## Rp1

Average thermal conductivity of steel

250 Btu/hr-ft2-F/in

Assume other parameters, if needed. Compute the outside diameters and the thickness of the inner and outer walls at the chamber, at the throat, and at the nozzle exit.

9. Determine the hole sizes and the angle setting for a multiple-hole, doublet impinging stream injector that uses alcohol and liquid oxygen as propellants. The resultant momentum should be axial, and the angle between the oxygen and fuel jets (y„ + Y/) should be 60°. Assume the following:

(Cd)f 0.91 Fuel pressure 400 psi p0 71 lb/ft3 Oxygen pressure 380 psi pf 51 lb/ft3 Number of jet pairs 4 r 1.20 Thrust 250 lbf

Actual specific impulse 218 sec Answers: 0.0197 in.; 0.0214 in.; 32.3°; 27.7°.

10. Explain in a rational manner why Fig. 8-10 has a maximum and how this maximum would be affected by the duty cycle, ablative material, heat loss from the thrust chamber, effect of altitude, and so on. Why does this maximum not occur at 90% burn time?

11. Table 10-5 shows that the RD 120 rocket engine can operate down to 85% of full thrust and at a mixture ratio variation of ±10.0%. In a particular static test the average thrust was held at 96% of nominal and the average mixture ratio was 2.0% fuel rich. Assume a 1.0% residual propellant, but neglect other propellant budget allowances. What percentage of the fuel and oxidizer that have been loaded will remain unused at thrust termination? If we want to correct the mixture ratio in the last 20.0% of the test duration and use up all the available propellant, what would be the mixture ratio and propellant flows for this last period?

12. Make a simple sketch to scale of the thrust chamber that was analyzed in Section 8.6. The various dimensions should be close, but need not be accurate. Include or make separate sketches of the cooling jacket and the injector. Also compile a table of all the key characteristics, similar to Table 8-1, but include gas generator flows, and key materials. Make estimates or assumptions for any key data that is not mentioned in Section 8.6