Howitzer Rocket Launcher Lessons
One of the builders said that capturing the rocket ejection by camera was impossible, as it is pulling over 600 g’s and going 1000 ft/sec. …a supersonic launcher, before the rocket motor lights…
Little did he know that we did a little trigonometry in advance.
We assumed that there would be no way to use human reflexes to catch the action, so we decided to use continuous motor drive with the camera shooting 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, and used the arc tangent to calculate the camera tilt angle on the tripod. So, if the input assumptions were correct, we would be guaranteed to have at least one shot with the rocket in frame. (you know who did the math… made him very proud…)
• 4 fps
• Shooting 1/8000 second exposures to freeze the motion
• Used tripod to anchor the angle and composition
(and dampen my startle reflexes =)
On the final test, the rocket came back ballistic and slammed down two feet from the tripod. Classic for a rocket safari.
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