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Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48027291) Attached to: The Physics of Space Battles

The assumption here is that the exhaust is in the form of a gas.

Okay.

Once it passes through the constriction of the rocket nozzle, it expands (the effect is to turn thermal random motion of the particles of the exhaust into directed velocity).

Explain how "it expands" does not equate to expanding beyond the boundary of the shielding.

After leaving the bell, there are no more restrictions to expansion of the gas aside from the small amount of matter in space.

Again, explain how "it expands" does not equate to expanding beyond the boundary of the shielding.

And how it cools to background radiation levels BEFORE "it expands" hits the shield boundary.

Because THAT is the issue you've been skipping.

And again, so what?

Because "stealth" probably does not include "dying of old age 200 years before getting out of your own back yard".

Then use physics to make that argument not assertions that I brought up Voyager.

I already have. But you keep skipping over it. I just did it again at the beginning of this post.

Here it is again:
PHYSICS says that the exhaust will expand. Eventually the exhaust cloud will be larger than the area covered by the "shield". At which time the exhaust will be visible.

You claim that the exhaust will cool to the same level as the background radiation before that. Yet you do not explain HOW it will cool that much.

You keep confusing "cool" with "background radiation". Going from 3,000 K to 2,000 K is "cooling". But 2,000 K is not the same as "background radiation".

Stealth isn't perfect. It would be relatively hard against large, sensitive detectors.

Then it is not "stealth".

You are not "invisible" if you depend upon the enemy being blind.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48021233) Attached to: The Physics of Space Battles

Do you need me to post the distances that you did not understand?

kilometers 350,000 is about Earth to the Moon
kilometers 200,000,000 is about Earth to Mars
kilometers 39,900,000,000,000 is about Earth to Alpha Centauri

Light travels about 1,000,000 kilometers an hour.

So what you're saying is that from a million plus kilometers away, a ship with a forward profile of maybe a few score meters ...

That is just 3x the distance from the Earth to the Moon.

And only 1/200th of the distance from the Earth to Mars.

And that isn't even counting the kilometers of shielding that you kept insisting upon.

area of a circle = pi r r
So a circle with a radius of 2 kilometers (you've proposed larger shielding) would give an area of 12,566,400 square meters. Which should be very easy to spot at 1,000,000 kilometers.

It's the laws of physics. And the math isn't that difficult, either.

Comment: Re:I don't like it. (Score 1) 123

deviating from the formula is almost always a way to make a crappy book

Go grab the last 20 titles in any genre. You'll see that most of them adhere to the tropes of that genre and are still crap.

A good author can write a good story even with the most formulaic plot.

A good author can write a good story even while subverting the established tropes of the genre.

But that's not important in this specific case. Martin can still change the specific tropes for individual characters in order to "twist" the ending from the predictions. (Boy meets/loses/gets girl) becomes (boy meets/loses/dies-in-battle-to-impress girl who married the local royalty once boy had left).

Since the "mathematical model" was wrong there, who's to say it isn't also wrong in X?

Comment: I don't like it. (Score 1) 123

Nevertheless, this statistical approach to literature could introduce the process of mathematical modelling to more people than any textbook.

Until the writer reads that analysis and intentionally deviates from it.

In which case you've just shown them that mathematical modelling is unreliable.

When the real lesson should be not to use a tool for a job for which it was never intended.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48020755) Attached to: The Physics of Space Battles

You just quoted my explanation "rapid expansion of the propellant in a vacuum in addition to the above mentioned thermal radiation".

I quoted you to point out that your explanation was not an explanation. Explain how the exhaust will cool to background radiation levels.

I didn't bring up Voyager, that was brought up by the article on the impossibility of stealth in space.

I'll quote you, again:

Similarly, the two Voyager spacecraft have easily detectable signals because those signals are directed by a high gain parabolic antenna at Earth, because the signal has a narrow bandwidth, and because there's a huge dish at Earth to pick up the signal.

That is what you posted. And they will take 300 years to reach the Oort cloud.

You first have to show that.

Easy. I'll use the analogy of Harry Potter and the Cloak of Claimed Invisibility.

You claim that a cloak of invisibility is possible.

I say that physics says it is not.

You say that it is possible ... as long as you use tactics to take out anyone who isn't blind.

I say that if it was an invisibility cloak you wouldn't need tactics to take out anyone who isn't blind. The cloak would make you invisible. They would not see you. Tactics do not beat physics.

But you keep insisting that the cloak makes you invisible ... as long as there isn't anyone who can see you.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48018201) Attached to: The Physics of Space Battles

Except it won't be glowing.

Tell me more about how it is going to cool off to background radiation levels.

