Tuesday, August 14, 2012

N 5800 minimum diameter attempt at blackrock!

The specs: 

Aluminum fin can: 3/16 inch heat treated 6061 fins
Fins were beveled on the leading and trailing edges
Fins were welded onto a 1/8 inch fin can that fit directly over the motor case
High heat epoxy was used to smooth fillets for aerodynamic purposes
Nose cone: Performance Rocketry spiral wound fiberglass/graphite Titanium tip with shoulder, made by Eric Foster at BadAzz Rocketry, and seated tightly and correctly in the nosecone
Body: Performance Rocketry carbon
Recovery: Same end dual deploy. The area above the motor case reserved for recovery material was about 6 inches, plus the inside of the nosecone.
Nosecone shoulder was carbon, 6 inches long, tightly fit.

Electronics: Jackson created a very innovative av bay. Because space was at a premium in the rocket, he used the unused space above the motor case and below the internal motor retainer. Jackson fit a block of wood over the smoke grain holder, and mounted the 2 ravens on that. The wood insulated the ravens from the heat of the motor. We tested the set up to make sure that the motor did not overheat the electronics. It is too bad that we never got the chance to verify that this innovative av bay works. The design should have also protected the batteries from the cold air at 60,000 feet had we gotten there.

The parts:

The rocket: 

The flight:

The aftermath:


10 years ago if you had told me that an N motor could break 60,000 feet, it would have blown my mind.  It is a bit shocking that even this rocket could not take the motor.  The exact start of the failure is unknown, although the author suggests it was the fins breaking off.  I really have to wonder how a welded fincan could be broken.  Perhaps an extremely heavy welding method is needed next time?  Could the fins have been warped resulting in severe stress?  How about this particular shape of fin in the mach 2 - 3 regime?

I am excited to see this team fly an N 5800 at near minimum mass, by attaching fins directly to a fin can, and then the motor case.  Clearly, however, the welding needs to be more substantial!  If someone could possibly afford it, cutting an entire fin can out of a single block of aluminum would offer superior strength.  But how much more expensive would that be in a 4 inch fin can?  (With fins extending out 5 inches in both directions!)

Read more at TRF

1 comment:

Saad Mirza said...

Fin flutter! Needs CFD analysis