6 ms·
I think you just invented the dirigible?
by PatentTroll 9y ago
I think you just invented the dirigible?
- projectramo 9y agoHa, yes. I guess another way to phrase the question would be: why don't they use dirigibles to solve extended air time problems?
- mikeash 9y agoDirigibles require huge volumes, because the lifting power of gas is small. Those huge volumes make for a relatively weak, slow, and difficult-to-maneuver craft. A big reason why airships disappeared in favor of airplanes was that airships had a really tough time handling or avoiding bad weather because of these limitations.
- acchow 9y agoI assume huge volumes are also easily detectible?
- mikeash 9y agoSeems reasonable. All else being equal, your radar cross section is proportional to your actual cross section. Plus it's probably easy to spot a blimp with your eyes.
- jp555 9y agoI have a blurry recollection of seeing an aircraft design that was a combination of an airplane and a dirigible. It looked like a poofy manta ray, an inflated rigid lifting body or flying wing. It wasn't quite VTOL & needed a very short runway, but it also gained more maneuverability in flight. Maybe it was too much of a compromise though.
- theophrastus 9y agoPerhaps you're thinking of the infamous 'Deltoid Pumpkinseed'[1][2] ? [1] https://en.wikipedia.org/wiki/AEREON_26 https://en.wikipedia.org/wiki/AEREON_26 [2] https://www.amazon.com/Deltoid-Pumpkin-Seed-John-McPhee/dp/0374516359/ https://www.amazon.com/Deltoid-Pumpkin-Seed-John-McPhee/dp/0...
- cr0sh 9y agoYou mean this one? http://mashable.com/2017/05/24/airlander-butt-plane-successfully-flies/ http://mashable.com/2017/05/24/airlander-butt-plane-successf... There's actually been more than one of these types of aircraft (known as Lighter Than Air - or LTA Aircraft), either as an idea or prototype throughout history.
- astebbin 9y agoCould it be this one [0], or its predecessor [1]? [0] http://www.latimes.com/business/la-fi-lockheed-martin-aircraft-20160308-story.html http://www.latimes.com/business/la-fi-lockheed-martin-aircra... [1] https://en.wikipedia.org/wiki/Lockheed_Martin_P-791 https://en.wikipedia.org/wiki/Lockheed_Martin_P-791
- sk8ingdom 9y agoThat type of vehicle is called a hybrid airship! [1] https://en.wikipedia.org/wiki/Hybrid_airship https://en.wikipedia.org/wiki/Hybrid_airship
- DrScump 9y agoThe lifting power of helium is small, as opposed to hydrogen. Also, helium has supply problems. Is it not possible to have a modern airship with hydrogen as its primary lifting agent?
- mikeash 9y agoHydrogen doesn't buy you that much additional lifting power. Air is about 1.2kg/m^3 at STP, so that's the theoretical maximum you can lift with a cubic meter of gas bag. (And you can only get that value if you could somehow hold a vacuum, of course.) Hydrogen is about 0.09kg/m^3 at STP, so you can lift about 1.1kg/m^3. Helium is about 0.18kg/m^3, so you can lift about 1kg/m^3. Helium is twice as dense, but that only costs you about 10% of your lifting power since both are so light compared to air. I see no reason you couldn't use hydrogen, but I don't know if anyone would want to take the risk. (Specific flaws of the Hindenburg aside, hydrogen is explosive across a distressingly wide range of mixture ratios with air.) If you did use hydrogen, I think the main motivation would be avoiding the use of scarce helium, not the minor increase in lift capacity.
- ForHackernews 9y agoIf it's an unmanned drone-blimp, the safety issue because somewhat less critical.
- gozur88 9y agoBut still critical enough to make it impractical. How would you do maintenance on a hydrogen airship without risking the people doing the maintenance? And you'd never be able to fly over populated areas.
- petre 9y agoIt is possible but we all know what happened to the Hindenburg. Using hydrogen is asking for a fire to happen. https://en.m.wikipedia.org/wiki/Hindenburg_disaster https://en.m.wikipedia.org/wiki/Hindenburg_disaster
- jianshen 9y agoI wondered why this wasn't applied to suitcases to make them lighter and then common sense kicked in regarding just how much actual helium would be required to lift even an empty suitcase...
