Looking for Commonalities

[robject]

Traveller is, from a Mahanian analysis, entirely pelagic.

What Wil said. Every system is a tiny island on an eternal sea. And each island is at least one week distant from its closest neighbors.

There are no true roadblocks, except perhaps fuel (which we haven't told Michael about, yet):

Jump drives -- the engines used for interstellar travel -- are fuel hogs. To jump one parsec, a ship must devote about 10% of its volume to jump fuel. This fuel is burned to rip a hole into jumpspace and dump the ship into its trajectory to a target world. A bright jump flash flares at the entry point.

We can't communicate with realspace from jumpspace. We don't even know what jumpspace is. Space opera. Probably not subspace (Babylon 5) nor wormhole-space. Definitely not warp (Trek), nor a space folding device (Dune). Not like the charted-routes of Star Wars' hyperspace; jumpspace can be entered any point further than 100 diameters from a significant volume/mass (such as a star, planet, moon, or even another ship).

One week later, plus or minus a handful of hours, the ship emerges, with another jump flash, at its destination.



So, fuel requirements are designed on purpose to be a limitation for everything interstellar. It affects how far your ships can travel, versus how much payload they can carry. A gigantic dreadnought has a logistics problem if it can't refuel. It needs tanker squadrons and expensive and brittle supply lines, or a local source.

Enter oort clouds and gas giants, both of which are useful sources of fuel. Gas giants are closer to a target mainworld (for example), but are also likely to be heavily defended. Oort clouds, on the other hand, cannot be rigorously defended, and are a bountiful source of ice, but are a long ways from your target -- and the mainworld will know you've arrived via your huge number of jump flashes showing up clustered around a particular target time. Surprise (if it's important) is lost.



These fuel requirements also work with drive capabilities to limit the practical maximum size of an interstellar empire (about ten thousand star systems, centered on a capital system). Granted, that size is still staggeringly huge for any individual to deal with.

 

[robject]

There is one geographic feature: stellar density.

The average density is one star system every other parsec. A subsector map has around 30 to 40 star systems on average, out of 80 parsec-sized hexes.

There are some areas where the density is extremely low, as in one or two star systems per thousand hexes. These are, essentially, "mountain ranges": generally uncrossable without extensive and expensive supply lines, or sufficiently high tech. Slow going at any rate.

 

[Condottiere]

In theory, there are not enough ships assigned to a Sector to really defend every world.

As regards mutually assured destruction, Solomani ideology would prevent them from doing that to human worlds that they want to recover, as long as it isn't strategic and being heavily defended, since their objective is to recover lost territory, not dead worlds.

Diplomatic consideration may prevent them doing it to the Cats.

 

[esampson]

So what stops Mutually Assured Planetary Destruction. If my homeworld is hit by an assault an defense is impossible, it means the next option is destroying their homeworld with everything I have. If distance matters not, the Space Triad goes live and Space Combat is no longer an Opera battle, but a hot potato match.

Reaching an enemy's 'homeworld' would be nearly impossible. For the most part ships are capable of jumping from 1 to 6 parsecs at a cost of 10 to 60 percent of their volume in fuel. Using detachable fuel pods a ships could, in theory, burn up 60% of its volume, eject the pod, and jump 6 parsecs. It could then burn another 60% of its volume out of its internal supplies and jump another 6 parsecs. At that point it is absolutely impossible for the ship to have 40% of its volume in fuel. Space has to be taken up by drives, the bridge, quarters, and weapons, so at absolute best a ship could only burn another 30% of its volume (and I'm doubtful of that. In all likelihood it would be limited to 20% or less because drives, quarters, etc. would take up too much of the ship, but lets go with 30% in case I'm wrong) and jump another 3 parsecs.

That's 15 parsecs at which point a ship would absolutely have to refuel. There is simply no way for the ship to go further without refueling. Now if you go to http://travellermap.com/?x=6.351&y=7.112&scale=4.140625 you can see how large the Imperium is. Each of those large squares is 32 parsecs wide and 40 parsecs tall. Our theoretical ship can only cross half of one of those and has no room for weapons or defenses.

Typically, a battle is launched from 4 parsecs away or less so the only systems in danger are those around the periphery. The invading force would have to capture the system, repair, refuel, rearm, and then launch again. Each time it does this it will suffer losses. It is also pretty much unthinkable that people won't be able to jump out of the system to warn nearby systems of the invading forces, so the element of surprise will quickly be lost.

