AMRAD at Hamvention
mo at ccr.org
Sat May 12 21:12:52 CDT 2012
A big issue with H2 tankage is that embrittlement is a serious problem which is
magnified by the high pressure need to get much H2 a given volume.
I suspect that makes cylinder re-use a rather riskier proposition,
enough so that it probably wrecks the usual cylinder gas economics.
Most places I know of that really use externally supplied H2 take it as a cryo-slurry
because of the volumetric efficiency of storage and transport.
Btw - it was NASA that figured out how to slurry H2 because that's the
only way to carry enough to actually use it fuel. Even pure LH2 has crappy
density compared to slurry. The most amazing part is that it's done easily with a catalyst
instead of insane pressure and the slurry is far more stable and flows better
In the fuel lines than pure LH2.
Just one more area of technology that barely existed at all before Project Apollo -
Producing, handling, and using cryogens in industrial quantities.
Sent from my iPad so please excuse the jammy fingers.
On May 12, 2012, at 8:29 AM, "Robert E. Seastrom" <rs at seastrom.com> wrote:
> "fgentges at mindspring.com" <fgentges at mindspring.com> writes:
>> An impending problem is the getting helium and such flights
>> will have to switch to hydrogen.
> I have a couple of small helium tanks (60 cubic feet, refillable) that
> I periodically get filled to take to parties. Instant "favorite uncle
> status", btw.
> Recently got one filled and the bill came to something like $80.
> That's up from $60 last time I got one filled. An identically sized
> tank of C25 for the MIG welder (75% argon, 25% CO2) is $30-ish, to
> give you an idea of price differential.
> It's ironic that we're in the situation we are, since the main source
> we have is by fractional distillation from natural gas and we're at
> record production levels of natural gas in these last years (the same
> sorts of formations that trap natural gas also tend to trap helium
> that's a product of radioactive decay). The record production is due
> to fracking and has resulted in record low prices (when adjusted for
> inflation), to the point that it there is an economic incentive to use
> gas insted of coal for base load power generation in many cases.
> Unfortunately cryogenic use of helium, e.g. in MRI machine magnets
> (largest use) and shield gas use (chip fabs in particular) is also at
> record high levels.
> I tried to get a cylinder of hydrogen at Arcet down in Manassas. They
> said they didn't stock it and kind of treated me like I was nuts to be
> wanting such a thing. I thought this was pretty ironic considering
> that the place is all full of propane and acetylene cylinders, both of
> which scare me a lot more than hydrogen.
> I wouldn't use it for balloons for kids, but for something like Doug
> did I'd be all over it. Only 8% better lift power (inconsequential)
> for H2, but I can't help but wonder if it would leak out of rubber
> balloons more slowly due to the molecules being fatter (it's diatomic).
> Food for thought...
> BTW, I'm planning to be at Dayton this year. :)
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