1. An Introduction to Space Propulsion
An Introduction to Space Propulsion
Stephen Hevert
Affiliate Professor
Metropolitan State College of Denver

2. What Is Propulsion? Initiating or changing the motion of a body
Initiating or changing the motion of a body
Translational (linear, moving faster or slower)
Rotational (turning about an axis)
Space propulsion
Rocket launches
Controlling satellite motion
Maneuvering spacecraft
Jet propulsion
Using the momentum of ejected mass (propellant) to create a reaction force, inducing motion
At one time it was believed that rockets could not work in a vacuum -- they needed air to push against!!

3. Jet Propulsion Classifications
Air-Breathing Systems
Also called duct propulsion.
Vehicle carries own fuel; surrounding air (an oxidizer) is used for combustion and thrust generation
Gas turbine engines on aircraft…
Rocket Propulsion
Vehicle carries own fuel and oxidizer, or other expelled propellant to generate thrust:
Can operate outside of the Earth’s atmosphere
Launch vehicles, upper stages, Earth orbiting satellites and interplanetary spacecraft … or
…or go karts!
… a rocket powered scooter!

4. Space Propulsion Classifications
Systems that use an expellant (e.g. on-board propellant)
Stored Gas or Vapor
Compressed gas
Ammonia
Butane
Nitrous Oxide
Chemical
Liquid
Solid
Hybrid
Electric
Electrothermal
Electrostatic
Electromagnetic
Nuclear
Nuclear thermal
Nuclear electric
Antimatter
Solar
Solar thermal
Solar electric
Beamed Energy
Laser thermal
Microwave thermal
Microwave electric
We’ll look at some of these today…
Systems that do not carry an expellant (extract energy/force from external source)
Sails
Solar sails (light or solar wind)
M2P2 (charged particles)
Beamed Energy
Laser reflector (light sail)
Microwave (Starwisp)
Tethers
Stationary
Rotating
Electrodynamic
Pumped
Aero/Gravity Assist
Aero assist
Aero braking
Aero capture
Gravity assist
Breakthrough Propulsion Physics
Space drives (warp drives)
Wormholes
Antigravity
Interstellar Ramjet
Bussard drive

5. Space Propulsion Applications
Tactical Missiles
Sounding Rockets
Ballistic Missiles
Terrestrial/Atmosphere/
Suborbital
Realm of Existing Technology
Earth to Orbit
Launch Vehicles
blog.wired.com
In-Space
Orbit Transfer
Earth Orbiting
Upper Stages
& Satellites
Lunar Missions
Interplanetary Missions
Space Exploration
The Future
Interstellar Space Exploration
Star Trek!!

6. Space Propulsion Functions
Primary propulsion
Launch and ascent
Maneuvering
Orbit transfer, station keeping, trajectory correction
Auxiliary propulsion
Attitude control
Reaction control
Momentum management

7. A Brief History of Rocketry
Wan-Hu tried to launch himself to the moon by attaching 47 black powder rockets to a large wicker chair! (…Chinese folk tale)
onenew.wordpress.com
China (1232 AD)
Earliest recorded use of rockets
Black powder
Russia (early 1900’s)
Konstantin Tsiolkovsky
Orbital mechanics, rocket equation
United States (1920’s)
Robert Goddard
First liquid fueled rocket (1926)
Germany (1940’s)
Wernher von Braun
V-2
Hermann Oberth
Russia (USSR)
Phenomenal contributions…
Korolev, Glushko, Keldysh
Dr. Goddard
goddard.littletonpublicschools.net
Prof. Tsiolkovsky
Dr. von Braun

8. Stored Gas Propulsion Primary or auxiliary propulsion
Fill
Valve
Pressure
Gage
High Pressure Isolation
Regulator
Filter
Thruster
Propellant
Tank
Low Pressure Isolation
Primary or auxiliary propulsion
High pressure gas (propellant) is fed to low pressure nozzles through pressure regulator
Release of gas through nozzles (thrusters) generates thrust
Currently used for momentum management of the Spitzer Space telescope
Propellants include nitrogen, helium
Very simple in concept

