Yeah, I hear ya Ken. I also spent 20 years processing HTPB propellants. At the
beginning I’m thinking – wow, this is so much better than processing candy and
BP, but decades later after processing a few paraffin hybrid grains, it’s hard
to go back. I too like the concept of melting the composite. No stuffing around
with diisocyanates, no fastidious moisture protection or drying of ingredients,
no shelf life concerns, no vacuum processing and cleaning up processing
equipment after and as you said, leftovers- just re-melt and use in the next
batch – win win win…
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of roxanna Mason
Sent: Tuesday, 7 July 2020 1:45 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Making composite APCP in Australia
The beauty of these modified asphalts is you can tailor the ratio of
ingredients to the season and expected ambient temperature,i.e. winter/summer
mixes. We did this with the standard GALCITE 61 by adjusting the oil to asphalt
ratio, oil being the plasticizer. Of course the finished motors were kept out
of direct sunlight much as you would do in summer time in an air conditioned
house, treat your motors as yourself. In extreme situations like in the desert
w/o AC we would rotate the motor once before launch but that maybe happened
once or twice in 10 years.
Wasn't really that bad at all, we never lost a motor due to grain slump. I
really prefer asphalt over HTPB and I've worked extensively with both systems.
K
On Mon, Jul 6, 2020 at 3:08 PM Joe Bowen <joe.b.bowen@xxxxxxxxx
<mailto:joe.b.bowen@xxxxxxxxx> > wrote:
In that paper it mentions both a 2-part (asphalt/TPE) and a 3-part mixture
(asphalt/TPE/ACRYLOID) and it seems to indicate that the 3-part mixture is
harder to manufacture (mixing within toluene and then vacuum oven drying).
What's the benefit of going through the extra trouble to make the 3-part
mixture? I'm intrigued, I'd rather not have to deal with PBAN or HTPB anymore.
Also, I've heard of people using asphalt for hybrid fuel grains but heard of
issues with asphalt melting out of the nozzle on a warm launch pad, do you
think that would be less/more of an issue with these additives?
Thanks,
Joe
On Mon, Jul 6, 2020 at 11:19 AM roxanna Mason <rocketmaster.ken@xxxxxxxxx
<mailto:rocketmaster.ken@xxxxxxxxx> > wrote:
Hello Joshua, I encourage you to look at an alternative to HTPB and their toxic
isocyanate curing agents, that being modified asphalts.
Yes roofing tar, road paving asphalt with an ingredient to lower its processing
temp so AP can be used instead of KP, potassium perchlorate with its high burn
rate exponent. See attachments of work I conducted with Dr. John Rusek at the
Rocket Lab at Edwards AFB in California back in the 80's. Performance equal
even exceeds HTPB/AP/Al with an increase in density as a bonus. Asphalt SG ~ 1
compared to HTPB ~0.9. Kraton is the key additive with which you can formulate
your own modified asphalts otherwise there is a supplier right here in
California that supply the AC type asphalts mentioned in the Edwards report..I
got a free 5 gallon sample by just asking nicely.
THe finished propellant has another bonus, it's reusable so any excess you make
can be remelted. You can use a version that's compatible with your hot Aussie
summers.
FYI, I also used to work with the Rocket Research Institute back in the 70's
with the original GALCITE asphalt rockets that ran Pc at 3000 psi using surplus
5" steel HIVAR rocket motor cases. We routinely launched rockets 20-100KFt all
legally under FAA waivers.
But with these modified asphalts you can now use low exponent AP Pc<1000 psi.
Good luck with Blessings,
Ken
On Mon, Jul 6, 2020 at 6:47 AM Joshua Carr <admin@xxxxxxxxxxxxxxxxx
<mailto:admin@xxxxxxxxxxxxxxxxx> > wrote:
Hi Terry,
The next step I am about to take is to purchase your book from
aeroconsystems.com <http://aeroconsystems.com> .
Is this the best place to buy it?
Also, I would like to ask your opinion on something, I hope you don't mind.
Given your chemistry background, do you have any recommendations for
understanding ignition and chemical reactions?
After a lot of reading (and a uni course or two) I still haven't found a decent
explanation of what is happening at the fundamental level.
The same is the case for binders and diisocyanate or curing agents ect.
I have learnt a bit about this process, such as bond types, from expanding foam
and rubber making.
But it seems a lot of books on rocketry leave these things out.
Anyway just a thought of mine, if you are reading thanks for your time and hope
to speak again soon.
Kind regards,
Joshua Carr
---- On Fri, 29 May 2020 00:19:56 +0930 Terry McCreary
<tmccreary@xxxxxxxxxxxxxxx <mailto:tmccreary@xxxxxxxxxxxxxxx> > wrote ----
Hello Joshua and the rest of the list, I was on the TRA BoD during most of the
BATFE lawsuit. If memory serves (sometimes it doesn't anymore...:-\) that suit
consumed a bit more than two-thirds of a million dollars over a 10+ year
period.
Initially Judge Reggie Walton ruled that BATFE had deference to classify (as an
explosive) virtually any material they chose. TRA+NAR appealed, the appeals
court didn't buy the "due-deference" argument, and the suit went back to Walton.
At some point BATFE decided that the burn rate of safety fuse was a guide to
classification; anything that burned faster than that was to be classified as
an explosive. A 1000+ page document was submitted, "proving" that APCP burned
at tens of meters/second and was therefore an explosive.**
TRA+NAR provided just a couple dozen pages which included citations from actual
peer-reviewed publications by actual rocket scientists. Within those
publications were some ballistic properties of a few hundred propellant
mixtures, most having burn rates @1000 psi on the order of 1 cm/s, and none
exceeding about 3 cm/s.
Following Judge Walton's ruling in favor of TRA+NAR, a request for recovery of
fees was made. The amount recovered was well under $100K... oh well, we WON!!
https://www.courtlistener.com/opinion/2400163/tripoli-rocketry-v-bureau-of-alcohol-tobacco/?
Best -- Terry
**BATFE's legal team apparently went to the W.C. Field's School of Law and
Heavy Machinery Operation: "If you can't dazzle them with brilliance, baffle
them with bulls++t." And somewhere in their submitted document was
proof...that if a rocket motor was clamped tightly enough to a steel rod, upon
ignition the case would rupture and undergo RSD---rapid spontaneous
disassembly. ;-)
On 5/27/2020 10:34 PM, Joshua Carr wrote:
In Australia we need a full on explosives license to do what you fellas in the
USA take for granted.
Sure Tripoli and the rest of you guys went to fight for APCP a while back, but
it would be great to share some wisdom to us Aussies down under (the industry
ain't exactly booming here).
Regards,
Joshua Carr
--
Dr. Terry McCreary
Professor Emeritus
Murray State University
Murray KY 42071