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The Second Age of Airships
The Telegraph has a story about a new generation of airships. It says "It's a new vehicle. It's a hybrid because we're combining helium lift, aerodynamic lift, a hovercraft landing system, and vectored thrust... If you can get beyond the word airship — because that has a lot of history — people think about them differently."
we'll have peak helium.
http://news.slashdot.org/story/10/07/05/2159215/Price-Shocks-May-Be-Coming-For-Helium-Supply?from=rss
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I will forever associate the word "airship" with Final Fantasy VI. Damn you, early-mid 1980's birth!
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We should save it for heart shaped balloons and making funny voices at parties?
So, it's like a cruise ship, but faster. And that's a bad thing? Obviously it doesn't compare favorably to a jet airliner if your only objective is to get from A to B, but if your objective is to enjoy the ride (kinda like on a cruise) then it seems pretty awesome.
They are not the first trying to revive the airship. Several years ago, CargoLifter was developing a "second generation airship". Despide heavy subsidaries they've gone insolvent, because the engeneering required to create an actually useful airship is not exactly trivial, and the list of potential customers is astonishingly small. Well, at least they left a damn big hangar that now contains a nice amusement park.
Half as dense as helium (so twice the lifting power),
Uh, no? It's being lifted by air pressure caused by air density of about 1.2 g/L; helium has a density of 0.1786g/L, so a vacuum would at most supply 14% more lift. Hydrogen at .08988g/L supplies 7.5% more lift-- hardly twice the lifting power.
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The other problems with hydrogen are (a) that it leaks out of just about everything even faster than helium does and (b) your safety statement is utterly unproven - because nobody has recently built full size airships and compared the safety record to current winged aircraft, which are quite extraordinarily safe. Historically, airships in the 1930s might have been safer than airplanes - but since then airplanes have had over 70 years of technical advancement which have paid off massively.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Next, zombies in London.
Those aren't zombies, they are members of the House of Lords.
Hydrogen is the correct answer, but people don't want to hear it because of the images of the Hindenburg crash.
This is ridiculous. The Hindenburg crash isn't 9/11: it was nigh 80 years ago and I'm not even distantly related to anyone who died on it. I have no emotional connection to the disaster whatsodamnedever. I reject hydrogen in airships because it's dangerous as hell. There are just too many potential sources of ignition (sparks from machinery, static discharge) for it ever to be safe enough for flight, if we hold it to the same standards of safety that commercial jets are.
Gasoline burns hotter than hydrogen, but thanks to the Hindenburg crash video, we don't have hydrogen cars either.
Gasoline burns, hydrogen explodes. There's a difference. And the issues with hydrogen cars are a multi-paragraph post that I don't feel like writing right now, but (lousy energy density, present impossibility of storage, no infrastructure) are the main reasons, not lingering Hindenburg memories. Who on earth modded GP Insightful?
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You can tell the difference by how zombies occasionally will visibly be in possession of a brain while using their mouth.
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Now imagine the costs if the thing must always take off at constant load. It would be like old sailing ships that had to fill up with gravel ballast to make safe return trips (because if they returned empty the wind could simply push them over.) Currently an Airbus 380 can transport about 150t of freight one way, and if it makes the return journey empty, OK it is a wasted trip but it requires less fuel for takeoff, which is significant on short hauls.
If you try to solve the problem by having pumps to transfer gas from the envelope to storage tanks, to control the buoyancy, you have to factor in the cost of ferrying around the pumps and the tanks. It is not impossible, but it would be complicated and expensive and require extensive safety testing before it could be certified. Much of the simplicity relative to an airplane would be lost - and you still end up with something that requires as much or more room as a 380 - a helicopter replacement this is not.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Oh, jeez, the "rocket fuel" BS again. Might want to read this:
http://www.airships.net/hindenburg/disaster/myths#flammable-cover
rj
Dammit, it said "IN-flammable" - how was I to know?
vacuum would at most supply 14% more lift
OK, so let's fill our airships with vacuum. More lift and absolutely no danger of it going up in flames! Well, there's the problem of how to get the pressure with vacuum. But that's easy to solve: Just put enough dark energy in. If it can inflate the complete universe, it surely can also inflate a little balloon.
The Tao of math: The numbers you can count are not the real numbers.
Lockheed's P-791 airship has been flying around Palmdale for several years now. This is a product of Lockheed's Skunk Works. It is slightly heavier than air, and those four "feet" are lift fans. This has advantages and disadvantages. It takes fuel to stay up, for one. On the other hand, takeoff and landing are easier; the craft can land on a runway and taxi as a hovercraft. No mooring mast required.
The P-791 looks far more controllable than any previous airship. Rudders and elevators are ineffective at low speed. The P-791 has four propellers, each fully and independently steerable in two axes, plus speed, and maybe blade pitch. Plus the four lift fans. So it is controllable in all six degrees of freedom, even at zero speed. With classic airships, having twenty controls to manage by hand would be hopeless. With flight control computers, it's possible, once the airship has been characterized. That's really what flight tests of the P-791 are for - figuring out the control strategies. In the video,it's clear that the propellers are all being steered independently, which indicates computers and sensors are busily working to stabilize the beast. This is probably an easier job for the Skunk Works controls team than any of the stealth fighters they've done, all of which are unstable in all three axes.
The Zeppelin NT has a similar, but less flexible system, with three steerable fans plus a lateral tail rotor, all controlled by a fly-by-wire system. I suspect that the Skunk Works put more degrees of freedom into their prototype than are really needed, so that they could experiment with different control strategies and find the best way to control their unusual craft.
The Zeppelin NT has a compressor system, so they can reduce lift by compressing some helium into a high pressure tank and letting some of the ballonets deflate a little. This is preferable to dumping ballast or helium.
I seem to recall that was one they confirmed. The crash only occurred because of a combination of the two. The flammable paint is what allowed the fire to easily spread to other gas bags. Had they used helium gas, or a non-flammable paint, the airship would have been able to make a safe, controlled landing.
The video i watched was in black and white...i was under the impression colors hadn't been invented yet!
is there a Turner Colorized version somewhere?
(1) one only needs the "modern" technology of the "compressor" to re-compress the gas into dense storage cylinders. They _used_ to vent the gas because the compressors and storage were more expensive and heavy than the cheap replacement gas. Modern technology can solve this really easy. You can fit 80 cubic feet of air (so probably like 100 cubic feet of helium) into a scuba tank, and it would be quite heavy thereafter. Intelligently done, a large number of flexible ballon-like bladders and one or two semi-rigid (pressurized) bladders would be easily sufficient to change the overall displacement of an airship by up to 50 percent without even getting into "high" pressures (e.g. more than three atmospheres or so in the pressurized fixed-size bladders). It's not rocket science, its basic pressure mechanics and displacement.
(2) many of the craft being discussed are only "mostly buoyant", with vectored thrust and lifting bodies etc, so that the static weight of the craft is neutrally boyant, then only the thrust to lift or fly the cargo is spent. E.g. the goal is to make the weight of the _vehicle_ free. Think of the helicopter. Right now we have to maintain thrust to lift the copter and the people, which uses far more fuel than just lifting the people.
(2a) once you are lifting only the cargo weight, crashes are lots safter as something with the weight of the cargo but the drag profile of the whole vehicle will have a much lower in-atmosphere terminal velocity, unless of course someone decided to shape it like a giant dart pointing straight down. 8-)
So, Good Sir Nay-Sayer, yes, if nobody actually thinks about the problem, then ballast becomes a hassle. But then again, if nobody thinks about breaks, a speeding car is quite a problem as well.
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