I dunno, a lot of people would think that sustained damage on a rough landing =/= crashed.
Clearly, the ideal rigid dirigible would use a fusion reactor as a power source: that way, the inner cells would provide buoyancy while also containing deuterium fuel and the outer cells would be constantly being filled with helium waste product from the reactor.
What could possibly go wrong?
Like the sun? Dirigibles are one of the few vehicles where covering it in solar cells actually provides a non-negligible amount of power.
Tomato, tomahto.
–Mark
Controlled flight into terrain.
People don’t “travel” on cruise ships, they cruise on cruise ships – that is, they don’t use them to travel from A to B, they use them to enjoy the cruise experience – which includes massive amounts of space and almost unlimited amenities – while visiting many different ports and usually returning to the point of departure. There’s a reason the transatlantic passenger ship business is basically defunct despite the luxuries of ship travel – time really is important to most people. I believe the Queen Mary 2 is the only such such vessel still in transatlantic operation and it only does it part time. Passenger airships would suffer from both slow speeds and limited space and capacity, plus the aforementioned weather limitations.
I saw the video. It didn’t look very controlled to me.
It was more like “oh shit why is this thing going nose first into the ground” whump. They do win bonus points for being the slowest uncontrolled crash I’ve ever seen.
Everyone walked away … so it was a good landing … just a little bumpier is all
I would find certain routes at certain altitudes very appealing. Not sure it’s a viable business option.
Controlled doesn’t mean the pilot was actually in control, just that the aircraft responded to its control inputs as designed. A pilot stalling a perfectly functional plane into the ground would also be “controlled flight into terrain.” Admittedly, there may have been a malfunction here, but it certainly seemed like the engines and control systems were still functional. Maybe something to do with its ballasting systems?
I’d say back in the day use of hydrogen gas was, largely, a safe thing. The *Graf Zeppelin * had nine years of service without blowing up. Despite allowing smoking on board (in a very restricted area).
What killed airships was not the *Hindenberg *blowing up, it was that fixed-wing aircraft were becoming more and more viable and reliable in their own right. Airplanes can carry stuff in more types of weather faster, and don’t require a massive ground crew or huge storage buildings.
The maximum altitude for the golden age of airships had as much if not more to do with the crew than the machine. Those things weren’t pressurized.
Although it’s not done commercially it is currently used in gas ballooning. In fact, for the first time in decades there’s an active gas balloon club in the US, with some interest in forming additional ones in different regions. There is a gas balloon race scheduled* for Oct 1st from Albuquerque, NM
I know of at least one club in Germany that, after paying for the installation delivery pipeline, gets the ‘waste’ hydrogen free from a nearby energy plant.
Since hydrogen balloons need to be made of a non-static creating materials, the envelope is made of different, & heavier, fabric/load tapes than that of a helium balloon so one doesn’t get twice the lift.
- Gas balloon events are long distance, they can go for 2-3 nights & over 1000 miles. Both local & downrange/medium term forecasts can delay the start of the event.
Building the cabin to allow pressurization for higher altitudes would dramatically increase its weight, reducing the passengers/crew/cargo that could be carried, possibly to the point of zero. You’d also need emergency oxygen systems to cope with sudden loss of cabin pressure - and they’d need to be more substantial than those of a commercial airliner, since you couldn’t descend nearly as fast as a commercial airliner; occupants would need supplemental oxygen to last longer.
Is vacuum buoyancy in air impossible at any scale?
if it was possible to, say, manufacture 1mm evacuated glass microballoons which were buoyant in air, then a LTA airship could be constructed by enclosing a very large number of them in a larger container.
Even if the microballoons had a finite lifespan due to the gas permeability of their shell, this could still be managed - because exhausted microballoons would sink to the bottom of their container, where they could be skimmed off and recycled as raw feed material for the realtime manufacture of more evacuated microballoons.
