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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
A libertarian shat on my carpet once. Claimed the free market would sort it out. -Ford Prefect(8777)
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.
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.
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."
Oh, jeez, the "rocket fuel" BS again. Might want to read this:
http://www.airships.net/hindenburg/disaster/myths#flammable-cover
rj
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.
Free Martian Whores!
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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How did this get rated insightful? I guess neither the mods nor you bothered to read the article.
These are hybrid vehicles. They aren't airships or balloons. It's not about lifting payload with gas alone; it's a lift hybrid system. The gas can offset anywhere from the weight of the vehicle to some percentage of the cargo. Thrusters and a lifting-body airfoil shape then provide the rest of the lift. From the research that has been done so far, this is feasible, practical, and economical. At this stage it is also economical to pump helium around to control the gas lift. Some designs use just fans to pump helium from large lifting bags into storage bags. Since the helium is at such a low pressure, it doesn't take much to move it and to change the buoyancy of the entire system.
Really, it's not as hard or as bad as you make out. It appears to be absolutely practical in the long run. And these guys have years of experience in this field now, which you do not, as near as I can see. In fact you just made up the stuff in your comment. Sounds good and logical, but what you said has no basis in the current facts of the field, and is certainly not relevant to the types of airships this company is designing. In the article one of the guys bemoans the fact that armchair airship "experts" such as yourself have a real negative impact on public perception of these hybrid air vehicles and negatively impact their ability to research this stuff.
(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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