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Author Topic: Return of the Zeppelins  (Read 816 times)
RJBowman
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« on: April 26, 2017, 03:51:40 pm »

The founder of Google is building an airship:
http://www.theverge.com/2017/4/25/15429486/google-sergey-brin-secret-airship

Reports say that the new airship will have a metal frame, and is being built in the old U.S.S. Macon hanger.

The Macon was 748 feet long, compared to the modern By comparison, the Goodyear Blimp is 192 feet long, and the Hindenburg was 804 feet long.
« Last Edit: April 26, 2017, 03:57:54 pm by RJBowman » Logged
Hurricane Annie
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« Reply #1 on: April 27, 2017, 03:47:05 am »



Interesting.  There is a movement back towards airships.  Various  large defence forces and   aero engineering  companies are researching and designing  new craft
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RJBowman
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« Reply #2 on: April 27, 2017, 05:14:11 pm »

They were successful during the first world war because they could fly higher than anything else and drop bombs on cities with impunity. Between the wars it became apparent that they were vulnerable to improved higher-flying planes and the didn't see much use during the second world war. After the war, the "type-B limp" airships (lacking metal frames and limited in size) proved to be cheaper and became an advertising medium for the Goodyear and others.

But this is among the first in a very long time to have a metal frame, and it will dwarf the advertising blimps that are currently in the skies.
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« Reply #3 on: April 27, 2017, 08:41:04 pm »

I have a feeling your post above would be ideal discussion fodder for the Guild of Icarus thread.

I'm about to embark on wroting the most difficult aspect of my novel's background: the technical case for a 19th C global war. The argument revolves around exactly what you wrote, but with one added degree of difficulty (and where the real Steampunk starts): the ships have to reach stratospheric altitude at least close to the Tropopause, in order to use the subtropical jet stream to do a stealthy approach on North America. I have estimated that with the jet stream, one could use an airship to circumnavigate 2/3 of the circumference of the earth in only 6 days, at a latitude of 35 degrees, which is where the weaker subtropical key stream is located.

Im debating starting a thread on Textual or just discussing at the Guild of Icarus.  Anyone interested?
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RJBowman
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« Reply #4 on: April 28, 2017, 04:22:14 am »

I'm about to embark on wroting the most difficult aspect of my novel's background: the technical case for a 19th C global war. The argument revolves around exactly what you wrote, but with one added degree of difficulty (and where the real Steampunk starts): the ships have to reach stratospheric altitude at least close to the Tropopause, in order to use the subtropical jet stream to do a stealthy approach on North America. I have estimated that with the jet stream, one could use an airship to circumnavigate 2/3 of the circumference of the earth in only 6 days, at a latitude of 35 degrees, which is where the weaker subtropical key stream is located.

How much larger would an airship have to be at that altitude to lift the same cargo it can lift closer to the ground?
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« Reply #5 on: April 28, 2017, 08:19:26 am »

I'm about to embark on wroting the most difficult aspect of my novel's background: the technical case for a 19th C global war. The argument revolves around exactly what you wrote, but with one added degree of difficulty (and where the real Steampunk starts): the ships have to reach stratospheric altitude at least close to the Tropopause, in order to use the subtropical jet stream to do a stealthy approach on North America. I have estimated that with the jet stream, one could use an airship to circumnavigate 2/3 of the circumference of the earth in only 6 days, at a latitude of 35 degrees, which is where the weaker subtropical key stream is located.


How much larger would an airship have to be at that altitude to lift the same cargo it can lift closer to the ground?


Bear with me as I'm not feeling too good tonight. Dental (molar) issues as well as sporting inflamed tonsils, either due to allergy or probably fighting an infection due to said molar issue, is making me extremely uncomfortable tonight. So I may be just writing jibberish.

The way a balloon works is that it displaces a volume of air around it. The difference in density between the gas inside the gas bag/envelope and the surrounding air determined the buoyancy of the balloon. As the balloon rises, however, the pressure inside it does not decrease at the same rate as the pressure decreases. Otherwise balloons would continue rising indefinitely. What happens is that the buoyancy force is greater on the ground and then slowly decreases as the balloon rises until it reaches it's "terminal altitude" (I'm going to call it that) when the buoyancy is exactly equal to the load carried by the balloon.

