Firefighting use of Zeppelins?
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Grupos de notícias: sci.military.naval
De: Vince Brannigan <vze2t...@verizon.net>
Data: Sat, 31 Aug 2002 16:00:36 GMT
Local: Sab 31 ago 2002 13:00
Assunto: Re: Firefighting use of Zeppelins?
Picosoft wrote: The towers are masonry > BTW, did we ever decide what the Brooklyn Bridge was made out of? vince É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: "Keith Willshaw" <keith@kwillshaw_NoSpam.demon.co.uk>
Data: Sun, 1 Sep 2002 15:59:17 +0100
Local: Dom 1 set 2002 11:59
Assunto: Re: Firefighting use of Zeppelins?
news:3D70E871.354EDDD0@verizon.net...
> Picosoft wrote: > > BTW, did we ever decide what the Brooklyn Bridge was made out of? > The towers are masonry Keith É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: simon <simona...@erols.com>
Data: Sat, 31 Aug 2002 20:59:05 -0400
Local: Sab 31 ago 2002 21:59
Assunto: Re: Firefighting use of Zeppelins?
Why? I'm not being a pain, I'm just curious. An airfoil is an airfoil, or
is there some scaling factor, (the airship body passes through its length over a much longer period of time than the wing on a plane) or is it because it is of (approximately) circular cross section. I gather that the reynolds number for airships is radicly different than for airplanes. No, realy, I'm curious to get a thumbnail dexcription of why the lift that the body an airship gets would be 10times less dependant on AOA than an aircraft wing. > >However > I think that a generous estimate. trying to be generous, I like the big old Zeppelins, but it is hard to come up with a worse job for them. Reading accounts of how barely controllable they were, it is difficult to imagine them lasting long near a forest fire before they were either sucked into an updraft, or simply torn in two by the winds. I would go so far as to say that you could probably NEVER get a rigid airship É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: Brad Meyer <bradm...@attbi.com>
Data: Sun, 01 Sep 2002 20:19:08 GMT
Local: Dom 1 set 2002 17:19
Assunto: Re: Firefighting use of Zeppelins?
The airfoil of, say, a Cessna 182 is radically different then that of
a F-16. The air ship is a poor airfoil and generates virtually no lift whatsoever. Because it is a close to (or at) neutral bouancy in the air, it can be moved up or down by thrust (much like a submarine in water) but changes in angle of attack of the airship have no more effect on the lift it produces then similar changes on a submarine. >. . . or This last. The shape generates little or no lift >is there some scaling factor, (the airship body passes through its length >over a much longer period of time than the wing on a plane) or is it >because it is of (approximately) circular cross section. É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: "Picosoft" <m...@worldnet.att.net>
Data: Mon, 02 Sep 2002 02:11:11 GMT
Local: Dom 1 set 2002 23:11
Assunto: Re: Firefighting use of Zeppelins?
Well, I'm pretty much done with this topic, but I can't let this go by. The
airfoil formed by the airship body only generates zero lift if the elevator (or engine thrust) is neutral. Otherwise it will generate *considerable* lift. Pretty much like an F-16 airfoil actually. É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: simon <simona...@erols.com>
Data: Mon, 02 Sep 2002 10:26:39 -0400
Local: Seg 2 set 2002 11:26
Assunto: Re: Firefighting use of Zeppelins?
Agreed, which is has lift with a greater AOA dependence?
> The air ship is a poor airfoil and generates virtually no lift But operational subs usually use lift generated both on the hull and the diving > whatsoever. Because it is a close to (or at) neutral bouancy in the > air, it can be moved up or down by thrust (much like a submarine in > water) but changes in angle of attack of the airship have no more > effect on the lift it produces then similar changes on a submarine. planes for controll. Using thrust is the provenance of small research subs and black ops where zero movement stationkeeping is required. In Das Boot, the reason that everyone ran to the front in a crash dive was to lower the bow, and thereby change the AOA of the sub. (admittedly, the presence of diving planes weakens my arguement, but see below. > >. . . or > This last. The shape generates little or no lift aircraft would seem to gainsay this. Look at it this way, when the elevator control surfaces rise, the lift on the tail surfaces DECREASES, and the tail drops. However, the AOA of the body of the Zeppelin increases and the lift ISTR that to much downangle on the ship resulted in the Shenendoah The problem for controlability is that said lift is proportinately smaller É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: "Picosoft" <m...@worldnet.att.net>
Data: Mon, 02 Sep 2002 00:59:28 GMT
Local: Dom 1 set 2002 21:59
Assunto: Re: Firefighting use of Zeppelins?
