[Discuss] Near space: Gas

Rick Osgood EMAIL HIDDEN
Tue Jan 24 13:34:11 PST 2012


All good points.  Can we get helium from another supplier?  Party store?
 That's where we rented helium from in the past.

On Tue, Jan 24, 2012 at 1:17 PM, Laura Harris <EMAIL HIDDEN> wrote:

> Except that the hydrogen flame is invisible in daylight :P
>
> The minimum energy for spark ignition [of hydrogen] at atmospheric
> pressure is about 0.02 millijoules. (via wikipedia)
>
> This is really low- cell phones can generate sparks at this level, so
> we'll need to be careful about such things as well as making sure all
> electronics in the capsule are turned off while inflating, the use of
> anything metallic or capable of making sparks close to or inside the
> balloon, and being careful to avoid any static discharges (esp. if the air
> is dry). Non-sparking wrenches for attaching hoses, etc. will be required
> (e.g., brass wrenches). Metallic tools coming in contact with hydrogen
> lines, fill ports, and valving should all be grounded. And so on.
>
> Yes, I'm paranoid about this- if we had an explosion, aside from the
> potential for physical harm, the press would be merciless (assuming they
> found out) and that in turn could create PR problems for other NS projects.
>
>   ------------------------------
> *From:* Rick Osgood <EMAIL HIDDEN>
> *To:* James Hukill <EMAIL HIDDEN>
> *Cc:* Laura Harris <EMAIL HIDDEN>; Ben Hallert - Vipmail <
> EMAIL HIDDEN>; "EMAIL HIDDEN Maker Space" <
> EMAIL HIDDEN>
> *Sent:* Tuesday, January 24, 2012 12:45 PM
>
> *Subject:* Re: [Discuss] Near space: Gas
>
> We can also use James' "cut down" mechanism idea to visually locate the
> payload at peak altitude. ;)
>
> On Tue, Jan 24, 2012 at 12:23 PM, James Hukill <EMAIL HIDDEN> wrote:
>
> Other upside, much easier to have an emergency down option.
> Small spark in the balloon and it will decelerate
>
> ;-)
>
>
> On Tue, Jan 24, 2012 at 12:20 PM, Laura Harris <EMAIL HIDDEN> wrote:
>
> Here are the relative boyancies:
>
>
>    - Gross buoyant lift of hydrogen: 1.1399 Kg/m^3,
>    - Helium is 1.0565 Kg/m^3.
>    - The difference is 10 grams (~.35 oz) more lift per cubic meter of
>    gas. Another way to look at it is that it takes about 8% less hydrogen than
>    helium to lift the same weight.
>
>
> The diffusion rate through solids for helium is about 65% of that for
> hydrogen. IOW, hydrogen 'leaks' about 35% more quickly than helium, all
> other things being equal. Shouldn't be an issue for our short flight- we
> can also add a tad more to make up the difference if we want to be really
> sure.
>
>
>
>   ------------------------------
> *From:* Ben Hallert - Vipmail <EMAIL HIDDEN>
> *To:* Rick Osgood <EMAIL HIDDEN>
> *Cc:* "EMAIL HIDDEN Maker Space" <
> EMAIL HIDDEN>
> *Sent:* Monday, January 23, 2012 9:48 AM
> *Subject:* Re: [Discuss] Near space: Gas
>
> Standard welding tank, prolly 250ft^3 I guess?  Whoops!  Forgot to ask,
> heh.
>
> - Ben
>
> On Jan 23, 2012, at 9:14 AM, Rick Osgood <EMAIL HIDDEN>
> wrote:
>
> Thanks Ben.  Do you know what size tank that is?
>
> Rick
>
> On Mon, Jan 23, 2012 at 8:45 AM, Ben Hallert - Vipmail <EMAIL HIDDEN>wrote:
>
> I called IWSI about lift gas and got done quotes:
>
> Tank rental is $5 a month
> Helium is not currently available (because of the shortage, might not get
> too much better soon)
> Hydrogen fill is $45.
>
> Regards,
>
> - Ben
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