong, as it has been some time since I've studied even elementary physics.

If I remember correctly, though, glass of similar type to that used on modern automobiles is opaque to infrared radiation, correct? I've always been told that's why cars heat so much in the sunlight - most/all the rest of the EM spectrum passes right through the glass, but after it impacts the surfaces inside, it loses some of its energy to the transfer of energies and since the glass is opaque to IR, the IR does not escape the vehicle.

I've always wondered if there was some possibility here for limiting the visible signature of a ship. For example, let's hypothesize a ship in a region of space that is artificially removed of micrometeorites and other particles that could damage the glass, just for simplicity of argument. Surround that ship with some sort of super-advanced glass shell that is separated from the ship by a layer of vacuum. Because vacuum is an insulator and glass is opaque to IR, could this be said to have at least a limiting effect on the IR output of the ship?

Now, I recognize that there's a reason there's so little glass on modern spacecraft - we just can't build it to the necessary stresses of pressure differences and particle impact. But in Traveller where we're already positing advanced ways of creating armor (bonded superdense, et al), couldn't some of that tech theoretically have crossed over into glass-analogues?

Let's ignore the engineering problems for a moment, though. Do the physics at least check out, or have I forgotten something vital?

-asp

 

[HG_B]

Let's ignore the engineering problems for a moment, though. Do the physics at least check out, or have I forgotten something vital?

-asp

Let's say you create the ultimate thermos bottle space ship. You have heat producing activity inside. If you don't radiate heat, soon the inside of the ship turns to molten slag....

 

[altasilvapuer]

Let's say you create the ultimate thermos bottle space ship. You have heat producing activity inside. If you don't radiate heat, soon the inside of the ship turns to molten slag....

D'oh, true enough. I knew there was something that had shot that idea down before, but couldn't remember what it was at the moment. I seem to often post too quickly and forget even my own arguments for having shot things down.

And even if we supposed some sort of subspace-linked heat sink or somesuch as has been mentioned elsewhere, then we have no real need for the bottleships. Oh well. I'll probably just have to stick to some nice handwavium, then; it has a greater cost-effectiveness rate for the shipyard, anyway.

-asp

 

[Dragoner]

Ship would detect something like the shuttle maneuvering thrusters , out to about the Asteroid belt from Earth.

???

That is roughly 164,557,800 km (eg 1.1 AU) from the target or 183 times the max 900,000 km limit in bk2. Where is this from?

 

[Dragoner]

I've always wondered if there was some possibility here for limiting the visible signature of a ship. For example, let's hypothesize a ship in a region of space that is artificially removed of micrometeorites and other particles that could damage the glass, just for simplicity of argument. Surround that ship with some sort of super-advanced glass shell that is separated from the ship by a layer of vacuum. Because vacuum is an insulator and glass is opaque to IR, could this be said to have at least a limiting effect on the IR output of the ship?

Now, I recognize that there's a reason there's so little glass on modern spacecraft - we just can't build it to the necessary stresses of pressure differences and particle impact. But in Traveller where we're already positing advanced ways of creating armor (bonded superdense, et al), couldn't some of that tech theoretically have crossed over into glass-analogues?


-asp

I don't think IR is completely blocked by auto-glass, UV maybe. Problem is that starships do a lot of different things, like refueling in Gas Giants and it wouldn't be the heat getting out but heat getting in that would be the real problem. Interior heat can be dealt with by a heat exchanger and radiated or stored and radiated later.

There is a lot to think about here in that what is the background radiation and how the sensor works, a passive sensor will have a lag, esp with a ship that is moving at near C coming in at a pass to fire and then orbit, such as using a planetary body to swing back around.

 

[HG_B]

D'oh, true enough. I knew there was something that had shot that idea down before, but couldn't remember what it was at the moment. I seem to often post too quickly and forget even my own arguments for having shot things down.-asp

It's not like we do this for a living. I lose track from time to time also.

 

[fusor]

At TL 7, a ship with 4 IR sensors could complete a 360 degree spherical sweep in ~1 hour. Ship would detect something like the shuttle maneuvering thrusters , out to about the Asteroid belt from Earth.

Again, you are pulling numbers out of thin air with no backup or evidence. And again, you are ignoring the basic physics which I described earlier.