Hell I don't even have hit the home world. I just target the bread world *those that feed the Empire with people, food, money, or strategic resources.*

If there are 'bread worlds' (something which people debate) then there are an awful lot of them. It's dangerous to look at the map of the Imperium and think of it as sort of 'space Europe' in size. In the medieval ages it would take roughly 2 months to travel from London to Rome on horseback. This was more or less normal travel and not the fastest that could be done with relays of horses (it was also far from the slowest as people on foot and heavy wagons could definitely take longer). In contrast it would take 28 weeks of Jump-6 travel (fastest possible) to go from Ruby to Capital.

In short, space is really big.

Also, destroying planets is really, really hard. Ships most likely don't carry enough ordnance to do it. Yes, we had enough missiles on Earth to do that, but that was something on the order of 60,000 warheads that were on missiles significantly bigger than those used by ships in Traveller. It might be possible, if an attacker gained 'space superiority' to probably scour the surface by firing asteroids at the planet but even that would take a tremendously long time to completely cover the surface and before that there's a good chance a counter-attack fleet would arrive.

Actually, why not detonate my gas giants in a doomed situation?

Detonating gas giants is well beyond the capabilities of people in Traveller. Doing so would take almost unimaginable amounts of energy. Probably something on the order of the amount of energy put out by a star for a prolonged period of time.

Realize, my education and professional training has me think like a dangerous monster with nothing left to lose, as a way to counter and stop actual dangerous monsters. If this is the Opera, as the bad guy, it is my job to commit as many atrocities as possible and break the morale of the good guy by the evil I carry out.

And honestly, espionage has to occur to protect these empires. Rarely do you have a last minute invasion. It would seem more appropriate for the setting that Big Battles occur rarely and rather skirmishes and spy operations are more frequent.

I definitely agree with this. Most 'warfare' between empires is probably cloak and dagger as opposed to direct conflict. It's just too expensive.

But in reality, stealth is always possible. No boarding action, no piracy, no insane raiders on the fringe? No computer attacks from a double agent 40 hours prior to attack? Has there not been an evil megalomaniac trying to brutally conquer the known universe?

The reality is that there is probably a critical 24 hours before each invasion where spies can either save the system or doom it.

Most arguments about stealth are addressed here: http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--There_Ain't_No_Stealth_In_Space. I should note that I do take some issue with the writer's tone of 'I don't know any way it would be done so it can't be done' because it smacks of the calculations some scientists use to make to show that it was impossible for a vehicle to travel faster than the speed of sound. Still, it does show that as far as we currently know there is no way to do it.

 

[Meeko100]

I'd say stealth in space is less about "being invisible" and more about "being as small as possible and hoping your forgot about"

There's a limit on how small a thing you can detect. Presumably. Can you detect each and every asteroid in the belt from Earth orbit?If IYTU that's feasible, then stealth is not feasible. But a small enough ship, reducing its sensor size to even smaller, at a far enough distance could feasibly be nothing really to see. A vessel that absorbs the majority of radar and lidar waves and is far enough away to prevent itself from being spotted by visual and IR scans, while not invisible, would be very hard to spot.

It'd be a specialty ship, all designed to reduce and eliminate emissions and reflections. And it'd need to avoid being close to other vessels that it might start appearing on sensors with some degree of fidelity.

The OTUs densometer kills the idea ("there's a source of gravity there sir. Its not appearing on any other sensors." "its the enemy, they're hiding!"), but its reasonable otherwise.

But this isn't thread isn't about stealth, is it? I should be away.

 

[Archangel620]

I'd say stealth in space is less about "being invisible" and more about "being as small as possible and hoping your forgot about"

There's a limit on how small a thing you can detect. Presumably. Can you detect each and every asteroid in the belt from Earth orbit?If IYTU that's feasible, then stealth is not feasible. But a small enough ship, reducing its sensor size to even smaller, at a far enough distance could feasibly be nothing really to see. A vessel that absorbs the majority of radar and lidar waves and is far enough away to prevent itself from being spotted by visual and IR scans, while not invisible, would be very hard to spot.

It'd be a specialty ship, all designed to reduce and eliminate emissions and reflections. And it'd need to avoid being close to other vessels that it might start appearing on sensors with some degree of fidelity.

