36th Annual Frontiers in Education Conference
San Diego, CA, Oct. 28-31, 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
http://users.rowan.edu/~marchese
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
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.
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)
N 2O
solid fuel
The Hybrid Rocket Motor Design Project
Objectives, Design Parameters and Constraints
GOX
aluminum
HTPB/Al
graphite
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 = 1.175 in
Maximum Fuel Grain Length = 12 in
Fuel: HTPB, HTPB/AL, PMMA, PE, UHMW or paraffin
Hybrid Rocket Motor Design Project
Theoretical Model: This is Rocket Science
Ab
m
m o
Liquid oxidizer
m f
rf
solid fuel
Ap
Pc
Tc, Xi, g
Fuel Regression Rate
 m 
rf (t )  a o 
 A (t ) 
 p 
Thrust Coefficient
n
 2 

C F  g 
g

1


g 1
2(g -1)
Fuel Mass Flow Rate
 m 
m f (t )   f Ab (t )a o 
 A (t ) 
 p 
Ae
At
n
g 1


2g   Pe  g   Pe P  Ae
1 -       
g - 1   Pc    Pc Pc  At


Thrust
Characteristic
Specific HeatExhaust
Ratio
Velocity


Chamber Pressure
n
 m o  
C * 
 
Pc (t ) 
m o   f Ab (t )a
At 
Ap (t )  



m
gC* g C *  om o 


 m fm f 
F  m C *CF
Specific Impulse
 Fdt  C C

g
g  m dt
*
I SP
o
o
F
Hybrid Rocket Motors
Thermochemical Model: This is Rocket Science
Ab
m
m o
Liquid oxidizer
m f
rf
Pc
solid fuel
Ap
Ae
At
Tc, Xi, g
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
C7.337 H10.982O.058 
m ox M ox
O2 
 m CO2 CO2  m H 2O H 2O  m CO CO  m H 2 H 2  m OH OH  m o2 O2  m oO  m H H
m f M f
1850
1.32
1800
1.30
 m 
g  g  o 
 m f 
1.28
1750
1.26
1.24
1650
g
C*(m/s)
1700
 m
C*  C *  o
 m
 f
1600
1550




1.22
1.20
1.18
1.16
1500
1.14
1450
1.12
0.5
1.0
1.5
2.0
2.5
3.0
O/F Ratio
3.5
4.0
4.5
0.5
1.0
1.5
2.0
2.5
3.0
O/F Ratio
3.5
4.0
4.5
Hybrid Rocket Motor Design Project
Theoretical Model Results
Ab
m
m o
Liquid oxidizer
m f
rf
Ap
Pc
solid fuel
Ae
At
Tc, Xi, g
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.
8
200
105
195
100
95
Specific Impulse [s]
7
Thrust [lbf]
Chamber Pressure [psia]
110
6
190
185
5
180
90
85
175
4
0
5
10
15
time (s)
20
25
30
0
5
10
15
time (s)
20
25
30
0
5
10
15
time (s)
20
25
30
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:
L
fuel grain length
port diameter
throat diameter
GOX
dp
de
dt
nozzle area ratio
nozzle exit diameter
aluminum
HTPB/Al
graphite
Final design drawings were generated for the combustion chamber and
the supersonic nozzle using Solid Works.
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
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
The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
GOX Mass Flow
Controller
Solenoid Valve
Pressure
Transducer
Thrust Chamber
Igniters
Load Cell
Linear Bearing
Nozzle
Mass
flow rate Deliver
was measured
and controlled
using capable
a Teledyne
Hastings thrust
The Objective:
a hybrid rocket
motor test stand
of measuring
HFC203
Flow Controller.
(0-10ignition
lb),Mass
chamber
psig),
oxygen mass
rate
(0-500
The
systempressure
consists(0-250
of dual
automotive
sparkflow
plugs
which
areSLPM)
energized
Thrust
was
measured
using
an Omega
LC101-25
load
cell. one junior mechanical
using
an
ETP
300ST
solid
state
induction
coil
The Team:
Two
senior
mechanical
engineering
students,
Chamber
engineering
pressure
student
was
andmeasured
one senior
using
electrical
an Omega
engineering
Pressure
student.
Transducer.
The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
Flow Controller
Solenoid Valve
Igniters
Pressure Transducer
Check Valve
The Hybrid Rocket Motor Design Project
Development of the Hybrid Rocket Motor Test Stand
Linear Bearing
Load Cell
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.
The Hybrid Rocket Motor Design Project
Test Firing (HTPB/20% AL/GOX)
The Hybrid Rocket Motor Design Project
Test Firing (Big Red)
The Hybrid Rocket Motor Design Project
10
100
8
80
6
60
Pc (Calculated)
4
40
Pc (Measured)
F (Calculated)
F (Measured)
2
20
0
0
5
10
15
Time [s]
20
0
25
Chamber Pressure [psig)
Thrust [lb]
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!
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.
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.
The Hybrid Rocket Motor Design Project
Is this valve open?