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Tubexpress

by TubeFreight LLC, PO Box 7951, Dallas, TX 75209-0951; email: rim@tubefreight.com
- or contact -
William Vandersteel. P.O. Box 417, Alpine, NJ 07620; Tel: 201 768 6014 Fax: 201 768 1653; email: ampower@att.net

FIGURE: Tubexpress capsule pipeline under a highway.

FIGURE: Tubexpress capsule being unloaded.

An automated system for moving general commodity freight through underground concrete pipelines, connecting nation-wide metropolitan centers. Cargoes are carried in free-wheeling vehicles (capsules) which are "pumped" through the pipelines with electric energy. A long overdue solution to automating the transportation of inter-city freight, rather than depending on long-haul trucks. TubeXpress on going development is carried out by TubeFreight L.L.C.

As the traffic volume on our highways continues to expand in the face of an essentially static infrastructure, the implementation of TubeXpress is only a matter of time. To the extent that TubeXpress will displace trucks on our highways, the following benefits can be expected.

Substantial reduction in the 5400 annual fatalities, along with countless injuries and untold property damage, attributable to the 200,000 police reported truck accidents in 1997.

Substantial reduction in damage to roadbeds, overpasses and bridges, 97% of which, according to the FHWA, is attributable to trucks.

Reduction in traffic congestion and exhaust pollution caused by trucks, thereby freeing the roads and highways for automobiles.

Marked reduction in energy use. Energy requirement for tube freight is about one quarter of that used by trucks. The use of electric energy, rather than diesel fuel, will drastically reduce total oil consumption.

Lower transportation costs results from automation in transit, smaller capsule size and just-in-time deliveries, which reduces warehousing and materials handling. As there is no access to the system during transit, custodial control is maintained, precluding pilferage and damage, lowering insurance costs.

TubeXpress operates underground or under water, unseen and unheard, with the system protected from the public and the public from the system. Environmental impact is virtually none.

SUMMARY

A concept is introduced for a bulk mode of freight transportation in which commodity cargoes are "pumped" through underground or underwater pipelines. The concept itself is not new, but a recent technical breakthrough has transformed the technology to a point where moving freight through underground pipelines becomes a cost-effective alternative to shipment by long-haul truck. Although the development of this new mode is still at an early stage, the technology is based on an extensive body of knowledge pertaining to existing pneumatic capsule pipelines which move products like coal. Tube freight, as the new mode is generally described, has the potential to displace a majority of long-haul trucks from the nation's roads and highways. When compared to long-haul trucks, tube freight is more economical, safer, more energy efficient, and environmentally friendlier. The tube freight system will operate automatically under computer control, so delivery times are precisely predictable, unaffected by surface traffic, accidents or weather. Preliminary studies confirm that tube freight is technically and economically feasible. The technology involved is state-of-the-art and nothing new needs to be invented. The major obstacle to tube freight's implementation is that the concept is little known, much less understood, by the transportation community.

HISTORICAL DEVELOPMENT OF TUBE FREIGHT

The concept of moving solid objects through ducts is not new. (For a history of the subject, see "Tube Transportation" by the Volpe National Transportation Systems Center (2).) Significant refinements in the development of pneumatic capsule pipeline (PCP) systems, (a forerunner technology to tube freight), began in the late 1960s. These PCP systems operated with multiple capsules in a continuous stream. Development of PCP technology was pursued independently by M. Robert Carstens in the United States (M.R. Carstens, TubeXpress Systems, Inc., unpublished data) and A.M. Alexandrov in the USSR (3). The work of both Alexandrov and Carstens was aimed at transporting bulk granular cargoes, such as coal, over limited distances. PCP systems are powered by pumping or blowing air and using the force of the air to move the cargo-carrying capsules. PCP systems compete, under site-specific circumstances, with conveyers, haul trucks and short haul rail for limited distances.