Unlike the spacecraft itself, rocket exhaust (chemical or otherwise) will cool rapidly to the microwave background temperature (rapid expansion of the propellant in a vacuum in addition to the above mentioned thermal radiation).

You are claiming that. But you have not explained how it would happen.

Sure, all of this can be detected by a large enough and sophisticated enough detector.

And you've just contradicted yourself.

If the exhaust has cooled to background radiation levels then it would blend in with the background radiation. It would not be detectable. No matter how "large enough and sophisticated enough detector" there was.

To claim that physics prevents stealth is to ignore the actual physics as well as tactical considerations like the size and mass of a viable detector.

And you've just contradicted yourself in that single sentence.

Tactics do not beat physics. So there is no "as well as". You've claimed that the exhaust would be as cold as the background of space while still driving a ship fast enough to cover distance X in time Y.

Not unless X is approaching 0 or Y is approaching infinity.

Like your previous example of Voyager. Which you did not like once I pointed out that it would take 300 years just to reach the Oort cloud.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48018155) Attached to: The Physics of Space Battles

There was no "them", only one point.

And you keep complaining that I addressed them. It was your post. If you did not like it then you should not have posted it.

This is remarkable. You were the one who started banging on about interstellar distances (and then interplanetary for some mysterious reason), not me.

Because distance is the point.

You do not understand that. But I will explain it again.

kilometers 350,000 is about Earth to the Moon
kilometers 200,000,000 is about Earth to Mars
kilometers 39,900,000,000,000 is about Earth to Alpha Centauri

Light travels about 1,000,000 kilometers an hour.

So the exhaust from your example ship will, eventually, disperse beyond your example shield. When that happens, the radiation given off by it will travel at about 1,000,000 kilometers an hour. That means that the math for determining when the enemy will see your ship's silhouette is very simple.

Not in the least, I'm arguing that the heat from the exhaust would have reached negligible levels by the time whatever miniscule amount of it got around the shield, mostly due to the vast majority of it being blocked by the ship and being blasted directly backwards.

I've already given you an example of a laser from Earth to the Moon. Here it is again.
"At the Moon's surface, the beam is about 6.5 kilometers (four miles) wide ..."
https://en.wikipedia.org/wiki/...
So you are claiming that the exhaust from your example ship is MORE tightly focused than a laser is.

The laws of physics disagree with that.

And as another poster pointed out to you, the exhaust isn't nearly as hot as some might imagine.

You don't know how hot I "imagine" it to be. All it has to be is hot enough to be detected. And since the instruments today can (probably) detect leftover radiation from The Big Bang it looks like the laws of physics contradict you again.

And yet again nobody is talking about going from Earth to Mars except yourself.

That is the distance that you quoted. Whether you understood what that meant in actual terms when you quoted it I'm sure that it sounded good to you when you posted it.

What you posted was:

So what you're saying is that from a million plus kilometers away, a ship with a forward profile of maybe a few score meters ...

Now "a million plus kilometers" might sound impressive to someone who does not understand the actual distances in space. But that is just 3x the distance from the Earth to the Moon.

And 1/200th of the distance from the Earth to Mars.

So, yes, detecting an object at that range is easy.

And yet again nobody is talking about going from Earth to Mars except yourself.

I'm pointing out that you do not know what the distances you are quoting mean in the real world.

It the laws of physics.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48016359) Attached to: The Physics of Space Battles

Who said I disagreed with them?

You are the one who keeps complaining about me addressing them. If you disagree with them then you should not have posted them.

Not that readers need it pointed out, but Mars has mysteriously entered the discussion.

There is no "mysteriously" about it. The distance you started quoting is less than the distance from the Earth to Mars.

In other words, interplanetary.

Interplanetary != Interstellar

Argh. You're comparing an exhaust, which rapidly cools off in space and generally acts very differently to a laser, to a laser.

No. I'm comparing the dispersal. You are arguing that the exhaust would not disperse.

In other words, you are arguing that the exhaust is focused BETTER than a laser.

And the heat has to go somewhere. It's one of the laws of physics.

You keep using that word. It does not mean what you think it means.

Yes it does. The heat of the exhaust does not vanish. Reaction mass does not vanish. Ships need a force to move them.

Physics.

I seriously have no idea where you're getting this stuff.

That you do not understand the distances involved.

In order for the ship to be hidden, it cannot be silhouetted against its own exhaust. Which means that the exhaust cannot cross the edge of the shield before it has cooled to background radiation. But the ship has to travel (at best) 100's of millions of kilometers (Earth to Mars) while the exhaust only has to travel 10 kilometers (at most) laterally before cooling.

In other words, your example ship would be a dark, shielded spot in the middle of a glowing cloud of its own exhaust. It would look like a bullseye.

