My spell check indicated humility instead of humility and my eyesight grows
problematic as I age,
but at any rate low humidity makes for better conditions for electrostatic
electricity.
The Van de Graaff generator always works best on a dry day or desert
environment.
BTW, that Germany incident mid 80's was a Pershing missile not Sargent.
Ken
On Sun, Apr 28, 2019 at 4:07 PM roxanna Mason <rocketmaster.ken@xxxxxxxxx>
wrote:
Anyone remember,cold war era, a fatal accident of a Sargent motor in
Germany during sub freezing temps with accompanying very low humility?
The ignition occurred after repeated lifting attempts of the motor setting
up a static charge/discharge in the propellant.
Yeah, a conductor separated by a dielectric, sounds like a capacitor.
Wonder what the breakdown voltage is between the aluminum particles
in close proximity in the grain and dielectric constant of each respective
binder. An insulating liner exacerbates the problem having no conductors in
the matrix. Would adding Al to the liner help lower the potential?
Ken
On Sun, Apr 28, 2019 at 1:08 PM Anthony Cesaroni <anthony@xxxxxxxxxxx>
wrote:
Solid fuel rocket motors (in particular the composite ones that employ
aluminized fuel) can emulate giant capacitors quite well. Extensive
grounding is employed whenever they are handled. Processes such as mandrel
extraction require special attention. The propellent potential voltage is
monitored during the extraction. The mandrel is pulled in short steps with
stops as soon as a voltage rise is monitored to allow the voltage to decay
to zero before proceeding. A serious and fatal accident occurred at
Thiokol
during mandrel extraction on a Peace Keeper missile that initiated over
100,000 pounds of propellant with 3 technicians in the building. The cause
was determined to be ESD IIRC.
Part of qualifying a new propellant formulation includes determining the
propellant's ESD sensitivity. One of these tests is STANAG 4490 and is
known
as the "Severe Human ESD Sensitivity Test". A propellant sample is
subjected
to a 25 KV discharge for 400ns at least 4 times and with multiple samples.
If the samples don't light, it passes. Experimenters should be aware that
it's not too difficult to unintentionally stumble into a formulation that
can be ESD sensitive. Most humans can't detect much less than 500 volts of
ESD potential. An ESD sensitive energetic could be capable of initiation
at
levels below that threshold under certain conditions.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On
Behalf
Of Henry Spencer
Sent: Saturday, April 27, 2019 2:13 PM
To: Arocket List <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: BN aerogels
On Sat, 27 Apr 2019, Anthony Cesaroni wrote:
I've been evaluating graphene to control ESD in propellants. You don't
require very much so it may actually be economical even at current
prices. If you want to find interesting and practical solutions for
propellant problems, the paint industry can be a good source.
Apparently the first commercial application of carbon nanotubes was adding
small quantities of them to plastic parts for cars, to make the parts
conductive enough for electrostatic paint-spraying processes. Those
processes are sort of ESD control in reverse -- even the barest hint of
conductivity is enough, they don't need *good* conductors -- and just a
pinch of short assorted (i.e. cheap) nanotubes makes a big difference.
Makes sense that the same sort of thing would work for solid fuels.
Henry