The OTUs densometer kills the idea ("there's a source of gravity there sir. Its not appearing on any other sensors." "its the enemy, they're hiding!"), but its reasonable otherwise.

But this isn't thread isn't about stealth, is it? I should be away.

The thread was about strategy of ship combat, so it is interesting to consider the "fire ship" strategy, where a specific group, not necessarily a nation, but rebels or whatever, might invest in this simply for the sake of reducing the cost of ship maintenance, and fuel.

Which by the way, OUCH, on the fuel. That is very important to know. Gas Giants, do they not run out to some extent, or is the fuel taken replaced naturally?

I think I am admittedly getting lost in the details, so let me try to abbreviate what has been told to me.

1) Technology limits fuel capacity and efficiency
2) Technology limits the operational time of combat missions
3) Technology limits communication and therefore supply lines and typical travel routes for couriers are prone to either attack or fierce guarding
4) Spying relies on old style months long and years long missions. So basically double agents and counter-espionage are practiced to try and delay the inevitable galactic war.
5) Ships can be small, and ships are expensive. Ships are not seen as expendable, but crews are.
6) We assume galactic economy and technology let's every world that is developed and at the peak TL can feed itself.
7) Ships do not engage in big battles, unless something significant happens. More than likely skirmishes occur between first waves and scouts, either intentionally to provoke, or accidentally due to a lack of FTL communications.
8) The description as every planetary or satellite as an island is actually how I described the ISS and the moon in my Master's Thesis.

Now, I saw earlier someone put up the three strategies for building a fleet, and I noticed the carrier vs. battleship dilemma. Are space carriers currently cost prohibitive, or feasible in the setting?

 

[Archangel620]

And I hope everyone realizes I have not been belligerent in intention, this has actually been really helpful. It helps me understand when I read how wars broke out or were fought, why they occurred that way.

Thanks everyone!

 

[warwizard]

The concept of fighters depends heavily on if you consider the no stealth in space to be the Rule. In my case I subscribe to the sensor rules found within TNE's Fire Fusion & Steel as modified by the errata: a weak enough signal far enough away cannot be detected, with rules for specifying exactly how weak and how far away the thing needs to be undetectable by a given sensor. This interpretation opens the door to the drone carrier scouting platform based on a long endurance small craft with low observables features that deploy long range long endurance drones that sport minimal passive sensors and a 1000 AU tight beam laser com, and a simple flight computer. In this paradigm you would launch your scouts to pass many light hours from the objects of interest and they would launch their 50 g capable drones that can obtain a high vector past the area of interest and have 50 g's of evasion to force a recon past the point of target lock where a conventional fighter would just die. The defenses would have honor harringtonesque laser clusters capable of firing hundreds of minimally damaging shots per second out to .5 light seconds, minimally damaging is at least 1 or 2 damage points where a damage point can mission kill up to 5 metric tons of equipment (but only causes system resets on 20+ mt equipment as per Brilliant Lances) even if the drone is armored to withstand 10 damage, there are still surface mounted mission critical items such as the sensor, the laser communicator emitter and antenna, the HEPLAR nozzles and the reactor cooling fins that will get hit after you shoot enough times at it.

So the old job of a cruiser at Jutland, which is to find the enemy, is taken up by the force of small craft with drones, which are able to survive into target lock range and hand off the target locks to other platforms that can maintain the target locks so obtained at 100 times the distance needed to obtain the locks. (another set of high agility drones with good sized LADAR active tracker)
This allows the fleet to vector missiles in from outside detection range and hand off the target locks to the missile's onboard tracker for terminal attack maneuvers. So the forward edge of battle becomes one of drones versus small point defense weapon systems. The drones trying to sneak or force their way to target lock the fleets valuable assets, and the defenders attempting to destroy, mission kill or spoof the drones.

If anyone cares I can back up my 50+ G drone designs with TNE FF&S. They quite change the nature of space warfare as originally set forth in the LBB rules.

A TL-F pirate/ commerce raider will be able to detect track and fire upon the TL B free trader without the free trader knowing anything is afoot till they detect a missile (or drone) heading at them at 10% the speed of light (50 g's for 2 hours) or 1 second per 30,000 Km, the missile only needs to get within 15,000 Km for it's nuclear bomb pumped X-Ray laser head to fire, and those X-Ray lasers will drill holes right through the free trader, yeah and the sand canister they threw as well. There is a poor chance that a single missile hit will mission kill the ship, as between cargo, fuel tanks, and crew quarters , some 75% of the ship's volume is non-essential.

