Related by context. Frequent words. (Click for all words.) 75 propulsion 72 hybrid propulsion 68 propulsion systems 62 electrically driven 62 electric powertrain 62 hybrid electric 59 hybrid powertrain 58 PEM fuel 56 PHEV 55 internal combustion 55 internal combustion engine 55 zero emission 55 electric motors 54 diesel engines 54 electric motor 54 powertrain 54 proton exchange 54 ultracapacitors 54 diesel engine 54 turbine engines 54 hydrogen fuel 54 combustion engine 53 internal combustion engines 53 hydrogen powered 53 Lotus Engineering 53 SOFC 52 diesel powered 51 powertrains 51 rotary engine 51 turbocharging 51 drivetrains 50 hydrogen 50 Hybrid Electric 50 diesels 50 combustion engines 50 microturbine 50 electrically powered 50 V6 engines 50 lithium ion 50 piston engine 50 electric hybrid 49 Li ion batteries 49 turbocharged engines 49 Lithium ion 49 powerplants 49 motors 49 conventionally powered 49 lithium ion batteries 49 lithium ion battery 49 Volt 49 Propulsion 48 aftertreatment 48 HEVs 48 scramjet 48 hybrid 48 microturbines 48 mechatronic 48 UQM 48 Hybrid Synergy Drive 48 TARDEC 48 unmanned aerial 48 ultracapacitor 47 Protonex 47 Orion spacecraft 47 hypersonic 47 drivetrain 47 rocket propulsion 47 electric 47 EVs 47 PHEVs 47 unmanned 47 fiber lasers 47 Chevrolet Volt 46 Lithium ion battery 46 HEV 46 CFRP 46 PowerBuoy 46 liquid hydrogen 46 nickel metal hydride 46 Fuel Cell 46 linear motors 46 lithium polymer battery 46 jet propulsion 46 kW 46 Electric Vehicle 46 #kW [001] 46 NiMH batteries 46 Li ion 46 inverter 46 Chevy Volt 45 turbo diesel 45 DMFC 45 electro optic 45 thruster 45 Enova 45 Li Ion 45 Vectrix 45 Aptera 45 powerplant 45 maglev 45 Hybrid