historical detective story:Uni-Jet

Jan 26, 2006 9 Replies
S

Back in 1964-1965 a company by the name of Uni-Jet made some 13mm x 57mm solid propellant motors. These were 1/2A2-x size motors.



Here's what G.Harry Stine had to say about them:



"George Molson used a very different and highly unusual solid propellant, and the reliability of his Un-Jet engines suffered as a result. The thrust time curve was dependent upon the number of days that had elapsed since the engine had been made. At a certain time after manufacture, the thrust-time spike at ignition became extremely high...and the nozzle left the party. Sometimes the paper casing ended up looking like a peeled banana. "



If you would like to see some pics , please go here and scroll to the bottom:



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You will notice that the casing states not to burn or incinerate and also has the standard "soak in water" to destroy.....



I am not a pyrotechnician/motor maker and thats why I am asking the question here as I know there are a number of very knowledgeable people here. Based upon the above description, are there any clues to what the propellant mixture might have be?



thanks in advance



shockie B)



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B

FYI, I have an assortment of these in my collection. I got them at a NARAM auction, and my guess is they came from Harry...

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S

jerry: does the description give any idication as to what was causing the described results after a period of time? Could/would it have been some hygroscopic effect?

As over time lets say the propellant absorbed mositure....would that account for the described catos?

Perhaps he was not applying enough pressure to packing the BP in the casings, and then with mositure the propellant became unattached from the casing?

could it be a formulation problem? what is meant by highly unusal and different ? instead of the 3 basic ingredients of BP, perhaps he used potassium percholrate? or ammoinium nitrate or sodium nitrate instead of potassium nitrate?

just wondering

shockie B)

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J

The BP curing over time made the propellant "better" and for a moment the nozzle was the right size. But when cured the nozzle is too small. Do not fire them. Tell the manufacturer (using a time machine) to increase the nozzle size.

Note that both the Estes D13 and E10 suffered the same fate. We now have the D12 and the E9.

Tech Jerry

Tell Estes to caugh up the E40!

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F

Estes never had an E10.

It was an E15. And it had a very teeny nozzle.

-Fred Shecter

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J

Correct. Please pardon my error.

Tech Jerry

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T

careful Jerry, some people might think you've gone soft :)

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S

jerry:

thanks... I wonder if these engines had formed combustion chambers as do all other BP rocket engines? would the dimensions of this change as the propellant cured? Since these engines were made in Albany, NY if these were allowed to air cure over time , the temperatures and humidities probably varied widely? Anybody ever seen a thrust time curve of these engines? I assume they were end burners with the characteristic thrust spike ?

shockie B)

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