From: John De Armond Newsgroups: alt.energy.homepower Subject: Re: Hydrogen is too dangerous for common use This myth Date: Mon, 21 Jan 2008 16:37:22 -0500 Message-ID: <sh3ap35sblpkcet9fu8t4ld4vttb34qbj8@4ax.com> On Sun, 20 Jan 2008 21:10:00 -0000, "collin" <rebel@prosof.net> wrote: >The hydrogen in the blimp burned the way I see it it didn't blow up. When >the hydrogen and the oxygen or air are mixed in the flamable range and then >the ignition takes place that is what I call blowing up. > >hydrogen being very light makes it kind of safe as it goes up and away. in >the blimp example above it is said more folks got burned from the fuel for >the engines than from the gas used for floatation. > >Are you stating that the flame spread speed of a combustible mixture of >gasoline and air is 22 times the flame spread speed of a flamable mixture of >hydrogen and air? That is what I would call 22 times more explosive or at >least a good portion of it. Yup. In my teenage years, being a chemistry nerd, I became interested in the Hindenberg because large amounts of hydrogen that I'd set on fire, including in large balloons, just didn't behave like what I saw in that newsreel footage. I did some research, including a trip to the Smithsonian Air and Space museum where I saw the display and analysis and discussed it with the curator on duty. What I learned was that the famous fire was NOT hydrogen burning. Oh, some of it burned with a practically invisible flame but most rose too quickly to ignite. A few calculations support that theory. What burned was the explosive nitrocellulose "nitro dope" used to coat the fabric to make it fairly rigid and gas tight. A contributing factor was the Magdalum (sp?) magnesium-aluminum frame that was also flammable, given enough heat. There was a piece of the frame on display at the Smithsonian that showed clear burn (and not melting) patterns. Leaking hydrogen perhaps contributed to the initial ignition of the fire but the Hindeburg was, in fact, a spectacular nitrocellulose burn. Nitrocellulose is more familiar as smokeless gunpowder and celluloid. Movie fans are undoubtedly familiar with how old celluloid film would burn explosively, many times burning down the movie house in the process. I used to enjoy buying up old guitar picks which were usually made from celluloid. They'd burn almost like flash paper. None of the rest of that silly post is worth commenting on but I thought I'd relate what I learned about the Hindenberg. John From: John De Armond Newsgroups: alt.energy.homepower Subject: Re: Hydrogen is too dangerous for common use This myth Date: Tue, 05 Feb 2008 08:04:45 -0500 Message-ID: <94ngq3hjjs6e205soa4c4jivhpe89o5bda@4ax.com> On Tue, 05 Feb 2008 10:00:16 GMT, nobody@nowhere.com (Rich S.) wrote: >It was also the Thermite paint on the skin. There was a Mythbusters episode >that explored the disaster. They mocked up three scale models and one did >include a thermite covering in proportion to what was recorded in the >original design spcifications, but the burn didn't appear to scale >accordingly. But, then again, it's hard to account for how fire behaves. >Fuel is fuel, no matter big or small. There was no thermite on the skin. How silly can they get (answer: with mythbusters (sic), there is no limit). The skin used aluminum dust as the pigment to reflect solar heat. Thermite is a mix of a metal oxide (normally iron but it works equally well for other metals such as copper) and aluminum dust. The aluminum dust reduces the iron oxide, producing aluminum oxide and metallic iron. The reaction is highly exothermic. The heat heats the iron enough to not only liquefy it but also to heat the substrate being welded (or burned through) to the melting point. The ratio of aluminum to the oxide is fairly important for there to be a proper oxygen balance. An excess of either reactant will result in reduced or no reaction. In the case of the Hindenberg, there was nitrocellulose, aluminum dust and cloth present on the skin. Piddle around with the oxygen balance a bit and you'll quickly see that the reaction was oxygen-starved. Way more fuel than available oxygen. Thus, the aluminum contributed little energy to the reaction. Aluminum dust is used as an energy booster in explosives. Tim McVeigh, for example, used aluminum to boost his ANFO explosive. For it to work, however, the proportions must be correct. There is little chance of that being the case on the Hindenberg skin. I don't have a TV so I've seen little of Mythbusters (sic) other than occasionally on youtube. What I have seen is pretty disgusting from a scientific perspective. If they'd titled the show "We blow things up for money" then it would be entertaining but not particularly accurate. John |