4.3.4.1 5kg Propulsion1

4.3.4.15 kg Propulsion

The propellants we selected for the 5kilogram payload launch vehicle were a hybrid first stage and a solid second and third stage. Our selection process involved the use of an optimization code which gave us the best results for a 5kilogram payload launch vehicle. The code gave us a propulsion system described in the following section.

The first stage of the launch vehicle uses a hybrid rocket motor, with hydrogen peroxide (H2O2) as the oxidizer and hydroxylterminated polybutadiene (HTPB) as the solid propellant. The H2O2 tank is pressurized using gaseous nitrogen. The nozzle is a 12º conical nozzle with liquid injection thrust vector control (LITVC) attached. The LITVC system is composed of four valves that allow H2O2 to be injected into the nozzle at a 90º angle to the centerline of the nozzle. A schematic of the LITVC can be seen below in Figure 4.3.4.1.1.

Figure 4.3.4.1.1 LITVC and Nozzle Configuration

In Figure 4.3.4.1.1, the nozzle is shaded grey and all LITVC components are highlighted in orange. The pipes are run from the H2O2 tank that is used for the hybrid motor, and then is distributed to each valve. The valves are connected to the controller which relays a signal for a certain valve to open and allow pressurized H2O2 to be injected into the main flow in the nozzle, which produces a side thrust. This side thrust allows for control of the launch vehicle during its ascent. The specifics of the propulsionsystem can be seen in Table 4.3.4.1.1.

Table 4.3.4.1.15kg Payload Stage 1 Propulsion Specifics
Variable / Value / Units
Vacuum Specific Impulse / 352.3 / s
Chamber Pressure / 2,068,000 / Pa
Mass Flow Rate / 23.571 / kg/s
Propellant Mass / 4122.85 / kg
Engine Mass / 193.49 / kg
Thrust (vac) / 75073.2 / N
Burn Time / 174.9 / s
Exit Area / 1,198 / m2
Exit Pressure / 2,821.167 / Pa

A conical nozzle was chosen because of the solid particles of propellant that will be coming out of the combustion chamber. The combustion process does not necessarily combust the fuel 100% and these particles can deteriorate a nozzle if it is let’s say Bell shaped. Some of our early MAT codes had values based off of a 12° conical nozzle and that is one of the reasons we decided on this cone angle for the final design. Also having a smaller cone angle reduces the divergence loss at the exit of the nozzle. A picture of the nozzle can be seen below in Fig. 4.3.4.1.1.

Figure 4.3.4.1.1: Our 12° conical nozzle

The second stage of the launch vehicle uses a solid rocket motor, with hydroxyl-terminated polybutadiene/ ammonium perchlorate/ aluminum (HTPB/AP/AL) as the propellant. The nozzle is a 12º conical nozzle with LITVC attached. The LITVC has the same configuration as the first stage, with the exception of the H2O2. Since there is no H2O2 already present due to the solid motor, a pressurized tank is added in a curved configuration sitting beneath the solid motor. The tank wraps around the nozzle and is pressurized with gaseous nitrogen so that the H2O2 can flow into the lines for injection. The specifics of the propulsion system can be seen in Table 4.3.4.1.2.

Table 4.3.4.1.25kg Payload Stage 2 Propulsion Specifics
Variable / Value / Units
Vacuum Specific Impulse / 309.3 / s
Chamber Pressure / 6,000,000 / Pa
Mass Flow Rate / 4.739 / kg/s
Propellant Mass / 1009.33 / kg
Engine Mass / 75.72 / kg
Thrust (vac) / 15256.9 / N
Burn Time / 213.0 / s
Exit Area / 0.070 / m2
Exit Pressure / 11,453.660 / Pa

The third stage of the launch vehicle uses a solid rocket motor, with hydroxyl-terminated polybutadiene/ ammonium perchlorate/ aluminum (HTPB/AP/AL) as the propellant. The nozzle is a 12º conical shape. The specifics of the propulsion system can be seen in Table 4.3.4.1.3.

Table 4.3.4.1.35kg Payload Stage 3 Propulsion Specifics
Variable / Value / Units
Vacuum Specific Impulse / 309.3 / s
Chamber Pressure / 6,000,000 / Pa
Mass Flow Rate / 0.215 / kg/s
Propellant Mass / 38.37 / kg
Engine Mass / 8.56 / kg
Thrust (vac) / 692.4 / N
Burn Time / 178.4 / s
Exit Area / 0.003 / m2
Exit Pressure / 11,453.660 / Pa

Author: Stephan Shurn

Ricky Hinton

Jerald A. Balta