[psas-avionics] Smoke generators...

Dave Camarillo dave.camarillo at gmail.com
Thu Oct 7 23:13:03 PDT 2010

I suspect that if a glo-plug technique were used, there's some maximum
volume of fluid you could spray over the glow plug, after which the fluid
would simply cool the glo plug instead of burning the fluid. I suspect this
would boil down to an energy conversion problem based watts into the plug
and energy required to combust the fluid... But it would have a calculatable
upper bound (and the existence of the upper bound would key to know and
sufficiently avoid in such a design)...

One idea I was pondering, not sure if it's a good idea, perhaps using some
kind of fine white dust or powder, perhaps powder from drywall filler or
baking flour and a mechanical worm-drive feed mechanism to drive the
material out at a specific volume per second... The ultrasonic atomizer
would probably work for this too... I'm not sure how well this would work,
but there's no hot-things involved....

My gut feeling says that if an thermo/electronic approach was chosen,
perhaps with glo plug(s) or nichorme wire or other elements, sufficient
safety could be put in place to avoid fire on the ground. One can design
some simple circuitry that will get you 99.9+ percent reliability, and if
you really cared, you could assume worst case scenario, and know the max
thermal output of the glo plug and design the frame such that it can
dissipate the heat fast enough to keep surface temperature down below X
threshold, where X is consider a safe threshold for not starting fires...

On Thu, Oct 7, 2010 at 8:39 PM, Doug Ausmus <dausmus at gmail.com> wrote:

> As a licensed pyro, I agree- do NOT use a pyro technique for the smoke.
> Yes, Potassium Nitrate and melted sugar ignite... in fact it is a very
> effective rocket fuel! And it burns WAY too fast for this application and is
> quite hot, but it does make smoke <g>. Smoke compounds have things that make
> them burn very slow (I have a very slow burning, non-flaming formula for
> creating huge volumes of smoke), and there are easy methods to ignite them
> 100% with an e-match using some special ignition formulas, but that's all
> beside the point- I highly suggest that you do not use pyro to generate the
> smoke for visual air flow in this application.
> Smoke fluid (such as castor oil), using a glow plug is a good idea, but
> drowning it may not give you the results you actually need- in addition
> there is a significant lag between energy and smoke, so controlling it per
> velocity (although a good idea) may not perform quickly enough to give you
> the smoke you need when you need it.
> Another thought occurs to me, however, what about a non-smoke solution?
> There are very benign foggers (not actually smoke) for theatrical use that
> make non-toxic 'smoke'. Three questions that would need to be answered:
> 1) can there be a miniature light version?
> 2) if so, can it produce enough smoke for the velocities that will be
> experienced?
> 3) Can it be energy efficient?
> Last idea:
> Will a miniature Ultrasonic atomizer work sufficiently well enough (with
> some fluid to simulate a smoke or fog) to provide the "smoke" volumes needed
> for the velocities experienced?
> If so, same questions as above.
> Doug
> On Thu, Oct 7, 2010 at 5:21 PM, Keith Packard <keithp at keithp.com> wrote:
>> On Thu, 7 Oct 2010 15:38:16 -0700, Dave Camarillo <
>> dave.camarillo at gmail.com> wrote:
>> > It seems like it should be OK to light stuff on fire and/or make smoke
>> > electrically anytime after the motor has started up... I hope that
>> wouldn't
>> > be frowned upon?
>> It has been; the concern is in having something burning after the rocket
>> lands.
>> The desert is dry, and the rocket often lands far from roads which make
>> fire fighting difficult. And, yes, rockets have landed and caused
>> significant fires.
>> --
>> keith.packard at intel.com
>> _______________________________________________
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