Nyrath

Re: Warp Drive article on the Discovery website

You explanation looks good to me. With the exception of the twin paradox.

Explanation of the Twin Paradox to follow. Those who don't care can skip the rest of this post.

One twin being older is due to simple relativistic time dilation.

The Twin Paradox is due to the fact that since Relativity says that everything is relative (i.e., there are no preferred frames), you can say that the rocket left Earth then came back, OR you can say that the rocket stayed stationary while the Earth and the entire universe move away then came back.

If you take the first view, the twin on the rocket should be younger. If you take the second view, the twin on Earth should be younger. They cannot both be younger than each other, so it is a paradox.

The paradox is resolved when you take acceleration into account.

http://en.wikipedia.org/wiki/Twin_paradox

Re: Particle Beam

I'm also starting to think about the degrees of difference there would be' date=' if any, between an Electron, Positron, Proton, and a Neutron Accelerator.[/quote']

Well, on the one hand, the first three can be defended against by using powerful electrostatic fields, since they are charged particles. Neutrons are uncharged, so are unaffected by such fields.

 

On the other hand, the weapon has to have some method of accelerating the neutrons in the first place. So whatever the weapon uses, can also be used as a defense.

Re: Space Warfare II - Stealth Reconsidered

The original statement was that any device that doesn't produce waste heat is a "perpetual motion machine". I was only wondering if a superconducting loop would produce waste heat, and if not, would it be a "perpetual motion machine"?

 

Because at that point, either you have an actual "PMM" in existence, or you have something that doesn't produce waste heat and is not a "PMM" -- calling the "no waste heat = PPM" definition into question.

OK, you are going to get more information that you wanted.

There are three classes of perpetual motion machines:

Class 1: This produces energy from nowhere. It violates the law of conservation of energy.

Class 2: This converts waste heat into useful energy. It violates the second law of thermodynamics.

Class 3: This eliminates friction and other dissipative forces so an object moves forever. It does not violate any laws, but is not generally very useful.

A superconductor is a perpetual motion machine class 3. A machine that does not create any waste heat is a perpetual motion machine class 2. The latter is the one being discussed.

Re: Particle Beam

From my research in space war, the major difference between a laser strike and a particle beam strike is that the laser deposits its destructive energy on the surface of the target, while a particle beam actually penetrates a little bit which deposits its destructive energy inside the target. Note we are talking penetration measured in millimeters to centimeters.

So from my standpoint particle beams would have the piercing advantage or something like that.

This of course has nothing to do with the Star Hero write up, I just thought I'd throw it out for your consideration.

Re: Space Warfare II - Stealth Reconsidered

Yeah' date=' you are. Any device that doesn't produce any waste heat is a perpetual motion machine.[/quote']

 

Superconductors?

 

An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source. [1]

 

From http://www.kilty.com/pmotion.htm

Superconductivity also seems to be an example of a process that runs forever. Most physics textbooks explain that superconductivity is not perpetual motion because it is not a classical effect. It is a macroscopic quantum effect--sort of like a room sized atom, and we know that atoms are forever. They do not "run down." However, it seems to me that the unavoidable imperfections in the superconductor and its enviroment almost guarantee that this macroscopic atom will eventually stop.

Re: Space Warfare II - Stealth Reconsidered

Just remember' date=' FTL changes everything. Superscience in general does that. Once you can pop out of hyperspace, turn on your cloaking device and sneak around using your reactionless drives, the laws of the universe are whatever you say they are.[/quote']

Yes, but then you have to be very careful not to go too far the other way.

 

Say that your FTL lets you go from any point A to any point B with no limit, and your ship is undetectable while in transit. The result is that most interstellar wars would last about five minutes.

 

The first warning that the Cyber-octopoids of Gamma Privia V have of a declaration of war from the Blortch of Delta Slimeball III is when a flight of Blortch space bombers pop out of hyperspace over Privia and carpet bomb the place with planet-cracking warheads.

 

The flight of space bombers then make the jump home to Slimeball. Only to discover that in the ten minutes they were away, a flight of Cyber-octopoid bombers had coincidentally given the same treatment to Slimeball. The End.

 

The reader takes the novel and hurls it across the room.

 

This is why powers in the Hero System have limitations.

Re: What would happen - and at what cost?