9. Chemical Propulsion Classifications
Liquid Propellant
Pump Fed
Launch vehicles, large upper stages
Pressure Fed
Smaller upper stages, spacecraft
Monopropellant
Fuel only
Bipropellant
Fuel & oxidizer
Solid Propellant
Launch vehicles, Space Shuttle, spacecraft
Fuel/ox in solid binder
Hybrid
Solid fuel/liquid ox
Sounding rockets, X Prize
en.wikivisual.com
news.bbc.co.uk

10. Monopropellant Systems
Fuel Fill Valve
Pressure
Gage
Isolation Valve
Filter
Thrusters
Propellant
Tank
Nitrogen or helium
Hydrazine
Hydrazine fuel is most common monopropellant.
N2H4
Decomposed in thruster using iridium catalyst to produce hot gas for thrust.
Older systems used hydrogen peroxide (H2O2) before the advent of hydrazine catalysts.
Typically operate in blowdown mode (pressurant and fuel in common tank).
Thrusts of 1 to 400 N (0.2 to 100 lbf ) are common.

11. Monopropellant Systems
5 lbf thrusters used on the Compton Space Telescope (Gamma Ray Observatory)
Northrop Grumman
1 lbf thrusters
manufactured by Northrop Grumman

12. Bipropellant Systems
FUEL OX P
Isolation Valves
Engine
Thrust Chamber
Nozzle
A fuel and an oxidizer are fed to the engine through an injector and combust in the thrust chamber of the engine
Combustion products accelerate in a converging-diverging nozzle
Hypergolic: no igniter needed -- propellants react on contact in thrust chamber
Cryogenic propellants include LOX (-423 ºF) and LH2 (-297 ºF).
Igniter required
Storable propellants include kerosene (RP-1), hydrazine, nitrogen tetroxide (N2O4), monomethylhydrazine (MMH)

13. Bipropellant Thrusters
AMPAC-ISP
Astrium
AMPAC-ISP
Bipropellant thrusters are used for orbit transfer and for attitude control, with thrusts ranging from 4 to 440 N (1 to 100 lbf )

14. Liquid Propellant Systems
Pump fed systems
Propellant delivered to engine using turbopump
Gas turbine drives centrifugal or axial flow pumps
Large, high thrust, long burn systems: launch vehicles, space shuttle
Different cycles developed.
H-1 Engine Turbopump
A 35’x15’x4.5’ (ave. depth) backyard pool holds about 18,000 gallons of water. How quickly could the F-1 turbopumps empty it ?
Ans: In ~27 seconds!
F-1 engine turbopump:
55,000 bhp turbine drive
15,471 gpm (RP-1)
24,811 gpm (LOX)
F-1 Engine Turbopump
Photos history.nasa.gov

15. Rocket Engine Power Cycles
Gas Generator Cycle
Simplest
Most common
Small amount of fuel and oxidizer fed to gas generator
Gas generator combustion products drive turbine
Turbine powers fuel and oxidizer pumps
Turbine exhaust can be vented through pipe/nozzle, or dumped into nozzle
Saturn V F-1
crosslink/winter2004/03_sidebar3.html

16. Rocket Engine Power Cycles - cont
Expander
Fuel is heated by nozzle and thrust chamber to increase energy content
Sufficient energy provided to drive turbine
Turbine exhaust is fed to injector and burned in thrust chamber
Higher performance than gas generator cycle
Pratt-Whitney RL-10
science.nasa.gov
crosslink/winter2004/03_sidebar3.html

17. Rocket Engine Power Cycles - cont
Staged Combustion
Fuel and oxidizer burned in preburners (fuel/ox rich)
Combustion products drive turbine
Turbine exhaust fed to injector at high pressure
Used for high pressure engines
Most complex, requires sophisticated turbomachinery
Not very common, but very high performance
SSME (2700 psia)
crosslink/winter2004/03_sidebar3.html
shuttle.msfc.nasa.gov

18. 1.78 million lbs thrust (SL) 1.5 million lbs thrust (SL)
The Big Engines…
RD-170
1.78 million lbs thrust (SL)
LOX/Kerosene
F-1 Engine
Saturn V
1.5 million lbs thrust (SL)
LOX/Kerosene
Main Engine
Space Shuttle
374,000 lbs thrust (SL)
LOX/H2
spaceflight.nasa.gov

19. Solid Propellant Motors
Fuel and oxidizer are in solid binder.
Single use -- no restart capability.
Lower performance than liquid systems, but much simpler.
Applications include launch vehicles, upper stages, and space vehicles.

