[BProckets] Re: Help with NC chemistry

[flint hapirat]

Thanks for the comments and valuable information
David!!!
I highly appreciate the help.
I'll give NC a shot or two more, just for the fun of
it. Your message does clear things!!!
As I mentioned, I do have some successful binders that
work nicely.
I'll have to use a longer core rod and that's it...
THANKS!!!
Flint
p.s
I did try gun powder grade NC - I got a very nice
paste, but no motor. It was simply too soft (the
grain)... but then again - it was just a preliminary
experiment. 


--- David Sleeter <d.sleeter at adelphia.net> wrote:

> Flint said:
> 
> > I have tested all the binders that I have (except
> for
> > guar gum...Here is my problem -
> > I tried using NC at a concentration of 1ppb in
> 100cc
> > acetone (ping pong balls = ppb). Adding 3ml of NC
> > laqour to 10gr of BP does the trick and
> > casting/ramming is easy.
> > It's even easier to work with, and the flight is
> WAY
> > WAY better!!! A VERY rapid liftoff and flight.
> Very
> > impressive. Far superior to the rest of the
> binders
> > (no surprise though).
> >  BUT -
> > Out of 3 motors 2 will fly like a bat from hell,
> but
> > the last one will cato (crossette like!).
> > I'm assuming the problem lies in cavities left by
> the
> > evaporating acetone, even tough I'm ramming the
> stuff.
> >
> Dave Sleeter says:
> 
> In the mid-1990s, while doing the propellant
> development for my book,
> "Amateur Rocket Motor Construction", I too
> experimented with numerous
> binders, and among them was nitrocellulose. For my
> own work I used
> single-based rifle powder, because it's basically
> pure nitrocellulose, you
> can buy it at any gun shop, and it's compartively
> cheap. As Flint has tried,
> I dissolved it with acetone. At normal atmospheric
> pressure the propellant
> grains made with NC burned beautifully, but at
> elevated pressures, just like
> Flint's nozzless motors, they exploded.
> 
> To get accurate data on my propellants' performance
> I built a device that
> worked like a Crawford bomb, a stainless steel
> chamber where I could test
> the burn rate of sample propellant grains at
> controlled pressures up to 200
> psi in an atmosphere of pure nitrogen. To read and
> set the pressure I used
> an Ashcroft test gauge with a stainless steel
> Bourdon tube.
> 
> I too thought that NC would make a GREAT binder
> because it was readily
> available and easy to work with. My propellant
> test-grains were essentially
> like Flint's nozzleless motors, 5/16" dia. grains
> packed into small lengths
> of convolute cardboard tube.
> 
> I remember how disappointed I was to discover that
> propellant grains that
> burned beautifully at atmospheric pressure would
> explode with just a modest
> increase in pressure. Though I can't locate my notes
> on the subject, I
> remember that the critical pressure was amazingly
> low, something like 25-35
> psi, and FAR below the operating pressure of a good
> black powder motor.
> 
> NUMEROUS experiments in which I varied the amount of
> NC would not solve the
> problem, so in frustration I called a professional
> rocket engineer-friend,
> and he suggested the following. Black powder is a
> "low explosive", and NC is
> a "high explosive". At atmospheric pressure, the
> burn rate of NC is SLOWER
> than the burn rate of BP, so at atmospheric pressure
> a BP grain made with an
> NC binder works fine. But as the operating pressure
> is increased, the burn
> rate of the NC RAPIDLY overtakes the burn rate of
> the BP. My
> pressure-chamber experiments seemed to indicate that
> this was happening at a
> pressure oa 25 to 35 psi (as read on the Ashcroft
> gauge).
> 
> If the burning surface of the NC-component of the
> grain receeds faster than
> the BP it is supposed to bind, it leaves behind a
> zone of POWDERED BP that
> burns explosively and causes the motor or the grain
> to CATO. In my own
> experimental test-burns, at anything over 25-35 psi,
> my test-grains didn't
> just fall apart, they exploded like firecrackers.
> 
> Regarding Flint's experimental motors, my guess is
> that the ones that SEEM
> successful and go "like a bat from hell" do so,
> because their operating
> pressure is staying right at or just below the
> critical point, and the
> grains are just beginning to disintegrate. The
> motors that CATO are the ones
> in which the operating pressure has exceeded the
> critical point, causing the
> propellant grain to explode.
> 
> I struggled with BP-NC mixtures for several months
> before I realized that,
> barring some more elaborate (and impractical)
> chemistry to slow the burn
> rate of the NC, NC could NOT be used as a binder in
> BP rocket motors. Hope
> this helps,
> 
> David Sleeter
> 
> As my
> 
> 
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