 

[mike wightman]

Carriers carrying fighter class ships are a waste of time at the higher TLs due to the total ineffectiveness of fighters in the line of battle. They do have their uses as a scouting force, and for planetary attacks.

The more useful type of carrier for the line of battle is the tender which carries ships called battle riders into combat.

The tender has the jump engines and fuel to provide strategic mobility, the battle rider does not usually have a jump engine or fuel of its own so all of its hull is available for weapons, screens, armour and manoeuvring engines.

The tenders are usually left in reserve or even in the outsystem.

Tenders can be huge up to 1000000st being described in canon, while the riders can be anything from 20000dt to 50000dt.

Battleships have the advantage in that if they are losing a battle they can jump away, battleriders can only escape by fleeing to the outsystem.

 

[mike wightman]

And I hope everyone realizes I have not been belligerent in intention, this has actually been really helpful. It helps me understand when I read how wars broke out or were fought, why they occurred that way.

Thanks everyone!

You are most welcome - it is an interesting discussion.

Be careful about historical and real world analogues though. Too many people fall into the trap of saying ship combat is like 'sub hunting' or some such paradigm and before long they are trying to use the model they are using as an analogy to explain the combat.

Space warfare in Traveller boils down to:

strategic movement, limited to one jump per week plus refuelling time
communication between systems is at the speed of your courier ships
battles only occur when both sides decide to fight each other or when one side has no choice

The battles themselves change in nature as you advance from TL to TL.

At low TLs fighters and fighter carriers can have a big impact, missile bays decide who wins.
At the mid TLs as computers get more powerful the small fighter can no longer hold its place in the line of battle and the weapon of choice for the battleships becomes the spinal particle accelerator, although missile bays still have a use. While the meson gun exists at this TL range they are difficult to hit and penetrate - you may get lucky but more likely you will never land a meson shot.
At the top end of the TL scale the meson gun starts to become a viable option (and a TL15 meson armed fleet can tear apart a TL14 or lower enemy) but for TL15 vs TL15 a mix of missiles, PA spinals and meson spinals are needed.

 

[Condottiere]

Communications lag does promote classical commerce raiding.

Trying to refuel at a gas giant is similar to submarine warfare, as prepositioned SDBs rise like barracudas to the upper atmosphere.

Stealth will be determined by game mechanics, as it is a capability that you'd want to incorporate.

 

[Nathan Brazil]

Which by the way, OUCH, on the fuel. That is very important to know. Gas Giants, do they not run out to some extent, or is the fuel taken replaced naturally?

The fuel is hydrogen, either refined/purified or not. In absolute science terms, Giants Giants have finite amounts of hydrogen and do not replenish, but for the practical purposes of stellar civilizations over the course of thousands of years they are effectively infinite. Jupiter masses like 1x10E24 tons and a dreadnought might grab 1x10E6 tons. Enough for around 1 quintillion refuels.

3) Technology limits communication and therefore supply lines and typical travel routes for couriers are prone to either attack or fierce guarding

(I canna break the laws of physics Captain - Scotty)
Technology in the timeframe we talk about cannot overcome the barrier that communication is at lightspeed or the speed of travel. 168 hours +/- 10% or so to a location within 6 parsecs away. Another 168 hours +/- 10% to get a response. Everything in the game or setting is impacted/limited by this. War at the operational level, communication, governance of worlds, economics and so on. Once that permeates into your thinking much of the setting falls into place.
There is Opera, to use your term, that ancient civs in the setting did find ways to circumvent that law, but the current civilizations do not have it, and as written do not develop it in the time frame we talk of.

Welcome Michael. I hope you enjoy discusssion with we crusty grognards.

 

[Selandia]

Communications lag does promote classical commerce raiding.

Amen ...as well as classical piracy

Trying to refuel at a gas giant is similar to submarine warfare, as prepositioned SDBs rise like barracudas to the upper atmosphere.

interesting analogy that force me to clarify my belief that there is no submarine warfare in Traveller's space combat, - hence my circa 1900 naval combat classification of TU Space battle-.

A) There is no submarine warfare in interplanetary combat.

