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
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2. Basic Vehicle Power Design Considerations for Propulsion
F Motion Resistance
Neglecting Acceleration, Aerodynamic Drag Forces and Auxiliary Power
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3. POWER DENSITY (HP/ton or Watts/kg)
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4. 4
.025 = Hallway
.06 = Low psi tires
.15 = Tracked vehicle
.3 = Easy Off-Road
.8 = Complex Terrain
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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
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6. 4 mph Silent Propulsion Design Point
Power Source Needed = 11.7 kW
JUST TO PROPEL VEHICLE,
NOT INCLUDING ANY ACCESSORIES OR AUXILIARY EQUIPMENT
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7. ALTERNATIVE FUEL OPTIONS
Power Density
Methanol Fuel Cell w/kg
SOFC w/kg
Sunpower Sterling Engine w/kg
Ballard Hydrogen Fuel Cell w/kg
Zebra Batteries w/kg
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8. Power Source Needed (min) = 64 HP = 48 kW
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
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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
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