1. ROCKET AND AIRPLANE PROPULSION
Dr. Daniel Kirk
Associate Professor and Associate Department Head
MAE Mechanical and Aerospace Engineering Department
Florida Institute of Technology
March 26, 2012

2. CONTENTS Basic overview of propulsion
Rocket vs. airplane engines: advantages and disadvantages
How to analyze with Newton’s second law
Rocket propulsion
Why do we use rockets?
Liquid and solid propellant types
Research examples
Air-breathing propulsion
Why do we use air-breathing propulsion systems
Civilian vs. Military engine example

3. BASIC OVERVIEW OF PROPULSION

4. ROCKET VS. AIR-BREATHING PROPULSION
Take mass stored in a vehicle and throw it backwards
→ Use reaction force to propel vehicle
All fuel and oxidizer are carried onboard the vehicle
Capture mass from environment and set that mass in motion backwards
→ Use reaction force to propel vehicle
Only fuel is carried onboard
Oxidizer (air) is ‘harvested’ continuously during flight

5. ROCKET PROPULSION

6. OVERVIEW: ROCKET COMPONENTS

7. TYPES OF ROCKETS
Bell X-1: XLR11

8. UNIQUE ROCKET APPLICATIONS

9. WHY ROCKET PROPULSION? Rockets provide means to:
Insert satellites into space
Space exploration (Atmospheric, solar system)
Precise, continuous or pulsed, momentum change
Weapons
Rapid change in momentum devices, such as car air-bags
Primary distinction is between chemical and electrical propulsion systems
These are only types of rockets in operation today

10. CHEMICAL: LIQUID AND SOLID SYSTEMS
Liquid Propellants
Fuel: LH2
Oxidizer: LOX
Solid Rocket Boosters

11. EXAMPLE: STS EXTERNAL TANK
External tank contains liquid hydrogen fuel and liquid oxygen oxidizer
~1,000,000 pounds of LO2
~200,000 lb LH2

12. SOLID ROCKET GRAIN GEOMETRY
Minuteman first stage motor

13. EXAMPLE: ELECTRIC AND ION THRUSTERS
Satellite orbit raising and station-keeping applications.
Thrust created accelerating positive ions through gridded electrodes, more than 3,000 tiny beams of thrust.
Ions ejected travel in an invisible stream at a speed of 30 kilometers per second (62,900 miles per hour), nearly 10 times that of its chemical counterpart.
Ion thrusters operate at lower force levels, attitude disturbances during thruster operation are reduced, further simplifying the stationkeeping task.
For more on Electric Propulsion:
Designer: Rocketdyne.
Developed in: 1999.
Propellants: Electric/Xenon
Thrust (vac): kgf.
Isp: 3,500 s

14. ENERGY LIMITED VS. POWER LIMITED
Electrical Rockets are Power Limited
Chemical Rockets are Energy Limited
Chemical rockets have lots of power, but not a lot of energy
Electrical rockets have lots of energy, but not a lot of power

15. ROCKET SELECTION GUIDE
MISSION REQUIREMENT
Non-Space Missions
Atmospheric / Ionospheric Sounding
Tactical Missiles
Medium-Long Range Missiles
Launch to Space
Impulsive DV in Space
Time critical maneuvers
Energy change from elliptic orbits, plane change from elliptic orbits
Non-fuel limited situations
Low Thrust DV in Space
Mass-limited missions
Non-time critical missions
Small, continuous orbit corrections, near circular orbits
ROCKET TYPE
Solid Propellant, 1-4 stages
Solid Propellant, 1-2 stages
Solid or Liquid Propellant, 2-3 stages (very high acceleration)
Solid, liquid or combination, 2-4 stages (2-4g), Possible: hybrid, 2-4 stages
Small solid propellant (apogee kick, etc.)
Bi-propellant (storable), liquids, monopropellant (storable) liquids. Future: nuclear thermal
Solar-electric systems:
Arcjet (a bit faster, less Isp), Hall, Ion (slower, higher Isp), PPT (precision maneuvers), Nuclear-electric systems, direct solar-thermal

16. ROCKET PROPULSION RESEARCH AT FLORIDA TECH

17. DEPARTMENT OF REDUNDANCY DEPARTMENT
Why so many engines?
Why not just use 1 big engine?

18. ROCKET SCALING EXAMPLE
Thrust scales with throat area, A*
Recall Thrust = (mass flow) x (exit velocity)
Mass flow depends on A*
A* scales with L2
Weight scales with volume, V
V scales with L3
T/W, therefore scales with 1/L
So what?
Take ‘baseline’ engine and makes 4, ½-size copies of it
1/4th A* of original
1/8th Volume of original
4 engines together produce same thrust as baseline, but only weight half as much!
Do same with half size engine, and make 16 quarter-sized engines
Together produce same thrust as original, but weigh a quarter of original
In theory, process could be continued indefinitely
Massively-parallel thrust system with a very high thrust to weight ratio

