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Author Topic: Airship Class  (Read 6486 times)
pakled
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« Reply #125 on: August 22, 2015, 12:46:00 pm »

Mebbe I'm oversimplifying, but I don't see how the EM works. I just feel it takes mass (of some sort) to move mass...this is what happens when you skip taking physics in school (shoulda coulda woulda...Wink
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GCCC
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« Reply #126 on: August 22, 2015, 04:52:53 pm »

Perhaps the same way as armies marching bands!


A sonic semaphore? This ship would "call out" fleet speed, formations, orders to fire...?

It Could Work - Young Frankenstein

https://www.youtube.com/watch?v=10KObAQFmlY
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MWBailey
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« Reply #127 on: August 24, 2015, 01:46:48 am »

Maybe it's similar to the almost-nil antigravitational nature of powered-up electret mic assemblies (or was that shot down?). I'm sure I read about that back in the 80s or 90s, in Popular Science or Popular  Mechanics...

Or maybe it was another one of those time-warp anomalies, like the one where everybody in hardware and DIY stores insist that bit braces never existed (often when there's an empty hook for such on the display wall behind them Wink )...
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« Reply #128 on: August 24, 2015, 03:21:04 am »

Mebbe I'm oversimplifying, but I don't see how the EM works. I just feel it takes mass (of some sort) to move mass...this is what happens when you skip taking physics in school (shoulda coulda woulda...Wink
It's possible that it's somehow converting EM energy into unidirectional kinetic energy, which it seems should be possible without violating conservation of energy. (That 30kN/kW figure sounds like over-unity, though.) I confess I don't understand the physics of it either (haven't read the papers) but then I don't understand how warp drive works and last I heard NASA was trying to fund a proof-of-concept prototype.
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« Reply #129 on: August 24, 2015, 03:48:47 am »

Mebbe I'm oversimplifying, but I don't see how the EM works. I just feel it takes mass (of some sort) to move mass...this is what happens when you skip taking physics in school (shoulda coulda woulda...Wink

The force wave / particle model ("duality") for matter and energy is something that you learn in the so called "Modern Physics" starting with the De Broglie-Bohm theory right after Einstein's Relativity, and before Quantum Mechanics.  In this case, photons have no mass but carry momentum (thus they can produce a pressure when impinging on a surface), and are thought to be the "other side of the coin" when looking at EM waves. In other words, depending at how you look at it, energy is either made of force waves (electromagnetic force waves) or particles with no mass, but with momentum called "photons."  So I'm not surprised you didn't hear of it, unless you started taking modern physics courses in college (even if just as an elective course).
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Narsil
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« Reply #130 on: August 24, 2015, 01:00:20 pm »


The big attraction of EM drives is that being able to generate thrust in the  (near) vacuum of space using only electrical power is very attractive.

The principal of conservation of momentum suggests that in order to give an object momentum in one direction (ie accelerate it) you need to give something else an equal amount of momentum in the opposite direction. Or put simple if you want to accelerate forwards you need to accelerate some other mass backwards. Jet engines do this by sucking in air heating it and accelerating it backwards through a nozzle, generating thrust in the opposite direction, rockets do something similar but they need to provide the mass as will as the energy, unlike a jet which used the air around it.

This means that a space craft, even if it can generate energy form a compact (eg nuclear reactor) or external (ex solar) source still need to carry and expend mass to generate thrust.

So turning electricity directly into thrust without needing to eject any net mass is clearly a good thing for spacecraft, but it's a whole different story going from that to flying cars and floating battleships.

The difficulty with conservation of momentum calculations is that it's only conserved in a closed system and it's only closed as long as kinetic energy isn't being converted to anything else. Most real world collisions don't show complete conservation of momentum as some kinetic energy is converted to heat, sound etc. For example modern cars are designed with crumple zones to dissipate as much energy as possible. 

