Gas Explosion Handbook

Hello Guys,

I have been a silent reader for the past few month (that does not mean that I did not do anything concerning airships) but yesterday I found something that I really want to share with you because it is very interesting. I found a online version of the Gas Explosion Handbook that tells you a lot about gases and how they explode. Espeacially page 4 (the page I linked to) tells you a lot about hydrogen flamabillity. Look at the last table on the page -- it gives hints on how to make hydrogen inflammable!

If you had a mixture of 43% hydrogen and 57% CO2 you would still get a lift of 186.3 g per m3! I think that is quite a good compromise:
A gas mixture that

• We can produce on our own (hydrogen by electrolysis, CO2 by …)
• Is inflammable
• Gives a lift of 186.3g per m3

I would like to know what you guys think about it.

Greetings,

erniejunior

Sounds Great, Ernie, I would like to look into that and study those charts.  Oddly enough I found similar information on CORN STARCH being a very explosive dust, more so than coal dust and could actually be used to blow up a building. LOL.

Thanks for the link. That chart is a good reference to have.

.186 kg per cubic meter is not great compared to 1.1 or 1.2 kg per m^3 that you can get from helium or hydrogen. (I think I moved the decimal places correctly)

Of course .186kg per cubic meter is far worse than 1.1 BUT: when using hydrogen you need to be able to convince people that it is safe in order to make them trust or even invest in the technology. I don't want to fly my airship far away from any civilisation, not sharing the experience with anybody else.
Hydrogen + CO2 is so far the only lifting gas that:

• Does not need to be heated (I don't like to heat the lifting gas because then I waste energy to stay up -> that is like an airplane)
• Is neither inflammable nor toxic
• Can be easily produced at home

Greetings,

erniejunior

What about all the energy that must be 'wasted' due to the drag of an envelope that is several times larger? I don't share your distaste for heating. I like it for a degree of control.

We have also considered other inerting gases like nitrogen and halon. They get heavy fast.
http://smallblimps.lefora.com/2011/01/14/fire-suppression-in-hydrogen/ 

Lest we forget that hydrogen will separate out of the co2 and you will have the heavy gas in the bottom of each bag and the hydrogen in the upper part.   If the gasses don't stay mixed they are of little use as a fire suppressant.   Hydrogen and helium mix fairly well, but the helium diffuses out faster than the hydrogen so it would have to be checked from time to time.
.   If you surround your hydrogen lift bag with  helium, even a small amount, it makes it insulated from fire, any that escapes is doing so in a pure helium environment and the hydrogen can be the bulk of the lift gas, being surrounded by helium, it no longer has to mix with the gas.   Say you had 7,000 cubic feet of hydrogen and 1,000 cubic feet of helium, that would be very affordable compared to 8,000 cubic feet of helium.   Of course you would need an internal net or structure, like the frame itself to keep the inner bag off of the outer shell.
    In theory, helium will diffuse into the hydrogen bags more rapidly than the hydrogen will diffuse out so the inner lift bags will gradually gain pressure.  Isn't that a kick in the head?

"Lest we forget that hydrogen will separate out of the co2 and you will have the heavy gas in the bottom of each bag and the hydrogen in the upper part. " Let's not make stuff up. Two gasses in a tank will mix over time, not separate.

Two gasses with as different a mass as H2 and CO2 probably would stratify if left at rest. But an airship in motion is hardly at rest, so its a bit much to expect them to separate to any useful degree.

Nitrogen is 3% buoyant so makes an decent envelope/buffer gas.  Ammonia is actually better yet, if you are willing to play with the nasty stuff. It has a low boiling point which means you can use it as both a lifting gas and ballast.

I share the opinion of guest and jamesg, that the gases will not seperate. That is because of diffusion forces.

But this sounds quite interesting:

In theory, helium will diffuse into the hydrogen bags more rapidly than the hydrogen will diffuse out so the inner lift bags will gradually gain pressure.  Isn't that a kick in the head?

-inventive47

This way it is quite easy to maintain a pressured bag!

@dude: I think we have two different designs for the airship in mind. I want mine to be able to stay up for weeks or even months to make long jurneys (even though the will be slow because of oversized bags). Therefore I can not waste energy to stay up. For me the main reason I like airships is that you do not have to apply energy to maintain height like an airplane. Maybe it is too radical to say that I do not want to use any energy for my lift. But e.g. the energy used in a hot air ballon is far too much for me.

Greetings,

erniejunior

Unfortunately the He will also diffuse out of the envelope even faster so its still a losing game.

Yes, and some hydrogen will also make it out of the lifting bag and then out of the outer envelope,   Hopefully the outer envelope can be a little extra thick to help out with that.   Having a thick outer shell would help in both rigidity for those who want little or no frame, and with attachment points for anchors or motors as well as reducing diffusion of lifting gas.   If helium is ten times more expensive per cubic foot, and helium were 25 cents it would be 2,000 dollars to fill it with just helium and weekly top offs of maybe $100 bucks, All hydrogen would be 200 dollars with weekly top offs of 10 bucks or less.  A 1 to 9 split would cost 200 for the helium and 180 for the hydrogen coming to 380 for a safe hydrogen ship.   In case anyone is wondering about co2 it is expensive also, at least for paint ball guns it is outrageous.
.    As for mixing gasses,  they will not stay mixed well in a round ship,  as a bowl  with cereal, when you turn the bowl the cereal may stay in the same orientation.   Hydrogen will separate from a heavy gas.   It would be better to partition the hydrogen off from the safety gas in order to have a safety zone.

As for mixing gasses, they will not stay mixed well in a round ship, as a bowl with cereal, when you turn the bowl the cereal may stay in the same orientation. Hydrogen will separate from a heavy gas. It would be better to partition the hydrogen off from the safety gas in order to have a safety zone. Please refer to your chemistry book on gas mixing. They will spontaneously mix. There is no post mixing stratification or separation. You are violating the laws of thermodynamics.

My apologies, Guest, I have studied Brownian motion and though it works for small containers that have heat energy the effect has not been commented on for very large containers or the atmosphere.  Gravity supersedes and  Helium and hydrogen rise through the atmosphere, mixed and then escape into space.   I would be happy to see that helium, for instance would mix in a room and stay that way.  Globally there is evidence that gases stratify, such as ozone.  I realize my mistake, however, such as during a fire, hot gasses, light gasses are up and cool oxygen is down low, but given enough time they will mix.   Hot air stays up, cool air stays down, so I have to wonder about large volumes of gas behaving like small containers in a class room.  Still, I hope you are right, for I want a helium oxygen atmosphere in the Enterprise's decks.  And I don't want to have to employ little fans everywhere to keep it mixed.

If you have   hot  and cold   you have motion  as  the hot cools  it  falls   and as  the  cool  heats it  rises . being  that  your  ship is in motion   and   making  turns  plus  the sun  angle is  always  changing   too ,   the gas    cant  do  anything  but mix .   In  a  class room ,   constant 72 degrees,    static table  test  it  might  separate .  But put a little heat source on one side  and  see  what happens  . 
  As  far as  a  passenger ship   goes  ,  your  going to  want  climate control  in  there  anyway = air movement .

I think the only way to end this debate is to try it out