CD4 Instructions
CD4 Specs
CD4 Charge Sizing
The CD4 unit is designed for deploying parachutes and recovery items in high power and amateur rockets at any altitude. From sea level to space. The CD4 unit can be used in both "low altitude" and "high altitude" configurations. The low level application is for flights under 20,000 ft. where there are no problems with the burning of a pyrogen. For flights over 20,000 feet, the CD4unit can be prepared for high altitude flights by "potting" the electric match heads with epoxy into the electric match holder. Either configuration accepts the two different sized of CO2 cartridges As in any type of ejection and recovery system, only after ground testing to confirm desired results, should you proceed with the flight. Remember to always ground test the rocket to insure that the ejection of recovery items and separation of rocket components is adequate.
Another benefit of the CD4 system is the elimination of Nomex protection parachute cloths and recovery line protection sleeves. These items often consume valuable recovery volume and never completely protect the recovery items from the burning of the pyrogen- black powder. Your expensive parachutes and recovery items can now be used many years with no damages. A year of research and testing went into the CD3 unit. From the initial tests conducted to determine exactly what was happening at high altitudes we discovered that not even a Davey Fire electric match would completely burn at altitudes of 55,000 ft. and above. Pyrogens placed in contact with the matches would not completely burn either, with noticeable drop offs in burn rates starting at 20,000 ft..
Many different types of pyrogens were tested including nitro-cellulose based, black powder, Pyrodex, Igniter Man pyrogen, potassium based pyrogens, Clear Shot, Red Dot, Blue Dot and "777 brand" pyrogens. Each exhibited different characteristics in their burning and burn rates. However, the common denominator was that none worked in vacuums of 3" Hg and lower. (Roughly 55,000 ft..) All of these compounds are pressure dependent for their burn characteristics. The lower the pressure, the slower the burn. (Burn rate co-efficient). There was a significant drop off in gasses produced at approximately 20,000 ft. (13" Hg). Incomplete combustion occurs at an alarming rate above this.
After some assistance from NASA, the units design could be finalized to incorporate both the needs of low altitude flights and high altitude flyers. At high altitudes, NASA pointed out that there can be no burn in a vacuum due to the lack of air molecules needed to transfer heat to sustain burning. (Heat transfer in both convection and conduction. Radiation plays little in the role of sustaining combustion). Anything that burns must maintain its individual ignition temperature to sustain the burn. At these high altitudes, the ignition temperature is not maintained, nor can it be transferred due to the lack of a medium to transfer (conduct) temperature- air molecules.
Another factor that contributes to the high altitude burn problem is that of cooling gasses. As altitude increases, so does the cooling of the expanding gasses due to the pressure differential. The expanding combustion gasses expand so fast that they cool, like that of a CO2 cartridge or air hose. This cooling effects the burning of the pyrogen. At high altitudes, the cooling extinguishes the burn as the cooling and expansion of gasses lowers the ignition temperature to below that of the ignition temperature of the pyrogen.
The physical characteristics of the pyrogen are also critical to the burn. The powders used in rocketry are granular and when they burn they "spray" the adjoining grains out. At low altitudes, the flame front and ignition temperature keeps up with the moving particles and a complete burn is accomplished. These ejection containers fail prior to all the pyrogen being burnt, with particles burning out side the canister. Keeping the granules in a confined area to insure complete combustion by maintaining pressure, is what's needed to produce the gasses needed to separate the rockets components for these canister types of applications. It is the burn rate of pyrogen (BP) and the physical properties of atmosphere that make the design of a deployment device difficult.
For these reasons, ROUSE-TECH recommends 20,000 ft.. as the cut-off altitude for successful deployment of any pyrogen based ejection system. Over 20,000 ft.. the lack of air drastically effects any compounds ability to burn. There is no magical altitude where things "don't work" as it is far more complicated than that, when dealing with different pyrogens, containers, air pressure etc.
Whether you are launching a rocket to 4,000 ft.. and wish to have a high tech system to compliment your rocket and electronic components, or if you are launching a rocket to high altitudes,you now have a system to do so safely and without damage to your expensive rocket and recovery components. And, never have to smell and clean the black powder residue from the rockets components.
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