Someone in another thread refered to this article and posted a link, but
Fox News had lost the article, and I've lost the original thread where
I saw the link. Fortunately, the author has a copy on his blog, so I'm
posting the link he sent me.
BTW, the entire blog is very well done. Worth reading.
Mark E. Hamilton
Trying to regulate APCP by requiring High Power rocketeers to get a Low
Explosive User Permit will substantially increase the number of LEUP's
that the BATFE has to process and track. One can also legally buy lots
more than just APCP when you hold an LEUP, so the action of the BATFE
could potentially end up increasing the amount of Real explosives (which
APCP is not) in the hands of the public. I think the real reason for the
action is that BATFE is acting like a typical bureacracy - trying to
extend its authority, budget and staff. Rocket engines are actually
still exempted from BATFE oversight by 27 CFR 55.141-a-8 since they are
"propellant actuated devices", an officially acknowledged position of
the ATF up to about 10 years ago. The question where this exemption was
discussed was taken out of their Q&A document about 3 years ago - after
amateur rocketry became a target - even though the PAD exemption hadn't
changed. Attempts by the ATF to illegally regulate these rocket motors
is the subject of a federal lawsuit filed in 2000 by a couple of amateur
rocketry groups. Still no judgment.
Saying APCP is an explosive is like calling dry ice an explosive since I
could put it in a sealed soda bottle. APCP is purposely designed to burn
without exploding (unlike black powder, which has a high burn rate
coupled with a high pressure coefficient - used in the Estes engines and
fireworks) or detonating - even when promoted with a blasting cap or det
cord (unlike TNT, a true high explosive. If anything, APCP is a little
too difficult to ignite and doesn't burn fast enough. I think the fact
that the ATF is trying to regulate something that is actually safer than
the alternative tells you that the safety of the public isn't their real
motivation. Flying these rockets is already well-regulated by the FAA
and amateur rocketry has an exceptional history of safety. Contrast it
to the number of people hurt each year by Radio Controlled model
airplanes, for instance.
Posted by Brad Hitch at July 7, 2003 11:33 AM
I agree 90% with Brad Hitch.
Black powder is not an explosive as tested. Only classified as an
explosive for "DOT shipping purposes". 1.1D. However a blasting cap
will not set it off. It will not sympathetically detonate or for that
matter detonate at all. It deflagrates.
Furthermore this poster made a mistake in that BP has a LOW pressure
exponent. It burns at close to the same burning rate at a wide range of
pressures. That is one of the reasons it is so suitable to small model
rocket motors as well as 12 inch guns.
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: email@example.com>
I don't have a strand burner, so to a large extent I have to depend on
published material. What I see in Kirk-Othmer (1993, Vol. 10, pg 111)
is that black powder typically has a pressure exponent from n=0.25 to
0.5 at 1000 psia and a burn rate of 10-15 cm/sec. On the previous
page are listed a number of CP formulations with pressure exponents
from 0.2 up to 0.5, but mostly around 0.3 with burn rates of 8 mm/sec
@ 1000 psia. Sutton (5th Ed., pg. 263) lists parameters for the CP in
the Minuteman first stage as 8.9 mm/sec and n=0.21. So it may have
been more accurate to say "higher" pressure coefficient instead of
"high" w.r.t. black powder. I think the conclusion that black powder
is alot closer to being an explosive than APCP is valid though, due to
its higher burn rate and greater increase in burn rate as the pressure
rises. Still nothing like nitroglycerin of course.
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