Good HTPB hardeners

[rocket_troy]

True! experience beats tables on the internet. I have been flying hybrids since 2004 starting with Rattworks. By now I have easily put 200lbs of N20 through my motors. O-rings were all BunaN70. No issues or hint of issues. The o-rings on the cold bulkhead could easily be reused 3-4 times if I wanted.

The handwringing of oring selection on an amateur hobby rocket motor where the oring exposure to N2O is on the order of minutes is fun, but mostly unwarranted in my honest opinion.

Note that I originally said that for static applications, BUNA/Nitrile should be okay. Your and just about every other application typically in HPR motors is not just static applications, but static applications well concealed from direct energy exposure. So, yes, BUNA/Nitrile would be acceptable.
As I also said, for dynamic applications (and I've done N2O subsystems with them and advised university projects using dynamic o-rings for N2O) you need to be much more careful about your material selection.

TP

 

[jderimig]

Note that I originally said that for static applications, BUNA/Nitrile should be okay. Your and just about every other application typically in HPR motors is not just static applications, but static applications well concealed from direct energy exposure. So, yes, BUNA/Nitrile would be acceptable.
As I also said, for dynamic applications (and I've done N2O subsystems with them and advised university projects using dynamic o-rings for N2O) you need to be much more careful about your material selection.

TP

Agreed, missed that. What would be a dynamic use case for hybrid rocket motor? Tribrid?

 

[rocket_troy]

Agreed, missed that. What would be a dynamic use case for hybrid rocket motor? Tribrid?

At the ultra extreme end where the only option should be Kalrez - positive displacement pumping of N2O.

I've used dynamic seals for N2O in throttling, in vent valves and special custom check valves. For these applications, EPDM is good enough.

TP