250-Foot Hybrid Airship To Spy Over Afghanistan 343
Toe, The writes "Gizmodo details the Long Endurance Multi-intelligence Vehicle (LEMV) (based on the P-791), a spyship from US Army's Space and Missile Defense Command capable of hovering at 20,000 feet. Planned for deployment in Afghanistan, the ship can float for three weeks and carry well over a ton of payload, apparently surveillance equipment. The video on Gizmodo of the P-791 shows that these ships are a hybrid not only of both buoyancy and propulsive lift, but also of both awe and hilarity."
Re:Afghanistan in....what? (Score:5, Informative)
Re:Afghanistan in....what? (Score:2, Informative)
It's grammatically correct, just a little awkward. To rephrase, "250-foot hybrid airship in which to spy over Afghanistan".
Re:Protection? (Score:5, Informative)
1) Are they really more efficient?
They're certainly better than helicopters for hovering and slow patrolling, but for transporting lots of people or stuff to a definite destination I doubt it. Given the typical shapes used, I can imagine them spending lots of fuel just fighting the wind or air resistance. Not going to be easy to beat ships or trains, or even normal planes.
Airships are fuel efficient if you don't mind going wherever the wind blows you.
2) What gas to use though?
I don't think there will be enough helium to go around:
http://www.wired.com/wired/archive/8.08/helium.html [wired.com]
http://www.usatoday.com/news/nation/2007-12-02-Helium_N.htm [usatoday.com]
So the options are hot air (which doesn't produce as much lift) or hydrogen (which has significant PR problems for airship usage).
I suppose this would be a smaller problem. Could use hydrogen both for fuel and for lifting.
Re:250-Foot ... ?! (Score:2, Informative)
No. I can't find anything discussing it, but I have a vague notion that the singular form is used when a distance is use as an adjective: "An 8 inch gap", "A 7 mile hike", "A 50 mile trip", and so on. O.k., so thinking about that enough to type it into a clear sentence led me to this, and the rule is that adjectives are not plural in English:
http://www.grammar-quizzes.com/adjective.html [grammar-quizzes.com]
Re:250-Foot ... ?! (Score:1, Informative)
No, there are no feet involved. "Foot" is an, albeit archaic and ambiguous, unit of length. When used in the form "number-unit noun", the unit is always in singular form, for example: a 200-kilogram man, a 1000-lumen bulb, etc.
Re:250-Foot ... ?! (Score:4, Informative)
Now, if you put it in the predicate, then you use the plural form: the airship is 250 feet long, the trip is seven miles, the entree costs twenty dollars, or the conference lasts three days.
If you have more questions like this about English grammar and usage, I'm available on Lang-8 (same username as here). HTH.HAND.
Re:Flashbacks.... (Score:3, Informative)
Actually Hindenburg was designed to be filled with hydrogen and wouldn't have flown effectively using helium. Graf Zeppelin II was the one that was designed to be filled with helium and start operation after Hindenburg, but it never got off the ground because of US trade restrictions on helium. Change from hydrogen to helium wasn't easy, lots of design changes had to be done and passenger capacity reduced. Hydrogen has significantly more lift and since it's cheap airships could vent it out easily to reduce buoyancy.
Re:Airships are meant to be elegant. (Score:4, Informative)
Re:Protection? (Score:5, Informative)
Reply from story submitter (Score:3, Informative)
Yes, it should be "2011." In the /. submission form [slashdot.org], there used to be a form-imposed length-limit on titles.
Now the limit appears to have been removed, but it is still enforced after submission.
So while I was preparing the story, the "2011" was in the Title field, but it got nixed on submission. My bad for not noticing the single missing word when I previewed the story.
Of course there is no Edit command on submissions. But I figured if the article got approved, someone would fix the title before sending it to the front page.
Re:Protection? (Score:5, Informative)
True but then again this thing will have a long slant range as well. At 20,000 ft it's sensors will have a very long line of site. Well outside of the range of those guns and probably the SA-2.
In a limited theater type war if anybody was to light up one of these with radar I am sure that it would get catch a HARM very quickly.
Think of this as a supplement for the E-3 and the P-3.
The P-3 is big and slow and so far none of them have been shoot down over Afghanistan. And yes they are actually popular sensor platforms in that theater.
Re:Protection? (Score:5, Informative)
The real problem is speed, or rather the lack thereof. Air travel became as popular as it is because it's so much *faster*. People might book an airship flight once a decade for the novelty, kind of like a cruise ship trip, but they're not going to hop on the blimp whenever they need to get to the other side of the country. The trip would take too long. Jets are faster, so they win.
