Q: What kind of lubrication should I use for Sky Ripper Systems motors?

      You should only use lubricants that are known to be oxidizer safe. Sky Ripper Systems recommends the use of Dupont Krytox® only. While it may seem expensive, you will use very little per launch. A small tube of Krytox® will last a few flying seasons.

Q: How many flights can I expect to get out of the reusable nozzle?

      The life span of the graphite nozzle has not yet been discovered. There are some original prototype nozzles in the Sky Ripper Systems inventory that are still in use after many flights and static firings. There are others that show signs of wear, however. The most important thing is to keep your nozzle protected when it’s not in use, as it can be easily damaged when it’s out of the motor.

Q: My nozzle is stuck in the fuel grain after the flight.  How can I get it out?

     The nozzle tends to stick in the PP grain due to the plastic shrinking around the nozzle shoulder as it cools after the burn.  It can become lodged in there pretty tightly.  The worst way to attempt to get the nozzle out is to 'bend' it out of the end of the grain.  This is almost a sure way to get it to break.  The best way we have found to remove the nozzle when it becomes stuck is to use a  hair dryer, oven, or other heat source to heat up the grain.  Then, give the nozzle a sharp radial twist, taking care not to bend up or down. 

Q: My 54mm nozzle is stuck to the cardboard liner tube after the flight.  How do I get it out?

     What happens here is that the plastic that is touching the nozzle melts under the heat, and gets stuck right to the cardboard tube.  It happens 100% of the time. We've tried different greases and lubes, but none have ended up working particularly well at combating this.  You may coat the lower 1-1/2" of the liner tube with a thin layer of Krytox®, which we have found may be helpful.  The two things we have done to help get the liner are;

     1) Carefully score almost all the way through the liner with a hobby knife, and peel away the layers of the liner like an onion until the liner is removed.

     2) Soak the whole assembly in water for a few hours, until the tube becomes saturated.  It'll then easily come apart.

     Once the nozzle is extracted from the liner, if it still remains stuck in the plastic fuel grain, refer to the question about removing the nozzle from a plastic fuel grain.

Q: What size is the vent tube?

      The vent tube for all Sky Ripper Systems motors is a standard 1/8” nylon tube. It’s the same line that is used as the 29mm system fill tube.

Q: What size are the threads in the vent hole?

     The vent tube hole is threaded for #8-32.  Some flyers have had good luck with threading the end of 5/32" nylon tube with a #8-32 die, and then screwing this threaded tube into the vent hole for a very solid attachment.

Q:  It's kind of hard to put the nylon tube into the vent hole through the small hole in the rocket body.  Do you have a tip to make this easier?

     Actually, Yes!  John Stein of Alabama reports that he uses a small diameter rod of plastic that he puts through the vent hole in the rocket, right into the motor vent hole.  He then uses this rod as a 'guide' by threading the vent tube over it.  The vent tube will follow the guide rod right into the motor vent without much effort.  Thanks for the tip, John.

    And, if you don't use the threaded vent option, Sky Ripper Systems has found that a small dot of CA (super glue) on the vent tube where it contacts the airframe will hold the vent tube solid during the fill, and will still be easily removed post flight.

Q: Do Sky Ripper Systems reloads require a HAZMAT charge to be shipped?

      No! While the Sky Ripper Systems reload kits do contain pyrotechnic elements , they can be shipped via USPS Parcel Post at no added cost, using the 1.4s exemption for toy propellant. Only Sky Ripper Systems, or Aerotech dealers can ship SRS reloads using this method, however.

Q: When will we see bigger motors from Sky Ripper Systems?

      Our production plan is to move up the line in size, taking on the next largest size as we go. We plan to have a 3 motor 54mm System, a 2 motor 75mm system, and a single 98mm M motor. The timeline for these projects can’t be static, as we slowly develop and carefully test each product before we make it available to the flying public. As of now, we can say that we hope to have the 54mm line certified in time for the summer flying season in 2005.

Q: Where can I find:

     Thrust Curves?

http://www.skyrippersystems.com/documents/performanceinfo.htm

     Rocksim Motor files?

http://www.skyrippersystems.com/documents/simulationfiles.html

     Motor dimensional information?

http://www.skyrippersystems.com/documents/Hardwareinformation.html