You know, the GGDT has the option of varying your altitude.
Defult model at sea level gives 411 fps, at 18 miles it gives 454 (partly an effect of less mass in the barrel to accelerate, partly an effect of more effective pressure)
Changing the model to something which I think approximates our system a bit better (burst disk; 1 cubic inch chamber with helium at 800 psi and 3000*C; .5" barrel 12" long with 1g projectile):
1273 fps @ sea level
1286 fps @ 18 miles
The Ultimate Potato Cannon
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boilingleadbath
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- Location: Pennsylvania, USA
Geez, somewhere a little north of Mach 1:shock:. Fabrication requrements are way outta my league but somebody's gotta build this puppy.boilingleadbath wrote: Changing the model to something which I think approximates our system a bit better (burst disk; 1 cubic inch chamber with helium at 800 psi and 3000*C; .5" barrel 12" long with 1g projectile):
1273 fps @ sea level
1286 fps @ 18 miles