20. Hybrid Motors Combination liquid-solid propellant
Oxidizer Tank
Ox Control Valve
Nozzle
Combination liquid-solid propellant
Solid fuel
Liquid oxidizer
Multi-start capability
Terminate flow of oxidizer
Fuels consist of rubber or plastic base, and are inert.
Just about anything that burns…
Oxidizers include LO2, hydrogen peroxide (H2O2) and nitrous oxide (NO2)
Shut-down/restart capability.

21. Propulsion Calculations
Rocket Equation
Thrust & Specific Impulse
Thrust is the amount of force generated by the rocket.
Specific impulse is a measure of performance (analogous to miles per gallon)
Units are seconds
Rocket equation assumes no losses (gravity effects, aerodynamic drag). Actually very accurate for short burns in Earth orbit or in deep space!

22. Specific Impulse Comparison
Stored gas
Monopropellant hydrazine
Solid rocket motors
Hybrid rockets
Storable bipropellants
LOX/LH2
sec
sec
sec
sec
sec
450 sec
Specific impulse depends on many factors: altitude, nozzle expansion ratio, mixture ratio (bipropellants), combustion temperature, combustion pressure
This thruster was used on the Viking Lander. It has a specific impulse of about 225 seconds.

23. Mission Delta-V Requirements
Mission (duration)
ΔV (km/sec)
Earth surface to LEO
7.6
LEO to Earth Escape
3.2
LEO to Mars (0.7 yrs)
5.7
LEO to Neptune (29.9 yrs)
13.4
LEO to Neptune (5.0 yrs) 70
LEO to Alpha-Centauri (50 yrs)
30,000
LEO = Low Earth orbit (approx. 274 km)
That’s actually very low….

24. Propellant Calculation Exercise
Determine the mass of propellant to send a 2500 kg spacecraft from LEO to Mars (0.7 yr mission).
Assume the 2500 kg includes the propellant on-board at the start of the burn.
Assume our engine has a specific impulse of 310 sec (typical of a small bipropellant engine).
Use the rocket equation:
Most of our spacecraft is propellant! Only 383 kg is left for structure, etc! How could we improve this?

25. Electric Propulsion Classifications Characteristics Electrothermal
www-ssc.igpp.ucla.edu
Classifications
Electrothermal
Electrostatic
Electromagnetic
Characteristics
Very low thrust
Very high Isp
> 1000 sec
Requires large amounts of power (kilowatts)
This image of a xenon ion engine, photographed through a port of the vacuum chamber where it was being tested at NASA's Jet Propulsion Laboratory, shows the faint blue glow of charged atoms being emitted from the engine. The ion propulsion engine is the first non-chemical propulsion to be used as the primary means of propelling a spacecraft.

26. Electrothermal Propulsion
rocket.itsc.uah.edu
Electrical power is used to add energy to exhaust products
Resistojet
Catalytic decomposition of hydrazine is augmented with high power electric heater
800 – 5,000 W
Arcjet
High voltage arc at nozzle throat adds thermal energy to exhaust
Various gaseous or vaporized propellants can be used.