B) Once you get to the athmosphere of a planet (athmospheric combat), Gaz giant or otherwise, its a multi fluid (gazeous, liquid, with various interfacing conditions) environment that may be rich in exoctic echographic, IR or EM local phenomenons known only (or best) by the defenders. You then have "Terrain" effect, like shoals and less well known reefs in costal combat.

SDB would not be like submarine but "flying submersible" as they are able to move freely between gazeous and liquid environments, operate indefinitely in both and probably wage war from the interface zone where they benefit from liquid cover while being able to "see" or strike (when benefited) from the gazeous zone by intermitent "surface peek". So we are here in solid Sci-Fi. Modern naval warfare might be the closest... even if a bit short for lack of flying submarine

Trav space combat isn't -tactically- really pelagic inasmuch as the space around the island and the space between the islands is water. There is athm around the planet but not between the planets. Strategically, yes why not.

have fun

Selandia

 

[esampson]

I'd say stealth in space is less about "being invisible" and more about "being as small as possible and hoping your forgot about"

There's a limit on how small a thing you can detect. Presumably. Can you detect each and every asteroid in the belt from Earth orbit?If IYTU that's feasible, then stealth is not feasible. But a small enough ship, reducing its sensor size to even smaller, at a far enough distance could feasibly be nothing really to see. A vessel that absorbs the majority of radar and lidar waves and is far enough away to prevent itself from being spotted by visual and IR scans, while not invisible, would be very hard to spot.

It'd be a specialty ship, all designed to reduce and eliminate emissions and reflections. And it'd need to avoid being close to other vessels that it might start appearing on sensors with some degree of fidelity.

The OTUs densometer kills the idea ("there's a source of gravity there sir. Its not appearing on any other sensors." "its the enemy, they're hiding!"), but its reasonable otherwise.

But this isn't thread isn't about stealth, is it? I should be away.

One of the biggest issues with a space ship is its heat. Asteroids produce no heat and so are difficult to spot. A ship, on the other hand, produces a lot of heat. The interior of the ship is close to 300 degrees above the near absolute zero of space. Even with reasonable insulation some of that heat leaks out into space as infrared radiation and has to be replenished by life support.

What about unreasonable amounts of insulation? What if the ship has absolutely perfect insulation? In that case everyone on the ship dies. Human beings produce heat. Since none of that energy can escape due to the perfect insulation the interior will continue to heat up until everyone roasts to death, and that's an absolutely best case. In reality far more heat will be generated by the power plant, life support (it has to do more than heat the ship), lighting, etc. and all of that heat energy will have to be removed from the ship.

So the absolute minimum amount of energy the ship has to emit is equal to the heat produced by the crew (about 100 watts per person) plus the heat produced by the mechanisms of the ship. Of course that setup assumes perfect or near perfect insulation. In such a setup a ship beyond Pluto that suffers life support failure actually begins to heat up inside (or at least remains close to the same temperature). Usually we imagine ships in that situation as getting very cold and the crew forced to don vacc suits or cold weather gear. This means that the ship's life support is generating extra heat to offset energy that escapes.

But that amount of energy isn't really that significant, right? A couple of kilowatts out millions of kilometers away isn't going to be detected. Well, we detect signals from the Voyager 1 space probe at a distance of 18 billion kilometers and its signal is only 20 watts, and that's with TL 8 equipment.

Now again, I don't personally think that means that stealth is a complete impossibility. In theory you could design a ship with extremely high insulation and then add radiators to deal with normal heat buildup. When the ship 'runs silent' the radiators are closed off and the ship stores the heat internally via some sort of sink (such as liquid hydrogen which will absorb a pretty large amount of heat). However, it is considerably more complicated than a coat of radar absorbing material and some electronics.

 

[warwizard]

But that amount of energy isn't really that significant, right? A couple of kilowatts out millions of kilometers away isn't going to be detected. Well, we detect signals from the Voyager 1 space probe at a distance of 18 billion kilometers and its signal is only 20 watts, and that's with TL 8 equipment.

QUOTE]

Actually that is not a fair example, we know the course of that object to a fine certainty having made measurements of it's trajectory for the past 40 years or so. It's a tracking job not a detection job, we are using a very small field of view sensor that is pointed exactly where we expect it to be. A more fair detection task is the search for near earth objects that may be on trajectories to come near or impact earth, and these objects are receiving heat from the sun at a rate of: measured by satellite as being 1.361 kilowatts per square meter, and yet some bus sized objects (3 to 4 Dt) manage to approach to within hours of their closest approach before being detected.

