Results 1 to 8 of 8
Like Tree2Likes
  • 1 Post By delft
  • 1 Post By delft

Modern Airships

This is a discussion on Modern Airships within the Members' Club Room forums, part of the China Defense & Military category; I just described why we cannot expect to see Zeppelins return in the cul-de-sac thread. But a lot of work ...

  1. #1
    delft is offline Senior Member
    Join Date
    Nov 2009
    Posts
    3,155

    Modern Airships

    I just described why we cannot expect to see Zeppelins return in the cul-de-sac thread. But a lot of work is being done on very high flying unmanned airships and there are good reasons to continue to think about cargo and even passenger airships.
    One point: fuel consumption. Hindenburg with four diesel engines of 1200 PS ( PS is a little smaller than hp ) reached a speed of about 130 km/h max., so will have used four times 600 PS to fly at her cruising speed of 100 km/h. Assuming 250 grams per PS.h she would have burned less than four tons of diesel fuel in the 61 hours from Frankfurt to Lakehurst. She loaded seven tons for such a journey - that includes fuel for services and reserves so the calculation is reasonable. She could carry 72 passengers, mail and a few tons of cargo. Only taking into account the passengers that is about 55 kg per passenger for a transatlantic journey. It was about 1000 kg per passenger with Concorde to mention the other extreme. The world might be hit by a solar storm that might cause flying at 10,000 meters to become dangerous over a large part of the world for a few days, or Betelgeuse might have blown up and cause disruption over a period of months(?). The magnetic field of the Earth might turn over and cause trouble for years or centuries, we don't know yet. No reason to abandon flying tomorrow, but enough reason to think about alternatives. And one point stands out. There is no reason to travel with great speed and in the discomfort of an airliner seat, accepting tasteless airline food in order to make contact with someone far away: the internet is much faster. When you're not in a hurry you can travel in an airship with much more comfort, even work while travelling and arrive fresh to meet your friend at the other side of the world.
    I hope other members will be interested in technical speculation as well as in reviewing modern successful and failed airship projects.
    Kurt likes this.

  2. #2
    Kurt's Avatar
    Kurt is offline Junior Member
    Join Date
    Dec 2011
    Posts
    681

    Re: Modern Airships

    Nice idea to discuss. Airships seem to me among the easists flying devices to navigate. Would it be possible to downsize an airship in order to make it affordable for commuting to work or for a cruise around the world? A kind of caravan airship? This might only be leased at first until higher production numbers lower prices, but I would like to go on a tour of the world with it.
    As a technical note, I'd prefer a foam system in the airship ballon that is capable to enclose the gas in case of severe structural damage in order to allow for save landing.

  3. #3
    paintgun is offline Junior Member
    Join Date
    Jan 2010
    Posts
    982

    Re: Modern Airships

    the boon of the airship is also a disadvantage

    low speed and large displacement gives economical operation and low cost possibilities
    but on the other hand incur poor maneuverability, poor speed handling, and relatively low speed

    an airship traveling in a violent storm system, or in adverse weather condition, as in the past, proven to be risky and dangerous
    as it is unable to escape the weather system with the low speed, or manage itself in flight under extreme conditions

    as to remedy this, rather than traveling at 100km/h, maybe boost the speed to 250-300km/h
    small air-blimp/airship structure to benefit from the buoyancy, combined with large surfaces for flight controls without incurring much drag
    think of the flying characteristics of the early biplanes/triplanes, or even better put some biplanes on it to harness some lift!

    the technical feasibility of such thing of course remains questionable

    ---------- Post added at 02:25 AM ---------- Previous post was at 02:24 AM ----------

    and although the romanticism of an airship will not be complete without piston engines powered propellers, the design can utilize modern efficient turbofan engines

  4. #4
    delft is offline Senior Member
    Join Date
    Nov 2009
    Posts
    3,155

    Re: Modern Airships

    @Kurt
    The drag of an airship is mostly friction drag which is proportional to the square of the air speed and to the square of a linear dimension, while the volume and the lift are proportional to the cube. Therefore a small airship can only be usable at a low air speed ( for the typical Goodyear blimp of 7000 cu.m, 7 tons it is about 70 km/sec max. ) so it is very vulnerable to high wind speeds. You have to store the ship in a pretty large hangar or deflate it if a high wind comes along.

    @paintgun
    You objections are valid and have to be considered by anyone designing a ship. I hope soon to find the time to offer my considerations in this thread.
    Kurt likes this.

  5. #5
    Join Date
    Aug 2005
    Location
    Universal Health care 'Reeducation' camp
    Posts
    4,565

    Re: Modern Airships

    Here's an interesting one for you Part blimp part helicopter
    Boeing: Boeing Teams With Canadian Firm to Build Heavy-Lift Rotorcraft

  6. #6
    Kurt's Avatar
    Kurt is offline Junior Member
    Join Date
    Dec 2011
    Posts
    681

    Re: Modern Airships

    This can only be invented for Canadians or Siberians.

  7. #7
    delft is offline Senior Member
    Join Date
    Nov 2009
    Posts
    3,155

    Re: Modern Airships

    Quote Originally Posted by TerraN_EmpirE View Post
    Here's an interesting one for you Part blimp part helicopter
    Boeing: Boeing Teams With Canadian Firm to Build Heavy-Lift Rotorcraft
    This concept was first tried by an American, Frank Piasecki, in 1986: Piasecki PA-97 - Wikipedia, the free encyclopedia. I have doubts about the influence of the flow through the rotors on the forces on the balloon and I don't like to have to ferry the craft over hundreds of kilometers to escape from a strong storm. I also don't like the no doubt heavy charge for the helium. For this function I would much prefer a craft with the configuration of the Mi-12 and with the dynamic components of the Mi-26. The trouble with Mi-12 would now be solved with better design software.
    BTW I hadn't heard about this craft so I suppose it is not getting anywhere.

