Winston
Lorenzo von Matterhorn
- Joined
- Jan 31, 2009
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In my search for something technically interesting and possibly useful to do with hobby rockets, I considered compressed air (for non-pyrotechnic safety) tube launched, aerodynamic, instrumented probes to attach to one of Reed Timmer's tornado intercept vehicles to be launched into the outer and inner circulation of tornadoes. Reed had previously done something similar with more crude, compressed air launched, non-aerodynamic instrumented projectiles, then didn't continue the practice for unstated reasons, perhaps because of cost, poor results, etc.
Anyway, after reading up on the large(ish) R/C drones now being used by professional tornado researchers, I abandoned the idea. However, the compressed air tube launch idea stuck with me. Drop the "useful" bit and it's still technically interesting.
What I'm thinking of: a vertical 2" PVC pipe launch tube with a horizontal 3" PVC pipe compressed air reservoir (2" Schedule 40 PVC pipe has a 280psi rating; 3" Schedule 40 PVC pipe has a 260psi rating; max to be used: 100psi) with a 6" PVC (I'd much prefer 6" HDPE, but try to find it) pipe surround around the reservoir for burst safety with no-go zones at both ends of the reservoir; a sabot (split pool noodle - fits nicely when slightly compressed into 2" PVC pipe); 3D printed sabot base "pusher" (if needed); 3D printed dart or rocket; modified sprinkler valve for rapid air dump using large orifice 12V truck air bag suspension/air horn solenoid valve ($18 shipped on eBay) as the modified sprinkler valve's upper chamber pressure release instead of the manually actuated air nozzle release used in the mod video below and typically used for spud guns:
Sprinkler valve theory of operation
https://www.spudtech.com/content.asp?id=21
Fast Hacks #4 - Sprinkler Valve Modification for an Air Cannon
[video=youtube;H4uT0wUzvK0]https://www.youtube.com/watch?v=H4uT0wUzvK0[/video]
Reservoir pressurization would be supplied by a 12V tire inflation pump with pressure gauge. Streamer or parachute deployment would be accomplished via compression spring released by altimeter. If an 18mm composite motor is used, the launch air valve would be triggered by an IR flame sensor port after ?? delay (perhaps combined with an acoustic and/or launch tube pressure sensor as confirmation of actual motor ignition). I wonder what effect a 100 psi ambient pressure jump and extremely high acceleration would have on a just-ignited 18mm composite motor during the instant it spends travelling down the launch tube. ;-)
Launch force (thrust) at 100psi: pi*r^2*100psi = 314 pounds.
Additional safety considerations:
https://www.spudtech.com/content.asp?id=16
Anyone know of anyone doing this sort of thing before? Comments and suggestions?
Anyway, after reading up on the large(ish) R/C drones now being used by professional tornado researchers, I abandoned the idea. However, the compressed air tube launch idea stuck with me. Drop the "useful" bit and it's still technically interesting.
What I'm thinking of: a vertical 2" PVC pipe launch tube with a horizontal 3" PVC pipe compressed air reservoir (2" Schedule 40 PVC pipe has a 280psi rating; 3" Schedule 40 PVC pipe has a 260psi rating; max to be used: 100psi) with a 6" PVC (I'd much prefer 6" HDPE, but try to find it) pipe surround around the reservoir for burst safety with no-go zones at both ends of the reservoir; a sabot (split pool noodle - fits nicely when slightly compressed into 2" PVC pipe); 3D printed sabot base "pusher" (if needed); 3D printed dart or rocket; modified sprinkler valve for rapid air dump using large orifice 12V truck air bag suspension/air horn solenoid valve ($18 shipped on eBay) as the modified sprinkler valve's upper chamber pressure release instead of the manually actuated air nozzle release used in the mod video below and typically used for spud guns:
Sprinkler valve theory of operation
https://www.spudtech.com/content.asp?id=21
Fast Hacks #4 - Sprinkler Valve Modification for an Air Cannon
[video=youtube;H4uT0wUzvK0]https://www.youtube.com/watch?v=H4uT0wUzvK0[/video]
Reservoir pressurization would be supplied by a 12V tire inflation pump with pressure gauge. Streamer or parachute deployment would be accomplished via compression spring released by altimeter. If an 18mm composite motor is used, the launch air valve would be triggered by an IR flame sensor port after ?? delay (perhaps combined with an acoustic and/or launch tube pressure sensor as confirmation of actual motor ignition). I wonder what effect a 100 psi ambient pressure jump and extremely high acceleration would have on a just-ignited 18mm composite motor during the instant it spends travelling down the launch tube. ;-)
Launch force (thrust) at 100psi: pi*r^2*100psi = 314 pounds.
Additional safety considerations:
https://www.spudtech.com/content.asp?id=16
Anyone know of anyone doing this sort of thing before? Comments and suggestions?