In any experiment one of the most difficult things is accounting for the energy going in and out of the system and, indeed, deciding where your system boundaries are both in terms of the physical measurements and how you design the mathematical model.
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« Reply #131 on: August 25, 2015, 03:14:52 am »

I'm going to stoke the fires of discord here,  Roll Eyes , but I found this physics forum "trash talk" interesting.  Often pure scientists will "trash talk" engineers and assasinate their character if they feel that engineers are inferior to them (which is often the case).

This is a forum entry on the EM drive a couple of years ago, when the Chinese were about to build their experimental setup....

http://physics.stackexchange.com/questions/23725/is-the-emdrive-or-relativity-drive-possible

Quote
It is impossible to generate momentum in a closed object without emitting something, so the drive is either not generating thrust, or throwing something backwards. There is no doubt about this.
Assuming that the thrust measurement is accurate, that something could be radiation. This explanation is exceedingly unlikely, since to get mN of radiation pressure you need an enormous amount of energy, since in 1s you get 1 gms−1 of momentum, which in radiation can only be carried by 3×105 J (multiply by c), so you need 30,000 Watts of energy to push with mN force, or at least a million Watts for 80 mN. So, it's not radiation.
But a leaky microwave cavity can heat the water-vapor in the air around the object, and the heat can lead to a current of air away from the object. With a air current, you can produce mN thrusts from a relatively small amount of energy, and with a barely noticible breeze. To get mN force, you need to accelerate 300 cm3 of air (1 gram) to 1 m/s every second, or to get 80 mN, accelerate 1m3 of air (3000 g) to 0.2 m/s (barely perceptible) and this can be done with a hot-cold thermal gradient behind the device which is hard to notice. If the thrust measurements are not in error, this is the certain cause.

So at best, Shawyer has invented a very inefficient and expensive fan.

EDIT: The initial tests were at atmospheric pressure. To test the fan hypothesis, an easy way is to vary the pressure, another easy way is to put dust in the air to see the air-currents. The experimenters didn't do any of this (or at least didn't publish it if they did), instead, they ran the device inside a vacuum chamber but at ambient pressure after putting it through a vacuum cycle to simulate space. This is not a vacuum test, but it can mislead one on a first read.

In response to criticism of this faux-vacuum test, they did a second test in a real vacuum. This time, they used a torsion pendulum to find a teeny-tiny thrust of no relation to the first purported thrust. The second run in vacuum has completely different effects, possibly due to interactions between charge building up on the device and metallic components of the torsion pendulum, possibly due to deliberate misreporting by these folks, who didn't bother to explain what was going on in the first experiments they hyped up.

Since they didn't bother to do a any systematic analysis of the effect on the first run, to vary air-pressure, look at air flows with dust, whatever, or if they did this they didn't bother to admit their initial error, this is not particularly honest experimental work, and there's not much point in talking about it any more. These folks are simply wasting people's time.

As for people wanting to know how photons can "push," here are some notes on why photons can have a momentum while not having mass.  In Einstein's Special Relativity, the concept of "Relativistic Mass" is raised.  An object behaves as if it had a variable mass that increases and goes to infinity as you approach the speed of light.  So you can ignore the Rest Mass (or if you will call it the "true mass" of a photon - in this case exactly equal to zero) and say that there is an "apparent mass" proportional to its momentum:

http://physics.stackexchange.com/questions/2229/if-photons-have-no-mass-how-can-they-have-momentum

Quote
There are two important concepts here that explain the influence of gravity on light (photons).

The theory of Special Relativity, proved in 1905 (or rather the 2nd paper of that year on the subject) gives an equation for the relativistic energy of a particle;

    E2=(m0c2)2+p2c2

    where m0 is the rest mass of the particle (0 in the case of a photon). Hence this reduces to E=pc. Einstein also introduced the concept of relativistic mass (and the related mass-energy equivalence) in the same paper; we can then write

    mc2=pc

    where m is the relativistic mass here, hence

    m=p/c

In other words, a photon does have relativistic mass proportional to its momentum.

De Broglie's relation, an early result of quantum theory (specifically wave-particle duality), states that

    λ=h/p

    where h is simply Planck's constant. This gives

    p=h/λ

Hence combining the two results, we get

    m=E/c2=h/λc

again, paying attention to the fact that m is relativistic mass.

And here we have it: photons have 'mass' inversely proportional to their wavelength! Then simply by Newton's theory of gravity, they have gravitational influence. (To dispel a potential source of confusion, Einstein specifically proved that relativistic mass is an extension/generalisation of Newtonian mass, so we should conceptually be able to treat the two the same.)

There are a few different ways of thinking about this phenomenon in any case, but I hope I've provided a fairly straightforward and apparent one. (One could go into general relativity for a full explanation, but I find this the best overview.)

« Last Edit: August 25, 2015, 03:20:09 am by J. Wilhelm » Logged
MWBailey
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« Reply #132 on: August 25, 2015, 02:35:47 pm »

Found this while cleaning out my files, apparently of the horrifically gigantic  airship Wulfenbach from the Girl Genius universe. I don't remembe r where I got it, but it's a (horrifically gigantic) Airship, so...

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GCCC
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« Reply #133 on: August 25, 2015, 06:46:23 pm »

A self-contained floating palace, fleet transport, and engineering and manufacturing craft?
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Miranda.T
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« Reply #134 on: August 25, 2015, 07:24:47 pm »

I'm going to stoke the fires of discord here,  Roll Eyes , but I found this physics forum "trash talk" interesting.  Often pure scientists will "trash talk" engineers and assasinate their character if they feel that engineers are inferior to them (which is often the case).

(Snip)



I do suspect that, as the originally linked article infered, the EM drive will eventually end up in the same box as cold fusion and anti-gravity gyroscopes. I think if we want exotic drives on out ariships, we might do a little better with this type of thing: http://www.space.com/30221-plasma-rocket-technology-nasa-funding.html

Yours,
Miranda.
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J. Wilhelm
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« Reply #135 on: August 25, 2015, 07:56:36 pm »

I'm going to stoke the fires of discord here,  Roll Eyes , but I found this physics forum "trash talk" interesting.  Often pure scientists will "trash talk" engineers and assasinate their character if they feel that engineers are inferior to them (which is often the case).

(Snip)



I do suspect that, as the originally linked article infered, the EM drive will eventually end up in the same box as cold fusion and anti-gravity gyroscopes. I think if we want exotic drives on out ariships, we might do a little better with this type of thing: http://www.space.com/30221-plasma-rocket-technology-nasa-funding.html

Yours,
Miranda.


Sadly, I agree.  Looks like the experiments themselves are not being done carefully enough. Nothing outside of some new physics could explain thrust on this machine (in the trash talk above someone mentions that radiation pressure impinges far to small a force to compare to the claims, assuming the EM drive is leaking EM radiation, which is basically the only way scientists can explain EM thrust).

It's still good that the US and Chinese governments did the experiments IMHO, because scientists often are too scared to sully their reputations exploring the phenomenon.  Let's not forget NASA is a government agency whose mission is to explore.  Someone has to do the dirty job.  Perhaps there's a physicist out there smart enough to figure what is going on.
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« Reply #136 on: September 28, 2015, 10:18:36 am »

So, what have we here...?


La Sortie de l'opéra en l'an 2000, c. 1902
https://en.wikipedia.org/wiki/File:Sortie_de_l'op%C3%A9ra_en_l'an_2000-2.jpg
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Caledonian
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the dragon's called Salmacis


« Reply #137 on: September 28, 2015, 10:29:59 am »

So, what have we here...?


La Sortie de l'opéra en l'an 2000, c. 1902
https://en.wikipedia.org/wiki/File:Sortie_de_l'op%C3%A9ra_en_l'an_2000-2.jpg


flying cars?


