Fwd: Motor Design Review Re-cap

[Cal Poly Space Systems]

Hi everyone,

 

For those of you who were not in attendance the design review was very productive. Here's a quick recap of what was discussed:

1. The results of Chemical Equilibrium Analysis were discussed. Inputs were based off an AIAA paper describing  HTBP in a hybrid motor application.

   CEA Parameters
   HTPB enthalpy of formation[1]	1272.6 kJ/mol
   HTPB chemical formula	C200H302O2
   N20 enthalpy of formation	82 KJ/mol
   N2O chemical formula	N2O
   Chamber Pressure	500 psi (3447 kPa)
   Exit Pressure	14 psi
   O/F ratio	6

   Theoretical Isp	249 s
   Combustion Temp	3375 K
   Chamber Velocity	228 m/s
   Density at Throat	1.9014kg/m^3
   Sonic Velocity at Throat	1087 m/s

2. The requirements for the motor were discussed: 450 lbf with a total impulse of 4800 lbf-s
3. Motor sizing was based off the thrust requirements, and assumed an ISP of 210s.
4. A single circular port was chosen due to favorable characteristics in a long duration burn.
5. Motor parameters are given below.

   Grain Length	23.8[in]
   Initial port diameter	1.655 [in]
   Grain outer diameter	3 [in]
   # injector holes	32
   Injector hole diameter	.034 [in]
   Throat diameter	.955 [in]
   Exit diameter	2.187 [in]
   Nozzle length	2.4 [in]

6. The nozzle will be a parabolic approximation of a method of characteristics solution.

We discussed the instrumentation needs for the first test fire

• Pressure transducers: nitrous tank, in the flow just after the nitrous tank (for flow rate), Throat of the nozzle (for chamber pressure)
• Thermocouples: Latency on high temperature thermocouples is too high to capture transients, not practical
• Load Cell: thrust, nitrous tank weight

The matlab code for all the calculations is included. Run the singlePortGrain.m program. All required functions are included in the Hybrid Calcs.zip folder

Current CAD files are included, the main assembly is hm_7.SLDASM in the hm7(DEC-11-15).zip

If you have any questions about the code or CAD email me at awhit...@live.com.

If you are available and would like to work tomorrow:

George and I will be working on the injector plate tomorrow around 11 AM.

Steven will be working on trailer equipment by 11 AM as well.

Have a great break,

Adam