Airship-to-Orbit?

"Ron Wanttaja" wrote

Back when I was just a young engineer, the test organization I was in did
leak testing for the fuel tanks for the first Air-Launched Cruise Missiles
(ALCMs). Said tanks were pressurized with helium, with a sniffer to chase
down the leaks.

Ron Wanttaja

So how did it let you know it found a leak? Did it start talking to you in
a real high, squeaky voice? g
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.690 / Virus Database: 451 - Release Date: 5/22/2004

On Fri, 28 May 2004 23:59:27 -0400, "Morgans"
wrote:


"Ron Wanttaja" wrote

Back when I was just a young engineer, the test organization I was in did
leak testing for the fuel tanks for the first Air-Launched Cruise Missiles
(ALCMs). Said tanks were pressurized with helium, with a sniffer to chase
down the leaks.

Ron Wanttaja

So how did it let you know it found a leak? Did it start talking to you in
a real high, squeaky voice? g

That's why they didn't have *me* do it. They couldn't tell the
difference. :-)

Ron "Patton didn't sound like George C. Scott, either" Wanttaja

I know this is quite a leap.....but can someone explain to me why breathing
helium causes your voice to go up in pitch? I have never heard a really good
explanation of this phenomenon.

Dave

On 29 May 2004 19:58:03 GMT, (VideoFlyer) wrote:

:I know this is quite a leap.....but can someone explain to me why breathing
:helium causes your voice to go up in pitch? I have never heard a really good
:explanation of this phenomenon.

It's really aerodynamics and Reynolds numbers - but the short version
is something like this.

The sound of your voice comes from your vocal chords vibrating. They
vibrate in the airstream created by you exhaling.

Regular air, which is mostly Nitrogen and Oxygen. is much thicker than
helium. Like it says earlier in this thread, helium atoms are much
smaller than N2 or O2, and they go through passages much easier. It's
like comparing lacquer thinner to maple syrup. The Robinson helo uses
helium to inflate the emergency floats not because it's lighter, but
because it gets through the plumbing faster, so the floats inflate
faster.

So, when helium goes past your vocal chords it doesn't exert much
force on them. In order to get them to vibrate, your mussels have to
pull them much tighter - which means, when they do vibrate, they're
vibrating much faster, light a tight guitar string vrs a loose one.

On Sat, 29 May 2004 19:58:03 +0000, VideoFlyer wrote:

I know this is quite a leap.....but can someone explain to me why breathing
helium causes your voice to go up in pitch? I have never heard a really good
explanation of this phenomenon.


My understanding was that the speed of sound in Helium is higher than the
speed of sound in air (about 3x faster). I think this is because helium
atoms are lighter, so to exert the same pressure they need to move faster.

If you take a resonant cavity of fixed length - like a hunting-horn - then
the wavelength of the fundemental is fixed. But if it is filled with
helium, the speed of sound is higher, so the frequency that has this
wavelength is also higher (Speed of sound = Wavelength x frequency).

I think the combination of your voice-box, windpipe, lungs and mouth also
works as a resonant cavity - though it's clearly more complex than the
parabolic shape of a hunting-horn cross-section and other effects may be
involved.

I'm not 100% sure whether my explanation is correct, or even whether it
contradicts that of Richard Riley - but I'm left wondering whether the
maximum frequency of your voice goes up if you inhale helium. According
to my explanation, I expect it would.

In a hunting horn, the highest note I can ordinarily play is certainly
limited by how taut I can make my lip-muscles. I assume the limit to the
tautness of my voice-box also sets the highest note I can sing. If Richard
Riley's explanation holds, I would predict your voice should go up as you
inhale helium but its maximum pitch should stay the same.

nb... I'm told the helium in party balloons contains lots of hydrocarbon
gases and can stop your heart if you inhale it and get unlucky.

anonymous coward ere

nb... I'm told the helium in party balloons contains lots of hydrocarbon
gases and can stop your heart if you inhale it and get unlucky.

Could be. Most old helium comes from natural gas wells and used to be stored in
big tank farms as the national helium reserve. Today, you can get helium from a
liquid air plant that is close to pure.

I have always been afraid of taking big breaths of ANYTHING with no oxygen in
it. I don't need some sort of reverse osmosis of oxygen leaving my blood. To
experiment with helium and voices I would recommend heliox mixed gas from a
technical diving establishment.

-- Charlie Springer

anonymous coward wrote:

(Speed of sound = Wavelength x frequency).


???

Richard Lamb wrote:

anonymous coward wrote:
(Speed of sound = Wavelength x frequency).

???

Wavelength meters, frequency 1/sec, gives meters/sec = speed

-- Charlie Springer

On Mon, 31 May 2004 02:23:15 +0000, Regnirps wrote:

Richard Lamb wrote:

anonymous coward wrote:
(Speed of sound = Wavelength x frequency).

???

Wavelength meters, frequency 1/sec, gives meters/sec = speed

Or alternatively:

Wavelength (yards/1760), frequency (cycles/hour) = speed (miles per hour)

(for the benefit of American readers)

AC

-- Charlie Springer

anonymous coward wrote:

On Mon, 31 May 2004 02:23:15 +0000, Regnirps wrote:

Richard Lamb wrote:

anonymous coward wrote:
(Speed of sound = Wavelength x frequency).

???

Wavelength meters, frequency 1/sec, gives meters/sec = speed

Or alternatively:

Wavelength (yards/1760), frequency (cycles/hour) = speed (miles per hour)

(for the benefit of American readers)

AC

-- Charlie Springer

Funny.

I thought frequency was the inverse of wavelength.

x time 1/x = 1 ???