Airship Aircraft Carriers

[Gondor]

I can vaguely remember trying to do accurate volume calculations for curved fuel tanks while doing Auto Engineering in the middle 60s. It always drove me nuts, especially as we used slide rules in those days! (I still have mine......  )

I too  still have my trusty slide rule !  But how many people  in 21st century would even know what one was,  let alone how to use one.  My sons can,  but they have a head of  environmental systems design  and a senior maths lecturer as grandparents. 

Still have my old slide rule as well. The ones that threw me were the circular ones and then I went to the National Computer Museum at Bletchley and saw all the different types of "slide rule" 

I to have a slide rule, never use it and only did for a few weeks while at school as a cocky teenager. THought I could do better than useing the silly calculators we had at the time.

Gondor

[PR19_Kit]

Perhaps this monster size airship is about big enough to consider carrying the facilities to liquefy and store some lifting gas when the air wing launch?

I'm not sure if that's possible as the gas of choice would be helium and that only occurs in air to a minute percent, 0.00052% by volume normally, so extraction like that would really be impractical. The largest source of helium is by fractional distillation of natural gas, and carrying such a plant abord the 'ship AS WELL AS the source supply would be equally impractical I'd suggest!

Various circular slide rules are in use in the General Aviation field, usually to calculate the angle-off to be flown in a cross-wind. Nowadays they probably use their GPS units or iPhones instead, but the slide rules are stilll available.

My straight one is a Thornton, I just dug it out and did a few calculations. Mrs_PR19 is regarding me a with a strange look on her face.... 

[Rheged]

[My straight one is a Thornton, I just dug it out and did a few calculations. Mrs_PR19 is regarding me a with a strange look on her face.... 

I've just done exactly the same.  In my case, Madame Rheged went scratting around in her bureau, and triumphantly  produced hers too!  A brief phone call to my dad, and he confirms that he still has his spiral rule....a cylindrical device which, if stretched out as a ruler, would be 4 foot six long!!

[KJ_Lesnick]

Everybody

1: Would space reduction be acceptable if there were only quarters for 2/3 people onboard (like a submarine people are on duty and will not need quarters when they're on duty)?
2: Would an airship with capacity for 18 aircraft with foldable wings, ordinance and fuel for an acceptable number of sorties be cheaper in cost than an aircraft carrier?


PR19_Kit

I'm not sure that the ZMC-2 used ballonets to contain the gas, at least it doesn't SAY that it used them.

Yeah, but I'm talking about a rigid framed airship with semi-monocoque construction and geodetic construction.

When they'd launched their air group the mega-ship would rise to its pressure height.

And what would that be?  
1: Could the planes get back up to meet the airship?
2: If you got above a certain height you'd need oxygen bottles to keep the people from winking out

At the pressure height valves opened and dumped some of the gas whether the crew liked it or not, thus the loss of air group lifting gas that I mentioned earlier.

At least you'd be burning off fuel (the airship and the aircraft onboard), I don't think it would offset completely.


kerick

Were you thinking of an airship with a flight deck on top of the gas containing structure? I've seen some pictures of such and was wondering if that was what you were planning. My question with that arraigment was about the balance of the airship. Wouldn't that be very top heavy and subject to rolling over?

During the 1940's there were ideas hatched about airships with runways mounted up top... if stability was a concern, you could mount them off the bottom.


joncarrfarrelly

Could you imagine trying to fill a single volume the size of the Hindenburg?  

I didn't suggest that -- I suggested a metal framed airship with perhaps a metal skin or some means of absorbing damage (what kind of skin was the Akron and Macon made out of?) as they'd be bound to take some.

[deathjester]

Would it not be feasible to counteract the 'excess' lifting force by angling the engines down a bit...?

[Hobbes]

Perhaps this monster size airship is about big enough to consider carrying the facilities to liquefy and store some lifting gas when the air wing launch?

I'm not sure if that's possible as the gas of choice would be helium and that only occurs in air to a minute percent, 0.00052% by volume normally, so extraction like that would really be impractical. The largest source of helium is by fractional distillation of natural gas, and carrying such a plant abord the 'ship AS WELL AS the source supply would be equally impractical I'd suggest!

I think the idea is to pump helium from the envelope and compress it to reduce lift, then release the compressed gas back into the envelope to increase lift.

