Wednesday, February 16, 2011

Engineering Challenge Part II - 3D Printed Rockets

A few months ago I wrote about an extracurricular rocket design activity that a number of Z Corp. R&D team members took part in. I finally had a chance to sit down and write the update which is timely given that Apollo 13 heroes Gene Kranz (Mission Control Director) and Jim Lovell (Astronaut) recently took the stage at SolidWorks World 2011 to tell their story of that famous NASA mission.

Many lessons were learned during our Z Corp. rocket design project. One of which is that just because you can print it doesn’t mean it will fly straight, or in some cases, fly at all. On the other hand, a surprising number of unconventional rockets did fly, and few straight. An oversimplification of designing a rocket for stable flight is that the center of gravity must be above the center of pressure or the central point of aerodynamic forces on the rocket. In other words, the cg should be closer to the nose and the cp closer to the tail. When designing rockets with crazy geometries, figuring out if it will have stable flight is pretty straight forward and relatively quick. By tying a string at the center of gravity and swinging the model around, the rocket will flies nose cone first if the cg – cp relationship is correct. If not, an adjusted model can be quickly 3D printed on a ZPrinter and tested in the same manner until stability is achieved.

Here are some photos of the rockets we designed, 3D printed on a Z Corp. ZPrinter:

Surprisingly, some of the designs above that look like they should not fly actually do, and some of the designs that look like they should fly don’t. Then again, the opposite is also true in that some of the designs that look like they have no business flying live up to their expectation. What is noteworthy is the number of rocket designs that went from design to test flight in a very short amount of time due to the ZPrinter's incredibly fast speed.

These two videos represent the extremes of success and failure:

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