27. Electrostatic Propulsion
Electrostatic forces are used to accelerate charged particles to very high velocities
Xenon Ion Thruster
Xenon propellant
Xenon is ionized by electron bombardment
Thermionic cathode
Positively charged particles accelerated by grid
Electrons routed to second anode and injected into beam to neutralize
aerospace.engin.umich.edu
ESA’s SMART-1 uses a xenon ion propulsion system (XIPS)

28. Electromagnetic Propulsion
Electromagnetic forces are used to accelerate a plasma
A gas consisting of positive ions, electrons
5000 – 9000 R
Neutral beam is produced
Higher thrust per unit area than electrostatic thruster
Classifications
Magnetoplasmadynamic
Pulsed plasma
Electric discharge creates plasam from solid Telfon
Hall effect
Developed in Russia
Flew on U.S. STEx mission (1998)

29. Interstellar Missions – The Future
The challenges are formidable
Immense distances…
Alpha Centauri = 4.5 LY (closest interstellar neighbor)
1 LY = 9.46x1012 km = 5.878x1012 mi
Universe = ~156 billion LY across
Immense size & mass & energy & speeds required…
Propulsion systems with dimensions of 1000’s km
Power levels 1000’s x greater than Human Civilization now produces ( > 14 TW est.)
Speeds ~ .4c - .6c (c = speed of light)
Trip times… Robotic Rendezvous goals
4.5 LY in < 10 years
40 LY in < 100 years (radius of nearest 1000 stars)
Relativistic effects…
Because of time dilation and mass increase; length contraction
On telecommunications
From collisions with interstellar matter

30. Consider the Voyager I Spacecraft…
spacetoday.org
29 years after launch in 1977:
It had travelled ~100 AU
Far beyond Pluto
~150 million km
13.9 light-hours from sun
Moving at 17.4 km/s
0.006% of the speed of light
One of the fastest man-made vehicles
It would take another 74,000 years to reach Alpha Centauri at this rate
Advanced technologies and breakthroughs will be necessary to reach the stars…
Source: Frisbee, R., “Impact of Interstellar Vehicle Acceleration and Cruise Velocity on Total Mission Mass and Trip Time,” AIAA , July 2006

31. Future Propulsion Technologies
Interstellar Ramjet
Beamed Energy
Bussard Drive (1960)
Electromagnetic scoop gathers interstellar hydrogen for propellant
EM “Scoop” is 1000’s of km in size!
Laser Light Sails
Driven by massive space-based laser and space-based optics
bibliotecapleyades.net
daviddarling.info

32. Future Propulsion Technologies- cont
Matter-Antimatter
Other Space Drive Ideas…
Highest energy per unit mass of any reaction known in physics
Energy released by annihilation of matter by antimatter counterpart

33. Future Propulsion Technologies- cont
Breakthrough Physics
Yes, NASA funds research on
Wormholes
Warp drives
Wormhole: a “shortcut” through the spacetime continuum
bibliotecapleyades.net
daviddarling.info
When I began my career in the late 1970’s, we’d joke about electric propulsion being the “propulsion of the future…and always will be!” Today it is used on communications satellites and interplanetary spacecraft.
What does the future hold for interstellar propulsion? Now it is the “propulsion of the future”... but will it always be?

34. References Theory and design
Sutton, G. P. and Biblarz, O., Rocket Propulsion Elements, 7th ed. ,Wiley, 1987
A classic; covers most propulsion technologies
Huzel, D.K, and Huang, D. H., Modern Engineering for Design of Liquid Propellant Rocket Engines (revised edition), Progress in Aeronautics and Astronautics, Vol. 147, American Institute for Aeronautics and Astronautics, 1992
Dieter Huzel was one of the German engineers who came to the U.S. after WW II.
Humble, R. W., et. al., Space Propulsion Design and Anaylsis (revised edition), McGraw-Hill, 1995
Covers chemical (liquid, solid, hybrid), nuclear, electric, and advanced propulsion systems for deep space travel

35. References - cont Rocket engine history
Macinnes, P., Rockets: Sulfur, Sputnik and Scramjets, Allen & Unwin, 2003
Clary, D. A., Rocket Man: Robert H. Goddard and the Birth of the Space Age, Hyperion Special Markets, 2003
Ordway, F. I. and Sharpe, M., The Rocket Team, Apogee Books, 2003
The story of Werner von Braun, the V-2 and the transition of the German engineers to the United States following WW II
Sutton, G. P., History of Liquid Propellant Rocket Engines, American Institute for Aeronautics and Astronautics, 2006
New, over 800 pages of rocket engine history

36. When things go badly…