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Self - reflating unmanned hydrogen blimp

Practical
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(+9)
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Was originally "Self - inflating unmanned hydrogen blimp"

There's no reason why an unmanned dirigible shouldn't use hydrogen as a lift gas.

Hydrogen is cheap, and in reality relatively safe.

The proposal is for a long endurance maritime surveillance drone.

A conventional blimp envelope supports a gondola containing the instrumentation and control systems, hydrocarbon fuel, and the powerplant. This is an air-cooled hybrid unit driving a generator. The propulsion system uses vectored-thrust electric motors. The battery can of course be pre-charged from ground supplies, so full power is always available at launch.

The exhaust from the engine is cooled, and water condensed. This is filtered, and can be used as ballast for altitude control. As the blimp consumes fuel, its weight decreases; recovering water compensates for this.

Power from the engine can be switched to the drive fans, or used to charge a lithium-ion battery array. When maximum speed is required, both engine power and battery power are fed to the fans. When speed is low, and the battery is fully charged, electricity is used to electrolyse stored water. The hydrogen is fed into the envelope to replace diffusion losses; the oxygen goes back into the engine air intake to improve combustion.

This means that the powerplant can be run at constant revs and peak efficiency, constant temperature, and optimum output. A small turbodiesel is envisaged, improving performance at higher altitudes, which can be enhanced by use of electrolysis.

The envelope will have an internal "ballonet" to allow for the expansion of the lift gas at higher altitudes without the need for (wasteful) venting.

8th of 7, Sep 27 2016

Zeppelins over England by Kenneth Poolman https://www.amazon....pelins+over+england
An excellent work. [8th of 7, Sep 27 2016]

balloon solar collector http://www.electrif...ator-generates.html
[scad mientist, Sep 27 2016]

[link]






       No mention of fire, explosions, death, gleeful human inconveniences, crashes, pitfalls (literal or symbolic) or inadvertent population control...?   

       This is actually a great idea! Fresh bun for you [+]
whatrock, Sep 27 2016
  

       // No mention of fire, explosions, death, gleeful human inconveniences, crashes, pitfalls (literal or symbolic) or inadvertent population control...? //   

       Everyone has an off day now and again.
8th of 7, Sep 27 2016
  

       Hydrogen isn't flammable unless Oxygen is introduced, so I've never been able to figure out why we stopped using it as a lifting gas after the Hindenburg.
As long as the gas is kept compartmentalized and pure then any fires should be contained to small areas and not compromise the entire hull. (+)
  

       A lethal mixture of politics and public pressure, is why.   

       German airships bombing London in 1915 - 1917 were repeatedly hit by shrapnel and light machine gun fire. Several sustained structural damage and crash-landed, but none caught fire.   

       It wasn't until special explosive/incendiary ammunition was developed that the RFC and the RNAS succeeded in shooting them down in flames. Even then, sustained fire was needed, not just a short burst; 100 - 200 rounds from a Lewis gun at close range.
8th of 7, Sep 27 2016
  

       Your hydrogen envelopes could be sleeved with nitrogen, readily abundant and actually slightly buoyant in its own right, or carbon monoxide from the engine to guard against explosions.   

       Edit: modifications helpful when operating near a Lewis.
whatrock, Sep 27 2016
  

       The War Office thought that exhaust from the engines was cooled and discharged into the envelope, providing an inert blanket. This would have made it very difficult for riggers and other crew inside the hull. However, no such measure was implemented, or indeed needed.   

       <link>
8th of 7, Sep 27 2016
  

       Carbon monoxide is also flammable when mixed with oxygen.
notexactly, Sep 27 2016
  

       /The exhaust from the engine is cooled, and water condensed. This is filtered, and can be used as ballast for altitude control. As the blimp consumes fuel, its weight decreases; recovering water compensates for this./   

       very slick. Original to this scheme?
bungston, Sep 27 2016
  

       No. But the electrolysis idea probably is.
8th of 7, Sep 27 2016
  

       After the title and first couple sentences I was expecting this to be solar powered. If you depend on hydrocarbon fuel, you've got to come down occasionally or send fuel up. Yeah, solar panels can be heavy, but if you can work out a way to incorporate thin film panels as part of the skin or if you can make the whole envelope into a giant solar concentrator like a scaled up version of <link> you might be able to get somewhere.
scad mientist, Sep 27 2016
  

       No, has to be hydrocarbon fuel, if for nothing else but to wind up all those bearded tree-hugging sandal-wearing eco-fascists.
8th of 7, Sep 27 2016
  

       This is an awesome idea. Excess heat can be bled off to heat the hydrogen as well for a bit of extra lift.
AusCan531, Sep 27 2016
  

       I also think the blimp should collect solar energy. It also should collect rainwater. Then it can use some of the solar energy to electrolyze the water, to produce hydrogen that can replace losses leaking out of the blimp.
Vernon, Sep 27 2016
  

       If that's what you want, go build it. Ours runs on oil.   