- teraflop 9y agoIt's not even an issue of how much helium is needed; no amount of helium will make a typical suitcase buoyant. Filling it with helium at ambient pressure wouldn't produce nearly enough lift, and increasing the pressure would make it heavier, not lighter. What's needed is not mass, but volume.
- Sohcahtoa82 9y agoI feel like you're being deliberately obtuse. I think jianshen meant how big of a helium balloon you'd need, not how much helium you'd have to put inside the suit case.
- lostlogin 9y agoMaking them a vacuum would help better.
- tpeo 9y agoThey are used to solve extended air time. That's what a weather balloon is. If what's bugging you is why lighter-than-air vehicles aren't used for commercial transportation, that's an entirely different issue.
- zeropoint46 9y agoweather balloons are typically not up for that long, 90 or so minutes on average. So I don't think that's solving the extended air time. In fact they are pretty much designed to go up and pop and come back down. Lighter than air in general can be used to solve extended air time, and we're back to dirigibles, not weather balloons.
- NickSharp 9y agoProject Loon seems to be doing fine. They're using balloons to keep equipment aloft for months at a time.
- zeropoint46 9y agosure, but I wouldn't exactly call that a weather balloon.
- tpeo 9y agoWell, I'm disappointed that the majority of their flights are this short. I thought there were some of them which were permanent atmospheric weather stations. But short flight times don't really have to be the case, because it seems that they can fly for extended periods of time: one of NASA's balloons stayed up for 46 days [0]. The US air force also uses balloons as surveillance stations, though I don't know the actual flight time of these [1][2]. JLENS was supposed to stay up for 30 days at a time. [0]: https://www.nasa.gov/centers/wallops/news/supertiger-record.html https://www.nasa.gov/centers/wallops/news/supertiger-record.... [1]: https://en.wikipedia.org/wiki/Tethered_Aerostat_Radar_System https://en.wikipedia.org/wiki/Tethered_Aerostat_Radar_System [2]: https://en.wikipedia.org/wiki/JLENS https://en.wikipedia.org/wiki/JLENS
- exhilaration 9y agoThe U.S. military is way ahead of you, they've been used for extended surveillance in war zones since 2004: http://www.nytimes.com/2012/05/13/world/asia/in-afghanistan-spy-balloons-now-part-of-landscape.html http://www.nytimes.com/2012/05/13/world/asia/in-afghanistan-... and even domestically: https://theintercept.com/2017/04/24/nsa-blimp-spied-in-the-united-states/ https://theintercept.com/2017/04/24/nsa-blimp-spied-in-the-u... And before that, I believe surveillance blimps have been used in some form or another since the 19th century.
- vilhelm_s 9y agoNot to mention outside Washington DC. :) https://www.washingtonpost.com/news/the-switch/wp/2015/10/28/the-army-lost-control-of-a-giant-unmanned-surveillance-blimp/ https://www.washingtonpost.com/news/the-switch/wp/2015/10/28...
- traviscj 9y agoJesus, they shaped it like a giant bomb. No wonder everyone is uncomfortable. :-/
- walrus01 9y agoHelium is rare and expensive and becoming even more so as time goes on. Hydrogen has this nasty habit of being extremely flammable. Rigid or semi-rigid airships when scaled up are really difficult to moor and arrange ground handling for, which is why some of the recent prototypes that have been flown integrate skirts and reverse-hovercraft like suction apparatus that can hold them down on a flat field. The empire state building was originally intended as a Zeppelin mooring location, but the plan was abandoned due to wind and inability to control a zeppelin to that level of precision.
- throw_away 9y agoNot sure what the flight-time is, but this is pretty cool (helium-filled RC craft that looks like an airliner and flies indoors): https://www.youtube.com/watch?v=2Kk5EGpYuck https://www.youtube.com/watch?v=2Kk5EGpYuck
- jandrese 9y agoThe article said that the lighter than air aircraft got blown around by the wind too much. They needed a drone that could loiter over a specific area for an extended period of time, presumably acting as a communication relay for disaster or war zones.
- novaleaf 9y agoprobably because the need is real, just not the "for natural disaster" reason they gave.
- samstave 9y agoI assume you're only asking what address to send the summons to, huh?