Strap-On Video Rocket

9 responses to “Strap-On Video Rocket”

1. 

   Todd Huffman

   Feb 13, 2008 at 7:59 am

   Congrats!!!

   Suspense! Drama! Excitement!

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2. 

   Gwênlyn

   Feb 13, 2008 at 8:16 am

   Wow, dizzying video.

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3. 

   Alireza7

   Feb 13, 2008 at 3:48 pm

   I watched the video. Very nice indeed! I was wondering if it was possible to attach the camera in such a way that a bit of horizon could also be seen (might have been a nice view!). Also the video made me think about free spinning of the rocket around the roll axis. Do they usually control this DOF in more advanced missiles (such as millitary ones)?

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4. 

   Alireza7

   Feb 13, 2008 at 4:02 pm

   After a second thought, I think the answer to the previous question is probably yes. Becasue the free spinning produces coriolis effects when the missile moves in a curved path, changing the dynamic and producing problem. But if the roll motion is sensed, the dynamic will be predctable and consequently controllable (making the answer to the previous question both yes and no!).

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5. 

   jurvetson

   Feb 14, 2008 at 5:28 pm

   Yes. There are a few options for horizon capture:

   1) The bulkhead coupler is angled, so I can tilt further out by attaching farther down by a little bit, and reduce the amount of rocket in frame (it’s a bit much here, but I like to have some in frame for context). It’s not the horizon, but I think I could tilt 30° outward.

   2) 45° mirror. This is the best way to shift the perspective 90° without ruining the aerodynamics or having to retrofit a video bay inside the rocket. (My goal is an easy swap of the video cam across a fleet of rockets). With the mirror, you can also go half-n-half, with part of the frame shooting down and the other part reflected out horizontally. The two images are nicely sync’d in time too.

   3) Pan-tilt camera. If I was to start over with a fancy design, I could consider a pan-tilt camera (no longer strap-on most likely though) that captures a near-360 view of the horizon from apogee (the best view for this). Tom is planning one of those for our high-altitude project…

   Spin: Spinning in our rockets comes from asymmetries in the build (usually slight variation in the fin angles; here the camera plays a role). You gain stability (so you can launch bigger motors before becoming a land shark), but you lose altitude… and make for a dizzy video… I will see if there is less spin on the other two rockets I plan to strap on to (a GLR Firestorm54 with integrated fin can and Phoenix BH2000 with air-started side booster motors).

   More advanced missiles control many factors and can even fly without fins. We are not allowed to use dynamic stabilization or guidance… yet. Maybe one day.

   ’til then, we design the fin area and weight placement (CP<CG) so as to be stable, and to put the fins on straight as as to not spin much.

   And sometimes you get real lucky when the rocket arcs over. Here’s a shot of Half Moon Bay from a simple Estes Oracle video rocket (modified to take a motor 4x larger than the kit is designed for):

   

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6. 

   Alireza7

   Feb 14, 2008 at 8:16 pm

   I got my answer. Thanks for the elaborate reply. … and the Moon bay shot is nice. You should be lucky for something like this to happen.

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7. 

   DixonTJ

   Feb 14, 2008 at 11:45 pm

   Love the corkscrew contrail (well not contrail to be exact… smoke)… Great flight!

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8. 

   Rocketman8911

   Feb 17, 2008 at 10:56 pm

   Does it get the L730 next month?

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9. 

   jurvetson

   Feb 18, 2008 at 4:45 am

   I’m thinking April or May… Would like to try the camera on those subsonic flights first, and then go for broke…

   Reply