(Courtesy of Star Rocketry)


Launching the Rocket


Make sure you have enough N2O for the rocket you plan on launching. Most N2O tanks have the weight of the tank stamped to the neck near the valve. Weigh your tank and subtract the weight on the tank. You should at least have enough N2O that is required for your oxidizer tank plus at least five pounds to be on the safe side. Now get your O2 pressure regulated to about 90 PSI. Of course also ensure you have enough O2 for launch too!

Place a piece of masking tape on your ignition wire so that at least 2" is above the top end of the tape. Then put the top edge of the tape 3/4" down from the top of the O2 filler tube and wrap the tape around the tube. Now bend 1" of the top 2" lead of the ignition wire down so it is about at a 60 to 90 degree angle from the filler tube. When you slide your rocket over the ignition wire you will have to bend it down a little more so that it will slide through the nozzle. You want the end of the wire to touch or be as close to the inside wall of the fuel grain as possible. This should light your fuel grain up with no problem.

On the "L" and "M" grains I actually tape the ignition wire to the grain (Click Here For Illustration). You could also do this for your "J" grains if you would like but I do not think you will have a problem if you follow the procedure I outlined above.

Before going any further ensure that your electronics for your recovery system are turned ON!

The fill solenoid is activated by setting the mode selector rotary switch on the launch control box to "Fill" and pressing the activate switch. This opens the N2O solenoid, allowing the liquid N2O to flow through the hose, up through the fill tube on the launch stem, through the Kline Valve, and then into the oxidizer tank. The oxidizer tank has a vent tube which runs from the top of the tank to a port on the side of the injector bell. When the liquid N2O reaches the top of the vent tube, it vents from the port and out a vent hole in the side of the rocket. This venting N2O is visible from the control area and indicates that the rocket is ready to launch. This will take about 35 seconds for a 440cc motor system. When the tank is full you are now ready for the launch sequence.

(If the launch must be aborted for any reason, a filled flight oxidizer tank may have to be dumped. This is accomplished by moving the rotary switch on the launch control box to the "Dump" position and pushing the activation toggle switch. This activates the dump solenoid, located on the N2O solenoid assembly, which allows the N2O to escape through the Kline Valve, back through the hose, and out the dump solenoid. After reason for aborting is resolved go back to previous paragraph to initiate fill process.)

Have the count down commence and when the count down gets to "2" release the toggle switch so that N2O is no longer filling the oxidizer tank. Move the rotary switch on the launch control box to "Fire" position and at "0" push the activation toggle. Initiating the fire sequence causes the ignition module and the oxygen solenoid to activate simultaneously. The high voltage from the ignition module transformer causes the wire in the combustion chamber to arc instantly, a few milliseconds later the oxygen reaches the combustion chamber, and in the presence of oxygen, the insulation on the wire burns rapidly, igniting the fuel grain.

Keep the activation toggle pushed until the rocket launches from the pad. A flame will be coming out through the motor nozzle from the fuel grain and oxygen burning inside the combustion chamber. This will eventually burn the tie strap holding the fill stem in the Kline Valve. When the tie strap is burned through the pressure from the N2O in the oxidizer tank forces the fill tube out of the Kline Valve and the N2O mixes into the preheated combustion chamber causing the rocket to launch.


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