  8. #8
    delft is offline Senior Member
    Join Date
    Nov 2009
    Posts
    3,155

    Re: Modern Airships

    Let me describe how I think you might approach the use of airships for transporting containers or people, remembering that low fuel consumption and, for people, good comfort, better than possible with airplanes, are their main strengths.
    Airships must avoid getting into bad weather, especially over land. So they should operate mostly over the sea making use of any storm blowing their way but avoiding thunder storms. They can go over land, where it is no more than 1000 or 1500 meters above sea level and hook on to a landing mast at no higher than say 500 meters above sea level and at wind speeds lower van 10 (?) m/s, getting away before it raises to 16 (?) m/s.
    This means that at time you might have to avoid Western Europe and/or China. In which case the ship must have the range to go somewhere else and work there. They also must have a cruising speed that is reasonable compared to occurring wind speeds. You will, of course, be dependent on excellent weather forecasting.

    To bring this all together and compare with the largest airships yet built, Hindenburg and her sister Graf Zeppelin II:
    Hindenburg had a length of 244 meters, a diameter of 41.2 meters, a cruising speed of 100 km/h, a maximum speed of 125 km/h flying at 500 to 2000 meters using four diesel engines of 1200 PS or 900 kW. The mass was 200 tons and she loaded 7 tons of fuel to fly from Frankfurt to NAS Lakenhurst in about 60 hours. The fuel fraction was thus 3.5%. Real fuel consumption will have been between 4 and 5 tons.
    Let's keep the calculations easy and look at a ship with a range of 20000 km and a cruising speed of twice Hindenburg's. Weather forecasting over 100 hours can be done reliably all over the world.
    For a Hindenburg type ship we get:
    Cruising power and fuel consumption per hour are 8 times Hindenburg's, so fuel fraction would be 3.5 * 8 * 100 / 60 % , which is about 47 %, a quite unrealistic number especially when we remember that the engines are also eight times as powerful. But we wouldn't estimate the fuel consumption of the Boeing 787 by comparison with the Boeing 247.
    Let's change the airship. By putting co-axial propellers at the aft end of the ship and arranging that the propeller blades can have cyclically changed angles of incidence you get rid of the need for fins, rudders and elevators, their weight and drag, as well as the engine nacelles. The propulsive efficiency will be raised from 70 % to over 90 %. When we then increase the diameter by a factor of 1.5 the drag of the clean hull will be increased with the same factor and the power to reach a given speed will be about the same as for Hindenburg, while the mass is a factor 2.25 larger at 450 tons. That brings the fuel fraction back to about 21 %. Using hydrogen as fuel reduces the fuel fraction by a factor of 3.5, bringing it back to 6 % and using fuel cells or gas turbines with heat exchangers which give about twice the efficiency of 1930's diesel engines takes it back to 3 %. These are very crude calculations but bring us to the right order of magnitude. Also reducing the speed by 10 % will reduce the power by 30 %, fuel consumption by 20 %.

    Before going on let's look at an alternative technology: Wing in Ground Effect machines. Large WIG machines are supposed to fly at an altitude of a few meters and a speed of 500 km/h. They need a large excess of power to get going and might use that excess to cross busy shipping lanes and even short stretches of land, for example flying at 50 meters parallel to the Suez canal. But for take off and landing they are virtually bound to coastal sites, while an airship make choose to go from Szechuan to either the Pacific or the Indian Ocean. Perhaps we should develop both.

    I think the structure of a modern airship should be based on the Metalclad concept that was developed in Detroit in the 1920's. There is little information on the web about this concept. but see ZMC-2 - Wikipedia, the free encyclopedia, NAS Grosse Ile Aircraft and Popular Mechanics - Google Boeken.
    The ship would be built from large panels of fiber reinforced plastic on rings of the same material and with a triangular section. The rings and the bulkheads within them prevent surging if the lifting gas just as in Zeppelins forming gas cells. A membrane is fitted in each cell attached near the mid height of the ship and large enough to be sucked to the roof of the ship. The lifting gas is fed into the cell above the membrane. As there is no pressure over the membrane other than that due to its weight diffusion of gas out of the cell and air into it will be very small. All gas pressure is carried by the hull of the ship.
    In ships of this kind it is possible to safely use hydrogen. By leading all hydrogen fuel into the gas cells and feeding the engines out of them you are constantly purging the lifting gas. Helium ships spent a month each year having their gas purged. By evaporating more hydrogen than the engines use you can increase static lift and by evaporating less you reduce the lift. The cold hydrogen is also used to win water out of the engine exhaust to serve as ballast water.

    A lot more can be said on this subject but I think this is enough to suggest that serious research and experiments should be started.

Similar Threads

  1. Modern Naval Warfare
    By IDonT in forum Navy
    Replies: 2
    Last Post: 12-24-2011, 04:08 PM
  2. modern Praetorian Guards
    By utelore in forum Professional Discussions
    Replies: 3
    Last Post: 07-07-2009, 01:18 AM
  3. Is a modern battleship feasible?
    By F40Racer in forum Strategic Defense
    Replies: 32
    Last Post: 05-17-2007, 01:11 AM
  4. Best modern day jet fighter simulator?
    By New2u in forum Members' Club Room
    Replies: 1
    Last Post: 10-26-2006, 11:39 PM
  5. Modern and upgraded J-7
    By utelore in forum Air Force
    Replies: 7
    Last Post: 10-22-2006, 10:52 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •