[Elecraft] Ballons and Gas (WAS: ridge vent as antenna?)

[EricJ]

No question, hydrogen can be handled safely. I didn't make it clear, but I
was recommending against a ham generating their own hydrogen for a 160m
balloon. Given the cost of helium and the flinty skin of most hams, some
would try it. The Europeans race gas balloons all the time without any
drama, but they know what they are doing.

It used to cost us about $1600 to fill a 30,000 cu. ft balloon with helium
and it's good for only one flight. Someone else mentioned one of the
problems with a gas balloon as an antenna. As it cools, the gas contracts,
and with less volume, it descends, so you need enough excess helium to
assure it will still have enough lift when it contracts.

In the manned balloons, we left the appendix at the bottom wide open. Of
course the helium wants to stay in the balloons since it rises so there is
no problem with it being open. During the day, the gas heats up and instead
of expanding the balloon and risking a rupture, it vents out the bottom
appendix, but in the evening when it cools and contracts, it sucks air in
and contaminates the helium. You compensate by ballasting. That's what
limits the flight...eventually the helium is too contaminated to produce
enough lift and you are looking for things to throw overboard. That won't
happen with a latex balloon that would be sealed at the bottom.

Anyway, the expense is a problem, but for the possibility of an outstanding
160m signal in a contest, it might be worth looking into. Keep in mind that
it could be a useful way to EXTEND an existing vertical. Since you are only
lifting the extension, the size of the balloon and therefore the expense
will be less.

Eric
KE6US
www.ke6us.com



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ron D'Eau Claire
Sent: Monday, March 27, 2006 6:35 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] Ballons and Gas (WAS: ridge vent as antenna?)

Very interesting Eric!

Of course, along that line of hydrogen safety, the Hindenburg was a HELIUM
dirigible. Although the Germans had an excellent safety record with
hydrogen, they understood the danger vs. small extra lift from using that
gas and the Zeppelin company designed the Hindenburg to use the safer helium
gas. 

Unfortunately, the Nazi party had taken control of the German government by
the time the helium was needed and the USA - who had the only supply
available - decided not to allow the export of the helium gas to Nazi
Germany. 

So the Hindenburg flew with hydrogen in her lift cells. After all, the Graf
Zeppelin had flown over a million miles safely with hydrogen. The Hindenburg
herself hundreds of thousand miles with hydrogen in her lift cells before,
on her second long voyage of 1937, regrettably flew into history.

Makes one wonder what aviation history had been like if she were carrying
helium as originally planned...

Ron AC7AC