1. 36th Annual Frontiers in Education Conference
San Diego, CA, Oct , 2006
THIS IS ROCKET SCIENCE: DEVELOPMENT AND TESTING OF A HYBRID ROCKET MOTOR IN A ROCKET PROPULSION COURSE
Anthony J. Marchese
Mechanical Engineering
Rowan University
201 Mullica Hill Rd.
Glassboro, NJ 08028

2. Overview This is Rocket Science: The Hybrid Rocket Motor Project
Motivation for a project based learning experience in rocket propulsion
Context: Description of the rocket propulsion course
Description of the project: objectives, requirements and constraints
Development of the analytical model
Design and fabrication of the hardware
Development of the hybrid rocket motor test stand
The Engineering Clinic
Test results
On going tests

3. Introduction to Rocket Propulsion (ME 412)
Course Objectives
Introduction to Rocket Propulsion (ME 412)
Rocket propulsion draws upon the fundamental concepts of thermodynamics, chemistry, fluid mechanics and heat transfer to design propulsion systems. At the conclusion of the course, each student will be able to:
Analyze the performance of an ideal rocket engine.
Select propellants and choose a rocket propulsion system based on mission requirements.
Perform thermochemical calculations to determine the rocket chamber temperature and chemical composition for any propellant combination.
Design a liquid propellant rocket engine by considering the propellant combination, combustion chamber, injector, igniter, nozzle, heat transfer and cooling characteristics.
Design a solid propellant rocket motor based on the propellant combination, burning rate laws and grain design.
Design a hybrid rocket motor based on the propellant combination, burning rate laws and grain design.
Build and test a 10 lbf thrust hybrid rocket motor.   Measure specific impulse, characteristic exhaust velocity, thrust coefficient and compare to theoretical calculations.

4. Motivation for the Hybrid Rocket Motor Project
Private Sector Opportunities in Space Exploration
On October 4, 2004, SpaceShipOne became the first private manned spacecraft to exceed an altitude of 328,000 feet twice within a 2 week period, thereby claiming the $10 million Ansari X-Prize.
SpaceShipOne was powered by a hybrid rocket motor (liquid N2O, solid polymer fuel)
N2O
solid fuel

5. The Hybrid Rocket Motor Design Project
Objectives, Design Parameters and Constraints
Objectives of the semester design project:
Design, build and test a hybrid rocket motor.
Develop a theoretical model that predicts the performance of the hybrid rocket motor as a function of time.
Compare measured performance with theoretical model.
Constraints:
Oxidizer must be gaseous oxygen (GOX)
Maximum Chamber Pressure: 115 psia, Ambient Pressure: 14.7 psia
Maximum GOX flow rate: 500 SLPM
Minimum initial thrust: 5 lbf
Fuel grain outer diameter = in
Maximum Fuel Grain Length = 12 in
Fuel: HTPB, HTPB/AL, PMMA, PE, UHMW or paraffin

6. Characteristic Exhaust Velocity
Hybrid Rocket Motor Design Project
Theoretical Model: This is Rocket Science Ab
solid fuel Ap
Liquid oxidizer At Ae Pc
Tc, Xi, g
Fuel Regression Rate
Thrust Coefficient
Specific Heat Ratio
Fuel Mass Flow Rate
Characteristic Exhaust Velocity
Thrust
Chamber Pressure
Specific Impulse

7. Hybrid Rocket Motors Thermochemical Model: This is Rocket Science
The NASA CEA Chemical Equilibrium computer code was used to calculate Tc, g, MW, C* and Xi as a function of oxidizer to fuel ratio.
fuel + oxidizer  products + energy

8. Hybrid Rocket Motor Design Project
Theoretical Model Results
The detailed analytical model was used to predict the variation in fuel flow rate, O/F ratio, chamber pressure, thrust and specific impulse (Isp) with time.

9. The Hybrid Rocket Motor Design Project
Concept Design and Parametric Design
The theoretical hybrid rocket motor model was also used iteratively optimize their final design to choose the following parameters:
fuel grain length
port diameter
throat diameter
nozzle area ratio
nozzle exit diameter L dp dt de
Final design drawings were generated for the combustion chamber and the supersonic nozzle using Solid Works.

10. The Hybrid Rocket Motor Design Project
Fabrication
Combustion chambers were fabricated from aluminum round stock using manual lathes
Supersonic nozzles were fabricated from graphite using a CNC turning center

11. The Hybrid Rocket Motor Design Project
Fuel Formulation
Hydroxyl Terminated Polybutadiene (HTPB) was formulated, mixed with aluminum particles and cured.
Other fuels such as PMMA, HDPE and UHMW were machined from solid round stock

12. The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
Mass flow rate was measured and controlled using a Teledyne Hastings HFC203 Mass Flow Controller.
Thrust was measured using an Omega LC load cell.
Chamber pressure was measured using an Omega Pressure Transducer.
The Objective: Deliver a hybrid rocket motor test stand capable of measuring thrust (0-10 lb), chamber pressure (0-250 psig), oxygen mass flow rate (0-500 SLPM)
The Team: Two senior mechanical engineering students, one junior mechanical engineering student and one senior electrical engineering student.
The ignition system consists of dual automotive spark plugs which are energized using an ETP 300ST solid state induction coil

13. The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
Flow Controller
Solenoid Valve
Igniters
Pressure Transducer
Check Valve

14. The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
Load Cell
Linear Bearing

15. The Hybrid Rocket Motor Design Project
Data Acquisition
Data acquired included:
instantaneous chamber pressure,
thrust,
oxygen mass flow rate and
high speed dynamic chamber pressure
The data were acquired using an Agilent 34970A Data Acquisition Unit with GPIB interface and an HP 54645D digital storage oscilloscope
With these data, each team was able to measure specific impulse (Isp), characteristic exhaust velocity (C*) and thrust coefficient (CF) and compare these measurements to their analytical models.

16. The Hybrid Rocket Motor Design Project
Test Firing (HTPB/20% AL/GOX)

17. The Hybrid Rocket Motor Design Project
Test Firing (Big Red)

18. The Hybrid Rocket Motor Design Project
Experimental Results
The analytical models reproduced the experimental data reasonably well.
When the variation in actual oxygen mass flow rate was taken into account, analytical results matched the experiments very well!

19. The Hybrid Rocket Motor Design Project
Ongoing Work
The system is now being used for a research project on the effect of fuel type on combustion instability of hybrid rocket motors.

20. The Hybrid Rocket Motor Design Project
Conclusions
At the beginning of the semester, students showed very little awareness of the space program and its significance (both historic and contemporary).
This condition is surprising to the generation who grew up wanting to be astronauts.
The hybrid rocket design project was successful in introducing a new generation of students to rocket science.
The hybrid rocket motors were inexpensive, relatively easy to build and safe.
The hybrid rocket motor test stand was an effective junior/senior level design project. Total project cost was approximately $2000.
The test stand is now being used for scholarly pursuits.

21. The Hybrid Rocket Motor Design Project
Is this valve open?