They do?
I’m involved in the RC model crowd in this area (roughly defined as Indiana, Ohio, and Illinois) and all the model jet guys I’ve encountered run their machines on JetA, just like the big boys.
And that gent out in Ohio with the Part 103 jet-powered Mitchell Wing runs on JetA, too.
Wasn’t aware there were propane powered jets… [shrug]
Last balloon ride I took was $135 for two full hours in the air, plus a muffin-and-champaign breakfast thrown in at no extra charge.
Shop wisely.
Heck, the airplanes I rent start at $140 for two hours AND I have to buy my own breakfast!
Even after base efficiency, we would also have to keep in mind the relative luxury involved.
Yeah, people have said that additional luxury would be a benefit of airships, but if that’s not as important we can up the passenger miles/gallon even more. It might make it economically feasible, if petroleum products become the major expense in flight, versus labor costs.
On the other hand, you wouldnt want to cramp the conditions too much, since the flight would take much longer.
BG:
Actually, those compartments did wonders for the Titanic. Without them, she would’ve sank a lot quicker than she did.
So…you proved your own point. 
For that price, I hope they threw in Urbana too! 
Yes.
I didn’t mention a single thing about model jet engines using propane. Where do you see that?
Did you read these previous posts?
You are obviously a savvy shopper.
Yeah - at 5:30 am, before my first morning dose of caffeine. Got a problem with that?
The “jet hobbyists” I know all happen to do RC models… maybe you know a different crowd. I’m a prop-plane hobbyist, as is my husband - the major difference being the size of the airplanes we fly, and if I crash mine it hurts a lot more. Next time you want to exclude a whole bunch of people from consideration it would help if you were more specific with your terms. “Hobbyist” is pretty broad.
I specifically excluded model jet engines.
I can’t get any more specific than:
Please take the time to read what I wrote before you take issue with it, and we can avoid the whole “being more specific” thing altogether.
You said “I’m not famillar with”, not “no one is allowed to mention”. Lighten up.
Just for giggles and why-nots, here’s some pix of the incredible airships of the famous 19th-Century American inventor-adventurer, Frank Reade, Jr. (artists’ conceptions based on the chronicles of the amazing Mr. Reade’s adventures as told to Luis Senarens): http://www.bigredhair.com/airships/index.html
I’m not any kind of engineer, so don’t beat me up too much about the exact facts and figures implied by this post. Instead, think about the possibilities. Call me an amateur futurist.
People on this thread have suggested light, ultra-rigid carbon composite tanks that could be drained down to vacuum. These would be more bouyant than the same tanks filled with helium or hydrogen, as well as saving the money needed to obtain and distribute these gasses. Of course, current tech cannot create such tanks, but it may be possible in the forseeable future.
Someone also suggested coating the hull with solar cells. Those are fairly expensive now, but should get cheaper every year.
It was also suggested that maneuvering props be run on electricity.
All of these ideas can come together. Imagine if the ship had multiple vacuum tanks and a photovoltaic coating. Then imagine that a couple of the tanks are instead filled with hydrogen. That hydrogen could be used to run a fuel cell to produce electricity. As the H[sub]2[/sub] is used up, the tank would actually start to provide extra lift, since the tank would slowly empty without adding in anything in place of the H[sub]2[/sub]. Between the solar cells and the fuel cells, you’d have all the electrical power you need for maneuvering, the various pumps needed, and to run the passenger and crew areas of the ship. The main emission of the ship would be water vapor.
Another futurist thought I had while reading this thread is that the world may someday have much cheaper helium sources. Right now, He[sub]2[/sub] is pretty expensive, since it can only be mined in a few places worldwide. In the future, we may develop commercial fusion as an energy technology. This would produce a lot of waste helium.
So, as technology marches on, the economies of airships will shift. It isn’t at all hard to imagine airships becoming cheap enough to build and run. It’s just a question of how long that march will be.
I don’t see the vacuum tank becoming a useful lifting body in the near or even distant future. The extreme strength levels found in carbon fibres or more recently in buckytubes apply to tensile loads, but it’s hard to translate that strength into compressive situations such as a large evacuated shell.
You also have to consider how much extra lift you get from vacuum - a cubic metre of air weighs about 1.2 kg, so you get that much lift for each cubic metre displaced. A cubic metre of helium weighs 0.17kg and a cubic metre of hydrogen weighs 0.08g, so helium gives 1.03 kg lift per cubic metre, hydrogen gives 1.12kg, and vacuum gives 1.2 kg. It’s a lot of trouble to go to for a fairly small lift advantage, and the weight of the rigid shell compared with a balloon canopy would probably more than offset it.
The suggestion of electric props powered by a motor-generator doesn’t really make sense for airships. Essentially this is using electricity as a transmission. The system is used in locomotives and quarry trucks because it allows a large range of torque conversion (equivalent to gearbox with hundreds of gears) but it isn’t necessary for airships and carries a weight and efficiency penalty. It would make more sense to put individual IC engines or turboprops in outboard cupolas, the way they used to in fact! (The petrol-electric cars coming onto the market now offset the efficiency penalty because the engine can is run at high output all the time, where it is most thermodynamically efficient. Unlike cars, an airship engine does not run at a fraction of its maximum output most of the time and so it wouldn’t gain the same improvement.)
Solar electrical power is a neat idea, and there are some thin-film technologies that are lightweight and comparatively cheap. Their conversion effeciency isn’t so great yet, but with all that collecting area they might well be viable. Another notion is to make the bottom half of the blimp internally reflective and the top half transparent, and focus the sunlight up onto a strip of solar cells running in a line across the top facing inwards. In eihercase electric props would of course be required.
I love the idea of hydrogen fuel cells running off the hydrogen in the balloon itself! Even without the vacuum tank concept, you can store a lot of extra hydrogen in a balloon that’s at higher than atmospheric pressure, and in that situation the strength of carbon fibres and buckytubes can be easily exploited. Interestingly this is not a new idea - it was considered long ago as a fuel for the IC engines of airships but was never found to be reliable. These days we can build IC engines that will burn hydrogen but a fuel-cell electric-prop combo might well give better efficiency, and works very nicely to supplement solar electric power or be supplemented by it.
http://www.hq.nasa.gov/office/pao/History/SP-4404/part1.htm
Check out the solar powered airship with rechargable fuel cells at the end of this article! Don’t know if the project ever got off the ground though.
http://wireless.iop.org/articles/feature/1/9/3/2
Personally I’d love to see airships come back, but then I also want flying boats and steam trains back so I can have a ride on them…
Just get a fusion reaction going inside the dirigible and convert hydrogen to helium!
matt --I was trying to link the 2 ideas of “tilt rotor control” and “electrical motors”.
This obviously simplifies the problems of fuel lines.
It’s a logical idea and quite elegant. It’s becoming increasingly popular in large seagoing ships to use generator-motor transmission and house the motor and propeller in an external pod below the stern. The whole pod can be rotated to point the propeller in any direction, so you can dispense with the rudder and auxiliary thrusters and still turn on the spot.
For a large airship with a whole bunch of tilt-rotors all over it, a single engine-generator and a bunch of electrical motors might turn out to have more advantages than disadvantages - prop speeds down to zero, instant prop startup and of course the fuel line issue. Could be important when you’re parking the thing or trying to hold it steady in gusty wind. If someone ever builds one, feel free to crow! I promise to accept it with bad grace to make it more satisfying.
Now I’m off to watch Sky Captain while eating enough toffee popcorn to make me hyper.