The way to pose the question is to say, if I have just enough volume in this gas bag to just *barely* lift this load mass at sea level (terminal altitude is 0 ft), then what gas bag volume do I need to just *barely* carry the same load at 33000 ft?

The buoyancy of an object in air is defined as the weight *of the air* displaced by the envelope/gas bag. The sum of forces in the y axis is equal to the buoyancy of the balloon minus the weight of the balloon:

ΣFy = ρair(h) g Vbag(h) - mload g = 0

Where
ρair(h) is the density of air as a function of altitude h (i.e. the air density varies with h)
Vbag(h) is the volume of the gas bag as a function of altitude h (i.e. the volume of the bag is also a function of h)
mload is the mass of the load (all contents of balloon including lifting gas) to be carried by the balloon.
g is the gravitational acceleration (at 33 000 ft there's negligible difference from sea level).

if the load mass is constant at sea level (h=0) as well as altitude h=33000ft = H, the we can say that

ρair(0) g Vbag(0) = ρair(H) g Vbag(H)

whatever the volume of the balloon V(H) may be at 33000ft (noting that the volume of the gas bag is not a linear function of altitude).

This implies that

Vbag(H) / ( Vbag(0) ) = ρair(0) / ρair(H)

That is, the ratio in volume depends on the ratio of atmospheric density at sea level vs altitude. We don't even need to mess with the density of the gas inside.

According to the International Standard atmosphere, at 33 000 ft the atmosphere is 0.3325 times as dense as at sea level

http://home.anadolu.edu.tr/~mcavcar/common/ISAweb.pdf (I picked this table for general friendliness to the reader)

so Vbag(H) / ( Vbag(0) ) = 1/0.3325 = 3.007

The volume of the gas bag must be almost 3 times as large at 33 000 ft. Two ways to look at the actual size of the craft:

A) If the envelope is a cylinder of radius R and constant length L, such that Vbag = π Rbag2 L then
 
 Vbag(H) / ( Vbag(0) ) = π Rbag2(H) L / π Rbag2(0) L = 3.007

which implies that a constant length diameter requires that

Rbag(H) = √(3.007 Rbag2(0) )  = 1.734 Rbag(0)

The gas bag will be 1.73 times the diameter required at sea level.


B) Another way is just to lengthen the cylinder. At which point L(H) = 3L(0) just a long Zeppelin, 3 times as long as usual.

You can probably balance the diameter and length to make it more reasonable. The challenge will be in dealing with inflating and deflating gas bags during the night/day cycles, and naturally the weight of the structure will always be a limiting factor.

Also note that by the time you get to 60000 ft the airbag grows to an unmanageable size. I'm guessing (need ro run numbers otherwise it's just a wild guess), that 33 kft would be close to the limit for a Duralumin or similar structure.


~ ~ ~

Here's something on stratopsheric unmanned craft today

https://www.nytimes.com/2014/08/26/science/airships-that-carry-science-into-the-stratosphere.html?_r=0
« Last Edit: April 28, 2017, 06:20:16 pm by J. Wilhelm » Logged
Angus A Fitziron
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« Reply #6 on: April 28, 2017, 10:12:10 am »

Hmmm... interesting that this new venture uses metal for the frame, presumably an aluminium alloy. Zeppelin NT uses carbon fibre composite frames which are incredibly light but still very strong, more so than aluminium. So, that's a surprising choice. The other issue I see with any useful expansion of airship use is the dependency on helium. It is a finite resource which costs a lot of money to just store in case of future requirements. I would be much more optimistic to see research being done to make the use of atmospheric pressure hydrogen a viable and safe lifting gas.
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« Reply #7 on: April 28, 2017, 10:27:14 am »

If you don't mind, I''l be moving the thread to Metaphysical. We've had several threads written on exactly the same subject (new airship tech) before. It seems to be a quintessential Steampunk subject...

The reason I'm proposing the stratospheric altitude is because over the Pacific Ocean you can have wind speeds from 27 m/s (60 mph or 52 knots) over 70 m/s (156 mph or 132 knots) even in the subtropical jet steam (33,000–52,000 ft) which is the weaker one of two kinds (the other being the Polar Jet Stream at 30,000–39,000 ft with speeds from 25 m/s (57 mph or 49.6 knots to over 110 m/s = 247 mph = 214 knots ).