NASA's WISE spacecraft (also an IR telesope) took six months to complete an all-sky survey in 2010.

A 360 degree sky survey done in one hour would be too low resolution to identify anything. And even if it was done in any detail, there'd be far too much data to process in merely an hour.

I like how it is blindly assumed that data is magically instantly readable by users. It won't be. For starters, gigabytes (at least) of data will be coming in, which takes time to process. Some degree of processing will have to be done on all that data too, which will require computer time (and lots of computers). And then the data will have to be interpreted (presumably by humans). All of that would take time.

 

[whartung]

NASA's WISE spacecraft (also an IR telesope) took six months to complete an all-sky survey in 2010.

A 360 degree sky survey done in one hour would be too low resolution to identify anything. And even if it was done in any detail, there'd be far too much data to process in merely an hour.

Well, that's the riddle isn't it. The NASA survey was likely very high resolution as NASA tends to focus on very deep objects nowadays.

At the same time, an IR scan is likely fairly consistent from run to run (when you take in to account the motion of mapped objects). So, a lower resolution scan may be enough to identify "anomalies" (i.e. stuff that's different enough from earlier scans to be flagged), which can then be target with higher quality scanning devices. This might give a higher performance scan with less time.

 

[steventirey1985]

WISE also took only 1 picture every 11 seconds, and 8 images of each position. And was also trying to detect the infrared glow of brown dwarfs (coolest stars), other stars, and other galaxies. And could detect something as cool as 70 kelvin (-300 degrees F or -203 degrees C). Oh, and the biggest thing. They weren't in danger or threat of combat, and can afford to take time.

Ships would not care about detecting things around other stars, or even at the far edge of the system they are in. Even there, they are still so far away it would take a week to get to them.

So, given the fact that there would be no need to detect things as far away as WISE, and given that what they do want to find is so much closer and therefore the resolution doesn't have to be as great, and also given that were talking about a time 2 and a half thousand years from now, there should be no reason a ship can not scan its surroundings in a short amount of time.

Also, just by being in the system, the star will heat up the object to easily detectable levels. The space station and shuttles have to have special coatings to keep their surface temperature down to a "safe" 248 degrees F (120 degrees C). Bare metals can get as hot as 500 degrees F (260 degrees C). Compared to the background temp, things like that stick out like a sore thumb.

And before you accuse me of pulling number out of thin air, all my numbers come straight from NASA.

 

[fusor]

True, but how easy do you think it would be to make a 'combat-ready' full sky survey on a moving (or even accelerating, and continuously-vector-changing) spaceship? As you point out, you can't afford to take time in such a situation.

HG_B used an example of shuttle engines being detectable from the asteroid belt (1-2 AU away). Those are many orders of magnitude less powerful than 1 GW reactor, and would be even less detectable at such distances for the same reasons.

And sorry, but I don't buy the "it's the far future, a ship can magically scan its surroundings in a short amount of time" argument at all. They still have to deal with the same physical issues that get in the way for us today. How do they solve those problems?

 

[steventirey1985]

First, no one cares what is happening at 1 AU. That is 8 minutes away at even the speed of light. Even at 6G acceleration, that is still 30 hours away. Even the next planet down the line is 16 hours.

Second, as for movement, our satellites (and most other things in orbit) are already traveling around the earth at 17,000 miles per hour (27,200 kph). That is 7.5 kilometers per second, or 7500 meters per second. The extra 10-60 meters per second added from maneuver drive acceleration would not change a thing.

Third, I never claimed it was magic. But even our current technology would be considered magic to people 2 and a half thousand years ago. We know it isn't magic, its technology. But those ancient people wouldn't know the difference. Just like how, 2 and a half thousand years from now, their technology could seem like magic to us. Its not, of course. Just seems that way.

Asking how someone in the future would deal with those problems is like asking how someone 2.5 thousand years ago would deal with our current problems. We have better understanding, and can come up with solutions. Just like, 2.5 thousand years from now, they would probably have solutions to things that cause us problems. We don't have a clue what those would be, just like ancient man would have no clue how to solve our modern problems.

 

[fusor]

First, no one cares what is happening at 1 AU. That is 8 minutes away at even the speed of light. Even at 6G acceleration, that is still 30 hours away. Even the next planet down the line is 16 hours.

