Direct fire air rocket
Posted: Mon May 09, 2016 10:05 am
For my thesis I'm designing a direct fire rocket using water rocket technologies (just without the water). Before anyone has a fit about the recklessness of such a heinous act: Safety is the most important aspect of the thesis.
The idea is to have a launcher setup that could be used as artillery or direct-fire device in airsoft or paintball anti-vehicle or anti-fortification roles. Having some experience in the sport, I can assure you I've paid the utmost care to err on the side of caution whenever the situation arose. It wouldn't be the first time someone doesn't pay attention to what you're shooting and stroll right into the projectile's flight path.
It is constructed around the Gardena launcher system and uses a ring fin in order to fit into a launch tube (which is both for guidance as well as safety, it is a thin-walled pressure vessel after all). The nosecone is made of foam and is hemispherical, with a layer of foam between nosecone and bottle as a buffer zone.
The entire rocket prototype weighs in at just a smidge under 100 grams, and has a maximum velocity at burnout of about 37 m/s if pressurised to the max pressure of 6 atmospheres(depending on the launch angle, that is). The maximum pressure stems from impact safety precautions, not bottle burst limits.
Here's a video of the latest test fire:
The rear end of the launch tube has holes drilled into it to prevent the buildup of pressure behind the rocket as that might cause it to exceed the safe speed limits, but I think it needs more holes as it flies almost 5m further than calculations indicate.
As most of the experts on the combination of PET bottles and rocketry reside on this part of the internet, I'd thought this would be a good place to share
The idea is to have a launcher setup that could be used as artillery or direct-fire device in airsoft or paintball anti-vehicle or anti-fortification roles. Having some experience in the sport, I can assure you I've paid the utmost care to err on the side of caution whenever the situation arose. It wouldn't be the first time someone doesn't pay attention to what you're shooting and stroll right into the projectile's flight path.
It is constructed around the Gardena launcher system and uses a ring fin in order to fit into a launch tube (which is both for guidance as well as safety, it is a thin-walled pressure vessel after all). The nosecone is made of foam and is hemispherical, with a layer of foam between nosecone and bottle as a buffer zone.
The entire rocket prototype weighs in at just a smidge under 100 grams, and has a maximum velocity at burnout of about 37 m/s if pressurised to the max pressure of 6 atmospheres(depending on the launch angle, that is). The maximum pressure stems from impact safety precautions, not bottle burst limits.
Here's a video of the latest test fire:
The rear end of the launch tube has holes drilled into it to prevent the buildup of pressure behind the rocket as that might cause it to exceed the safe speed limits, but I think it needs more holes as it flies almost 5m further than calculations indicate.
As most of the experts on the combination of PET bottles and rocketry reside on this part of the internet, I'd thought this would be a good place to share