Add to that the propulsive speed of the airship itself! The polar jet stream is stronger but not so convenient because it tends to meander a lot more, often splitting into eddies. But the subtropical jet stream can reach much more useful latitudes and tends to be much straighter.

It must be noted that Jet Streams only flow from West to East unlike the Trade Winds (Easterlies) which have Westerlies. This is a problem because it means that transport from Europe to the Americas is slow while transport in the opposite direction is fast.

I've estimated an average speed of 85 mph over the Pacific from Midway to North Texas, and an average speed of 126 mph from Turkey to South Japan for an unpropelled balloon. This translates to 5.5 days to *drift* from Austria to Texas over Eurasia. Pretty close to 2/3 of the circumference of the globe along the 35 degree parallel! If propelled, then an airship would even be faster.

The Hindenburg had a maximum cruising speed of 84 mph. So assuming a Sub Tropical Jet Stream with a 156 mph tail wind speed and maximum engine-driven speed of 84 mph, you'd cruise at 240 mph. More dramatically at the "hot spots" of the Polar Jet Stream you'd cruise at 331 mph! In contrast, a WWII B 17 flew at 200 mph and B-29 Super Fortress flew at a maximum 300 mph.





Animation of Polar Jet Stream:
https://upload.wikimedia.org/wikipedia/commons/6/62/Aerial_Superhighway.ogv




« Last Edit: April 28, 2017, 11:20:39 am by J. Wilhelm » Logged
SeVeNeVeS
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« Reply #8 on: April 28, 2017, 10:54:40 am »

Possibly the hot air emitted from google users rage and body temperature over intrusive spying and activity logging could be just enough to lift this device to its desired altitude, just a thought.
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RJBowman
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« Reply #9 on: April 28, 2017, 03:51:34 pm »

I would be much more optimistic to see research being done to make the use of atmospheric pressure hydrogen a viable and safe lifting gas.

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J. Wilhelm
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« Reply #10 on: April 29, 2017, 07:39:27 am »

I would be much more optimistic to see research being done to make the use of atmospheric pressure hydrogen a viable and safe lifting gas.



Hydrogen is always a handful. The molecule is basically two protons with electrons, which makes it very difficult to contain. There is in fact, no container that will hold hydrogen indefinitely. Turning it into a stable gel (I heard someone say that a long time ago) at ambient temperature would be practical, but not useful un this application, where you may have to pump gas in and out of onboard containers as the craft ascends and descends, or just due to heating with the solar day and night cycle. The risk resumes as soon as you expand it into a gas.
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James Harrison
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« Reply #11 on: April 29, 2017, 11:04:39 am »

There was an interesting documentary on UK television a few years ago about aerial warfare in World War One- basically it centred on dispelling the myth that a hydrogen airship is a flying bomb.  Yes, hydrogen is flammable.  But it will only burn in the presence of oxygen (remember the fire triangle- you need fuel, oxygen and heat for a fire).... turns out that the gas cells inside a zeppelin (which were made of cow guts) were, pretty much, competely gas tight- that is, oxygen couldn't permeate them.  So inside the cells was a pure hydrogen atmosphere. 

So when a fighter plane took shots at them.... yes, the bullets penetrated the gas cells, which then leaked.... but if you were expecting a fireball you'd be sorely disappointed. In the absence of oxygen the tracer round wouldn't go off and ignite the thing.  (Of course there would be oxygen leaking in through the bullet holes in the gas bag but there'd be so little of it in there as to be useless). 

The way we solved this problem was to alternate the rounds in the machine gun- one round to rip huge holes in the gas bags, the next round being the tracer shell to ignite the escaping hydrogen.   

It's more difficult to ignite a hydrogen-filled bag than is commonly thought- or rather, you need specific circumstances to get it burning.  That famous picture of the Hindenburg burning up is misleading- it's one of a set of several, the first of which quite clearly shows flames starting around one of the release valves at the top of the envelope.  The gas cells didn't catch light until comparatively late in the crash.



If you look at this photo for instance, the airship's well alight but still in trim.  It's not falling out the air- yet.  Suggesting, to me at least, that it's the outside covering on fire and that the 'burns at the drop of a hat' gas inside is, at this point, not burning. 

