[Discuss] Near-space balloon: Foam ball located and purchased

Thomas A Ramsey EMAIL HIDDEN
Mon Oct 31 19:11:15 PDT 2011


 I'm liking the nylon all-thread idea but I am a little concerned with 
 it's strength. If we only have the one all-thread and it breaks our 
 strips we lose the bottom half on the rig. I also don't trust velcro AT 
 ALL. If it becomes wet or consistently stressed it will disconnect. Zip 
 ties are great but difficult to reuse (they can in fact be reused). If 
 we decide against zip ties I propose using multiple all-threads. Perhaps 
 three or four; one down the center then the others at 45 degrees from 
 the top center straight (nearly so to avoid each other) through. Nylon 
 to keep weight down. I know it may make for more supports to work around 
 but we should be able to handle it.

 I really like the strobe ideas as well. If we do have a separate strobe 
 rig I think it may need to be insulated as well. I've read temperatures 
 as low as -60 to -70 Celsius at the altitude we expect to go and most 
 consumer grade electronics like leds are only rated about -20.

 -Tom

 On Mon, 31 Oct 2011 14:35:59 -0700 (PDT), Laura Harris wrote:
> We can use nylon all-thread for the central support rod, if we go 
> that
> route. Long velcro-enabled straps would be reusable and strong though
> a bit heavier that zipties (but not by much). If we used a net, we'd
> still want to secure the halves together (unless you were thinking of
> drawing the net up into a tight neck at the top . . .). I'm leaning
> towards the nylon all thread center support rod approach, personally.
>
> As for the interior construction, the interior walls, floors, and
> ribbing are 5mm foam-core. I was thinking of using gold mylar film 
> for
> the reflective insulation, but we can go without it and fill dead
> areas with extra foam.
>
> Reasoning behind a partial hard-shell was assuming the ball will land
> bottom down so a full shell could be avoided to save weight. Still, 
> it
> would definitely make it a tougher rig- more likely to survive for
> reuse. I was thinking of using fiberglass with epoxy resin for the
> hard shell.
>
> Idea for paint scheme: paint the bottom 3rd black and the rest red.
> Black so it is easier to see on the way up (against the sky) and red
> so it stands out on the ground. Also, a fluorescent colored 
> parachute.
>
>
> We can use 1-watt LEDs for strobes. With the short duty cycle a 
> strobe
> requires, we won't need heat-sinks for the LEDs and they are bright
> enough to be easily seen in daylight. A simple 555 timer driving a 
> FET
> switch is all we'd need for a driver. Another thing we can do is hang
> a strobe from the tether. That way its weight is not considered part
> of the 6lb payload limit (if I understand the FAA regs correctly). 
> One
> of those little waterproof xenon strobes doesn't weigh much, either.
>
> -------------------------
> FROM: Rick Osgood
> TO: Laura Harris
> CC: Ben Hallert ; "EMAIL HIDDEN"
> SENT: Monday, October 31, 2011 1:58 PM
> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
> purchased
>
> I just had another thought about the design of the chassis that we
> didn't bring up at our meeting yesterday. We need to be careful about
> the material the payload is made of as well as the GPS placement. The
> eTrex doesn't have an external antenna so we need to make sure it can
> get an accurate GPS lock from inside the payload. So any metal above
> it would be a bad idea. So the chassis needs to be insulated but with
> material that the GPS radio signals can get through.
>
> On Mon, Oct 31, 2011 at 1:51 PM, Rick Osgood  wrote:
>
>> Ben, so your idea would be to have the cord come through the sphere
>> via a hole in the top and then attach to the inside of the bottom
>> half? I want to make sure I understand your idea correctly. That
>> sounds like it could definitely work and I like that it would remove
>> the requirement for extra reinforcement on the top half. Only
>> downside would be having the rope going through the payload where it
>> could get in the way of the electronics.
>>
>> Laura, I think the zip ties idea could be cheap, simple, and
>> effective. It would be nice to have something that didn't require
>> cutting and replacing the zip ties every time we open and close it
>> though.
>>
>> The last balloon I did, we just had a threaded rod going all the way
>> through the center of the payload vertically. There was a washer and
>> a nut on each side to hold the two pieces tightly together. Then a
>> small horizontal hole was drilled through the threaded rod at the
>> top so we could stick a sort of hook through it where the line was
>> attached. The threaded rod was nice and strong but it will add more
>> weight and then you have a metal rod going all the way through the
>> center of the payload which can make the inside electronics layout
>> more difficult. You can see it in some of the photos from this site:
>> http://www.toddfun.com/2011/02/20/high-altitude-balloon-launch-2/
>> [17] . Here is one example photo:
>>
>> On Mon, Oct 31, 2011 at 1:29 PM, Laura Harris wrote:
>>
>>> Ohh- that looks good, Ben.
>>>
>>> One idea for holding the halves together is to use a pair of
>>> extra-long nylon zip ties running longitudinally at 90 degrees to
>>> each other- grooves formed in the surface would keep them from
>>> sliding off. They're strong and light and they avoid the need for
>>> any hardware.
>>>
>>> -------------------------
>>> FROM: Ben Hallert
>>> TO: Laura Harris
>>> CC: Rick Osgood ;
>>> "EMAIL HIDDEN [4]"
>>> SENT: Monday, October 31, 2011 1:12 PM
>>>
>>> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
>>> purchased
>>>
>>> May I suggest that instead of attaching the cord to the top, we
>>> run it
>>> down and attach it to where the battery bay is? This way the whole
>>> thing is 'sitting' on the cord and we can cut any weight created
>>> by
>>> reinforcements that would reach to the top of the sphere. Namely,
>>> the
>>> only 'strength' needed would be at the bottom where it's already
>>> planned to exist. This also reduces risk of retrieving just the
>>> top
>>> of the sphere. :) I've attached a modified version of the
>>> drawing.
>>>
>>> - Ben
>>>
>>> On Mon, Oct 31, 2011 at 12:51 P.M, Laura Harris wrote:
>>> > The ball comes split in half so it's just a matter of holding
>>> it together in
>>>> flight. I've attached a pic of a sketch showing a preliminary
>>> idea for
>>>> construction.
>>>>
>>>> ________________________________
>>> > From: Rick Osgood
>>>> To: Laura Harris
>>>> Cc: "EMAIL HIDDEN [9]"
>>> >
>>>> Sent: Monday, October 31, 2011 10:54 AM
>>>> Subject: Re: [Discuss] Near-space balloon: Foam ball located and
>>> purchased
>>> >
>>>> Sweet! Do you plan to mold something around the sphere? I'm
>>> curious to see
>>>> your final design and how we will be able to open it up and
>>> mount
>>>> everything.
>>>>
>>>> On Mon, Oct 31, 2011 at 9:53 AM, Laura Harris wrote:
>>>>
>>>> I found a 12" dia hollow polystyrene foam ball and purchased
>>> one. Should be
>>> > here in a few days. This is it:
>>>> http://www.plasteelcorp.com/mm5/merchant.mvc [12]?
>>>> This dramatically accelerates the build progress. :)
>>> > L
>>>>
>>>>
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>>>>
>>>>
>>>>
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