Starting in 1968, a 10-year research and development program under the direction of Carstens developed algorithms and computer simulations of the dynamic behavior of a pneumatic capsule pipeline system (Carstens, proprietary TubeXpress data). Because a heavily loaded PCP system involves many capsules rolling through a pipeline and controlled only by pressure in the air pockets between them, design of a PCP system must be based on simulated operation of the system. A reasonable simulation must account for the injection of discreet masses (capsules) into the air stream, acceleration of these masses after injection, acceleration of these masses as the capsules traverse grades in the pipeline, and separation of the capsules from the air stream at the downstream terminal. Simulation is of particular importance because pneumatic capsule systems tend toward dynamic instability in a resonant mode (because their behavior is typical of a lightly damped spring-mass system in which the capsules act as masses and the intervening air pockets as springs). The control problem is complex because, once the capsules leave the pump station, direct control of capsule spacing and velocity is lost. A major drawback of all air-pumped systems is the throughput capacity limitation imposed by the valves and airlocks needed to enable the capsules to bypass the air pumps. This throughput limitation effectively precludes use of pneumatic capsule pipeline systems for transporting commodity freight.

In 1980, William Vandersteel of Alpine, New Jersey invented and patented (U.S. Patent No. 4,458,602, 1984) the embodiment of a new concept for motivating a capsule pipeline system. Rather than pumping air to propel the capsules, as had been the practice up to that time, Vandersteel proposed to impart thrust to the capsules directly, recognizing that the closely fitting capsules act like pistons, pumping air in a long cylinder, thereby motivating other capsules in the line. Though various means of inducing thrust to the capsules could be considered, Vandersteel proposed the use of linear induction and/or linear synchronous propulsion, whereby an electromagnetic thrust is induced in each capsule as it passes over magnetic induction coils. These coils could be spaced at intervals, for linear induction propulsion, or continuously, for linear synchronous propulsion.

Propelling the capsules directly, instead of by pumping air, is a fundamental advance that not only raises the throughput capacity of capsule pipeline systems by at least one order of magnitude but also, more importantly, avoids the restriction imposed by the airlocks and valves. The system therefore can operate continuously without interruption or distance limitation. For the first time, it is now practical to consider capsule pipelines for the automated transportation of general commodity freight, in direct competition with surface transport.

PROPOSED DESIGN PARAMETERS FOR THE TUBEXPRESS SYSTEM

The TubeXpress system, as currently envisaged, is designed to transport general commodity freight of the kind now hauled by long-haul trucks. The proposed tube system uses 2-m (6.5-ft) inside diameter reinforced concrete conduits, similar to those used for sewage, drainage and water ducts. A concrete bed is placed in the lower quadrant segment to form a base in which the rails and propulsion components are flush embedded. Also embedded are tubes for power and control cabling, along with conduits for fiber optic lines.

Continuously circulating through the main tubes are a constant number of capsules fitted with wheels, running on steel rails. When a capsule reaches its assigned destination it is sidetracked at speed onto a parallel track where it is brought to a halt and processed. As currently proposed, each capsule has a cargo volume of 11.33 m3 (400 ft3) and will support a maximum load of 8 metric tons. The capsules' internal dimensions are 11.33 x 11.33 x 7.62 m (4 x 4 x 25 ft) to accommodate palletized freight. Each capsule is fitted with seals at the capsule ends, which clear the pipe wall by about 2.54 cm (I in.), resulting in a drag coefficient of about 1000. The intervening air pockets, trapped between adjacent capsules, act as buffers to prevent collisions while they provide pneumatic linkage for the capsule stream. The linkage gives rise to energy regeneration as the stream of capsules moves up and down grades.

A characteristic of these capsule pipeline systems is that, for any given cross- sectional area of the conduit, there is an optimum operating condition in which energy consumption is at a minimum. This is because a given throughput can be achieved with a few capsules operating at high speed or a larger number of capsules operating at a lower speed. Aerodynamic losses rise with Increasing capsule speed, while the rolling resistance goes down with a lesser number of capsules, assuming a constant load per capsule. Conversely, as the capsule speed is reduced, aerodynamic losses decrease but the number of capsules increase, thereby causing a rise in the total rolling friction. Somewhere between these extremes, the system will operate with minimum energy consumption.

