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

  • From: Richard Dierking <richard.dierking@xxxxxxxxx>
  • To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
  • Date: Mon, 25 Jun 2012 08:47:50 -0700

I think you are right Allen.  Also, I'm liking Kramer's thoughts about adding 
ribs and stringers.
Richard

Sent from my iPhone

On Jun 24, 2012, at 8:54 PM, Allen H Farrington <allen.farrington@xxxxxx> wrote:

> Well, first of all, to really do a balloon tank, it has to always be 
> pressurized "think the Estes Dude rocket". The mass you save by making it 
> work under 1 G only rather than under 10 Gs isn't much.
> 
> As for the end-caps, in order to make them withstand the pressure, you can 
> use flat ones but the extra mass in them and their epoxy attachments will 
> probably outweigh the mass savings in the sidewalls.
> 
> For a L3 rocket, I would recommend NOT doing something like a balloon tank. 
> Pro rockets don't use them much any longer since they're not especially 
> efficient  with newer metal alloys (except for the legacy Centaur upper 
> stage). Some rockets like the Falcon 9 use monocoque tanks for the LOX, but 
> I'm not sure that they're technically balloons..
> 
> You're going to have enough new stuff to deal with so I recommend purchasing 
> the tubing. You can certainly use a cardboard tube as a mandrel for making a 
> fiberglass or CF tube (there are YouTube videos on how to do this, but 
> basically you layup the tube and then soak it in a pool for a day or so to 
> pull out the cardboard) but it's so easy to purchase these types of tubes. In 
> fact, Public Missiles has some 6" tubing that's only about 38g per inch. Very 
> light. I've used their 3" carbon tubing and while pricy, it can withstand a 
> LOT of Gs. Like crashing nose-first into the playa nearly under power...don't 
> ask me how I know this ;-0
> 
> Well, my 2 cents...for what it's worth.
> 
> Allen
> --------------------------------------------------------------------
> Allen H. Farrington
> 818-653-2284
> web: http://www.allenfarrington.org
> 
> On Jun 24, 2012, at 4:25 PM, Richard Dierking wrote:
> 
>> So flatwall ends will not work (i.e. they must be domed)?  Would they create 
>> too much stress at the attachment point to the sidewall?
>>  
>> Please tell me more about this Allen.
>>  
>> Thank you,
>> Richard
>> On Sun, Jun 24, 2012 at 3:14 PM, Allen Farrington <allen.farrington@xxxxxx> 
>> wrote:
>> 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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>>> //www.freelists.org/list/roc-chat
>>> 
>> 
>

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