Yes, which is why I'm mystified that HG_B keeps bringing it up as if it's relevant.

Second, as for movement, our satellites (and most other things in orbit) are already traveling around the earth at 17,000 miles per hour (27,200 kph). That is 7.5 kilometers per second, or 7500 meters per second. The extra 10-60 meters per second added from maneuver drive acceleration would not change a thing.

It could change a lot, actually. Those satellites in orbit aren't accelerating (well, beyond what they might be doing naturally if they have an elliptical orbit). A ship going through evasive maneuvers or accelerating at 1-6G *is* accelerating significantly though, causing a lot of stress on what are probably exquisitely sensitive bearings and components, knocking them out of alignments and so on. When satellites are launched, their components tend to be locked down to avoid such damage by the launch accelerations and stresses.

If the sensors are automatically locked down the moment that accelerations start, that would imply that such scans won't actually be possible to do such searches in combat conditions. To me that makes a lot more sense than saying that it is possible to do full-sky surveys at sufficient resolution and process the data in less than an hour (by which time it's probably out of date anyway).

Third, I never claimed it was magic. But even our current technology would be considered magic to people 2 and a half thousand years ago. We know it isn't magic, its technology. But those ancient people wouldn't know the difference. Just like how, 2 and a half thousand years from now, their technology could seem like magic to us. Its not, of course. Just seems that way.

I would say we're much smarter than ancient people. There's no reason for us to just throw our arms in the air and say "it's the future! We can't figure it out!". We understand science and technology and the physical problems today well enough to propose solutions, even if they can't be built yet. I don't think we should sell ourselves short here

 

[steventirey1985]

It could change a lot, actually. Those satellites in orbit aren't accelerating (well, beyond what they might be doing naturally if they have an elliptical orbit). A ship going through evasive maneuvers or accelerating at 1-6G *is* accelerating significantly though, causing a lot of stress on what are probably exquisitely sensitive bearings and components, knocking them out of alignments and so on. When satellites are launched, their components tend to be locked down to avoid such damage by the launch accelerations and stresses.

If the sensors are automatically locked down the moment that accelerations start, that would imply that such scans won't actually be possible to do such searches in combat conditions. To me that makes a lot more sense than saying that it is possible to do full-sky surveys at sufficient resolution and process the data in less than an hour (by which time it's probably out of date anyway).

As someone already mentioned in an earlier post in this thread, a turret tracking a target at 30k kilometers needs to be so precise as to move only 0.0000334 degrees. Targets at longer ranges means the turrets have to be even more precise in their movements. Now, if a ship is "going through evasive maneuvers or acceleration, causing a lot of stress on what are probably exquisitely sensitive bearings and components, knocking them out of alignments and so on", and yet are able to still have such a very, very fine degree of precision control, there is no reason the sensors couldn't have that same treatment.

 

[HG_B]

Well, that's the riddle isn't it. The NASA survey was likely very high resolution as NASA tends to focus on very deep objects nowadays.

At the same time, an IR scan is likely fairly consistent from run to run (when you take in to account the motion of mapped objects). So, a lower resolution scan may be enough to identify "anomalies" (i.e. stuff that's different enough from earlier scans to be flagged), which can then be target with higher quality scanning devices. This might give a higher performance scan with less time.

Correct. I was referring to objects of apparent magnitude ~8-12 in the IR band. very bright and quick to scan for. NOT much dimmer, interstellar objects that take a longer exposure time.

 

[fusor]

Now, if a ship is "going through evasive maneuvers or acceleration, causing a lot of stress on what are probably exquisitely sensitive bearings and components, knocking them out of alignments and so on", and yet are able to still have such a very, very fine degree of precision control, there is no reason the sensors couldn't have that same treatment.

Thing is, that's an assumption. You're saying "we've figured that the turrets and sensors must be exquisitely sensitive, so they must be able to handle the stresses". We've established that they require that level of sensitivity to work, but that doesn't mean that they can survive the stresses of acceleration.