It's the laws of physics.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48016295) Attached to: The Physics of Space Battles

If you're going to bring that up, please remember that the above observation is completely irrelevant ...

You were the one who brought up the Voyager craft as an example.

If you want to make the ships that difficult to detect then you are going to be travelling that slow. 300 years to reach the Oort cloud. It's the laws of physics.

"Probably very hot" is considerable fail right there.

In your opinion. The point being that it is hot enough to be detected. Now you can argue whether it is or is not but I'd once again refer you to physics.

Further, the "shielding" that everyone talks about just isn't that heavy.

So far I haven't seen anyone posting what that "shielding" is made of.

But it does not matter except that more shielding requires bigger engines.

The reason it does not matter is that the exhaust will, eventually, travel further to the side than the shielding can shield. Then it will be seen as a glowing cloud behind the shielded ship.

The whole concept of shielding for stealth revolves around the exhaust NOT being able to travel X distance to the side before cooling to background temps BEFORE the ship travels Y distance forward.

Given that X is usually measured in, at most, 10's of kilometers while Y is measured in THOUSANDS OF MILLIONS of kilometers I think that the math should be self explanatory.

But, just in case, it means that the exhaust would have to travel laterally at a rate that is less than 1/100,000,000,000 the speed of the ship.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48016073) Attached to: The Physics of Space Battles

There were two sentences out of dozens in that post that I actually wrote.

They are a direct quote from you. If you disagree with them then you should not have posted them.

It's like the terracotta army, except straw men.

You are disagreeing that a ship needs reaction mass? So you are postulating a reactionless drive.

So what you're saying is that from a million plus kilometers away, a ship with a forward profile of maybe a few score meters ...

The distance from the Earth to Mars is about 200 million kilometers.

Your example ship would be closer than Mars is. A lot closer.

... with a several kilometer wide umbrella to disguise the exhaust bits that weren't sufficiently collimated before they cool off and become indistinguishable from the background noise, especially at those distances, this ship will stand out like a sore thumb?

There is a reflector on the Moon. People aim lasers at that reflector. Those lasers diffuse over distance. "At the Moon's surface, the beam is about 6.5 kilometers (four miles) wide ..."
https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment
That's from the Earth to the Moon. So even if you could focus the reaction mass a tightly as a laser it would spread out over a lot more than "a several kilometer wide umbrella" would cover even if you were only as far away as Mars.

Your example ship would be a dark shielded spot in a glowing cloud of its own exhaust.

It would look like a bullseye.

Our equipment can't even pick up large asteroids before they're a few days away.

Yes it can. It does that all the time. You are confusing spotting them with projecting their course over time.

No, as another poster memorably put it ...

Quoting someone else who is not disproving it is not the same as disproving it.

It is physics. Unless you want to argue that the laws of physics do not apply ...

It doesn't magically shine through the ship like a lighthouse.

No one said it did. I've been saying that it forms a cloud behind the ship. And that cloud glows.

Nope. I'm claiming it can be hidden across much shorter distances under circumstances which are broad enough to be tactically useful.

Unless you're talking about being closer than Mars ... how did it get closer to Mars without being detected?

Yes, that heat the article that you steadfastly refuse to address, addresses.

Saying that the answer is somewhere else is not addressing my point. Quote it. Like I quoted the Wikipedia article on how much the lasers diffuse between the Earth and the Moon.

You're not a humanities guy by any chance?

Just someone with a background in physics.

I mean do you have any clue how small of a profile we're talking about here at these kinds of distances?

You are now talking about a distance less than the distance between the Earth and Mars. So something blocking out part of Mars would be very noticeable. Not to mention the Sun would be reflecting off of it. And that's not even addressing the interplanetary material that you had previously discounted.

Interplanetary != interstellar.

kilometers 350,000 is about Earth to the Moon
kilometers 200,000,000 is about Earth to Mars
kilometers 39,900,000,000,000 is about Earth to Alpha Centauri

There is no stealth in space.

Comment: Isn't random 50%? (Score 1) 113

by khasim (#48015371) Attached to: Mystery Gamer Makes Millions Moving Markets In Japan

So he can hit 6 out of 10.

Wouldn't random chance give him 5 out of 10?

And that's not even factoring in whether his comments are correct. And most people do NOT give accurate reports of their own winning/losing patterns.

And his self-reported "strategy" is to buy what other people are buying and to sell when they sell.

So who is selling when he is buying? Wouldn't he constantly be behind the curve? Paying too much for the stock and selling for too little?

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48015347) Attached to: The Physics of Space Battles

No, you're deliberately and obviously ignoring the article.