As long as they calculate the trajectory properly. But yeah' date=' that's a bit scary.[/quote']

 

Yes, but the point is when the Martian colonials decide that they want to be free of the tyranny of Earth, they can start by gathering up a dozen tramp freighters and annihilating every major Terran city and plunging the planet into nuclear winter.

 

This is one of the consequences of John's Law

Re: Space Warfare II - Stealth Reconsidered

Also; how the fark am I going to sneak up on my damned players if all my ideas get shot down?

You tell your players that the campaign is set in the SciFi universe of your choice where stealth exists but scientific accuracy does not. Problem solved.

Re: Space Warfare II - Stealth Reconsidered

And listening isn't my problem; comprehending is my problem. I apologize if we are constantly repeating tired old arguments. Believe it or not' date=' I am learning something.[/quote']

I apologize if I came across as a little bit testy.

But as you figured, yes these are the same tired old arguments.

 

Indeed, this entire thread is a shining example of Nicoll's Law: It is a truth universally acknowledged that any thread that begins by pointing out why stealth in space is impossible will rapidly turn into a thread focusing on schemes whereby stealth in space might be achieved.

Re: Space Warfare II - Stealth Reconsidered

I just hate that your website is blocked at work' date=' Nyrath.[/quote']

Hrn. I wonder why? Does it give a reason?

 

At my work they use SonicWall, it blocks all sorts of sites under forbidden categories like "firearms". But it lets my Atomic Rocket site through.

Re: Space Warfare II - Stealth Reconsidered

Somewhat less' date=' actually; solar cells aren't black, so it might be producing something like 1000W of waste heat and 167W of reflected light.[/quote']

True.

Of course as far as stealth is concerned, reflected light is about equally bad to waste heat.

Re: Space Warfare II - Stealth Reconsidered

My first thought is you don't have to get rid of all your waste heat. Just enough to satisfy 1/r^2 such that your level of heat less than the level that can be detected at that range. The more efficient you are the closer you can get to your less stealthy opponent.

True, but with current technology, you are not going to be able to get very close.

If the spacecraft are torchships, their thrust power is several terawatts. This means the exhaust is so intense that it could be detected from Alpha Centauri.

The Space Shuttle's much weaker main engines could be detected past the orbit of Pluto. The Space Shuttle's manoeuvering thrusters could be seen as far as the asteroid belt. And even a puny ship using ion drive to thrust at a measly 1/1000 of a g could be spotted at one astronomical unit (i.e, the distance between the Earth and the Sun).

I've calculated that a spacecraft the size of a submarine with all power turned off could be detected at a range of about 150 times the distance between the Earth and the Moon (129 light-seconds or 38,800,000 kilometers).

This is with current off-the-shelf technology. Presumably future technology would be better.

Thank you for your anecdote about your uncle, it was pertinent.

Re: Space Warfare II - Stealth Reconsidered

Yes, I'm familiar. But then you're claiming that the Second is a mathematical proof?

 

I'm not talking about wacko ideas like perpeutal motion machines. I'm just trying to leave the door open for things we might not have discovered yet, and constantly bashing even the most novel and unusual idea with "the second law says no!" before it's even tried strikes me as counterproductive and silly.

http://en.wikipedia.org/wiki/Perpetual_motion#Use_of_the_term_.22impossible.22_and_perpetual_motion

The quote is in a page about perpetual motion, but it applies to any attempt to invest effort in something forbidden by the second law.

Yes, it is remotely possible that some flaw may be found. But after almost one thousand years of experiments failing to find a flaw with the second law, most scientists have better things to do with their time.

Re: Space Warfare II - Stealth Reconsidered

Could you build a system that recycled as much heat / emissions / waste as possible to bring the waste heat - and thus detectable emissions - "near zero?"

Forgive me but you are apparently not listening. It is impossible to recycle waste heat. The best you can do is pump the heat from one spot to another. If you use a radiator to throw the heat overboard, you are creating a huge thermal emission that will be visible for Astronomical Units away. If you do not throw the heat overboard, the temperature inside the spacecraft will grow until the crew dies and things start to melt.

Keep in mind that the background of deep space is at a chilly three degrees above absolute zero (-454.27 degrees Fahrenheit). Anything hotter than that will show up like a signal flare at midnight.