I'm saying the turrets and sensors are exquisitely sensitive, and so they are much more likely to be unable to handle the stresses without being locked down (and therefore not very useful while under acceleration). Combat would have to occur when the ship is NOT under acceleration. There's nothing preventing the ship from starting to accelerate once the sensors etc are locked down, but it seems to me that combat turns are more likely to be a sequence of "stop accelerating - take sensor readings - (optional: fire weapons) - lock down sensors and turrets - start accelerating" and repeat as required.

A solution to this might be to make the combat turn longer to allow a ship to allow it to do all that effectively. That does have some interesting implications - it means for example that a ship firing on a target cannot be accelerating or even changing its vector, which makes it easier to predict its position. But this won't be 'dogfights in space' by any means.

 

[HG_B]

As someone already mentioned in an earlier post in this thread, a turret tracking a target at 30k kilometers needs to be so precise as to move only 0.0000334 degrees. Targets at longer ranges means the turrets have to be even more precise in their movements. Now, if a ship is "going through evasive maneuvers or acceleration, causing a lot of stress on what are probably exquisitely sensitive bearings and components, knocking them out of alignments and so on", and yet are able to still have such a very, very fine degree of precision control, there is no reason the sensors couldn't have that same treatment.

Actually, in Trav people and ship eqip don't experience acceleration due to inertial comp & artificial grav.

 

[steventirey1985]

Thing is, that's an assumption. You're saying "we've figured that the turrets and sensors must be exquisitely sensitive, so they must be able to handle the stresses". We've established that they require that level of sensitivity to work, but that doesn't mean that they can survive the stresses of acceleration.

I'm saying the turrets and sensors are exquisitely sensitive, and so they are much more likely to be unable to handle the stresses without being locked down (and therefore not very useful while under acceleration). Combat would have to occur when the ship is NOT under acceleration. There's nothing preventing the ship from starting to accelerate once the sensors etc are locked down, but it seems to me that combat turns are more likely to be a sequence of "stop accelerating - take sensor readings - (optional: fire weapons) - lock down sensors and turrets - start accelerating" and repeat as required.

A solution to this might be to make the combat turn longer to allow a ship to allow it to do all that effectively. That does have some interesting implications - it means for example that a ship firing on a target cannot be accelerating or even changing its vector, which makes it easier to predict its position. But this won't be 'dogfights in space' by any means.

There is nothing in any Traveller version that indicates that a ship can not fire or use its sensors while accelerating. Nor that anything has to be "locked down" during acceleration. At least not that I am aware of. Nothing limits their use whatsoever. What this means is, is whatever stresses or problems that would arise in such a situation would have been removed by whatever technology they have.

You can say what you want. But the game says the exact opposite. Sensors and weapons can be used while accelerating, at no penalty, in the same exact way they can be used while stationary, so therefore they must be able to cope with whatever stress is caused and the movement of the ship. If acceleration and other stresses interfered with how they operate, than if would of been clearly stated it that it would. So while I may be assuming something based on what the books say, you are assuming something with no rules evidence other than "Well, I don't think it would work." Brecause while it is possible to rip holes in the fabric of space/time itself to send a ship across the stars, weapons capable of destroying stars, or to teleport vast distances with the power of your mind alone, it is apparently impossible to build a functioning sensor array.

 

[sabredog]

A solution to this might be to make the combat turn longer to allow a ship to allow it to do all that effectively. That does have some interesting implications - it means for example that a ship firing on a target cannot be accelerating or even changing its vector, which makes it easier to predict its position. But this won't be 'dogfights in space' by any means.

For the big line-of-battle type ships this would make things more sensible, but as ranges closed how would it affect this? Some weapons can't even be used unless at "close range" and some ... missiles....work better at long for some reason and are penalized at short even though short range isn't so close the usual suspects like detonating too close to the firing ship would apply.

Not mention a shorter flight time ought to make them harder to defend against since there would be less time to stop..slow down..take a bearing...line up the shot, etc..as you mentioned. Plus missiles are fire and forget little jobs - just salvo off hundreds of the buggers and they'll know what to do without having to go through anything more complicated for aiming than having the target types programmed into the guidance package on the missile - and it could even be prioritized.

So, should things maybe be reversed? Beams better at long. Missile worse at long. Beams get worse if you maneuver, and the closer you get the more dangerous all the weapons get offensively, but maybe not as defensive weapons? It knd of even works that way today.