If a TubeXpress system operates at a throughput of 1000 tons per hour (TPH) in each direction with a capsule speed of 10 meters/sec (32.8 ft/sec or 22.4 mph), the capsule spacing will be 209 m (686 ft) (center-to-center) operating with a headway of 21 seconds. This interval easily allows sufficient time for side- tracking and reinserting capsules as they arrive at, and depart from, the terminals. Capsules are supported on four flangeless steel wheels, rolling on flush-embedded flat steel rails. Rubber-tired guide wheels are fitted at the four end corners, along the horizontal centerline of the capsule, ensuring that the support wheels track the rails and the seal clears the pipe wall. Rolling resistance of steel wheels on rails is low. Because there are no "headwinds", aerodynamic losses are confined to the friction between the moving air columns and the pipe wall, along with some eddy current losses at the seal edges. Flangeless wheels reduce the wear and friction characteristic of railroad wheels on rails. The rolling resistance of the rubber-tired guide wheels is low because they operate with very light loads most of the time.

The capsule stream is kept in motion by linear induction and/or linear synchronous propulsion. Magnetic coil stators, flush embedded in the concrete base, induce magnetic thrust in each capsule in much the same way as the stator of an electric motor induces a rotational thrust in the rotor. The central computer control system monitors the speed of each capsule, while preventing resonant longitudinal speed oscillations and ensuring that capsule spacing remains uniform. The induced magnetic thrust must be greater when capsules run upgrade and less or negative when running downgrade. With capsules operating at an average speed of 10 m/sec (22.4 mph), coast-to-coast transit is under 5 days. The system can operate at greater speeds and higher throughputs with the expenditure of extra energy.

A central computer controls the entire system, monitors the location and speed of all capsules, maintains a record of cargo content, and assigns the origin and destination for each capsule. Concurrently, toll charges for each shipment are recorded and billed to the shipper.

LINEAR INDUCTION VERSUS LINEAR SYNCHRONOUS PROPULSION

Conceptually, any rotary motor has a linear counterpart. Although all electric motors operate on principles of electromagnetic interactions, there are different kinds of motors. Polyphase synchronous motors and induction motors both use alternating current as input. The choice between linear induction and linear synchronous propulsion systems is under study, but either system could be used to propel the capsules. In general, linear synchronous motors can achieve better energy conversion levels than linear induction motors, but at the price of a higher cost per motor. Linear synchronous motors are better suited for precise control of capsule spacing, while such control is more difficult to achieve with linear induction motors. For linear synchronous propulsion, the secondary, mounted on the capsule, is in the form of permanent magnets, eliminating the need to energize electromagnets. The primaries for linear induction motors can be spaced at intervals, whereas a linear synchronous motor generally requires a continuous primary. The choice between linear synchronous and linear induction motors depends on specific system designs and operating conditions.

ECONOMIC CONSIDERATIONS FOR TUBEXPRESS

Economic analysis of tube freight made to date suggests that a TubeXpress system can compete with trucks, even with the cost of the tube freight infrastructure included, provided the system is installed in corridors with sufficient freight traffic. The economic analysis takes into account all installation and operating costs, with system infrastructure amortized over 30 years, and with freight charges competitive with current rates charged by trucking companies. A competitive shipping rate for interstate trucking is 8 cents per metric ton per mile. The chart below shows that installation of a TubeXpress system in high- traffic corridors will cut the cost of freight shipment to rates significantly less than 7 cents per metric ton per mile.

Assumptions:

Pipe installed for $300/ft per single pipeline
Motor and control systems are $1,000,000/mi per pipeline
Terminal cost is $250,000/mi per pipeline
Capsules are $7000 each
All above costs financed at 7% for 30 yr
Energy cost at $0.06/KWH
Maintenance, personnel, and overhead costs are $40,000/mi/yr per pipeline

Note: Consumer cost is based on breakeven cost is for first year of operation. Breakeven costs for future years will depend on the inflation of variable costs vs. inflation of revenue.

FIGURE: Graph showing Tubexpress cost profile.