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Hurricane Annie
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« Reply #12 on: April 30, 2017, 09:45:41 am »



In the late 1800s   and early 1900s, long narrow [ cigar shaped ] aircraft were  observed  in the skies over the eastern US  and South Island of New Zealand.  It is now thought  these sightings may have been of proto type air ship  test flights. There was another flurry of N.Z. sighting in thr late 1960s

https://www.google.co.nz/amp/s/northatlanticblog.wordpress.com/2016/08/25/mystery-airship-sightings/amp/]https://en.m.wikipedia.org/wiki/Mystery_airship[/ur
[url]https://www.google.co.nz/amp/s/northatlanticblog.wordpress.com/2016/08/25/mystery-airship-sightings/amp/

http://www.ufocusnz.org.nz/content/THE-NEW-ZEALAND-UFO-WAVE-OF-1909/53.aspx
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Hurricane Annie
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« Reply #13 on: April 30, 2017, 09:50:22 am »

Can one imagine the special effects in a film set in a Victorian / Edward ian era airship . The heaving  skin, the sounds,  the lighting. It would  be like being  inutero. 
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RJBowman
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« Reply #14 on: April 30, 2017, 07:14:04 pm »



This is considered to be a predecessor to 20th century UFO "flaps"; the combined result of rumor, hoaxterism, and mass hysteria.
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J. Wilhelm
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« Reply #15 on: April 30, 2017, 11:13:37 pm »



I can see the headlines in the newspapers. "Sailors off the California Barbary Coast reported a massive cylindrical object in the sky, so high above the ground as to be above all the cloud cover. Naval officer's report claims that the mysterious object's speed was estimated to be close to 300 knots and it's altitude was measured to be in excess of 5 miles!"
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Hurricane Annie
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« Reply #16 on: May 01, 2017, 06:00:43 pm »

One  can only imagine the awe and disbelief,  tinged with fear,  that would have struck rural farm labourers as they watched experimental aircraft looming over the horizon .   They would have been in absolute bafflement  of a scene that defied explanation  from their  previous experience.   If they did have it explained them, they would not believe it .

How would  they explain it to themselves , to reconcile it in their own mind, and with authorities denying  the events .
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« Reply #17 on: May 03, 2017, 10:16:24 pm »

The only obstacle I see about high flying airships in a Steampunk setting, is that as a writer you have to advance the state of the art in atmospheric research by about 50 years... For some reason scientific study of the atmosphere did not happen until the turn of the 19th C and practical exploration did not happen until well into the century. This is one aspect where I must exercise my Steampunk neurons.

https://en.wikipedia.org/wiki/Léon_Teisserenc_de_Bort
http://www.century-of-flight.net/new%20site/balloons/stratosphere.htm




« Last Edit: May 04, 2017, 12:08:11 am by von Corax » Logged
James Harrison
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« Reply #18 on: May 04, 2017, 08:08:13 pm »

The only obstacle I see about high flying airships in a Steampunk setting, is that as a writer you have to advance the state of the art in atmospheric research by about 50 years... For some reason scientific study of the atmosphere did not happen until the turn of the 19th C and practical exploration did not happen until well into the century. This is one aspect where I must exercise my Steampunk neurons.

https://en.wikipedia.org/wiki/Léon_Teisserenc_de_Bort
http://www.century-of-flight.net/new%20site/balloons/stratosphere.htm



For some reason this made an idea suddenly pop into my head.  I don't know from where.  Napoleonic aerial warfare.... I'm sure the Battle of the Nile would have looked very different had the French used hot air balloons to bomb Nelson's wooden walls.
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J. Wilhelm
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« Reply #19 on: May 05, 2017, 07:56:19 am »

*snip*

For some reason this made an idea suddenly pop into my head.  I don't know from where.  Napoleonic aerial warfare.... I'm sure the Battle of the Nile would have looked very different had the French used hot air balloons to bomb Nelson's wooden walls.

Now wouldn't that be something?  There needs to be an excuse for an alternate world having accelerated research into the atmosphere. It might as well be a military event. The real-world history is curiously sparse in those types of studies, save the near death experience of Henry Coxwell and James Glaisher in 1862. Obviously too late and too meager to wake the interest of people like Léon Teisserenc de Bort 40 years later. Perhaps something like a great military defeat that could convince the think tanks of the time that the sky had now become as militarily important as the ocean sea?

This is a most vexing problem. Normally history is full of curiously early spark events.
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