1. MAE 5391: Rocket Propulsion Overview of Propulsion Systems

2. Rocket Technologies
Titan IV and Delta IV

3. Propulsion Technology Options
Thermodynamic Systems (TE KE)
Cold Gas Thrusters
Liquids
Monopropellants
Bipropellants
Solids
Hybrids
Nuclear (NE TE KE)
Electric Systems
Electrothermal (Resistance Heating)
Electrostatic (Ion with E field F=qE)
Electromagnetic (plasma with B field F=JxB)
With the exception of electrostatic and electromagnetic, all use concept of gas at some temp flowing though a converging/diverging nozzle!

4. Chemical Limitations Why we have thermo!
Vexit= nozzle exit velocity (m/s)
Ru= universal gas constant ( J/kmol*K)
T0= chamber temperature (K)
Pe= exit pressure (Pa)
P0= chamber pressure (Pa)
M= molecular mass of gas (kg/kmol)
g= ratio of specific heats (no dimensions)

5. Cold Gas Cold Gas: Expand a pressurized gas through a nozzle Gas
Molecular
Weight
Specific
Impulse (sec)
Air
28.9 74
Argon
39.9 57
CO2
44.0 67
Helium
4.0
179
Hydrogen
2.0
296
Nitrogen
28.0 80
Methane
16.0
114

6. Liquid Monopropellant
MonoProp: Decompose a single propellant and expand the exhaust through a nozzle
Parameter
Value
Catalyst
LCH 227/202
Steady-state thrust (N)
Isp (sec)
Propellant specific gravity
1.023
Average Density Isp ( sec)
236.8
Rated total impulse (Nsec)
124,700
Total pulses
12,405
Minimum impulse bit (Nsec)
0.56
Feed pressure (bar)
Chamber pressure (bar)
Nozzle expansion ratio
61:1
Mass flow rate (gm/sec)
Valve power
27 W 28 VDC
Thruster mass (kg)
0.52
3 N2H4  4 NH3 + N ,280 joules

7. Liquid Bi-Propellant
BiProp: Combust (burn) two propellants (fuel + oxidizer) in a combustion chamber and expand exhaust through a nozzle
Storable Isp sec
finert=
Cryogenic Isp 320 – 452 sec
finert=
Finert =
Finert=

8. Solids
Composite propellant, consisting of an oxidizing agent, such as ammonium nitrate or ammonium perchlorate intimately mixed with an organic or metallic fuel and binder.
Advantages
Simple
Reliable
High density Isp
No chamber cooling
Disadvantages
Cracks=disaster
Can’t restart
Hard to stop
Modest Isp
Thrust function of burn area, Isp = sec
Finert= , 2/3 of motors have fiinert below 0.2

9. When solids go bad!

10. Hybrids
Hybrid: Bipropellant system with liquid oxidizer (usually) and a solid fuel
Isp= sec
Finert=0.2
Catalyst Pack
Combustion Chamber
Nozzle
Test Stand
Load Cell
Fuel Element
H2O2/PE Hybrid Test Set-Up
Polyethylene fuel rod

11. Nuclear Thermal Propulsion
NERVA Program
Thrust = 890,000N
Isp = 838 sec
Working fluid = Hydrogen
Test time = 30 minutes
Stopped in 1972
Finert= (shielding)

12. Electrothermal-Resistojets
Working Fluid
Thrust (mN)
Isp (sec)
Power (W)
Cp (kJ/kg K)
Tc (K)
hydrogen 37
546
100
14.32
1000
water 93
219
2.3
nitrous oxide
141
144
1.0
Electrothermal-- electrical energy is used to directly heat a working fluid. The resulting hot gas is then expanded through a converging-diverging nozzle to achieve high exhaust velocities. These systems convert thermal energy to kinetic energy

13. Electrothermal-Arcjets
In an arcjet, the working gas is injected in a chamber through which an electric arc is struck. The gas is heated to very high temperature (3000 – 4000 K), Arc temp =10,000K on average, and much greater in certain regions in the arc.
Power = 1.8 kW, Isp = 502, Thrust = 0.2N, Propellant = hydrazine

14. Electrostatic-Ion Propulsion
Electrostatic-- electrical energy is directly converted into kinetic energy. Electrostatic forces are applied to charged particles to accelerate the propellant.
Deep Space 1 = 4.2 kW, Thrust = 165 mN, Isp = 3800 sec
7000 hours of operation is becoming the standard!

15. Electromagnetic-MPD Thruster
Electromagnetic-- electromagnetic forces directly accelerate the reaction mass. This is done by the interaction of electric and magnetic fields on a highly ionised propellant plasma.
NH3 MPD, F=23 mN, Isp= 600 sec, P=430 W
Stuttgart, Isp=5000sec, F=100N, P=6 MW, hydrogen

16. Pulsed Plasma Thrusters
Isp = sec
P = 1 – 100 W
Thrust = 5mN/W

17. Hall Effect Thruster Power = 50W – 25kW Isp = 500 – 3000 sec
Thrust = 5 mN- 1N

18. Propulsion System “Cost”
Performance issues
Mass
Volume
Time (thrust)
Power
Safety
Logistics
Integration
Technical Risk
The “best” (lowest “cost”) option optimizes these issues for a given set of mission requirements