Say' date=' you have some type of fusion reactors, which powered a variety of drive systems - ion and/or plasma drives or the like for in-system travel, the jump or whatever FTL drives (if they exist in the setting / our imaginary future reality for this conversation), and all the other stuff. Obviously, if your engines are actually providing thrust you can't mask that - but could your other systems be so efficient that you'd be [i']significantly harder[/i] to detect?

Obviously if your engines providing thrust, you will be visible from Pluto's orbit.

Typical fusion reactor designs I've seen are hard pressed to have efficiencies of 50%. For a typical ion drive, you'd need about one gigawatt of electricity. With a 50% efficient fusion plant, it would put out 1 gigawatt of electricity and one gigawatt of waste heat.

Or to where you might be mistaken for something other than what you are? Say a cruiser coasting along or parked in an orbit' date=' observing or whatever it is your ship(s) is there to do?[/quote']

Again this is covered in my website. Coasting along with the power plant off and the crew shivering in the dark, the detection radius will be reduced. Reduced from Pluto's orbit to a mere 150 times the distance from the Earth to the Moon (about 38,800,000 kilometers).

 

The trouble is, everybody will see you when you use your engines to insert yourself into your coasting trajectory. After that, your position can be calculated exactly according to the laws of orbital mechanics. If you light up your engine again to change your trajectory, again everybody will see it.

Re: Space Warfare II - Stealth Reconsidered

True to my second comment.

Now please explain my first.

Explained in the post above this. Heat is moved by the refrigeration cycle, but entropy is increased in doing so. If I am not explaining this adequately, it is because I'm not a professional teacher. You might be better off finding a high school physics teacher and asking them to explain.

True For that matter, referring to the first, refrigeration is possible inside the ship.

Now you say: "but what about the extra waste heat from generating the electric power needed for the refrigeration?" Good question.

It depends on how efficient the process is. If the efficiency is good enough, the refrigeration is more than the added waste heat, and no, that is not a perpetual motion machine.

Again, the refrigeration pumps heat from whatever is being refrigerated to somewhere else. The heat is still there, just relocated. Add to that the heat from the power source attached to the refrigerator. The heat just gets larger and larger.

BTW' date=' remember in most of the "atomic rocket" designs, the main power plant (be it fission or fusion) is an open system, it generates thrust by expelling reaction mass. This removes a great deal of heat from the system, even if other "waste" heat is not used to pre-heat the remass.[/quote']

Yes, I know about open cycle cooling, you might have read about it on my website. But the main thing that open cycle cooling is not is "stealthy". Which, if you recall, was the point of this entire thread.

Blasting out a sixty gigawatt plume of hot plasma is not the way to try and avoid being noticed.

 

 

Separately' date=' another simple example; if the power for the refrigeration comes from a solar array, how much waste heat is there?[/quote']

The current state-of-the-art solar cell arrays on the International Space Station are about 14.5% efficient. This means (in Earth orbit) every square meter of solar cell produces abotu 198 watts of electricity, and 1167 watts of waste heat.

Re: Space Warfare II - Stealth Reconsidered

Actually' date=' you're missing his point, though it's an artifact of clumsy wording. If you let a liquid move from a high pressure area to a low pressure area, and it transforms into a gas when doing so, its temperature goes down without external energy input, which looks like a second law violation. It's not -- modest pressure gas is higher entropy than a liquid, even if the gas is cooler than the liquid -- but using a careless definition of entropy it looks like one.[/quote']

 

Well, perhaps, but not according to the original post.

Using your argument, it appears to me that all existing refrigeration cycles violate the second law. The temperature is lowered by allowing (great) expansion of the working fluid, not by dumping it into another system. The only input is the (electric) power needed to recompress the working fluid.

The confusion seems to be due to the original poster conflating "temperature" with "entropy." The second law of thermodynamics states that in a closed system entropy increases. Therefore all existing refrigeration cycles do not violate the second law.

 

Refrigerators can pump heat from one place to another, but they increase entropy while doing so. Thus the second law is maintained.

 

In any event, the heat is not destroyed, just moved. That's why on a chilly day you always find the cat curled up near the bottom vents on the refrigerator, where all the heat pumped from the interior is jettisoned.

