[Discuss] Near space: Gas

Laura Harris EMAIL HIDDEN
Tue Jan 24 13:17:29 PST 2012


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.
>>
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>>________________________________
>> 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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