[Hobbes]

Some numbers:
Hindenburg could carry up to 72 passengers, call that 7200 kg of lift.

18 aircraft.
Fokker Dr.1 weighs 600 kg loaded incl 180 kg of payload. 180 kg of fuel plus ammo, let's say you want enough for 20 sorties per aircraft (a ridiculously small amount), that's 7 tons, plus 7 tons for the aircraft themselves. That's the lightest aircraft I can imagine, and it's only useful as a fighter.

Add personnel: HMS Illustrious has 348 air group personnel for 22 aircraft. That's 34 tons. Double that for tools, and again for accommodation. We're getting close to 100 tons (15x Hindenburg) and we haven't accounted for airship personnel, armament, etc.

I can't find much about the construction cost of an airship.

[PR19_Kit]

Hobbes has hit the other 'elephant aboard the airship' on the head. For just a minimal size and weight of an air group we're talking about a size factor of FIFTEEN! 

I think that makes further speculation somewhat pointless..........

[jcf]

R-100: Contract signed Oct. 22, 1924 fixed price of £350,000
length 709', beam 133', volume 5,200,000 ft³

ZRS-4/ZRS-5: Contract signed Oct. 6, 1928 fixed price of $8,000,000 for two airships.
length 785', beam 132' 6", volume 6,500,000 ft³

The F9C aircraft carried by the two big USN zepps, 4 per ship, had a fully loaded weight of 1,226 lbs each.

For all their size the big ships only had a useful lift load in the range of 152,000 to 160,000 lbs.

According to a note in Skyships:A History of the Airship in the United States Navy, the USN/Goodyear
experimented with a system of extracting and storing water vapour from the engine exhaust to compensate
for the weight changes caused by fuel burn, to reduce the need for helium valving. "The engineering
problems associated with water recovery preoccupied the program throughout the era of the large airship
and were never completely resolved."
Both ships also had internally mounted reversible engines with swiveling propellers.

Kendra, a simple google search will show the big Navy ships were covered with doped fabric and an aluminum
skin would not be any more bullet-proof. Contrary to what is shown on TV and movies, bullets don't bounce
off of airplanes, helicopters or cars, they punch right through. Armouring an airship to make it bullet-resistant
would be a waste of time as you couldn't get the damned thing off the ground.

[KJ_Lesnick]

deathjester

Would it not be feasible to counteract the 'excess' lifting force by angling the engines down a bit...?

To some extent probably, but I don't know to what extent.


Hobbes

Some numbers:
Hindenburg could carry up to 72 passengers, call that 7200 kg of lift.

And a P-40 or F4F is about half that, so 9 times that much weight would be the approximate weight of 18 P-40's.  

Now comes the questions: They will all make sense

1: How much fuel do one of these babies use per sortie?

2: How many sorties could a Lexington-Class or a Yorktown Class launch before needing an UNREP?
A: Now scale that number down to 18 aircraft
B: Assume no aircraft carries more than 500 pounds of bombs and nobody's carrying torpedoes
C: Then assume this ship has about 1/2 to 1/3 the endurance of a sea-based carrier (Think about it: It has a similar range to a carrier, but moves twice as fast -- less staying power)

3: Put that together and you have a general idea of the lifting requirements needed though their are other variables
A: Extra airframe structure for the larger vessel
B: More engines (though I'm thinking you could just use a larger prop right?
C: Possibly more guns needed to cover the vessel and their associated number of personnel to man them


joncarrfarrelly

ZRS-4/ZRS-5: Contract signed Oct. 6, 1928 fixed price of $8,000,000 for two airships.

So 4 million bucks apiece. 

My question: How much do you think an airship like the one I'm talking about cost if it was enlarged to carry 18 aircraft, increased defensive armament, geodesic construction, and armor-plating?

For all their size the big ships only had a useful lift load in the range of 152,000 to 160,000 lbs.

Okay so that means a crew complement of 91 and I assume that produces about 15,470 pounds of load

Kendra, a simple google search will show the big Navy ships were covered with doped fabric

I honestly thought they used some kind of rubber

an aluminum skin would not be any more bullet-proof.

