Modern Rigid Airship Technology.
A Modern airship can use all current avionics. The Akron was lost because it used a barometer to determine altitude. A radio altimeter would have prevented this loss. A number of airships flew into storms but standard aviation and marine meteorology can prevent this. The Hindenberg was filled with flammable hydrogen. Modern airships would use helium as a lift gas. Helium has a lift of 62 pound per thousand cubic feet as so call “sea level constants” which are basically low altitude, room temperature and moderate humidity. Think of a 10 x 12 foot bedroom with eight foot ceiling and a very small closet. That is 1,000 cubic feet. Because of the gas volume, airships will never be very fast. Basically, to double the speed, you need eight times the power and thus eight times the fuel consumption. You travel twice as far (airspeed) so, in effect, the “miles per gallon” goes down by a factor of four. The same tends to be true of marine vessels.
There are three basic types of airship, blimps, semi-rigid and rigid. Blimps are blown up somewhat like a balloon. Semi rigid airships traditionally have had a “spine” that extend beyond the gondola. The “Zepplin NT, which, in reality is not that much larger than the Goodyear blimps uses a connected rigid latticework that might be likened to a geodesic dome. Both blimps and semi rigids use “balloonettes” inside the pressurized helium that can be inflated with air to maintain pressure.
A rigid airship has a rigid frame like the zeppelins. Basically, gas envelopes inside hull are “pressure less”. Basically, if you hang a rigid airship in a hanger it will maintain it's shape. This is debatable but rigid is still better for large airships over a million cubic feet.
Compared to the Pre-WWII zeppelins use of helium is the critical difference but weight reduction is also important. A pound of the weight of the airship itself is a pound that can be used for payload or fuels. The older airships used an aluminum alloy for structural girders. A Modern zeppelin would rely heavily on carbon fiber. This and new design technology might reduce the “girder weight” by 50% to 75%. The hull, which is basically an arch design can be “pretense” with kevlar./aramid cord. This is the basic “arch” principle.
The gas envelopes used to be made of canvas cover with cow intestine “goldbeaters skin” or later acetate film stock. The same material technology used in the “plastic-metal” snack food bags, which give very low gas permeability (so the potato chips don't get stale) can be used. Obviously a more robust version can be used but some basic product. I read that the the Goodyear Blimps only purify the helium a couple of times a year. Blimps are pressurized, which increases permeability. Also, the gas cells are much smaller so the ratio of surface area to volume is far higher. A modern zeppelin could go a year, perhaps longer with no significant permeability loss or helium contamination. Basically, the modern zeppelin gas envelopes would weigh a lot less.
These is the outer covering or hull. With a zeppelin we are literally talking about “acres” of “skin” here. The old zeppelins basically used cotton sail canvas with several coats of paint. We have a lot of new, far lighter all weather fabrics. The Metrodome, has a “Teflon” roof more than 25 years old. The “Champion Air” hanger on Cedar between Crosstown and 494 is a fabric exterior. The new Denver airport has a fabric with a 65 year design life. The semi-rigid Zepplin NT has a “skin” close to the space walk space suits. We can make extremely durable “skins” that save a lot of weight. Keep in mind that weight save on the airship is fuel or payload.
As for shape, modern zeppelins will probably have the same basic profile as the Hindenburg. Some “tweaking” perhaps “fatter” but no major changes. For a propulsion system I tend to favor an electric drive system with diesel engines as primary power but diesel fuel turbines as backup power. You could start with proven “off the shelf” components and upgrade later to save weight. My favored drive system is an electric drive with vectored variable pitch propellers, probably six or eight at first with a Hindenburg sized airship. Vectored means that they can be pointed upward for “lift” or the opposite, downward if the airship lets too “light”. Variable pitch means that load and thrust of each unit can be controlled by changing the propeller pitch. For the short term helicopter systems can be used with the design “tweaked” in the future.
For now I would say that the first generation large airships should have six, preferably eight electric drive propeller units for redundancy. This might reduced in the future. I'm pulling numbers out my hat now but lets say that with gas turbines you have 7500 “surge” horsepower. If we figure ten pound of thrust per horsepower (just an educated guess) the zeppelin could take off 75,000 pounds “heavy”. Once in motion the airship would tilt a bit upward but the the “kiting affect” would allow it to operate with this overweight. This takes some fuel but it's relatively efficient. That is a trick to give more weight for fuel and payload.
My next focus is on naval zeppelin operations. More payload tricks here. BTW: Most people think of German Zeppelins in World War I as “bombing London” but the main effort was “Naval” and the German Zeppelins managed to keep the British navy in port during most of WWI. Even then, German used “amphibious zeppelins” to great advantage. Something I figured out but was surprised the WWI Germans also did.
No comments:
Post a Comment