That was a direct quote from your post. You posted it.

Actually the problem is you putting words in my mouth and then arguing with those words.

Are you going to stick to the facts as they are understood today? In order for a ship to move it needs reaction mass.

The vast majority of the exhaust will be hidden by the ship only as long as it approaches a lone target dead on. The umbrella just gives a few degrees more leeway which decreases the closer you get to your target.

And "vast majority" does not equal "stealth". You'd still show up as a glowing cloud of exhaust. That's the point.

You are aware that insulators and light blockers don't need to increase in mass proportional to the source being blocked right?

You were arguing about making them bigger. They DO increase in mass proportional to their size being increased. Make it twice as big and it weighs at least twice as much.

Not to mention that it doesn't need to be perfect, just good enough to beat the enemy's likewise imperfect sensors long enough to get close enough to strike.

Again, you'd show up as a glowing cloud of your own exhaust with a dark spot in the middle. To the defender it would look like a bullseye.

Dull radiation is as good as no radiation if the enemy can't tell the difference, and don't forget about the distances under discussion here.

That's a pretty huge caveat there. Why would the hypothetical defenders be LESS capable than we are today? Our equipment has (possibly) detected background radiation from The Big Bang.

So a new source would have to be less visible than that.

And off we wander down the garden path again.

Reaction mass goes out the back of the ship so that the ship can move forward. That's a fairly fundamental concept. And it is what you are arguing for hiding. Unless you are postulating a reactionless drive. Which is, again, its own error.

Just don't end up like a creationist or a feminist clinging fiercely to disproven articles of faith.

It is physics.

Reaction mass comes out the back of the ship.
You claim that it can be hidden across interstellar distances using a shield.
Along with all the other heat produced by the ship.

I say that you are wrong and that, in your example, the ship would be appear as a shielded dark spot in a glowing cloud of its own exhaust and that it would eclipse other objects behind it. Making it very easy to track.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48015143) Attached to: The Physics of Space Battles

That latter bit wasn't part of the article, it was just my own addition.

I'm replying to your post.

Even without shielding you can't see the exhaust through the rest of the ship.

And that is the problem. You take that and assume that:
a. the exhaust will always be hidden by the ship
b. shields can be put on the ship to hide the exhaust

The umbrella could be many kilometers across and of a lightweight material.

Lightweight is not the same as no-weight. Which gets back to the increase engines to support shields requiring more engines requiring more shields repeat.

Space is notoriously empty of those, hence the name.

While space is mostly empty space your reaction mass is not. Otherwise it would not be reaction mass. And you'd have postulated a reactionless drive. Which is a completely different error.

What heat beam, you've lost me. I'm talking about the ship's exhaust.

Ships have heat. Life support and engines if nothing else. This is NOT the same as reaction mass. You have to get rid of that heat AND the exhaust AND the heat of the exhaust.

With your proposal you'd show up as a glow of your own expanding exhaust cloud with a large dark shield in the center that eclipsed the stars/galaxies/nebula behind you.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48014921) Attached to: The Physics of Space Battles

And the linked article you refer to doesn't understand the idea of directed power.

That would be the part where they discussed whether shielding your engines would be possible. So, yeah, they do.

When engines aren't pointed at you, they have a much lower energy signature and aren't detectable all the way out to Alpha Centauri (though obviously a torchship is going to be pretty easy to detect just the same).

I think that you are incorrectly conflating those two statements. The engines give off reaction mass to move the ship forward. That reaction mass is probably very hot. Which means that it will radiate heat which will be seen.

Unless you are proposing some kind of reactionless drive. Which would probably violate Newton's Third Law of Motion.

And if you are going to use the Voyager craft as examples, please remember that it took 12 years to reach Neptune and will take THREE HUNDRED YEARS to reach the Oort cloud.

Comment: Re:There Ain't No Stealth In Space (Score 1) 442

by khasim (#48014819) Attached to: The Physics of Space Battles

And of course the engines can only be noticed if they're pointed vaguely in the direction of observers, otherwise the whole exterior hull would be the same temperature as the exhaust. It could be shielded reasonably well, even if you're stuck with elderly chemical engines.

The first problem with that is that it means you have to increase your engines to support the mass of the additional shielding.

Which means more engine heat that needs to be shielded.

Which means more heat shields.

Repeat.

The second problem with that is that the beam of heat "behind" you will still radiate in all directions if it comes in contact with any object behind you. And the beam will lose focus over distance. Which means that it will have more area in which to hit objects. While the energy will be weaker it should still allow your ship to be seen in profile.

And the most common object for the heat beam to hit would be your engine's reaction mass. That is, the stuff that your ship shoots out the back in order for it to go forward.

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