Gotta love a photography challenge – capturing a rocket shot from a pneumatic Howitzer.
One of the builders said that capturing the rocket ejection by camera was impossible,
as it accelerates from 0 to 1000 ft/sec in a quarter second (corrected from 1000 MPH).
So… we assumed that there would be no way to use human reflexes to time the action, so we decided to use motor drive shooting continuously from just before launch. We used the height of the rail, and the exit speed estimate and the distance of the tripod from the rail to calculate how far the projectile could travel in the 0.25 seconds between frames (4 fps camera), and used the arc tangent to calculate the camera tilt angle. So if the input assumptions were correct, we would be guaranteed to have at least one shot with the rocket in frame. I shot 1/8000 second exposures to freeze the motion, and used tripod to anchor the angle and composition (and dampen my startle reflexes =)
My pal Victor used some French software to post process the 16mm wide-angle perspective back into something less warped.
Shooting continuously with my camera – 0.25 seconds later — a custom g-switch sensed deceleration, and the flight computer popped the parachute streamer. Photo below.
This was an electronics test. Pulling 600 g’s can be a bit harsh. The rocket is a 38mm J570 case with a composite fin can on the rear and a 38mm avionics package and nose cone screwed directly into the forward motor closure. So it’s the ultimate in minimum diameter airframes. The flame-painted motor case is the rocket body.
This weekend, we hope to ignite the motor instead of popping the chute, and set the altitude record for any given motor size. 😉
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