Amongst many there are two major disadvantages with airships developed so far. (1) you rise by dropping ballest which is a parasitic load. You descend by releasing your lifting gas generating the need for more gas and wasting the gas itself. This did not matter when the gas was hydrogen but helium is becoming rarer. (2) The operating height is quite low. This is determined by the limited room for expansion in a rigid airship. It would be useful if they could reach the stratosphere avoiding the weather at lower altitudes for which because of their size they are poorly adapted. Non rigid baloons can reach the outer atmosphere at the begining of space. Here is a suggestion: Two chambers one above the other seperated by a concertined diaphragm. This can be light weight since unlike the outer envelope it is not exposed to the elements am nd the pressure difference either side is minimal. The upper chamber is filled with a certain amount of helium the vessel rises. As it does so the helium expands driving out air from the lower chamber thru a valve to atmosphere. A certain amount of pressure is mainained to preserve rigidity. At any time the ascent can be stopped by closing the valve. A choke controlling air flow can adjust rate of rise. When descending the valve is closed and air is pumped into the lower chanber by a pump driven by the propulsion motors.
It's already being done with a semi-rigid airship. The Aeroscraft http://aeroscraft.com/ http://gizmodo.com/5972973/the-titanic-aeroscraft-is-finished++and-its-awesome
Wonder where they got the idea - Billy Clanton? If so the idea was made universal apart from Zeplin. That's the trouble never send ideas by email ( or post to Nasa KK. ) Put them on a Forum or at least one that doesn't ban me
And whatever happened to Billy Clandon, Kuznets Krasovitch, Jonny Reb et al, et al ,et al,,,,,,,,,,,,,
The problem with airships is that you need a huge bag that you need to fill either with hydrogen that burns all too easily or helium which is twice as heavy and is expensive. The bag then makes it hard to move and control.
Air ships are just a bad idea, except for recreational purposes. They are "fair weather ships" and cannot maintain control of their bulk in an air storm. The lumber industry was going to look at a combination helicopter/air ship for log lifting, but I guess that didn't fly. Moi No
Hybrid seems a good choice: "A hybrid airship gets most of its lifting power (anywhere from 50% to over 80%, depending on exact design) from its gas envelope, but requires additional lift from engines to become airborne. Thus they are ‘hybrids’ of dirigibles and heavier-than-air craft like airplanes and helicopters. A number of hybrid airship designs have been attempted over the decades, including the helistat and the cyclocrane projects by the US Navy in the 1980s and DARPA’s WALRUS program, which ran from 2005 to 2007. Lockheed-Martin is continuing to pursue the technology with its P-791 project. Because these craft are heavier than air even when fully inflated, they can manage actual full landings instead of having to be moored. This makes maintenance as well as the loading and offloading of cargo and passengers much simpler. The craft’s engines are usually mounted on pairs of outrigger wings or struts along the vehicle’s horizontal axis. These engines are used both for lift and for forward motion, and are usually gimballed so they can rotate to direct the airflow as needed. Because of the slow speeds at which airships usually operate, propellers are the preferred mode of propulsion as they’re the most efficient at those velocities. Some hybrids were designed for straight vertical lift, like the helistat project from the 1980s, which had four helicopter engines attached to the gas envelop. Others are designed to take off and land similarly to airplanes, and require runways, such as the P-791. However, because of the low speeds, they require much shorter runways for both take-offs and landings than conventional airplanes. Some designers, like those behind the proposed 1000-foot long, 250-ton capacity Dynalift project, envision hybrid airships using conventional airport runways and flying the same routes, but only using 30% of the fuel of a modern jetliner. However, hybrids are derided in some aircraft circles as being the worst of both worlds, at least for the designs so far proposed. They tend to have poor aerodynamic characteristics, can be difficult to control, and are vulnerable to extreme weather and winds. Many of the airships seen in steampunk and alternate-world science fiction seem to be advanced hybrid designs." http://orbitalvector.com/Aircraft/Airships/ADVANCED AIRSHIPS.htm
I agree there are problems at low level - Billy Clanton suggested a saucer shape. However this is not the drift of my argument - please reread!
Add to this they require big hangers. They're good for conducting atmospheric studies, recreational tours, and hunting the U-boats. They definitely have a limited-purpose use.
