[roc-chat] Re: BP for Deployment of Main Question
- From: Richard Dierking <redierking@xxxxxxxxxxx>
- To: <roc-chat@xxxxxxxxxxxxx>
- Date: Thu, 8 Dec 2011 21:22:25 +0000
Other than the time it takes for a ground test and that sometimes stuff is
damaged and must be repaired; there are other considerations. Some of my
neighbors are already a little freaked out about the large rocket projects.
So, setting off a 4 gram BP charge would not be advised. We could go to a City
park, but previously, we were asked to leave by the City's park enforcement
officer (details only around the campfire). If we did the test at a school
field, I would probably end up in Quatmo. So, between advice, formulas, and our
gut, we'll come up with the correct amount. ;) Richard To:
roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: BP for Deployment of Main Question
From: Chris.J.Kobel@xxxxxxxx
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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