Travel Time Reductions and Energy Savings for Gravity-Augmented, Evacuated Tube Vehicle Systems

摘要

The use of gravity augmentation to accelerate an evacuated TVS affects the travel time, speed, and energy requirements for the system. For stage lengths of 3 to 10 miles characteristic of urban links, savings in travel time can be achieved by gravity augmentation over that for conventional systems operating on the surface. Savings in travel time are achieved however at the expense of higher vehicle speeds. Higher speeds lead to a more complex technological system. However, the incremental time savings decrease rapidly beyond relatively shallow tunnel depths; it simply does not pay to dig deeper. Most of the time saving for the 3 to 10 mile urban links is possible without exceeding vehicle speeds of about 200 mph. Station dwell times can be a significant fraction of the overall trip time which for the short stage lengths reduces the payoff for higher speeds. Since the speeds required do not exceed 200 mph, it may not be necessary to go more exotic propulsion alternatives such as linear electric motors or pneumatic accelerators; rotary electric motors driving wheels may be adequate. The energy requirements for the urban stage lengths were found to be essentially equal for two propulsion modes; boost/glide and continuous thrust. Acceleration and deceleration are such a large proportion of the urban stages that the energies are constrained to be similar. (Author)