Stealth in Space

[alex_greene]

No amount of stealth tech quite beats the simple expedient of just hiding behind a big rock, no matter where in the universe you are.

 

[simonh]

c) if it's anywhere near a threat to a station, planet or shipping lanes it will get blasted to bits.

You wouldn't want to shoot it, that just gets you lots more smaller objects which would actually be more of a threat to orbital facilities and shipping traffic. Unless its on a collision course with something, it'd actually be best to just leave it alone.

Indeed, I'm reminded of the idea of nuking incoming asteroids. You're trading an incoming bullet for incoming radioactive buckshot.

Simon Hibbs

 

[Reynard]

If the blast is effective, the buckshot has a much better chance to burn in the atmosphere or it's planned to deviate the flight.

 

[phavoc]

Guess it would depend on your explosives yield (blasting it). Or if you were planned on having other rounds. But yeah, I get your point. Blowing it up too close to have a 2nd or 23rd shot just creates a lot of smaller pieces. For orbitals, that's not a good idea. But if you have an atmosphere, smaller bits have a better chance of burning up.

Weren't there some plans to use the detonation to 'nudge' the asteroid off course? I think I recall reading that somewhere. My google-fu is failing me at the moment.

 

[Condottiere]

Target practice for the gunners.

Asteroids my only need a nudge to avoid planetary or (perhaps of more immediate concern) space station collisions.

 

[Bardicheart]

Weren't there some plans to use the detonation to 'nudge' the asteroid off course? I think I recall reading that somewhere. My google-fu is failing me at the moment.

Nudging one, if done early enough is one of the best solutions in theory (its all theory since no one has actually done this IRL, though there is serious research going on at NASA/JPL on the subject). A thruster attached while its still far enough away can steer an object that half a degree that would mean the difference between a strike and it missing by 100,000 km. The closer the object is, the more you have to nudge it and the harder it becomes.

The thing about Traveller is that ships are fast enough they can easily intercept and nudge a dangerous asteroid while its still far out in space. Since its possible to tow asteroids to a shipyard to build planetary hulls (High Guard p63) then the capability clearly exists to move asteroids onto non-dangerous trajectories. The only question is does a particular system have the ships capable and available to do it. But the tech and methods are certainly known in the 3I and for most systems I'm guessing its just not an issue.

Blowing up asteroids can be risky for several reasons. Some are mostly ice (especially those coming from the outer edges of the system), you could probably blow that up and it wouldn't present any danger to a planet, but orbital facilities would still face serious danger (a chunk of ice the size of your fist moving at around 40,000 kph would cause catastrophic damage to a section / module of the ISS, for example). Rocky asteroids often have high iron content (more common in the inner PBs), trying to blow one of those up would likely produce a collections of large chunks that are effectively still just as dangerous (and its the high iron types that don't always burn up, some can even explode, i.e. Tunguska was believed to have been an high iron meteor about 36 meters wide (Or in Traveller terms roughly 1750-1800dT)). Then you've got the "rubble piles", these are asteroids that are actually a collection of smaller asteroids drawn together by their own gravity. You try blowing those up, you end up with lots of asteroids and there is even a chance (given enough time and distance) the asteroid could reform (oh no, its Frankenroid, the asteroid that would not die... now playing on SyFy channel :lol: ).

If a particular system has a well developed sensor net, they'll likely be able to detect any asteroid large enough to be a threat and be able to plot its course. If its a threat they send something out to nudge it, or if its slow moving enough maybe a bounty to a miner to go harvest it and nudge it. Otherwise they'd just issue a "traffic advisory" and leave it alone, fostering a kind of complacent attitude about them. On the other hand systems with limited sensors and or lower TL might not see one coming at all (say our own Earth for example, the frequency with which large NOEs aren't discovered until after they've passed is a little alarming). I think that complacency high tech / industrial systems might have about asteroids is what might allow the idea to work. They'd be so used to tracking them, plotting their trajectories and if they aren't a threat just ignoring them that a smuggler might actually get away with it. At least as long as you weren't trying this stunt every 2 weeks... that would get a lil suspicious. An there's always that chance something goes wrong, maybe the smuggler didn't allow for the gravity effects of a nearby GG (they missed their astrogation check or piloting check when they pushed it) and their "rock" ends up nudged onto a dangerous vector... oops. Or maybe a miner shows up looking for a convenient payday... hey, whatcha doing latched onto that rock sonny, ya lost? Or maybe some local noble out for a joy ride decides to use it for a little target practice and to make matters worse that attracts a nearby patrol cutter who shows up to fine the noble for creating a traffic hazard when he notices the smuggler and.... oops. Okay, so I have a devious mind. 8)

But all this raises another question...

