Gas Passer : 無料・フリー素材/写真
Gas Passer / jurvetson
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
|---|---|
| 説明 | For high-altitude parachute deployment, I will be trying the Rouse-tech CD3 for the first time on Saturday with the All Carbon N1100 Moonburner launch. We just assembled the core of the motor this evening, and tapped the holes for the shear screws. On the playa, I will rig up a couple of these electrically-actuated CO2 cartridge-puncturing devices for a high-altitude drogue and a low-altitude main chute. The flight computer ignites a small pocket of black powder that rams a metal spike into the top of the CO2 cartridge, which then outgases, creating enough pressure to shear the screws, and separate the airframe, thereby deploying the chute. No reliance on large pockets of explosives, and no burn holes in the parachutes.Rouse describes the problems of traditional BP pyrogen ejection at high altitudes: “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 denominatorwas 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 whats 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.” |
| 撮影日 | 2010-09-22 17:03:29 |
| 撮影者 | jurvetson , Los Altos, USA |
| タグ | |
| 撮影地 | |
| カメラ | Canon PowerShot S90 , Canon |
| 露出 | 0.033 sec (1/30) |
| 開放F値 | f/2.0 |
| 焦点距離 | 6 mm |