[SS-Propellant] Propellant "settling"

[Rich Nakka]

Thanks anyhow, Randy, for trying the experiment. At least now we know 
that "settling" does not seem to be a plausible explanation for the KNSB 
odd behaviour. That in itself is valuable data.

Richard

dormans wrote:

> I cast a slug of KN/SB that was four inches long and 5/8th of an inch 
> diameter.   The casting tube was a piece of PVC pipe which I felt 
> would hold in the heat of the cast propellant and allowed the 
> propellant to cool slowly.  After it had fully cured, I marked the top 
> and bottom of the slug and then cut a one inch section from both the 
> top and bottom.  These sections were faced on the lathe and wrapped 
> with a layer of tape to act as an inhibitor.  The slugs were ignited 
> at the top with a propane torch and the burns video taped.  The burn 
> rates were essentially identical, so it seems that "settling" is not 
> an issue.  The burn rate was .245 cm/sec, same as I got for the BEM 
> grains.
>
> Randy
>
>  From: Rich Nakka [mailto:richnakka at rogers.com]
> Sent: Tuesday, November 15, 2005 4:58 PM
> To: dormans
> Subject: Re: [SS-Propellant] Launch of the Propellant Development 
> phase ofSS2S 
>
> Randy,
> Would it be feasible to test your theory with some of the grains 
> already cast for the BEM? Scrape off some of the top & see how it 
> burns? If this simple test suggests that "settling" may occur , it  
> might also be worthwhile for someone in the PDT to cast a test grain 
> ...what do you think?
>
> Richard
>
> dormans wrote:
>  
>
> Richard's, Paul Kelly's and NEAR's  motors that are cited as 
> exhibiting the triangular thrust curve  when using Sorbitol all used 
> bates grains that were presumably prepared in the same way.  A casting 
> tube filled from the top with molten propellant and allowed to cool.  
> Is it possible that the KN, being heavier, is settling a bit from the 
> top and leaving a thin layer of fuel rich propellant at the top?  So 
> that it's not the space between the grains causing the ignition delay, 
> but that half of the grain ends have this layer of fuel rich 
> propellant that is delaying ignition.  The use of an ignition primer 
> or pyrogen ignition would not necessarily help if this is the case. 
>  Has this already been considered?  It's an easy theory to test, just 
> trim a thin layer off the tops of all the grains after curing or maybe 
> it would be easier to top off the grains during casting with a thin 
> layer of KN rich propellant or KN/SU as Tony has suggested.
>
> Randy
>
>  
>
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>
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