Anhydrous Ammonia as a lifting gas? or is it explosive?

Hi everyone, I have been wanting to build a blimp   ever since I was a young lad.
We all know helium and hydrogen got their reasons:  the first is expensive and the other is flammable
I have been studying airship designs and gases. 
Among the lifting gases I am thinking about using ammonia as a lifting gas.  Beside that it is toxic and corrosive, It is  a little explosive (flam. limits: 15-25%) but at the same time  it says everywhere that it is "unlikely to explode in  air" and is a safe gas?

 It is offcourse nowhere as flammable as hydrogen or methane but How flammable is  ammonia,
I jsut cant get a picture as all the sources  are not clear how really explosive it  is.

 How dangerous  would it be to fly  a 300m3  blimp filled with  ammonia. I find it amusing that none is mentioning ammonia in relation to airship.

Regards
Carl

Two reasons come to mind:

1.If you pick a gas with much less lifting ability, the size of the ship for the same amount of payload is huge. This makes for bigger engines to overcome bigger drag, bigger envelopes means bigger costs.......

2. Nobody has talked about moisture diffusion. As water gets into the envelope and reacts to form ammonium hydroxide, you get a loss in lift and a corrosive condensate to deal with.

The big point to remember is that this is a Personal airship.  We're heading for small to keep costs down and performance up. The smaller you get with an airship the bigger the chalenges just to make it happen.

Thanx for the reply

The smaller lift of Ammonia : half of  Helium is really not the biggest problem the way I see it. 
 The corrosion and flammability are what to worry about however.

I am not a chemist  but  isnt  Anhydrous Ammonia just a pure gas with no need to react  with something  in order to produce a lifting gas?  I dont quite get you  on point nr 2?  I was thinking oof filling a bag with  Ammonia

A concern came to me now considering the material choice of the bag, it has to be anti corrosion.

Regards
Carl

Hey Carl, glad to have you.

Swampie was saying that once water vapor diffuses into the bag, it will react with the ammonia and make a corrosive liquid. I agree that the lift provided by ammonia is sufficient. But I am uneasy about the danger it posses from contact with it. I think hydrogen and methane are safer and less scary. There is also the possibility that ammonia will be more likely to react with the bag material. That could make choosing a bag material harder. 

Where is the water vapor coming from?

It comes from the atmosphere. I am not saying ammonia can't be used. I just don't see how it would be preferable to hydrogen or methane.

The process is called diffusion. Small water molecues wiggle through your envelope material. ( At the same time ammonia molecues wiggle out!) Ammonia disolves in water and then reacts to make ammonium hydroxide. As the envelope cools off ( night time or higher altitudes) the ammonium hydroxide condenses out. This is great if your gondola has waxed floors you need to clean but bad otherwise.

Let me  see if i got this right ,  Ammo  is  flammable right out of the supply tank  ?  Like methane  only  less?
Hydrogen  is NOT flammable in pure form  but only  when mixed with  air . If  true , Seem  like a clear  decision  to me .  
 Also  Ammo  is  now closely  guarded  /  regulated   because of the  stupid  meth  craze . It might be  quite the ordeal  to  buy it .

The available gases are:
Helium ---------more expensive, I cant afford it
Hydrogen------  flammable
Methane          less lift and yet flammable
Ammonia    hmmm....... I just cant find any info about how it would be in blimps,

   OR

Steam

I am just trying to think what gas is best, ammonia is  a "little flammable" "but  pretty unlikely to explode" in air as man sources say BUT at the same time they warn you about the danger of explosion.   A second thing about Ammonia is the corrosion. I simply dint know if it is even possible to find a material corrosion-resistant enough and  light enough...  The  horrible corrosion and the  bad availability of ammonia might rule out any ballooning completely!  But hey! weather balloons use ammonia----

Steam has better lift than ammonia and doesn't need expensive bags. But condensation might be a big  trouble, and  airspeed would be deadly

We have been talking about a round blimp lately. I think that type of airship would benefit from using steam (or high humidity hot air) for lift because of the shape and lower speed. That will reduce the amount of heat that is lost through the envelope. A little off-topic I know...

I am pretty sure all these gases require air to burn. 