People still use cars for cross-country travel. It appears that there's a serious misconception about airship speed here. Maybe we're used to seeing blimps lumbering around stadia (yeah, I typed stadia). These limp airships are only about 1/4th the size of classic rigid craft, and are intended to cruise around 30 knots. The Hindenburg made 85 mph on 4 diesel engines. The USS Akron could do 83 and the Macon 87. These were all built in the 1930s, and were designed to be much faster than surface vessels with much longer range than heavier-than-air ships. Assuming a modern passenger airship could do 100-200 mph, it could easily compete with high speed trains and cars -- even jets for trips under 500 miles or so. People use jet travel not for the speed advantage over airships, but rather for the all-weather availability. It would seem the military picked 20000 ft operational altitude to mostly avoid the problem of weather closer to the surface.
Re:Flashbacks.... (Score:2, Informative)
Re:Yeah right (Score:2, Informative)
I'm not sure he's advocating cutting off the soldiers from support. He just seems to be saying that the war is really stupid, and any and all investment in such a war is folly to the extreme. The rest of his post is just trolling.
But, that said, I am not sure if it would be betrayal. From my point of view, everyone who signed up to invade Afghanistan and Iraq betrayed me, betrayed the people of Iraq and Afghanistan, and betrayed the citizens of his respective nation. When it comes to randomly invading countries, I am a pacifist to the extreme.
You do realize that 9-11 was ordered by a guy living in Afghanistan, under the protection of the Taliban, right? You can say what you want about Iraq, but going to war in Afghanistan was IN RESPONSE to us being attacked. It was hardly random.
Re:Protection? (Score:3, Informative)
Re:Introducing the LCWBDS (Score:2, Informative)
These aren't a balloon, and they don't "pop". They run at about +1 PSI and have been tested to take several hundred rifle rounds and even several RPGs through them, with neither catastrophic failure, nor rapid enough loss of lift to prevent finishing a mission and returning to home base.
+1 PSI just doesn't gush enough gas out the hundreds of holes (which the material prevents from turning into a giant rip, and the low +PSI doesn't exacerbate rips either) that the gas tanks on board can't easily keep up with for hours.
So, comedy aside, no, a guy with a shotgun won't even be close to enough. And good luck firing a shotgun or rifle sitting in a lawnchair balloon, Mr. Pendulum. :)
Re:Protection? (Score:3, Informative)
Re:250-Foot ... ?! (Score:3, Informative)
BTW, its a 76.2 metre airship.
Efficiency, lifting body and steam airships (Score:3, Informative)
>1) Are they really more efficient?
>...2) What gas to use though?
Airships can be very efficient, but only when they are gargantuan. The lift goes with the volume while the cost and drag goes with the surface area, so the $/ton efficiency goes up linearly with size. Given some internal structural rigidity, airships can be reasonably fast without giant engines (roughly 100-200 km/hr for on the order of 100W / kg payload.) The problem is that you have to have someplace big enough to land and store them and some way of dealing with them on the ground when the wind kicks up. A lifting-body partially buoyant airship relaxes the need for extreme size, allows easier ground handling, and makes flying easier by allowing altitude changes to be less dependent on managing buoyant lift.
Helium is not an economical choice of lift gas - it is too expensive to vent yet will leak out slowly through any light-weight material, it is nonrenewable and far more useful for cryogenics than lifting. Hydrogen is dangerous if pure - it can safely soup-up a lift gas mixture, though. Hot air is low performance in every possible way. Ammonia is poisonous and some what flammable. Methane is flammable and does not perform as well as hydrogen.
Steam is actually the best lift gas from many points of view, giving 60% of helium's lift and being non-toxic, cheaply produced from water ballast and engine waste heat and is easily ventable for buoyancy control, but steam airship design does require some envelope insulation and provision for condensation collection.
In 2006 Slashdot had an article on a similar lifting-body airship design: "New Aircraft is Part Blimp and Part Airplane" [slashdot.org] where I commented [slashdot.org]:
The lifting body and wings allow the craft to operate under a much wider envelope of loads and buoyant lifts. A huge problem with airships is maintaining desired buoyancy despite variations in temperature, altitude, barometric pressure, fuel expenditure, and condensation or icing loading - helium is too expensive to vent when the airship is light and cannot be generated in flight as can hydrogen, hot air or steam*. Being able to descend or ascend without losing ballast or lift gas and to operate without massive ground crews and facilities should significantly reduce the operating expense associated with helium airships. The Ohio Airships people have gotten an amazing amount done with very little money, and they seem to be selling their idea effectively to US government buyers, so it seems possible that this design will avoid the fate of all the other large airship projects of the past 60 years.
The main innovation in the Ohio Airships design is in the novel rigid internal structure which uses a keel beam supported by stays (cables) from a tower in the manner of a suspension bridge. This should allow greater loads relative to the airframe mass, including positive or negative loads from the wings.
*Steam is potentially the most economical lift gas since it gives 60% of helium lift or 200% of hot air lift, is essentially free if generated as a by-product of a steam engine, and the airship envelope acts as a condenser for the engine, reducing weight. This makes both the lift gas and propulsion much more efficiently produced than helium bags or IC engines See www.flyingkettle.com for more details.