CHALLENGES

1

• CHALLENGES
• Dual Power Source results in low Power Plant
  power density
• Silent Propulsion with electric drive motors
  requires greater chassis weight
• As Power plants get larger AND Chassis get
  heavier
• Payload capacity will suffer
• Power Requirements can be reduced by
  compromising
• Payload weight
• Speed
• Terrain Severity
• ANY REDUCTION IN CAPABILITY DECREASES MILITARY
  USEFULNESS

2
Basic Vehicle Power Design Considerations for
Propulsion
V
F Motion Resistance
Neglecting Acceleration, Aerodynamic Drag Forces
and Auxiliary Power
3
POWER DENSITY (HP/ton or Watts/kg)
4
4
.025 Hallway .06 Low psi tires .15 Tracked
vehicle
.3 Easy Off-Road .8 Complex Terrain
5
4 mph Silent Propulsion Design Point Terrain
Severity Index 0.3 Wheel vehicle motion
resistance in soft soils OR 30 Slope
NEED Vehicle Power Density 5.85 W/kg Power
Source Density 39 W/kg Assuming 90
Transmission Efficiency and Power Source 15
GVW
6
4 mph Silent Propulsion Design Point
Power Source Needed 11.7 kW JUST TO PROPEL
VEHICLE, NOT INCLUDING ANY ACCESSORIES OR
AUXILIARY EQUIPMENT
7
ALTERNATIVE FUEL OPTIONS Power
Density Methanol Fuel Cell 6.2 w/kg
SOFC 14.4 w/kg Sunpower Sterling Engine
27.2 w/kg Ballard Hydrogen Fuel Cell 52.7
w/kg Zebra Batteries 150 w/kg
8
Design Point - GOAL Off-Road Speed 6
mph Terrain Severity Index 0.8 Motion
Resistance of 30 AND 60 Slope
Vehicle Power Density 21 W/kg 29 HP/ton Power
Source Density 159 W/kg Assuming 90
Transmission Efficiency and Power Source 15 GVW
Power Source Needed (min) 64 HP 48 kW JUST
TO PROPEL VEHICLE, NOT INCLUDING ANY ACCESSORIES
OR AUXILIARY EQUIPMENT
9
DESIGN POINT GOAL cont.

• By satisfying the low speed difficult terrain
  design point,
• The vehicle will also satisfy
• 30 mph on pavement
• 0 30 mph in 7.5 seconds