19. mROCKET PROJECT
Design complete rocket system, tanks, valves, turbomachinery, thrust chamber
Mass production, silicon-carbide material
Launch and orbital applications, T~ 5-15 N, Isp ~ 300 sec
Higher T/W than Space Shuttle

20. mROCKETS
Six Wafers
Eight Masks
Smallest feature ~ 10 mm
10 cm

21. NUCLEAR THERMAL ROCKET PROPULSION
NTP improvement: % improvement over best conventional rocket motors
Highly reduced mission times (1 year vs. 3 years to Mars)
Safety is major consideration and challenging to design

22. Non-nuclear testing is key to engine development
NTREES: NUCLEAR THERMAL ROCKET ENVIRONMENTAL ELEMENT SIMULATOR AT NASA MSFC
Non-nuclear testing is key to engine development
Design of experiment for NASA MSFC
Heat exchanger designed by Florida Tech students
Grooved Ring Fuel Element

23. What can happen to rockets in space?
Need an environment to study and perform experiments without gravity
Aircraft testing is a popular approach

24. Reduced Gravity Slosh Dynamics Study
F A S T
Illuminated by

25. AIR-BREATHING PROPULSION

26. AIR-BREATHING PROPULSION
Gas turbine engines power every modern aircraft and will for foreseeable future
Gas turbines used for land-based power application, rocket engine turbo-pumps, marine applications, ground vehicles (tanks), etc.
Many technical challenges remain to be addressed (Fuel Economy and Noise)
Fluid mechanics, thermodynamics, combustion, controls, materials, etc.
One of most complicated, parts, extreme environment device on earth
Enormous market: vast research and development $$
Market is so competitive that engines are sold for a loss

27. VARIOUS NUMBER OF ENGINE CONFIGURATIONS
2 Engines
3 Engines
4 Engines
6 Engines

28. COMMERCIAL AIRCRAFT: BOEING SERIES
707
757
727
767
737
777
747
787

29. BOEING (1973) vs (2009)

30. CROSS-SECTIONAL EXAMPLE: GE 90-115B
Compressor
Nozzle
Fan
Turbine
Inlet
Combustor
Why does this engine look the way that it does?
How does this engine push an airplane forward, i.e. how does it generate thrust?
What are major components and design parameters?
How can we characterize performance and compare with other engines?

31. TRENDS TO BIGGER ENGINES
1958: Boeing 707, United States' first commercial jet airliner
1995: Boeing 777, FAA Certified
Similar to PWJT4A: T=17,000 lbf, a ~ 1
PW : T=100,000 lbf , a ~ 6

32. HOW LARGE IS 777-300 ENGINE? 11 ft 7 in (3.53 m) 11 ft 3 in (3.43 m)
Engine is largest and most powerful turbofan built (11 ft 3 in (3.43 m) in diameter)
In this case, 737 cabin is a mere 3% wider than 777 engine

33. COMMERCIAL AND MILITARY ENGINES (APPROX. SAME THRUST, APPROX
COMMERCIAL AND MILITARY ENGINES (APPROX. SAME THRUST, APPROX. CORRECT RELATIVE SIZES)
GE CFM56 for Boeing 737
T~30,000 lbf, a ~ 5
P&W 119 for F- 22, T~35,000 lbf, a ~ 0.3

34. CHEMICAL EMISSIONS

35. AIRCRAFT AND ENGINE NOISE

36. AIRCRAFT NOISE

37. ENGINE TESTING: BIRD STRIKE

38. HOW SERIOUS CAN A BIRD STRIKE BE?

39. MACH 0.8 vs. MACH 8.0

40. SCRAMJET PROPULSION: X-43 MACH 10!

41. X-43A DETAILS

42. X-51: HYPERSONIC FLIGHT

43. Summary Propulsion is an exact, but not a fundamental subject
No basic scientific laws of nature peculiar to propulsion
Incorporates fluid mechanics, thermodynamics, combustion, structures, materials, etc.
Many exciting future opportunities: Rockets
Very large rockets for Moon and Mars missions
Very small rockets for pulse/orbital correction applications
Many exciting future opportunities: Air-Breathing Engines
Will propel airplanes for foreseeable future
Improved fuel economy
Reduced noise and chemical emissions
Exciting / challenging area in aerospace engineering