 

[Meeko100]

Well, the issue of heat is the main issue.

However, I also think that somebody came up with the idea that the external surface of a ship is the temp of most space objects. 2 K? I don't recall perfectly. That may not be right. But the rather large amount of liquid hydrogen probably could provide a large sink (at least 10% for starships, likely more for military ships. Heck, J2 is pretty standard for a lot of designs), just for a short while until it'd need to dissipate on some planet or asteroid.

I imagine some highly engineered stealth ship, with heat sinks and such could in theory be stealthy. With Batteries to run the ship, and turning off the fusion plant to reduce heat. It be a specialty design, no doubt. But its possible I think.

So a Thermal Sink, combined with EM absorbing coating and some smart maneuvering around other vessels, and stealth may be possible. It may be a marginal chance of being undetected, but better then being clear as day. Worth noting you wouldn't be able to stealth attack, unless you jumped in far enough out, and were able to "fade" from view and get away from your jump point to hide before the other ships get in range to get a clear scan on your ship.

Stealth would mostly be for small defending ships, maybe acting as hidden recon ships sending encoded messages through civilian channels to command, or to have some elite marine types hidden somewhere just to pop up and give the occupying guys a bad time. In a SSU, it could counterattack by itself, but I have doubts that you could hide a larger ship from detection at all. Maybe though. Depends on tech paradigms and what your ships can pull.

BUT YES, IT WOULD BE HARD TO DO.

 

[Meeko100]

If fighters are also being discussed, I'd say that unless you have some way to mitigate damage other then something that would need to get fixed then fighters may be less FIGHTer, and more recon craft for getting close scans and fixes on hostile ships. The idea of sending a small ship to go get beat up and potentially destroyed in battle when the exact same drive system in theory could just carry a really frickin huge bomb and blast whatever is on the other end to bits.

Forcefields or Shielding would make something like a fighter feasible in that it could get hit lightly, and then leave an not take permanent damage. A Fighter with laser and shields would be a nice idea compared to a massive bomb. Keeps your expensive carrier a nice 5 or so light seconds away, dodging about to prevent a good hit from landing (You'd need a 10 second lead on the target at 5 ls. 10 seconds hoping that very little changes on that ships course, assuming energy weapons. Missiles and you can just PD them.), but also still have a attack be laid on the enemy. The fighters just have to be tough enough to not get smeared by PD, and the mass of fire from the fighters could be enough to overcome the capitals (presumed) shields, or just bypass them completely with a something like missiles that may not be affected. (Yes, I know the OTU has repulsors that kill missiles, and that Beams are the ones that are free to blast, but fighters already need a lot of changing to be fighters in the sense Hollywood likes to think of them as.)

Fighters would likely have to be flown by humans, or by rather advanced computers that are smart enough to fly and perhaps dogfight with other fighters like a human would. The possible lag from fighter to carrier would make drones unfeasible, except as recon craft or dumb gun carriers.

Any small craft from the Traveller RAW likely are as the other folk have described, large(r) torpedo ships that intend to launch torps from a distance that makes PD hard, and to ensure that they don't get blapped from long distance on the way there. They don't have staying power to keep in the fight and they wouldn't have the ammunition anyway. Heavy armor would require heavy hitting to push through and most small craft don't have the armament necessary to fight a battle ship with maxed armor, unless they resort to having limited ammo. Carriers and Fighters (Bombers may be more appropriate to what they do, with Torpedo Boat being nice and specific) may be dragged along to have a sudden wave of hard to stop torpedoes pop out of the fighters, or to provide CAS for Planetary Assault, but they would be Auxiliaries to the Battleships and Cruisers for fighting.

So, as a summary; Fighters with Shields, feasible as small light ships that can be a persistent threat on the battlefield, considering the other changes that some form of shield would have on ship design (lighter immediate armor, shields taking the place of the lost armor). Fighters without shields, short wave of firepower that then have to rearm.

In a OTU world (which I get the feeling is what was mostly being discussed), fighters are going to be auxiliaries there to perform jobs other then fighting the big capital ships. Battleships win the Space, Fighters win the Planets.