Re: Generic SF Universe Project

But by understanding the way the universe works' date=' we can bring the world to life. In the end, how you build it isn't as important as being able immerse yourself in the game environment.[/quote']

Maybe for you, but your stable of players are going to be much more interested in the practical details: how much fuel does each use, what are the limitations, etc.

 

You can only immerse your players in the awe and wonder of the game environment a limited amount of time before their eyes glaze over.

Re: Black holes as high-tech power sources

Um... wow.

I did say high tech

Re: Space Warfare II - Stealth Reconsidered

As long as the increased entropy of the working fluid (via its state change from liquid to gas) is greater than the decrease in the entropy of the heat sink, second law is not violated.

 

Using your argument, it appears to me that all existing refrigeration cycles violate the second law. The temperature is lowered by allowing (great) expansion of the working fluid, not by dumping it into another system. The only input is the (electric) power needed to recompress the working fluid.

Right, the input of electrical power prevents violation of the second law. If there was no power input, there would be a violation.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html

(scroll down to Second Law: Refrigerator)

http://www.phy.duke.edu/~rgb/Class/phy51/phy51/node63.html

Without power input, it would violate the second law. There is a name for this: perpetual motion machine (of the second kind).

The earliest known example of somebody trying and failing to make a perpetual motions machine was in 1150 AD. In the almost 900 years since, people have been trying and trying to defeat the second law of thermodynamics, and they have failed every single time.

This is a good summary:

Use of the term "impossible" and perpetual motion

Re: Generic SF Universe Project

Just keep in mind the primary rule of the Hero system: focus on effects, not causes.

In other words, try writing up each of the FTL propulsion systems in the Hero system, in order to get a firm grasp on their differences. The real differences, not just the bafflegab explanations of how they work.

Re: What would happen - and at what cost?

The term I like is "MacGuffinite". Some incredibly valuable substance that is only found off Earth, as motivation to develop an interplanetary economy.

Like something which is the perfect diet pill, or the cure for male pattern baldness.

Larry Niven had his asteroid miners prospecting for magnetic monopoles.

Of course, if you somehow already have a space colony, common iron and other simple materials from asteroids are valuable since the incredibly high added cost of hauling such things up Earth's gravity well would be avoided.

Re: 'Misty caverns' on Enceladus moon

You know I'm going to incorporate this into my campaign.

That's why I'm posting it here. Campaign designers need all the help they can get.

Re: Space Warfare II - Stealth Reconsidered

What bugs me' date=' a lot actually, is when someone says "that would be impossible because it would violate the second law blah blah blah" about some novel effect that no one has actually tried to accomplish. Take for example a membrane that is permeable in one direction by gas molecules above a certain energy, and in the other direction by gas molecules below a certain energy (I think that's how it goes, bear with me). The assertion usually made is that it's not even worth looking for such a thing, because it "violates the second". How about we actually find out what's possible?[/quote']

Well, by analogy:

The laws of mathematics state that 1 + 1 = 2. But you do not see lots of people trying to find a way to make 1 + 1 = 3, valiantly ignoring the fact that it is impossible because it would violate the law of addition.

 

In the same way, chemists calculate the results of chemical reactions using the laws of chemistry in order to tailor chemical products. They do not spend all day mixing random chemicals in the hope of violating any of the laws of chemistry. Even though it would be nifty to stumble over a way of turning lead into gold.

 

I take it that you are unfamiliar with the concept of a mathematical proof?

http://en.wikipedia.org/wiki/Mathematical_proof

Proofs are obtained from deductive reasoning, rather than from inductive or empirical arguments. That is, a proof must demonstrate that a statement is true in all cases, without a single exception.

Re: Generic SF Universe Project

What I would LOVE to develop would be a recreation of the European empires during the age of exploration to the mid 1800's. Wherin each "nation" would be a separate race or faction. They would be a handful of small empires but powerful empires who have a long series of complicated relationships and varying and swinging alliances.

 

Vast new areas of relatively unexplored regions (like America and Africa). develping trade with empires with which the "Europeans" are on shaky ground (china). Also the "european" empires would be vying for control over some "virgin" rich, unexplored and undeveloped areas (think africa, india, Pakistan and america).

For the old RPG Traveller 2300, the developers made a simple geopolitical game and used it to generate the future history underpinning the RPG.

http://stalexone.tripod.com/gg2/2300game.htm

http://traveller.wikia.com/wiki/2300_AD