Propulsion Challenges:Past, Present and Future

Dr. Alan GarscaddenChief Scientist

Propulsion Directorate

Air Force Research Laboratory

2

Propulsion Correlations

Advances were made by prepared minds

• James Watt: latent heat concepts from Professor Black

• Charles Parsons: Astrophysics from father, Earl of Rosse

• Hans Von Ohain: physics training Gottingen by R. W. Pohl

Advances were made by access to other resources and technologies

• Watt: M. Boulton: manufacturing techniques

• Parsons: private wealth and large scale engineering

• Whittle: hindered by lack of either correlation

• Von Ohain: Heinkel-airframe design & engineering

3

Past Challenges

• James Watt and Matthew Boulton c1776

• Earl of Rosse and Charles Parsons c1890

• US National Bureau of Standards 1922

• Whittle c1930

• Von Ohain and Ernst Heinkel 27 August 1939

4

Past Challenges

James Watt and Matthew Boulton: seals, machining

----New lathe by Wilkinson

Earl of Rosse and Charles Parsons: higher engine speed & scaling----solution led to Dreadnaughts

US National Bureau of Standards: rejected jet propulsion because of calculations on efficiency: did not foresee higher speed and higher altitude flight

Whittle: limited by funds; by inefficient combustion

Von Ohain and Ernst Heinkel; combustion/ blade fatigue

5

HE 178

HeS-3B Turbojet

Ernst Heinkel (left) and Hans von Ohain

7

Present Challenges

• Increased Thermodynamic Propulsion Efficiency+10 to +20%

• Increased Transmission Propulsion Efficiency

• Higher Bypass Ratios10, may need gearbox between power turbine and fan 15, may need UDF: unducted fan

• Improved Materials

• Novel Thermal Management

8

Ideal Cycle Fuel Efficiency

(@Stoichiometric Limit)

Environment Temperature = 3050oF

Environment Temperature = 3800oFCooled cooling air

Environment Temperature = 2000oF

Significant Performance Growth Potential

9

VAATEVAATE

CooledCeramic

High Temp.Ni Disks

IntermetallicBlades & Vanes

CooledCooling

Air

Liquid/VaporCooled

+800oF

Advanced Materials, Cooled Cooling Air & Innovative

Designs Enable Next Major Turbine Temperature Increase

Cooling

10

Future Challenges

• Air Breathing Access to Space

• Combined Cycle

• Hypersonic Flight

• Long Range Strike

• Thermal Management

• Synergistic Fuels Management

11

Cruising Speeds of Insects, Birds, and Airplanes, and the Speed for Minimum Power Consumption

-5 -4 -3 -2 -1 0 1 2 3 4 5 6

reference Bejan

Pheasant

12

Propulsion Options in 3-D Space of ISP, Specific Mass and T/W

13

Air Breathing Access to Space and Combined Cycle Engines

• Expendable turbine engines to Mach 4

• Hydrocarbon fueled scramjet engines to Mach 8

• Liquid hydrogen fueled scramjet engines from Mach 8 to Mach 14

• Rockets from Mach 14 to Mach 26

• Re-entry mode(s)

14

New Propellant Technologies

• Monopropellants

• Alternative hydrocarbons

• Gelled hydrogen

• Metallized gelled propellants

• High energy density materials

reference NASA / TM-97-206228

15

New Propellant Impacts

• Significant higher density

• Boil-off reductions

• Slosh reduction

• Higher payloads

• Increased safety and reduced overheads

• Improved upper atmosphere performance

• Need improved thermal management

• Need improved controls

reference NASA / TM-97-206228

Hungarian-born Theodore von Karman is considered one of the great aeronautical scientists of the 20th century

Hans von Ohain at Wright Patterson

Air Force Base

X-15Air-launched,

rocket-powered hypersonic

research vehicle