Admittedly you're correct.  Regardless, the idea of having some armor plating beneath the skin still strikes me as a good idea and aircraft (fighters, bombers, etc) were fitted with them throughout WW2 to improve their ability to absorb damage.  The Vickers Wellington IIRC was able to carry armor plating due to it's structure.

Contrary to what is shown on TV and movies, bullets don't bounce off of airplanes, helicopters or cars, they punch right through.

I know that regular aluminum skin is pretty much useless against 7.62mm and 12.7mm bullets.  However as I said before regarding armor plating -- it can help an aircraft absorb damage and something this size could profit from this.  I assume bullets would fly though the skin as if it were air and punch holes in the gas bags, not to mention fuel tanks and stuff and send the thing down without any major trouble right?

[pyro-manic]

Armour plating would be so heavy that any armoured airship would not be able to fly. It's a complete non-starter.

To give you a very rough idea. Say a 10mm thick steel plate is needed to stop a bullet (perhaps a rather optimistic assumption, but useful for ease of calculation). The USS Akron was roughly 239m long, by 40m diameter. So to armour the envelope would require roughly (simplifying the envelope to a cylinder) 239 x (Pi x 20)m^2 of armour plate. That's roughly 15017 square metres of 10mm plating. 15017 x 0.01 = just over 150 cubic metres of steel. Steel weighs 7,850kg per cubic metre, so you're looking at over 1,177,500kg, or 1,177.5 tonnes of steel. Given that Akron's useful load-carrying capacity was about 82 tonnes, you'll see it's just not going to work.

Even if you decide to use some magic lighter material for the armour, or decide to only armour vital spots (control gondola, engines etc) you'll still find that the weight of the armour vastly outstrips the lifting capacity of the ship. Increasing the lifting capacity requires more gas and hence a much bigger envelope, which means a heavier structure, more engines, crew, etc. It's not going to happen.


And all you'd need to defeat such a beast would be a bigger gun. There were 37mm guns trialled on planes in the Great War, so fitting one (or two) to an airship-buster in the '20s or '30s would be triflingly easy, and you could field squadrons of such things for much less than one airship. That's to say nothing of ground- and ship-based anti-aircraft artillery, which would be putting 3" and bigger shells through it from miles away. No amount of armour plate will save you from that.

[deathjester]

Just use self sealing gas bags!  Any small calibre stuff will just go straight through, and not do any damage - and it won't weigh much more than the ordinary bags.

If you really want it to work, then the airship has to be shaped like a wing, and rely on both aerodynamic lift and its light than air properties.  Then you will find it can lift plenty of kit!

[KJ_Lesnick]

Armour plating would be so heavy that any armoured airship would not be able to fly. It's a complete non-starter.

So the idea is un-doable flat-out...

Just use self sealing gas bags!  Any small calibre stuff will just go straight through, and not do any damage - and it won't weigh much more than the ordinary bags.

Did we have that capability in the 1930's?  I know such capability existed for fuel -- it was dry rubber that sopped up gas like a sponge and sealed everything up.  I don't know if that'd work with air

[deathjester]

  No idea!  Bags laced with a special type of gum, made by Wrigleys!?! 

[deathjester]

Just found this:

The most commonly used lift gas, helium, is inert so acts as a fire extinguisher.[88] Modern airships have a natural buoyancy and special design that offers a virtually zero catastrophic failure mode.[89] While on long-haul flights weather patterns would be flown to avoid bad weather, the hull's mass largely damps the effect of turbulence, just as a large tanker rides through rough seas.[citation needed] An airship is usually a poor lightning target,[citation needed] as it is constructed mainly from composite materials. If it is struck, built-in protection devices minimize the risk to the vehicle and its cargo.[citation needed]

A series of structural vulnerability tests were done by the UK Defence Evaluation and Research Agency DERA on a Skyship 600, an earlier airship built by the Munk team to a similar pressure-stabilized design. Several hundred high-velocity bullets were fired through the hull, and even two hours later the vehicle would have been able to return to base. The airship is virtually impervious to automatic rifle and mortar fire: ordnance passes through the envelope without causing critical helium loss. In all instances of light armament fire evaluated under both test and live conditions, the vehicle was able to complete its mission and return to base. The internal hull pressure is maintained at only 1–2% above surrounding air pressure, the vehicle is highly tolerant to physical damage or to attack by small-arms fire or missiles.