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« Reply #138 on: September 28, 2015, 09:46:20 pm »

A mobile aeolian harp, perhaps?
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SeVeNeVeS
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« Reply #139 on: October 03, 2015, 12:08:57 pm »

Ok so may I ask what is the official prefix for an ordinary/ Steampunk airship?

We got SS...... steamship
          HMS..... Her Majesty's Ship
          USS.....  United States Ship or United Star Ship
          U.....    German submarines

My googlefu is rubbish and the search function here has let me down.

My initial thought was ASS.... Air Steam Ship, but that just seems wrong somehow....

SAS....... Steam Air Ship, nope, been taken and could get in trouble with the elite armed forces.....

Ideas???

I'm kinda building an airship and looking for a name, ASS Malstrøm  Roll Eyes
« Last Edit: October 03, 2015, 12:20:53 pm by SeVeNeVeS » Logged

Caledonian
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the dragon's called Salmacis


« Reply #140 on: October 03, 2015, 01:05:58 pm »

Ok so may I ask what is the official prefix for an ordinary/ Steampunk airship?

We got SS...... steamship
          HMS..... Her Majesty's Ship
          USS.....  United States Ship or United Star Ship
          U.....    German submarines

My googlefu is rubbish and the search function here has let me down.

My initial thought was ASS.... Air Steam Ship, but that just seems wrong somehow....

SAS....... Steam Air Ship, nope, been taken and could get in trouble with the elite armed forces.....

Ideas???

I'm kinda building an airship and looking for a name, ASS Malstrøm  Roll Eyes

Also SY steam yacht and RRS royal research ship

I think it would be SSA. Steam Ship for Areal (did. Spell that right?) use
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Matthias Gladstone
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« Reply #141 on: October 03, 2015, 08:10:42 pm »

I'm sure it's been mentioned, but "HMA" was the usual prefix for an airship in British service. American vessels used "USS".

For "normal" vessels, you also have (amongst others):
MV - motor vessel
ST - Steam tug
TS - turbine ship
NS - nuclear ship
SMS - Imperial German version of HMS
HMSb - HM Submarine

-Matt

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« Reply #142 on: October 04, 2015, 09:15:23 am »

Thanks Matt. Gives me some options to throw around.

Was thinking a Bandit Class........ ASS Bandit is just wrong on so many levels.......

May stick with HMA.  Undecided
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Matthias Gladstone
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« Reply #143 on: October 04, 2015, 11:35:05 am »

Thanks Matt. Gives me some options to throw around.

Was thinking a Bandit Class........ ASS Bandit is just wrong on so many levels.......

May stick with HMA.  Undecided

No comment on that!

My philosophy on it has always been that in a world where airships replace surface ships, they take their terms and traditions - so I tend to use SS, HMS etc for airships unmodified, as I would for a surface vessel - I find it saves on the cheese a little; but context is everything with these things.
-Matt
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« Reply #144 on: October 04, 2015, 08:03:24 pm »

One would think that simply adding the initial "A" (Air/Aerial/Aeronautical/Aether/etc.) to normal ships' designations would be sufficient to differentiate between nautical and aeronautical vessels, but then we run into Unfortunate Acronym Syndrome as pointed out by SeVeNeVeS, so if a derivation were made, one would have to be careful/creative with its placement.

The modern SAS (Special Air Service) was not founded until 1941; if you set your tales in the 19th Century, you could claim the real-world unit cribbed from your fictional aerocraft designation!  Wink

In reality, one can find numerous acronyms which are exactly the same, but stand for different things. Doing only the briefest of searches, I found the following:
SAS:  Special Air Service
SAS:  Statistical Analysis System
SAS:  Scandinavian Airline System
SAS:  Standards Aligned System
SAS:  San Antonio Shoes

All of these are registered trademarks or the equivalent for the entity with the acronym. So I'd say, whatever works best for your particular Steampunk milieu, go for it.
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