Supposing the above trick works and a smuggler / spy / what have you manages to ride an asteroid in system getting them close to the mainworld. Since the asteroid can't be on a impact trajectory (that would ensure it got unwanted attention) the best you can do is a near miss of say around 100,000 km (what would still be classed as a "near miss" but not one considered dangerous and so would probably be ignored). Looking at travel times for that distance (Traveller core p145) you're still looking at anywhere from 45 min to almost 2 hrs to make it down onto the planet. In a developed system it seems almost certain you'd be noticed at that point, the question is how fast could the authorities respond and intercept? How long, reasonably, would it take to get a ship close enough to get a sensor lock and identify your ship? And by identify I don't mean spotting it with an IR sensor, but actually gathering identifying info (i.e. hull markings) that would allow the authorities to put out an "APB" on your ship, making the smuggler a fugitive.

Its not that you wouldn't be seen at this point, unless they just have minimal sensor capability (i.e. poor system, low tech, sparsely populated, etc.) then they'll detect your ship but they may not be able to do much about it. If they can't get close enough to gather identifying info about your ship, that would make it hard to catch you later (why no officer, I've never made any illegal landings on Dedmik III... you say there was a 200dT ship making smuggling runs lately... well, I do own a 200dT free trader but you know there are a LOT of 200dT ships in the 3I... so you never got close enough to see any identifying markings... that's too bad, good luck catching the guy...). Likewise, I'm also assuming once the ship makes it onto the planet and mostly powers down its going to be pretty hard to detect (hmm, gives me ideas for some extra smuggling gear, camo / IR netting, holo-camo, electrochromic hull coatings for changing color and markings in a flash). At that point you unload your cargo, hopefully have a fuel source available if needed, and then when ready you make a mad dash to the 100D limit and jump out... again before anyone can intercept close enough to identify your ship (they might know its a 200dT ship, they might even know its a Beowulf class... but there are a LOT of Beowulf class ships around so...).

 

[Ishmael]

They're in the right ballpark. Assuming perfect conversion, accelerating a 1kg mass by 10m/s takes 50 Joules of energy, or 50 watts for continuous acceleration. If the Type S is 1000 metric tonnes (which I think it roughly is in Mega Traveller) then that's a power requirement of 100 mw for 2G acceleration, with no losses.

I'm afraid this isn't quite right.
When you accelerate more quickly, you're adding more kinectic energy to the object in a non-linear fashion.
E = .5 * mass * v^2, therefore the change in kinetic energy is propotional to the added velocity squared.

1000 tonne type S, 100% efficient drives
1g - 50MW
2g - 200MW
3g - 450MW
4g - 800MW
5g - 1,250MW
6g - 1,800MW

The energy converted to kinetic is not waste and is not radiated out for sensors to pick up.
The waste depends on the drive's efficiency. Once I dig my copy of MT but out of the attic, I'll check to see what it is in those rules.

I recall that many people were put out by MT's relatively wimpy power outputs compared to CT high guard as it prevented many of the larger classic ships from being duplicated with MT rules; large 6g, agiliy-6 ships were hard to build.

 

[simonh]

They're in the right ballpark. Assuming perfect conversion, accelerating a 1kg mass by 10m/s takes 50 Joules of energy, or 50 watts for continuous acceleration. If the Type S is 1000 metric tonnes (which I think it roughly is in Mega Traveller) then that's a power requirement of 100 mw for 2G acceleration, with no losses.

I'm afraid this isn't quite right.
When you accelerate more quickly, you're adding more kinectic energy to the object in a non-linear fashion.
E = .5 * mass * v^2, therefore the change in kinetic energy is propotional to the added velocity squared.

1000 tonne type S, 100% efficient drives
1g - 50MW
2g - 200MW
3g - 450MW
4g - 800MW
5g - 1,250MW
6g - 1,800MW
...

I match your excellent grasp of Newtonian Physics (sincerely, no sarcasm implied, that's a good spot), and raise you the Oberth Effect. I think if we were considering an external propulsive force acting on the vehicle you'd be right. As the vehicle goes faster, the external system has to do more work to apply a given force. However a rocket's efficiency goes up the faster it goes.

...But when the rocket moves, its thrust acts through the distance it moves. Force acting through a distance is the definition of mechanical energy or work. So the farther the rocket and payload move during the burn, (i.e. the faster they move), the greater the kinetic energy imparted to the rocket and its payload and the less to its exhaust.

de(k) = kinetic energy delta
dt = time delta
a = acceleration
v = the current velocity of the vehicle

de(k)/dt = a * v

So as the vehicle accelerates, it's going faster, so the energy it gains in KE from a given thrust goes up. In compensation, the gain in KE of the exhaust goes down.

Think about it this way. Firing from rest the fast moving exhaust of the rocket gets most of the KE while the rocket gets a small proportion of it. If the rocket is going at the same speed as the exhaust, the exhaust gains no KE and the rocket gains all of it (relative to the initial rest frame of reference).

This is also e.g. why a rocket can accelerate to faster then the speed of it's exhaust, while an external 'pusher' can't do that. Consider the solar wind acting on a solar sail. Once the sail is traveling as fast as the solar wind, it gains no more thrust from it.

Of course whether thruster plates are technically rockets is moot. We can consider them to be rockets with a stupidly high exhaust velocity and specific impulse such that Tsiolkovsky's rocket equation doesn't come into play.