The  steam  their  talking about is  a  super heated steam, very  Dry  .
  Hot  air  is  doable  and  safe , although  not long lasting .  but  Cheep  enough  to  not  discount  for  fun flying. and  the  ease it offers   about  airship  storage.  
  Hydrogen  still beats out  the other  gas options .  It is  NOT  flammable  in pure  form.  With an H to air envelope gage,  It  will be  as safe as it can  be .  .  At, half the price of  He.  but that  would still make this  an  expensive  hobby to  buy  the gas.   

I know the hydrogen is not flammable "alone" but if mixed with air and the slightest static spark will ignite the whole ship...  If I was to own a car with a hydrogen tank, thats another story, I would drive it without concerns as gasoline is more dangerous, but above all because, the hydrogen in a car IS in solid protective tanks of a small volum. Unlike a huge bladder blimp.   In a blimp on the other hand, it is a tiny sheet of material that is supposed to protect the gas, and the volume of a blimp is huge!. There is a big difference between a hydrogen driven machine and   a hydrogen filled blimp

My opinion

Yes , that is why  a  gas to air ratio  guage  would be  mission  critical   to  the  safe use of hydrogen .  If  you  know   at  any  given  time  what  the gas condition  is in,    your  safe.  If  you  see the  ratio  start to  creep  toward the  flamibility  point ,   dump  the gas.   It has to  reach  a  4%  air to H  ratio to get there.  Thats  a LOT of  air . 

So you would keep the mix less than 4% whole the time, correct? are you talking about the mix inside or outside the blimp? .. in any case a spark will ignite the thing if it is anything above 4%

This was recently discussed in another thread. In order to be ignited, the air fuel mix has to be within a range of like 4% to 75% to ignite. Inside the envelope, the ratio is too rich to ignite until it is about 25% air. Outside of the envelope, the mix is too lean until it reaches about 4-5% hydrogen. 

What I wanted to know is how does the "atmosphere" know that the hydrogen has a ratio now of  "4% in the air" when the hydrogen leaks outside the envelope in a very smal amount. I mean..., the air outside the blimp is endless and the tiny bit of hydrogen can yet become 4%

Good question. Flammability is usually tested in closed containers. In the atmosphere, it mixes in a non-uniform manner. Some small pockets will be at higher concentrations than others. It just matters what the mix is right at the point of ignition (with a spark for example).

Dont forget  hydrogen  rises  at 22 ft per second .  So  there  should be no  worries  for  a  flam  ratio  mix outside the envelope.  Unless it  was a  true  leak or  pinhole  that  somehow got into  an  ignition source.  OR  you  are using  gas bladders  INSIDE a  air tight  shroud.  If your  shrouding  the  bladders   it  has to have  good  ventilation  to keep  the  hydrogen  from  building up. 

Remember that ammonia and water is used to make a refrigerator that works on heat.  Water and absorb many times its weigh of Ammonia but heat the water and it is released.  So Ammonia can be recovered from the condensate water and the water retained to balance the burned fuel. 
Ammonia has been used as a fuel for combustion engines and is considered one of the best approaches to make hydrogen powered vehicles.  However; it has a narrow explosive range and the heat of combustion and the energy needed to initiate combustion without a catalyst means you are save in using it for a balloon.   (Canadian during the last fuel embargo tried to get Canada to use ammonia.  He drove around in an ammonia powered car.)
The skin of a balloon can be made from available materials.  Rip stop nylon coated with rubber:

EPDM rubber (ethylene propylene diene Monomer (M-class) rubber) 

EPDM sheeting is used to line and waterproof man made ponds. Most back yard water gardens and koi ponds use an EPDM liner.

Neoprene or polychloroprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. 

It is used for wet suits, waterproof automotive seat covers, in liquid and sheet-applied elastomeric roof membranes or flashings, and in a neoprene-spandex mixture for manufacture of wheelchair positioning harnesses. Because of its chemical resistance and overall durability, neoprene is sometimes used in the manufacture of dishwashing gloves, especially as an alternative to latex. In fashion, neoprene has been used by designers such as Gareth Pugh,Balenciaga, Lanvin and Vera Wang.

Aluminum is one metal that is compatible with ammonia.  Many plastics are used with ammonia including

Polypropylene and epoxy.

H2O is not permeable thru most plastic materials in discussion here. H2O contamination would mostly come from the filling process. Ammonia is an attractive lift gas because it does not have the outgassing permiability problem of H or He, and it it easily reduced, recovered into liquid form instead of having to super-cool or super compress it. However, it IS a nasty toxic stuff. Plus its not as effective as Hydrogen.