[SS-Propellant] Launch of the Propellant Development phase ofSS2S

[Rich Nakka]

dormans wrote:

>  Hi all,
>
> It sounds like we have a lot of work/fun ahead of us.  I think that a 
> mix of SB/SU as Miraglia has suggested, or KN/SU applied only to the 
> ends of the grain to as Tony suggests are definitely worth 
> investigation.  I used to use a 50/50 mix of SB/SU mainly as a means 
> of reducing the cost of the Sorbitol.  I always thought of it as a 
> performing like Dextrose.  Unfortunately I wasn't doing a lot of 
> static testing at the time, but in the static testing that I did the 
> SB/SU mix produced a thrust curve that closely matched the predicted.  
> I suspect that a ratio with more Sorbitol and less Sucrose would give 
> similar results.  The motor tested in the attached gif was an 
> unrestricted J-class motor; propellant was 60/40 OX/fuel and 50/50 
> SB/SU and gave a healthy isp of 122.
>
That thrust curve certainly shows no sign of the dreaded "triangular" 
shape. I wonder if this is because of the 50/50 SB/SU mix, or because 
the grain is unrestricted? Could it be that only BATES suffer from this? 
Perhaps due to non-normal burning at the segment ends?

> The thrust curve for NEAR's first firing of the Phenix motor was 
> fairly triangular , but the thrust curve from the 2nd firing was much 
> closer to the predicted (not nearly as triangular).  Does any one know 
> what the difference was between the two tests?  I can't find the 
> report on their site, but I think that I have a printed copy some where.
>
You're right, Randy, the 2nd firing was much improved. I'll contact a 
fellow at NEAR and see if I can get any info as to the possible reasons.

> I read that many commercial/military motors use an oxidizer having a 
> mixture of particle sizes (multi-modal mixtures) as opposed to 
> uni-modal mixtures mostly as a means to lower the viscosity thereby 
> making the propellant easier to process.  Something I think we should 
> look into to help with the large grains.
>
I would think that for large grains, viscosity would be less of an issue 
than for small grains. From my own experience, though, particle size of 
the KN makes a HUGE difference in the viscosity of the molten slurry.

> I would be happy to do some testing also; Peter and I will hopefully, 
> in addition to the BEM, also be firing a 4inch diameter N-class 
> Sorbitol motor soon.
>
Awesome. Looking forward to hearing about the N-motor results...good 
luck with it.

Richard

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