Star vs Circular BATES grain for liner preservation

[DannyB]

Hi everyone! So I'm getting tired of putting out all the money on phenolic liners for testing propellant, which I typically get two uses out of for static testing ex APCP. I notice that the liner burns through the fastest in between BATES grains and remains structurally sound where there is no gap between grains. My thought is that with a properly designed star or finocyl you can have a single long grain with nearly the same curve as BATES grains and there would be no gaps between grains for the heat to hit the liner. Am I on the right track with switching to stars to get more life from my liners? What other considerations come into play when using a single grain star vs circular core BATES? The only thing that comes to mind is heat at the aft end wearing out the phenolic, but even so I can turn long liners into gradually shorter liners and get many more uses then when they burn through in the middle. I'm also curious why we do not see more star grains (and none from AT as far as I know). All I can think of is the large single grain makes shipping prohibitive and hence marketability non existent. Thanks in advance for the discussion and your input!

-Dan

 

[MClark]

There will be scorching of the liner at the points of the star.

This thread probably should be in the Research forum

 

[DannyB]

Thanks for the reply and good point MClark! I appreciate the Pinter on thread location too, I'm as new as they come to posting. In your experience have you found the burn at the points to be as severe as the burn in between grains? If so I think my project is over... Thanks again for the input!

 

[G_T]

There are people on this forum who can answer from practice, and others who can answer from theory, but in the Propulsion forum discussions about the science and technology of rocket motors is discouraged. You'll need to get access to the Research forum, which is by request, and for US citizens only.

Gerald

 

[JackO]

I'd recommend you read Terry McCreary's book. The reason my group never went with pseudo-finocyl (star etc.) is because unless you're making very large diameter engines, that grain is going to be extremely difficult to cast and any bubbles in the propellant would leave to a CATO. Out of curiosity, where do you get your phenolic liners from? We'll be purchasing phenolic soon and always want to find the best deal.
-Jack

 

[cbrarick]

Hi everyone! So I'm getting tired of putting out all the money on phenolic liners for testing propellant, which I typically get two uses out of for static testing ex APCP.
-Dan

Danny:

They're right, the EX forum is the right place for the question. there are technical answers to your questions.
However, on a non-technical answer, I'll tell you I NEVER reuse a liner, ever.
It's just bad practice (although I'm sure someone will disagree and have a singular example)
If the cost of the liner breaks your budget, I'd rethink what you're doing, either go to a smaller size or stop.
In all honesty, you're not going to save money on EX unless you pump out a bunch of M's or bigger.

 

[cherokeej]

Worried about the cost of a phenolic liner, huh?

That liner is the least of your costs.