Howitzer Lessons

4 responses to “Howitzer Lessons”

1. 

   Victor1

   Sep 29, 2009 at 7:52 am

   …and the math too please! Wanna know what fps and shutter speed it took. The trig would be fun too.

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2. 

   jurvetson

   Sep 29, 2009 at 4:35 pm

   We assumed that there would be no way to use human reflexes, so we decided to use motor drive shooting continuously from just before launch. Sounds like you guessed that from your fps question. 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. 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!

   The ROCKETS Magazine story
   

   And .26 seconds later, the flight details
   

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3. 

   In Memoriam: jerryfi_99

   Sep 30, 2009 at 8:21 am

   Cool idea! That’s the biggest "potato cannon" I’ve seen (and there are quite few on the net). Did the rocket use fold out fins?

   Reply
4. 

   jurvetson

   Oct 1, 2009 at 8:32 pm

   It has a medusa head of plumping hooked to a pneumatic pump. So not quite like the potato cannons that ignite a gas.

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