Most airframes fail by column buckling. The overloading may either inertial and/or aerodynamic in nature, and long skinny rockets are more susceptible to it than short stubby ones so you can always blame the failure on g-loading or velocity as it is almost always a combination of the two, and it can be enhance by coning (roll-pitch coupling) which can be a problem in high performance rockets with marginal stability.
A column is normally very strong however a defect in the airframe such as a dent or crease can act as a stress concentrator to initiate folding, or it can be initiated by resonant vibration modes of the airframe. Longer tube resonate at lower frequencies with larger amplitude displacement excursions than shorter tubes which have higher frequencies but lower amplitude displacement excursions which again is why long skinny rockets will tend to fold up whereas short rockets on the same motor will not.
The vibrations can be induced by aerodynamic asymmetry in the vehicle, or from combustion instabilities in the motor, and high thrust fast burn motors tend to have more combustion instabilities than long burn low thrust motors. A common airframe failure point on minimum diameter rockets is located at the top of the motor where the airframe is no longer backed by the motor casing. This intersection acts as a stress concentrator and pivot point for airframe rotation.
Making the airframe stiffer increases the resonant frequency and therefore make the airframe more resistant to column bucking. This is why using a thicker airframe tube or using a full length coupler glued inside the airframe can often eliminate column buckling. Cutting all airframe joint perpendicular to the flight axis and using screws or rocket rivets to prevent joint movement will also help prevent column bucking.
Bob
Methinks it should move
Quite quickly I might add
Nate
While this rocket has more fin drag than your design, it is a minimum diameter 38mm BT rocket that survived the J510.
https://www.rocketryforum.com/showthread.php?60951-Bluefin-Tuba
Ari.
its been proven up to Mach 3 so I have to say yes to Mach 2. Also I agree with mikec.
Can you link me to that? I did a search and found nothing maybe I didn't look hard enough. I am just interested in the flight profile and the design of rocket. Thanks!
Great stuff! Thanks.Most airframes fail by column buckling. The overloading may either inertial and/or aerodynamic in nature, and long skinny rockets are more susceptible to it than short stubby ones so you can't always blame the failure on g-loading or velocity as it is almost always a combination of the two, and it can be enhance by coning (roll-pitch coupling) which can be a problem in high performance rockets with marginal stability.
A column is normally very strong however a defect in the airframe such as a dent or crease can act as a stress concentrator to initiate folding, or it can be initiated by resonant vibration modes of the airframe. Longer tube resonate at lower frequencies with larger amplitude displacement excursions than shorter tubes which have higher frequencies but lower amplitude displacement excursions which again is why long skinny rockets will tend to fold up whereas short rockets on the same motor will not.
The vibrations can be induced by aerodynamic asymmetry in the vehicle, or from combustion instabilities in the motor, and high thrust fast burn motors tend to have more combustion instabilities than long burn low thrust motors. A common airframe failure point on minimum diameter rockets is located at the top of the motor where the airframe is no longer backed by the motor casing. This intersection acts as a stress concentrator and pivot point for airframe rotation.
Making the airframe stiffer increases the resonant frequency and therefore make the airframe more resistant to column bucking. This is why using a thicker airframe tube or using a full length coupler glued inside the airframe can often eliminate column buckling. Cutting all airframe joint perpendicular to the flight axis to provide uniform column loading and using screws or rocket rivets to prevent joint movement will also help prevent column bucking.
Bob
Is that program Openrocket? I use Rocksim and don't recognize this program.
Doooo ittttt!!!!!!!!!!!!!!!haha ya I was thinking about that too but it also comes out to mach 2.3.
Doooo ittttt!!!!!!!!!!!!!!!
Loki J1000 gets a similar rocket to 18,000...
Am I remembering wrong or does he have a K in the works for that case too?
maybe but when I do the center of pressure shift it only has 1.14 calibers of stability at mach 2.28