sensing static electricity in a high power rocket

Discussion in 'The Projects Forum' started by gagreen, Oct 2, 2011.

  1. gagreen

    Thread Starter New Member

    Oct 2, 2011
    4
    0
    Hi everyone i build and fly high power rockets and recently came across something i would like to try to figure out. In the hobby we use altimeters, timers, and other electronics to control deployment times of drouges and main parachutes. the electronics go from basic to very indepth full on flight data recording. we mount the electronics the the center of gravity in the rocket in a sealed electronics bay with only vent holes to sense proper barometric pressures for altitude measurements. usually the housing bay is made of cardboard, phenolic, carbon fiber, plywood, or fiberglass depending on the project. within the housing is a sled usually made of wood or fiberglass that the electronics are mounted on. one of the recent projects a fellow rocketeer is building he used a piece of aluminum cut from an old pc case. I mentioned that that may build static electricity that could arc and fry the electronics.

    I am a novice in electronics. I have a background working avionics on fighter jets, a few years of electronics schooling but by no means a pro at developing or prototyping my own circuits. I would like to make some sort of small measuring device that will measure static electricity in flight, record the data, and develop a program to download the data. Its a tall order and i figured this forum may be helpful in working out the kinks i run into as well as finding out if its even a feasible idea.

    Thanks for your time
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What avionics did you work on? Branch? I was Radar/Missile Fire Control on the F-4J/S. Worked on more stuff like that after EAS.

    I don't see the piece of aluminum causing problems; it would keep the voltage potential the same all over the sheet. If you're concerned about static buildup, you could line the entire interior of the avionics bay with a sheet of aluminum foil; it would act more or less like a Faraday cage. It would also be very light in weight.

    I haven't read through the NAR guidelines on stuff like that, but I think you're supposed to keep things nonmetallic wherever possible. However, a sheet of aluminum foil would not represent a mass that would have any significant kinetic energy.
     
  3. gagreen

    Thread Starter New Member

    Oct 2, 2011
    4
    0
    I was integrated avionics in the air force. We covered all forms of avionics on the airframe. I worked f-117's f-22s and f16's while i was in. i am going to school to get my a&p currently so i can continue the trade on civilian airframes.

    the nar guidlines i believe only refer to no metallic airframe, fins, nose cones or other things that if a ballistic return to earth occurs would cause unecessary amount of danger. Nearly everyone is using aluminum motor retainers. so metals in the av bay esp very small amounts of them is no huge deal.

    i do believe it would be ok to just ground the electronics to the avbay sled. Personally if it were my sled i would wrap the aluminum in a layer or two of fiberglass so my electronics werent directly in contact with a conductive metal as a precaution.

    Personally I would like to see a measurement for myself of static build up in dif airframe materials, sub sonic vs transonic vs supersonic, varying altitudes, dif internal materials within the avbay etc.. I really just want to do a private research into static electricity and rockets it kind of adds a new element of excitement to the hobby when your not just watching it fly.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I did some work on the prototype YF-22 avionics in the mid-80's. It was interesting stuff. Dual 700MHz RISC processors doesn't sound like much nowadays - but back then, if you had a 386 PC running at 16MHz with 4 MB RAM, you were someone important. ;)

    As long as the avionics are enclosed in something conductive, there will be no way for static to affect anything, as everything within the enclosure will be at very close to the same electrical potential. Didn't you use pink bubble wrap in the USAF? That stuff is conductive. So are the Mylar Ziplock bags.

    If you wanted to bleed off static, I suppose you could run a thin gauge wire down the rocket body, out to one or more fins, to a point on the trailing edge of a fin.

    Do you remember seeing stuff that looked like small black tassels on the trailing edge of flaps on airliners? They're carbon impregnated fibers, and they're there to bleed off static electricity rather than let it build up.

    You can also use fabric softener sheets that are designed to be used in the dryer to treat your rocket parts to be anti-static. That's a trick I found out when I was reloading ammunition.

    Measuring static build-up might be somewhat of a challenge; virtually all electronics I can think of will break down under really high voltage.

    Ever hear of a Leyden jar?
    http://en.wikipedia.org/wiki/Leyden_jar
    If you had wires running into an avionics bay that was otherwise enclosed with aluminum foil, you'd probably wind up with something resembling a Leyden jar - not so good.

    However, there was an experiment where a pair of conductive pieces of foil were hanging vertically within an enclosure, then had a static charge applied to them; since like voltages repel, the two pieces of foil repelled each other. I don't know offhand how well something like that would work in a rocket, or how you'd detect the separation of the pieces of foil.
     
  5. gagreen

    Thread Starter New Member

    Oct 2, 2011
    4
    0
    the last paragraph was a kick back to my quantum mechanics class. I dont know if i will necessarily be able to pull of some sort of measurement and recording device of varying static electricity i just thought it was interesting enough to look into. ill dig around a little bit and tinker.

    Static discharge may be overboard idk if these rockets would be in flight long enough to require aircraft style discharging. It would be a cool conversational piece in the prep area or for school demo's to show the experimental importance of "playing with models". I have found carbon strands in lengths that one could run them through the booster section, epoxy into the fillets of the fins and run to the trailing edge of a fin fairly cleanly. when i get into level 3 hpr and start working with laminated honeycomb fins etc i may do a bit more investigation into the problem.

    For me personally ill stick with fiberglass and liteply for avbay sled material, its proven. The metal sled just got me thinking a whole lot deeper into the possibility of a static problem.

    Thanks for the input, after lurking around the site i have found a new interest in prototyping my own electronics rather than buying plug and play stuff.
     
  6. gagreen

    Thread Starter New Member

    Oct 2, 2011
    4
    0
    I am familiar with the foil experiment but i believe g forces and violent forces a rocket endures would make that nearly impossible to pull of properly.
     
Loading...