Simon Hibbs

- Considerably edited as this is a complex issue and at first I thought you might be right.

 

[Ishmael]

You're right, I didn't think of that.

Does this affect the change in kinectic energy of the ship itself ( based on the change of velocity each second ) ?
Or does it change the efficiency and thus the energy that the ship must expend to affect that change in the ship's kinetic energy?

This raises an interesting question; does this effect apply to Traveller's grav/thruster based drives? Or to drives where the propellant/reaction mass, is not also the source of energy?

In any case, I'm still going to investigate drive efficiency based on MT's numbers.
How much energy the drive needs vs how much kinetic energy the ship is given.
----------------------------------------
It is as I feared, and have long suspected.
MT's thruster plates quickly have efficiencies over 100%
I guess that this was a useless attempt to figure reasonable waste heat/radiations that a sensor might catch a look at.
And I'll have to redo thruster deign section to 'fix' that imtu.

 

[GypsyComet]

I recall that many people were put out by MT's relatively wimpy power outputs compared to CT high guard as it prevented many of the larger classic ships from being duplicated with MT rules; large 6g, agiliy-6 ships were hard to build.

Until it was realized, fairly late, that you didn't need to install 30 days of fuel for every single ship function. It was the fuel requirement that squashed MTs ability to match CT-HG.

 

[Wil Mireu]

I recall that many people were put out by MT's relatively wimpy power outputs compared to CT high guard as it prevented many of the larger classic ships from being duplicated with MT rules; large 6g, agiliy-6 ships were hard to build.

I thought that CT didn't include specific MW outputs for power plants - they only showed up in MT and TNE?

 

[GypsyComet]

I recall that many people were put out by MT's relatively wimpy power outputs compared to CT high guard as it prevented many of the larger classic ships from being duplicated with MT rules; large 6g, agiliy-6 ships were hard to build.

I thought that CT didn't include specific MW outputs for power plants - they only showed up in MT and TNE?

MT treated the starship approximations in Striker as gospel, and it all sort of cascaded from there.

 

[MarcColeman]

I too get frustrated with the attitude that we know everything today. As you point out, its unrealistic at best and the march of progress often stomps on such ideas.

I do like to have at least a minimal mechanic in place for something as important as stealth, however. Players are either going to have to use it, and so rig up something, or they will come up against it, and will have to deal with it somehow. In either case it can be abstracted to dice rolls well enough ("you roll a 14? You detect a Zhodani cruiser in the upper atmosphere!"), but it more interesting if you give some detail.

Of course that detail can degenerate into technobabble - or bovine postconsumer extrusion mass.

I love those ideas on IR. The backscatter on the dust gives the person doing the searching a chance to figure it out, but doesn't make it an automatic "there he is".

I've wondered about superconducting thread to dissipate ship heat. As long as you're not near a significant body can a ship trail out such a thread, the heat radiating along the length? If the thread is long enough, and thin enough, it would be difficult to pick out any one point. And the ship can reel it in when done.

Neutrino production is a problem I've recently been thinking over. That is an automatic production of fusion, difficult to stop without too many game side effects. So what if different types of energy production were used? Maybe solar panels or a fission reactor that emits harder to detect low energy antineutrinos (starting to sound a little technobabbly). These alternate energy sources would be used only when the ship is stealthed - they probably don't produce enough power to run drives, weapons and such, but enought to keep the ship going until the right moment.

Fusion process is tough to handle and very dangerous too.. We need to alternative sources of energy production and try to produce clean and safe energy.

 

[Wil Mireu]

Fusion process is tough to handle and very dangerous too.. We need to alternative sources of energy production and try to produce clean and safe energy.

Fission isn't terribly "dangerous" in and of itself, it's just that if it does go wrong then it can get pretty cataclysmic very rapidly.

Fusion is nowhere near as "dangerous" as fission though, even in the event of catastrophic failure - that IS the clean and safe source of energy that you're wanting. And it's also the only energy source that has enough 'energy density' for human needs to replace that of oil or gas or coal (and it's a lot cleaner than any of those too). Wind and Solar and Tidal and Geothermal are great, but they just can't generate enough juice for the needs of society on their own (or even together).

 

[simonh]

You're right, I didn't think of that.

Does this affect the change in kinectic energy of the ship itself ( based on the change of velocity each second ) ?
Or does it change the efficiency and thus the energy that the ship must expend to affect that change in the ship's kinetic energy?

This raises an interesting question; does this effect apply to Traveller's grav/thruster based drives? Or to drives where the propellant/reaction mass, is not also the source of energy?

In any case, I'm still going to investigate drive efficiency based on MT's numbers.
How much energy the drive needs vs how much kinetic energy the ship is given.
----------------------------------------
It is as I feared, and have long suspected.
MT's thruster plates quickly have efficiencies over 100%
I guess that this was a useless attempt to figure reasonable waste heat/radiations that a sensor might catch a look at.
And I'll have to redo thruster deign section to 'fix' that imtu.