       Did we mention that it's armed ? Well, it is.
8th of 7, Sep 28 2016
  

       Yes, it should definitely be solar-powered
hippo, Sep 28 2016
  

       /Did we mention that it's armed ? Well, it is/   

       If it were also legged, it could run along the ground, punching things.
bungston, Sep 28 2016
  

       // Did we mention that it's armed ? //   

       Ahh, the population control aspect. You have been exonerated.
whatrock, Sep 28 2016
  

       We haven't, it's just that these trousers are a bit tight.
8th of 7, Sep 28 2016
  

       I wonder if the extra ballast is really necessary. If you're too light because you've used up fuel, burn a little hydrogen. This may also replace the ballonet?   

       I also wonder if the complexity of electrolysis (you're not exactly dealing with the best water supply, filled with nasty products of combustion even if filtered) is worth it or if it makes more sense to just bring up some tanks of compressed hydrogen (or liquid in the form of methanol). Heavy at first, but lighter as used up.
Worldgineer, Sep 28 2016
  

       Just use solar to run de-humidifiers to pull pure CO2 right out of the air.   

       There's a video of a fellow in Greece who, after their economy tanked, does this, he stores the Hydrogen in half atmosphere tanks and sells the Oxygen.
It turns out that there is enough Oxygen present in the combustion chambers that he is running every gasoline motor on his farm, from generators to motorcycles, on straight Hydrogen and as an added bonus has tossed every radiator since the escaping gas alone is enough to cool the motor.
  

       Brilliant dude.   

       // If you're too light because you've used up fuel, burn a little hydrogen. This may also replace the ballonet? //   

       No. The ballonet allows a near-instantaneous response to pressure/altitude changes without venting gas or increasing the stress on the envelope. Burning hydrogen through the powerplant takes time, and one thing you don't want to do is waste any of your precious lift gas.   

       // I also wonder if the complexity of electrolysis (you're not exactly dealing with the best water supply, filled with nasty products of combustion even if filtered) is worth it //   

       It's distilled water. Yes, there's some oil in it, but the filter will grab that. Electrolyte will be needed for efficient electrolys, carbon electrodes are pretty resistant to poisoning.   

       // tanks of compressed hydrogen (or liquid in the form of methanol). Heavy at first, but lighter as used up. //   

       Not that much. The difference in mass between a 100 litre tank at 200 Bar and an empty one is not a lot, and they have to be cast steel; hydrogen diffuses really fast through aluminium, even thick aluminium.   

       The whole idea is to get rid of heavy storage tanks of compressed gas.   

       // de-humidifiers to pull pure CO2 right out of the air. //   

       That's one hell of a trick if you can pull it off ...
8th of 7, Sep 28 2016
  

       Woops, I meant H2O.   

       nobody drink the bottled water I handed out earlier...   

       <paroxysmal coughing>
8th of 7, Sep 28 2016
  

       I'd like to add one other little adaptation to this awesome collaborative resurrection of the commercial dirigible, and that is this;
There is no reason I can see why the hull itself could not be shaped as an Archimedes screw capable of extending or retracting its helical fins as weather allows which turns around a central axis, that the gondola itself is suspended from, to provide propulsion.
  

       Also:
//Excess heat can be bled off to heat the hydrogen as well for a bit of extra lift. — AusCan531, Sep 27 2016//
  

       If heat were bled off only on one side of the hull the extra lift from the expanding gas would provide sort of an impulse-drive as it would turn the hull.   

       You're not going to worm your way onto the project team that way, [2fries] ...
8th of 7, Sep 28 2016
  

       Never let it be said that I screwed my way to the top.   

       I wonder what property of a metal determines how well it allows hydrogen to pass thru. Atomic weight? Could one line aluminum tanks with thin gold foil and contain hydrogen better?
bungston, Sep 28 2016
  

       Erm, if you graphene as part of the skin, then you have a fuel cell in the making.   

       Not to be boring, but we did quite a bit of this in Your Own Vulcan Bomber idea.....   

       //pull pure CO2 right out of the air.   

       Well, with a Shaolin monk and some very small chopsticks...
not_morrison_rm, Sep 28 2016
  

       //has to be hydrocarbon fuel//   

       Ammonia might have only half the energy density as a CH2 chain, but it's lighter than air and liquifies @ 10atm, and fuel cells are much more efficent than ICE's.   

       Diborane is more powerful by weight than anything short of H2 (2x CH2), liquifies @ 50atm and is also LTA.
FlyingToaster, Sep 28 2016
  

       I think the problem people are having with "hydrocarbon fuel" is the fact that that is inconsistent with the "self sustaining" in the title of this Idea.
Vernon, Sep 28 2016
  

       Hmmmm ... OK.
8th of 7, Sep 29 2016
  

       Some humans flatulate hydrogen, depending on their gut microbiome. It ought to be possible to get cows to do the same. Therefore, a large enough cow- bearing blimp ought to be self-sustaining. Of course, the top surface would need to be flat and grassy to give the cows somewhere to graze, and a railing around the edge would be a good idea.   

       On the plus side, cows are nice friendly animals and are also highly edible.
MaxwellBuchanan, Sep 29 2016
  
      
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