(Courtesy of Star Rocketry)


Assembly of the Basic Fill / Fire Launch Control (BF/FLC) System


The basic fill/fire launch control system has several components, but is straight forward to set up and use. Your basic fill/fire launch control system is made up of the following components:

A gaseous oxygen (GOX) line: a 10’ stainless steel braided hose with red female 4AN fittings.

A nitrous oxide line: a 10’ stainless steel braided hose with blue female 4AN fittings.

The nitrous oxide solenoid assembly: consisting of fill solenoid, dump solenoid, a blue male 4AN fitting, and a CGA 660 tank valve fitting (a CGA 326 tank valve fitting is optional).

The GOX solenoid assembly: consisting of an oxygen rated regulator, a GOX solenoid, a red male 4AN fitting, and a CGA 540 tank valve fitting.

An ignition module: a high voltage transformer for igniting the ignition wire.

The launch control box: which has a safe & arm key switch, a LED power indicator, a three position (fill/dump/fire) rotary switch, and a momentary toggle actuator switch.

The launch pad junction box: which has color-coded outlets for plugging in the two nitrous oxide solenoids, the one GOX solenoids, and the ignition module.

100’ of control cable: connects the launch control box to the launch pad junction box.

Bag of 50# test nylon tie-down straps for securing the rocket to the launch stem assembly.

A roll of igniter wire: 24-gauge 2-conductor speaker wire.

You will also need a J/L fill stem assembly; a coaxial tube with an adjustable mount which slides over 3/8" to ½" launch rod and has separate male 4AN fittings for the GOX and nitrous oxide lines. M motor systems require an M launch stem assembly, 500’ of control cable, and the remote relay module.


Prior to set up and operation of the basic fill/fire launch control system, tanks of GOX and nitrous oxide must be procured. Most industrial gas supply companies or welding shops carry GOX and N2O. This will be the cheapest place to purchase N2O but they usually require you to use tanks that hold 66 pounds of N2O. Hot rod shops also carry N2O but their N2O is usually more expensive. They will, however, fill smaller tanks. The GOX tank valves are standard CGA 540. The N2O tank valves are usually CGA 660 for hot rod tanks and CGA 326 for industrial size tanks. DO NOT USE ANESTHETIC OR MEDICAL GRADE N2O! Use only Nitrous Plus or industrial grade N2O, both have sulfur dioxide or mercaptan to discourage abuse.

N2O tanks come with or without a siphon tube. Try to get one with a siphon tube so that you can have the tank right side up with solenoids on top. The siphon allows the liquid N2O to be sucked up from the bottom of the tank. The tanks without a siphon must be placed up side down in order for the liquid N2O to flow through the solenoids.

Now that you have your tanks we are ready to begin assembly of the basic fill/fire launch control system. You will need a large crescent wrench for tightening the tank valve fittings and a small crescent wrench to tighten the 4AN fittings. Begin by mounting the nitrous oxide solenoid assembly on the N2O tank. Attach the N2O line (the hose with the blue 4AN fittings). Take care not to over tighten the aluminum AN fitting. Next mount the GOX assembly on the GOX tank and attach the GOX line (the hose with the red 4AN fittings). Position the N2O and GOX tanks so that they will not fall over causing personal injury and/or damaging the solenoid assemblies.

Slide the fill stem assembly over the launch rod so that the assembly is resting on the blast deflector plate (for launch rails you will have to modify the fill stem assembly to fit the rail). The N2O and GOX tanks should be about six to ten feet from the launch pad. Connect the fitting to the corresponding color-coded 4AN fittings, red to red and blue to blue, with no kinks.

Hang the ignition module on the launch pad below the blast deflector so that it is protected. Now connect the color-coded plugs to the color-coded receptacles in the launch pad junction box. Plug the launch pad junction box into the 100’ control cable. Check again to ensure that all plugs are connected to the right color-coded receptacle.

Unroll the control cable out to approximately 100’. Attach the launch control box to the 100’ control cable. THIS IS A 12-VOLT SYSTEM. Attach the launch control box’s battery clamps to a 12-volt battery when you are ready to check the system.


Return to Hypertek 101

Return to Star Rocketry