 

[esampson]

But that amount of energy isn't really that significant, right? A couple of kilowatts out millions of kilometers away isn't going to be detected. Well, we detect signals from the Voyager 1 space probe at a distance of 18 billion kilometers and its signal is only 20 watts, and that's with TL 8 equipment.

QUOTE]

Actually that is not a fair example, we know the course of that object to a fine certainty having made measurements of it's trajectory for the past 40 years or so. It's a tracking job not a detection job, we are using a very small field of view sensor that is pointed exactly where we expect it to be. A more fair detection task is the search for near earth objects that may be on trajectories to come near or impact earth, and these objects are receiving heat from the sun at a rate of: measured by satellite as being 1.361 kilowatts per square meter, and yet some bus sized objects (3 to 4 Dt) manage to approach to within hours of their closest approach before being detected.

It is a fair example in that it illustrates that we can detect very minute amounts of energy at very long distances. Yes, we know where it is at pretty much every second but that has more to do with how quickly we can find it rather than whether or not we can find it (and we find it within seconds).

What documentation can you provide about the bus sized asteroids you are talking about? Saying "some" bus sized asteroids come within "hours of their closest approach" before we detect them doesn't tell me much. What is "some"? Half a dozen per year? A couple every month? Likewise "hours of their closest approach" isn't very helpful. A near earth asteroid is any asteroid with an orbit around the Sun that extends into the area between .983 and 1.3 AU. In theory we could be detecting one of these "hours before its closest approach" to Earth and still have it be further from us than Mars at perigee if it had a highly elliptical orbit.

Also, how many other asteroids are being detected? If we are detecting 1000 per month and missing 1 or 2 that does not bode well for stealth. Sure, it means there's the possibility that a ship that is running quiet can sneak by, but the odds are so bad that the drawbacks of rigging a ship that way wouldn't be worth it.

Finally, asteroids do not receive heat at the rate of 1.361 kilowatts per square meter. First, it's the area of their cross-section and not the entire area of their surface. The cross section of a sphere is 1/4 the area of its surface, so that's a pretty big difference. For another, that amount of energy would only be absorbed if the asteroid was totally black. Albedo of stone is usually between .2 and .4, so only 60-80% of the energy is absorbed.

 

[mike wightman]

BUT YES, IT WOULD BE HARD TO DO.

Not just hard, you would have to re-write the laws of thermodynamics. :CoW:

 

[esampson]

. . . we know the course of that object to a fine certainty having made measurements of it's trajectory for the past 40 years or so. It's a tracking job not a detection job, we are using a very small field of view sensor that is pointed exactly where we expect it to be. A more fair detection task is the search for near earth objects that may be on trajectories to come near or impact earth. . .

Actually, I just realized that this is extremely mistaken. When you look for a stealthed ship in Traveller you don't have to look at a wide area. Assuming that the ship was stealthed when it exited J-Space you look at the immediate area around the jump flash. The flash itself is detectable from a very long way away and there doesn't seem to be any way to conceal it, probably because of the immense amount of energy required to open a passage between J-Space and real space. Yeah, you might have some velocity when you emerge and they wouldn't know the direction of travel, but you are still talking about scanning an incredibly small piece of the sky by the time they swing the big sensors around and point them at you.

(100D from an Earth size planet is about 2,000,000 km. Assuming you are travelling at 140 kps, which is pretty damn fast*, at a 90 degree angle and it takes 5 minutes to point the big guns at you they would only have to search a 2.4 degree span or 1/10,000 of the sky)

As a Referee you could always say that someone has a super special jump drive that doesn't have a jump flash, but then you could also just give them a jump drive that lets them emerge well within the 100D limit, maneuver drives that can accelerate a ship at 20Gs, and shields that offer perfect protection against lasers, missiles, mesons, and particle beams, so such a drive is a little beyond the scope of stealth in the 'Traveller' universe.

The other possibility is a ship that isn't stealthed when it emerges from jump space which then becomes stealthed, but you're really no any better off there. They just turn the more sensitive sensors to the spot you were at when you disappeared.

(*140 kps was chosen because it is the velocity at which you would have to do a full burn at 2G to decelerate to a stop within 2,000,000 km if you were headed directly toward the planet. Obviously you could emerge with even more speed since you are moving tangent to the planet but that raises all sorts of problems since you now have to obscure your drive signature for prolonged periods of time and the higher the speed the longer that period of time will be.)