[roc-chat] Re: BP for Deployment of Main Question
- From: Chris J Kobel <Chris.J.Kobel@xxxxxxxx>
- To: roc-chat@xxxxxxxxxxxxx
- Date: Thu, 8 Dec 2011 12:59:56 -0800
Here's the relationships I use: (I believe Dave Flynn is the source)
E-charges: BP(g)=.00051xLength(in)xForce(lb)x(Peak Alt ASL/10K+1) ;
150-200 lbs
2-56 nylon bolts for shear pins; 35 lbs shear force each; 100 lbs w/o
pins, 200 lbs with
Only separation force, length, and altitude are input variables. The
diameter factors out.
Time for a ground test....
Chris
From: Richard Dierking <redierking@xxxxxxxxxxx>
To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
Date: 12/08/2011 12:44 PM
Subject: [roc-chat] Re: BP for Deployment of Main Question
Sent by: roc-chat-bounce@xxxxxxxxxxxxx
So Dave, how much BP would you suggest for a 7.5" diameter x 24" long
compartment with three 2-56 shear pins?
Richard
Sent from my iPhone
On Dec 8, 2011, at 12:19 PM, "Dave McCue" <dmccue@xxxxxxx> wrote:
> Please remember that electric match makers alway say to put matches in
series - it takes no more than a 1.5V AA cell to light one, so putting two
or three in series is no problem. THis also solves the problem of
monitoring two or more matches, sine a loss of continuity anywhere will be
detected by the electronics.
>
> I do series match wiring all the time when I use multiple ematches to
light big liquid propulsion engines. See links below:
>
> http://www.youtube.com/watch?v=FlkMiCtCxg0&feature=related
>
> http://www.youtube.com/watch?v=jOiaxfGpudM
>
> You can also see the unusual recovery system I came up with for these
rockets: side deployed! This is because the rocket is big and heavy, and
needs to land on it's side to avoid unplanned damage; we assume we will
break two fins upon landing.
>
> By the way, the big 1000 square-foot parachute is deployed by BP charges
that push out the pilot chute, with HPR recovery electronics making the
decisions. This was one of several low altitude flights to test the
recovery system.
>
> Dave McCue
>
> On Thu, 8 Dec 2011, Richard Dierking wrote:
>
>>
>> One possible failure mode: If it's in parallel, if one of the matches
is bad and doesn't have continuity, you will not know, because the
altimeter will detect continuity in the second and indicate that
everything looks OK. So one canister would go, but probably not be enough
BP for a successful deployment. We tested two matches in series
yesterday, and they both went fine. I've been using series for airstarts
and haven't had a problem (up to 4 engines). I thought people were crazy
when I first heard about using series, but when a match lights the "plasma
ball" becomes very conductive for a moment. However, I have not used
series for deployment charges, so thought it would be a good idea to hear
from people that had experience with this. Richard > From:
xsive.guy@xxxxxxxxx
>>> Date: Thu, 8 Dec 2011 10:39:46 -0800
>>> Subject: [roc-chat] Re: BP for Deployment of Main Question
>>> To: roc-chat@xxxxxxxxxxxxx
>>>
>>> Definitely in parallel. Otherwise, when the first one burns out the
>>> rest would stop getting current. By wiring them in parallel even
>>> after the first one goes the rest continue to get current.
>>>
>>> I'd like to know the answers to your other questions though.
>>>
>>> Thanks,
>>> Mike
>>>
>>> On Thu, Dec 8, 2011 at 10:09 AM, Richard Dierking
>>> <redierking@xxxxxxxxxxx> wrote:
>>>> Say your main deployment section is 7.5" diameter, 24" long and using
three
>>>> (3) 2-56 nylon shear pins. How much BP?
>>>>
>>>> Also, what's the advantage of using two or more deployment canisters
instead
>>>> of just one? For multiple canisters, would you wire in series or
parallel?
>>>> (One 9 volt battery and Perfectflite WD altimeter with main
deployment at
>>>> 1100'.)
>>>>
>>>> Richard Dierking
>>>> BTW: Kurt, we're not intending to turn the nose into a second stage
:-)
>>>>
>>>>
>>>
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>>>
>>
>
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