This invention concerns improvements in the gravity propelled transportation system disclosed in my United States patent application Ser. No. 438,230 filed Jan. 31, 1974, now U.S. Pat. No. 4,075,948, and patent application Ser. No. 466,609, filed May 3, 1974, entitled Rapid Transit System, issued as U.S. Pat. No. 3,954,064, May 4, 1976. In said patents there is shown a high-speed ground transportation system comprising a vacuum tube which arcs downwardly deep underground between two stations, a vehicle suspended in the tube by a frictionless magnet suspension system and propelled by gravity so that trips between stations are made with essentially no expenditure of energy. An object of this invention is to provide a more efficient suspension system, to provide a self-aligning vacuum tube between adjacent stations and to provide a safer vehicle design.
As pointed out in my aforementioned U.S. patents the increasing cost of fuel makes it desirable to provide a high speed ground transportation system that requires a minimum amount of energy expenditure. Most prior art systems expend vast quantities of energy which cannot be reduced below certain values because of fundamental laws of physics.
There are two basic reasons for energy expenditure: inefficiencies in the propulsion system and drag. All propulsion systems using internal combustion engines waste a great deal of energy which can not be significantly improved because of the second law of thermodynamics. Although electric motors do offer very high efficiency vehicle propulsion, the problem of supplying the required input electrical energy can become extremely difficult at high operating speeds. For example, efficient power pick-up from an electrified "third-rail" at speeds above 300 mph will be almost impossible. On-board energy storage systems such as batteries or fly-wheels will quickly run down at high speed operation and will require frequent recharging. More exotic propulsive systems such as pneumatic propulsion also lose substantial energy because of the second law of thermodynamics. The energy here is lost through the change in gas enthalpy during the expansion-compression process that is inherent with pneumatic propulsion. This loss can not be reduced below certain levels because the gas volume will be large.
Drag is another major reason for energy expenditure and is inherent in all prior art high speed transportation systems. Drag can be broken down into two main sources: aerodynamic drag and suspension drag. Although aerodynamic drag can be eliminated by enclosing the vehicle inside a vacuum tube, the drag generated by the suspension system can become very large. For speeds above 200 mph a non-contacting suspension system is absolutely essential. All known non-contacting suspension systems that can operate in a vacuum are based on magnetic forces. Unfortunately, many of these systems generate substantial drag forces known as "magnetic drag" that can be much higher than the drag forces inherent in steel wheel/rail contacting suspension systems. (One might conclude that magnetic suspension systems have little or no drag because they are non-contacting but this is not the case.)
In order to provide a low energy consuming transportation system, the system must have high efficiency regenerative propulsion and low overall drag. The gravity propelled system described in this invention and in my aforementioned U.S. Patents will provide such a system. The high efficiency regenerative propulsion is obtained by providing a sloping guideway tube between adjacent stations and allowing the vehicle to coast from one station to the next by transforming its gravitational potential energy into kinetic energy and back into gravitational potential energy. By providing a frictionless suspension system and evacuating the tube's interior, this transformation will be 100% efficient, i.e., the regenerative propulsion will be 100% efficient and there will be no energy expenditure.
One of the most important prerequisites for the construction of a gravity propelled high speed transportation system that consumes nearly zero energy will be the construction of a non-contacting suspension system that consumes no energy, that provides high stability and that will generate essentially zero drag at all operating speeds. Such a system does not exist in the prior art. Thus, one of the major objects of this invention is to provide such a system.
Consider a long rail constructed from blocks of permanent magnets with north poles facing vertically upward. If a similar, but shorter rail is aligned over the longer one with north poles facing downward, forces of repulsion will be generated. For some magnets, with sufficiently strong field strength such as barium ferrite magnets, the forces of repulsion will be sufficiently strong to keep the top rail levitated above the lower one. Setting aside the problem of stability, if the top rail is moved along the bottom rail, the motion will generate absolutely no drag forces whatsoever. This can be proved by applying the principles of electromagnetic theory which are too involved to present here. The analysis has been done however and can be found in a technical paper by R. Borcherts entitled "Mathematical Analysis of Permanent Magnet Suspension Systems", Journal of Applied Physics, Vol. 42, No. 4, Mar. 15, 1971, pp. 1528-1529. Although the levitating capabilities of rails of permanent magnets have been long recognized as a means for providing suspension systems for transportation vehicles (see Polgreen's article "Rail-Ways With a Magnetic Suspension", The Engineer, Oct. 25, 1968, pp. 632-636), their frictionless characteristics have not been fully utilized. Drag is usually introduced into these systems by the guidance systems that are required for rail alignment. Unfortunately, permanent magnet suspension systems are very unstable. Usually, these systems employ guide rollers that contact the vertical faces of guide rails. At speeds above 300 mph these rollers become unstable and can create significant vibration and bearing drag. The other method, which has been proposed for maintaining proper alignment, uses controlled electromagnets that act laterally on vertical faces of ferromagnetic rails. But these systems will generate substantial magnetic drag that increases with increasing speed which can become very great. In addition, these laterial guidance systems are inherent consumers of energy. The preferred suspension system provided in this invention will be based on utilizing drag-free permanent magnets for both levitation and laterial guidance so that the complete suspension system will be non-contacting, self-stabilizing, non-energy consuming and entirely drag-free at all operating speeds.
One important feature of the present invention provides a sloping, self-aligning, evacuated tube guide-way between adjacent stations that is ideally suited for high-speed gravity propelled vehicles. This will be accomplished by suspending the tube inside a deep underground tunnel at two anchor points near each station similar to the main suspension cables of a suspension bridge.
Each transit vehicle is divided into pressure tight sections so that if atmospheric pressure is falling in one section due to a puncture through its pressure hull, it will be possible for the passengers to evacuate it by moving to adjacent sections without pressurizing the vacuum tube or without requiring the use of any emergency rescue vehicle. The damaged vehicle would continue its journey toward the next station without any other disruption.
Other features of the present invention are disclosed hereinafter.