My first supersonic shred

6 responses to “My first supersonic shred”

1. 

   jurvetson

   Oct 17, 2011 at 2:16 am

   (launch photos and video here)

   Now, the engine is still smoking in free fall, with some body tube to the right…

   

   We scoured the playa to recover all of the bits
   

   The heavy stuff landed very close to Jeff’s hybrid R10,000 rocket out at the far, far away pads (nose cone on bottom left, N4000 motor and body to the right):
   

   Avionics Computer Bounce:
   
   While the connectors and pins are a bit bent on the HCX and LCX computers, I tested both of them today, and they are ready to fly again. The Duracell batteries ripped off, but we found them too. And the Balloon Boy GPS transmitter system survived the free fall to the playa, sending data the whole way:
   

   You can click on this to see the aftermath…. amazing damage, but we can rebuild her!
   

   Here is the launch video compilation (HD version).

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2. 

   Peter✔

   Oct 17, 2011 at 4:18 am

   Very sad! It surprises me this doesn’t happen more often, especially at such incredible speeds.

   Reply
3. 

   solerena

   Oct 17, 2011 at 4:46 am

   fun:)

   Reply
4. 

   rocketmavericks

   Oct 17, 2011 at 6:41 pm

   Fin Flutter!!! I warned James about the same thing before his came apart.

   Flutter of an elastic body is a self-excited vibration of that body while immersed in fluid flow. In the case of a rocket, flutter is associated with the aero-elastic characteristics of the fin/body combination while flying through the atmosphere. Flutter is typically the coupled motion of fin twist (torsion), fin plunge (bending) and possibly the rigid and/or flexible motions of the rocket body. Each component of the coupled motion is referred to as a degree-of-freedom. The discussion here will be limited to the motions of the fin itself and any body contribution will be ignored. In essence, it is assumed that the fin is rigidly fixed and cantilevered to an infinitely stiff body structure.Hence, the degrees-of-freedom will be limited to fin torsion and fin bending.

   The lowest speed attained when the fin sustains a neutrally stable oscillation is known as the flutter speed. Aero-elastic motions will be damped below flutter speed. At speeds just above the flutter speed, the motion will be divergent in one or both of the degrees-of-freedom. The divergence speed is associated with the minimum speed when both torsion and bending are no longer damped, where one degree-of-freedom is typically divergent and the other is neutrally stable. Structural failure usually occurs at divergence speed. Typically the divergence speed is only slightly greater than the flutter speed. Thus it is important that the prediction of flutter speed be used as a “never-to-exceed” design criterion.
   Fin flutter is a complex physical problem to characterize mathematically. Sophisticated structural and aerodynamic tools are typically used to perform flutter analysis. Finite Element Methods (FEM) may be used to characterize both the structure and aerodynamics. Other computational fluid analyses such as Finite Difference or Doublet Lattice Methods (DLM) may be used to characterize the aerodynamics. DLM is commonly used for subsonic flutter analysis. These tools are beyond the scope of this discussion. The discussion here is limited to classical structural and aerodynamic methods. Although the accuracy of the predicted flutter speed may be questionable, the physical trends can be studied.

   You need to enhance the kit you used with a composite lay-up that can better distribute the
   aerodynamic forces and handle the flutter and damp the oscillations appropriately for the vehicle flight envelope. Vehicle velocity is just too high for your hobby kit.

   I can show you how if you are interested, but the composite work will require more than JB Weld. 😉 Need a poor mans autoclave, some vacuum bagging, as well as some composite design software and several types of and weaves of glass tow.

   That BB motor is at the very edge of hobby rocketry. You are starting into experimental rocketry, where the men are separated from the boys. Cheapest alternative is to move to an all metal airframe with metal fins. I recommend T6061 Aluminum. Happy to help here also. I think we just move on to get that Q flown you have. Would be great for you and Leif to take the Carmack Prize, and we have the avionics to do it. Let me know….Always here to help.

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5. 

   TomiTapio

   Oct 17, 2011 at 10:12 pm

   Nice ethereal image.

   Reply
6. 

   Jim Rees

   Oct 19, 2011 at 2:55 am

   You didn’t test this in a Mach 2.5 wind tunnel before you flew it?

   Reply