Vacuum balloons, of any size, are impossible using any current technology. They might become possible at some point as technology advances: There’s no inherent law of physics against them. But right now, we’re not even close.
And old-time dirigibles might have needed a ground crew of hundreds, but that’s not the way we’d do it today. Nowadays, the ground crew would probably consist of one guy operating a very big machine, from within an enclosed control booth.
Not really; while hydrogen isn’t as nasty as, say, fluorine, it does have a low detonability threshold, diffuses rapidly, causes embrittlement in a variety of materials, and in general is pretty dangerous in large volumes, hence why it has largely been abandoned as a fuel for large rocket booster and aircraft applications except as an upper stage cryogenic fuel.
Helium, produced by radioactive decay of elements in the Earth’s mantle and collected and separated from natural gas, is potentially available in large volumes. While the US has elected to reduce the strategic reserves of helium gas which are stored against need, potentially available helium from natural gas reserves is far greater than projected need. Helium, of course, is the second most common element in the universe, and our sun blows away thousands of tons of “waste” helium every second. Obviously we can’t access that material today, but the Earth is a net producer of helium, which is chemically inert in any normal conditions and doesn’t pose any significant biological or energetic hazards unless stored at very high pressure.
As the atmosphere becomes less dense with altitude it requires a larger volume of low density gas to maintain the same buoyancy. At 20 kft the atmosphere is less than half as dense as it is at Mean Sea Level, which would require twice the volume, and corresponding structure. It doesn’t make sense for an airship to fly at a higher altitude than required to remain above low altitude weather and atmospheric turbulence, notwithstanding the inherent hazards of higher altitude operation (increased UV and cosmic radiation impingment, electrostatic discharge of the atmosphere, greater time to ascent and descent, less control authority of engines and aerosurfaces).
There are no airships using completely evacuated chambers because, as others have noted, the structural strength required to resist atmospheric pressure is too great. All airships use equalized pressure of hydrogen, helium, or high temperature air at lower density to achieve lift. It has been suggested that an extremely lightweight aerogel in an evacuated chamber could provide enough structural integrity to provide lift, but as far as I am aware no such substance with sufficiently low density has ever been produced in sufficient quantities to be used in this application.
Stranger
Nothing craps on one’s dreams better than hard #s and I think Machine Elf demonstrated pretty clearly why it’s not happening.
I’m not so sure about giving up on vacuum though. One is not talking about creating a perfect, or even a near vacuum necessarily. In order to make the concept workable, all you need to do is to evacuate enough air out of the cylinder to make the cylinder and its contents lighter than air. That should be less of an engineering challenge.
Still another route would be to have an appropriate gas in a partially evacuated cylinder, a gas that expands a lot. Heating the cylinders causes the gas to expand. You either drain it off and store it to reuse, design the cylinder to expand, and voila! You have lift.
Picture a hot air balloon/blimp hybrid.
Could that work?
You have to have a low enough density in the vessel to offset the weight of the material it is made from, while the cylinder has to have enough structural capability to resist the pressure differential between the 14.7 psi (sea level atmospheric pressure) and whatever internal pressure you have inside. That pressure differential adds up very quickly, and the tendency of a cylinder or sphere (which would be a geometrically preferable shape) to buckle under external load at any weakness or thickness differential at any point drives the minimum thickness, which will be vastly thinner than even the thinnest foil. See [THREAD=459843]“Can we make a floating metal ball?”[/THREAD] for a calculation.
Your second suggestion is exactly how a hot air balloon works, except it doesn’t rely upon compressive or bucking strength of the pressure vessel, just its tensile strength. It fills the balloon with hot air (or in the case of a blimp, helium) at the same pressure as the outside air but lower density, providing the needed buoyancy to achieve lift.
Using an evacuated vessel is not physically impossible per se, but it is way beyond any material we have available today. The only potential solid material that could have a net density lower than air and a structural capability to resist external pressure would be an aerogel or something similar.
Stranger