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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?
Airships make more sense for transporting cargo than people. They let you bypass the bottleneck of a port and let you take the cargo directly to its destination.
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.
What, exactly, makes it a dumb idea?
I've been on 5hr flights -- they're no fun. I can only imagine some of the really long flights must be friggin' brutal. Give it hotel amenities, a bar, a dance floor -- whatever -- and send people on a more leisurely trip without jamming them in like cattle and shoving them through airports. I can see it being a popular mode of travel.
Heck, just the romantic notion of it is kind of cool. I'd *love* to go on an airship voyage. It would be just plain old cool.
For leisure travel, it would be absolutely awesome way to see the world. I can see people paying to travel on one, if nothing else, for the novelty of it.
Lost at C:>. Found at C.
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
I think the acronym for Hybrid Air Vehicle has a lot of potential.
It is unwise to ascribe motive
Dammit, it said "IN-flammable" - how was I to know?
The claims of thermite paint being the cause of the explosion has been debunked. Mythbusters featured one of the better known debunking.
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.
Gasoline burns, hydrogen explodes
No, both burn and either will explode if ignited in an encloded space, just like gunpowder. Take a firecracker and empty the powder out and light it it will simply burn.
Hell, I made the "scientific discovery" that hydrogen burns and not explodes in the seventh grade.[journal] Where did you get the idea that hydrogen explodes? Mythbusters tanked that one, too.
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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?
A few relevant points:
- 20,000 feet is nearly 4 miles. You'd have to have a half-assed tracking system on a half-decent missile system to hit a target 4 miles straight up. An actual rocket-propelled grenade ain't gonna cut it. I'm not saying the tech isn't available, and I'm sure there are shoulder-mounted SAMs that can handle it, and I don't doubt that some insurgent groups might get access to them, but it's not what you can pick up at a Soviet Military Surplus store.
- If you hit anything "soft", your missile is going to punch two small holes through one of the balloons and continue sailing on by, and the thing is likely going to be able to coast to a landing for repairs, or even continue is mission. You'd have to hit something "hard" that would cause your missile to actually explode while inside the envelope or near a control system.
- An airship means there's plenty of cargo space. Including space for things like chaff, jammers, flares, and other incoming-divert-or-destroy sorts of technology. Military people tend to be pretty smart about including these things in their expensive tools if the tools have strategic value.
- The UAV's got good cameras and it's designed to look out, and if there's one there'll be lots of them. The launcher might be able to take out a single UAV, but with multiple eyes in the sky, how long do you think it'll be before that missile trajectory is tracked back to the source and a "return to sender, sealed with a kiss" is made using something very fast, very accurate, and very full of boom-boom? Repeat performances won't be terribly common.
And finally,
- These would be UAV (unmanned aerial vehicles) and, as such, relatively disposable. The military is looking to use airship tech to keep the aloft longer, since they won't need as much fuel just to stay up in the air where they are needed. They'll still be a hell of a lot cheaper than a recon plane, stay on mission longer, and not that much easier to hit. More eyeballs in the sky, longer, cheaper.
And as an aside, the resources expended on purchasing a missile capable of trying to take out something like this would be orders of magnitude higher than what's needed to set a car bomb or planted roadside bomb. In other words, the insurgents, with not unlimited resources, would have to choose between setting a whole bunch of car bombs, or buying one missile. One of these UAVs taken out could actually seen as a sort of perverse victory, since the insurgents expended a LOT of their own resources to get the tools to do it.
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(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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The main determinants of fuel consumption are: 1) speed; and 2) the surface area of the front of the vehicle (since that determines how much air must be pushed out of the way). Since airships are very large, they will never be fuel efficient unless they travel very slowly. If they travel very slowly, then we must ask: why not use a train or a ship? Trains and ships will always have vastly greater carrying capacity, because they don't require helium to lift their cargo which has modest lift for a given volume.
In short: if speed is not important, then trains and ships will always be far cheaper and carry far more; and if speed is important, then airplanes will always be faster and more fuel-efficient at high speeds.
Airships are neglected because they suffer from fundamental limitations and therefore have few uses.
Granted, airships may find niche uses. Airships do have several advantages: first, they can hover for long periods; and second, they require little infrastructure (like long landing strips, ports, or train tracks). Since they can hover for long periods, they have found a use as floating advertisements, and they may find a use as floating observation vehicles for the military. Since they don't require infrastructure, they may find a use in transporting cargo to areas which lack airports, train tracks, or ports. But they will never take over the bulk of transport between major areas, because of fundamental limitations of the technology.
Every few years, someone starts a company to revive the airship. The venture always fails, because o
f fundamental limitations of airships that will always prevent widespread adoption. Perhaps some com
pany will eventually succeed, but they will succeed in a niche market, not widely.
The parent of my parent post brings up putting rocks in sailing vessels as argumentative support, he is wrong for at least two reasons.
(1) Many modern non-sailing vessels still use ballast. The problem isn't old-timey nor is it "solved", nor is it _really_ the same issue as buoyancy with respect to airships. In a seagoing vessel the problem is that a non-trivial amount of the vessel must remain "above" the water over which the vessel must remain buoyant. As such, to remain upright, as cargo is loaded above the waterline, one must add weight below the water line to keep the ship upright. In an airship the entire ship is "submerged" in the air, so the issues are much simpler. That is, an airship and a submarine are in the same domain, but an airship and a sailing ship are not.
[ASIDE: One of the things the boat commander of a submarine must watch for is rolling over during initial dive. In surface operation, the sub is a surface ship, and its center of gravity is below its center of buoyancy just like any other ship. In underwater operation the center of gravity must be above the center of buoyancy or it won't sink below the surface. That moment when the two must cross is tricky, as they must "cross", not "pass each other". That is, if say the port side takes on ballast faster, the center of gravity would pass to the port of the center of buoyancy and the ship would roll. The normal way to make this happen most safely is to be under-way at the time of submersion or surfacing so that the wing-like bow planes and rudder etc. can be used to counter any small tendency to roll. The single most dangerous submarine maneuver is the static (non-moving) submerge. It is virtually never done as messing it up is expensive in both lives and equipment. Surfacing is safer than submerging as "blowing" the ballast tanks can right the ship very quickly if it starts to roll, and can be done before reaching the surface. That leads to that really dramatic "breaching" thing where a significant fraction of the sub leaves the water entirely before crashing back to the surface. Dramatic, "safe", but again, hard on the men and gear. (I hear it's fun though... 8-)]
(2) Ballast was much more spoken of, and "tricker" in the age of sail as the power source (the wind) wanted to push the ship over anyway. Additionally, _letting_ or even encouraging the wind to push the ship over a little (e.g. heeling) could lead to increased speeds and efficiencies.
(3) Ballast in seagoing vessels is more important and variable because you want enough to stay upright, but each little bit more than that sinks the ship a little more, causing more of it to interface with the viscous watter instead of the less-viscous air.
(4) Water can not be meaningfully compressed. Things "denser than" water also cannot be meaningfully compressed. (e.g. compressed enough to substantially effect displacement.) Air and lifting gas is eminently compressible. Consequently airships, in issues of both displacement and buoyancy, are completely dissimilar to anything seagoing (except a scuba diver in a wetsuit 8-) so none of the natures and limits you (grandparent poster) mention really apply as such.
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