[roc-chat] Re: High Alt, Multi-staging, and Balloon Structure

  • From: Allen Farrington <allen.farrington@xxxxxx>
  • To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
  • Date: Sun, 24 Jun 2012 15:14:53 -0700

The hard thing about the balloon isn't the sidewalls but the domes at the ends. 
Without them, you don't save any mass.

Allen
Terseness and mis-spelling courtesy of my iPhone

On Jun 24, 2012, at 11:05 AM, Richard Dierking <richard.dierking@xxxxxxxxx> 
wrote:

> Thank you Jack and Kurt for the great info on the waiver. 
>  
> Regarding Kurt's first question, good point.  But, I like to take risk trying 
> new stuff.  As usual, I will test along the way.  I'm thinking a level 3 
> project with properly weighted upper "stages" to simulate the stress on the 
> booster.  Kramer knows a lot about airframe design, so I'm considering ribs 
> and stringers.  Dang, it would be cool to try the balloon structure. 
> Again, has anyone heard about someone trying this before?
>  
> Richard
> On Sun, Jun 24, 2012 at 10:50 AM, Kurt Gugisberg <kurtgug@xxxxxxxxxxxxx> 
> wrote:
> I guess you can save a little weight going with a thin pressurized airframe, 
> but is it worth the cost to experiment with such an unknown factor 
> considering that it might collapse under the weight of the upper stage and/or 
> the strap-ons?    
> 
> Also, I don't think there is any problem with the FAA in flying something 
> like you are talking about.  You do have to submit your plans to have them 
> approved (at least with Aeropac) if you are going over 25K.
> 
> Kurt
> -----Original Message----- 
> From: Mike & Nancy Kramer 
> Sent: Jun 24, 2012 10:40 AM 
> To: roc-chat@xxxxxxxxxxxxx 
> Cc: Richard Dierking 
> Subject: [roc-chat] Re: High Alt, Multi-staging, and Balloon Structure 
> 
> For the airframe,
> 
> Yes there is there is thin carbon fiber cloth.  4oz cloth will be around .006 
> inch thick with a wet layup, 8 oz will be around .012 thick with a good wet 
> layup.  One thing to think about is having a thin ply on each side of the 
> paper / cardboard to make a sandwich structure.  Takes some practice but good 
> solid structure.
> 
> balloon construction, are you talking about a pressure stabilized tube?  If 
> so, by using VERY light ribs and stringers I think you can get a much more 
> reliable lightweight structure.
> 
> Mike kramer  
> 
> On 6/24/2012 10:22 AM, Richard Dierking wrote:
>> I got the high-alt bug at BALLS last year.  I saw some multi-stage projects 
>> attempt to reach high-alt, and they all didn't seem to do too well.  For one 
>> thing, I think it's difficult to design/build a stable N to M to M kind of 
>> rocket.  So, many people just build the P, Q, whatever large single stage 
>> rocket or reduce the number of stages to two.  I have ideas about a 3 stage 
>> rocket with strap-ons for the initial boost, and even have done some 
>> experimenting, but need some advice.
>>  
>> First, are there specific FAA restrictions on launching high altitude 
>> multistage rockets?
>>  
>> Again, I'm not planning minimum diameter, which I understand has some great 
>> advantages.  But, the method for the strap-ons requires some attachment 
>> depth.  Additionally, I like the idea of having some through-the-wall fin 
>> attachment.  So, I plan on using 6" tube with 98 mm mount, and 4" strap-ons 
>> with 75 mm mount.
>>  
>> To reduce weight on the first stage, I'm thinking about thin fiberglass over 
>> paper tube (I would like to use carbon fiber, but honestly, have no 
>> experience with this).  Then, stripping the layers of paper out from the 
>> inside of the tube, adding the motor mount, and being able to pressurize the 
>> inside to 5 to 10 psi (over ambient of course) for a strong balloon 
>> structure.  Has anyone ever done this for a amateur-type rocket?  Is there 
>> even such a thing as thin carbon fiber cloth?
>>  
>> I would like to try the 1st stage core with balloon structure for my L3 
>> project.  Is this too weird? 
>>  
>> I've messed around with modifying aquarium check valves and I think I can 
>> build a very simple and light pressure regulator to prevent over-pressure of 
>> the airframe.  Strength must be maintained, and it must be very robust 
>> during launch, because I'm also planning on using 3 or 4 strap-ons attached 
>> to the centering rings of the airframe..
>>  
>> Richard Dierking
>> Level 2
>> TRA 11366
>> NAR 84983
> 
> 
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