“Although electric aircraft engines are on the drawing boards and have been tested, they are limited to propeller designs which means slower and lower flying.”

Rail travel is more efficient than aircraft travel. With rail travel the rails support the weight of the vehicle and passengers/cargo. Power is required to overcome friction (mainly air) and to climb inclines due to terrain. With aircraft travel thrust is required for forward motion resulting in wing/fuselage aerodynamic lift that supports the weight of the vehicle. Hydrogen might be a potential nonpolluting power source for aircraft but the current nonpolluting method of producing hydrogen (electrolysis) requires a large supply of electricity.

For space-based solar panels microwave systems would be more expensive than laser systems but more suitable. Laser transmissions from satellites to earth could be blocked by cloud cover and misused. However, conversion from sunlight to microwave and microwave to electricity may not be adequately efficient.