> do you have the slightest idea what happens above a fire? Hint, hot air I meant to respond to this particular point, but I guess I forgot. This is is > thinner. Tehre are also updrafts. important and I should have dealt with it. You are, of course, correct, hot air is less dense, and in less dense air This is enough buoyancy to lift the ship, fuel and minimum of ballast.All If extremely low pressure is encountered then the cells will be able to Would all aboard be doomed? No. What you would do in this case is begin É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: Vince Brannigan <vze2t...@verizon.net>
Data: Mon, 02 Sep 2002 01:26:29 GMT
Local: Dom 1 set 2002 22:26
Assunto: Re: Firefighting use of Zeppelins?
Picosoft wrote: No, before the that transfers to the airship, it tends to lose buoyancy > > do you have the slightest idea what happens above a fire? Hint, hot air > is > > thinner. Tehre are also updrafts. > I meant to respond to this particular point, but I guess I forgot. This is > You are, of course, correct, hot air is less dense, and in less dense air > This is why I specify using only exactly how? vertical lift a la helicopter or something else? > engine power and not buoyancy to lift the water. > This way the 500,000 cubic again , how do you generate the vertical lift? > meter (max helium volume) airship needs to start with only 300,000 cubic > meters (or so) of helium. > This is enough buoyancy to lift the ship, fuel and minimum of ballast.All does the job more efficiently > If extremely low pressure is encountered then the cells will be able to this is silly ints not "low pressure" its low density. > withstand a fair amount of superpressure. Only in extreme instances would > helium need to be vented. Let's consider a worst case scenario: Let's assume > that all six rotors have been destroyed and the airship has been blown high > aloft and lost half it's helium. This would leave it very heavy and without > engine power. > Would all aboard be doomed? No. What you would do in this case is begin Vince É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: "Picosoft" <m...@worldnet.att.net>
Data: Mon, 02 Sep 2002 01:56:22 GMT
Local: Dom 1 set 2002 22:56
Assunto: Re: Firefighting use of Zeppelins?
"> > again , how do you generate the vertical lift? Since you have a whole thread on the V-22 (on that topic I substantially > see above. if you are picking up the water by helicopter lift, the agree with you, btw), you must understand the concept. Point engines up, spin rotors, lift water. A helicopter will NOT do this more efficiently. A helicopter has to lift its own weight in addition to any water. It has to carry 9 tons of helicopter for every ton of water. An airship's weight is supported by helium. All the engines need to lift is water. Actually this is not entirely true. If the fire is at a different altitude É necessário Acessar antes de postar mensagens.
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Grupos de notícias: sci.military.naval
De: Vince Brannigan <vze2t...@verizon.net>
Data: Mon, 02 Sep 2002 12:19:03 GMT
Local: Seg 2 set 2002 09:19
Assunto: Re: Firefighting use of Zeppelins?
you miss my point. as in the V-22 a helicopter can be optimized for the lift of
its rotor. A tilt rotor is suboptimal. The ratio on helicopter is not 9-1 > Actually this is not entirely true. If the fire is at a different altitude It has to carry all those crews. all of which add to the overhead > than the lake, then the airship will have to lift some of its weight to that > altitude. But even so the airship would be much more efficient than any > helicopter or airplane. In addition the airship doesn't have to return to > base after after every three water drops to refuel. It could probably > operate for twenty hours straight if two crews were aboard. vince É necessário Acessar antes de postar mensagens.
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