Not generally recognized is the substantial logistical cost attributable to the large volume of a truck or container, dictated primarily by the cost of the driver. To spread the cost of the driver over many tons of freight, the truck is much larger than the optimum size for minimizing handling and inventory carrying costs. By reducing the module size to that of a tube freight capsule, the materials handling, warehousing and inventory costs are reduced. To this should be added the substantial savings that are derived from the logistical ability to meet just-in-time (JIT) delivery requirements. The capsule, a low-cost vehicle with low demurrage cost, can serve the function of a storage bin or pallet, thereby further reducing materials handling costs.

The question is often raised: why not size the tube freight system to accommodate standard ISO containers and trailers? The tube diameter increase would raise the infrastructure cost exponentially and the system throughput capacity would be far greater than could conceivably be needed. In addition, and of more importance, the logistical benefit of the smaller module size of capsules, compared to trucks, would be lost. Not generally recognized is the substantial cost associated with consolidating cargoes to fill a truck and distributing the contents during deliveries. The much smaller content of a capsule alleviates this problem.

Although the infrastructure cost of a nation-wide tube freight system is substantial, it will prove to be less than the cost of expanding the U.S. highway system to accommodate the future growth in truck traffic, and the cost can be funded by private investment. Additionally, since trailer-trucks cause vastly more damage to highways than cars, shifting freight transport from trucks to tubes will yield a significant increase in the expected life of highways and substantially lower maintenance costs.

In considering the cost of underground reinforced concrete pipe, it is useful to keep in mind that, in the United States today, about 1.3 million km (over 800,000 miles) of reinforced concrete pipe has been installed. This is 20 times the length of the Interstate Highway system. These concrete pipes move sewage, water and drainag; yet the cost seldom precludes such investment. Virtually all of these pipes are installed in urban areas, whereas tube freight lines will generally run in rural areas, with lower easement and installation costs.

In comparing the economics of truck versus tube freight, account must be taken of the fact that trucks have nearly free use of the highways with their cost subsidized by the gasoline tax paid mostly by motorists. For example, the Texas Department of Transportation estimates that truck licensing in Texas only provides about 50% of the direct costs trucks cause for maintenance of the roads and highways. These costs do not include the substantial effect large truck loadings have in the original design of the road and highway projects. The tube freight infrastructure, on the other hand, will depend on private financing, though Federal and State government support could likely develop in the form of underground easement grants, tax exempt revenue bonds or direct subsidies. The main reason tube freight can compete is because trucking costs are high.

ENERGY CONSIDERATIONS FOR TUBEXPRESS

A fully implemented, nation-wide TubeXpress system could displace most of the semi-trailer trucks that now haul interstate commodity freight. In 1993, all trucks accounted for 24% percent of annual U.S. oil use. Of this total, long- haul trucks accounted for 44% or 10.4% of total oil use in 1993. To the extent that trucks are displaced, a fully implemented tube freight system will bring about a proportionate drop in total U.S. oil consumption. TubeXpress uses electric energy; hence the TubeXpress freight transportation system would no longer be at risk of becoming hostage to a foreign-imposed oil crisis. Tube freight is the only transportation system, except for conveyers, in which the vehicle (capsule) is passive and freewheeling, fitted with neither power, brakes, nor steering. The stream of capsules is kept in motion by stationary power sources. Because of this, the live-to-dead load ratio of capsules is much higher than for other cargo-carrying vehicles, which must haul their own motive power and fuel. CapsuIes will ride on steel wheels on flat steel rails and the capsules will be aligned with the rails and centered in the duct by four rubber- tired guide wheels, mounted at the four corners on the horizontal centerline of the capsule. All this results in low rolling friction, less than one tenth that for trucks. Because the rubber-tired guide wheels are lightly loaded, they contribute little to rolling friction.

Eliminating the dissipation of energy that occurs when trucks brake and accelerate is a major source for energy saving. Unlike trucks, which start and stop as they operate in traffic, the capsule stream moves continuously. Only individual capsules, as they arrive at their destinations, are electrically or pneumatically braked to a stop, but even this energy can be used to accelerate another capsule at the same location as it is phased back into the capsule stream. Because the capsule stream moves continuously, electric power consumption is steady, almost entirely in the form of base load energy.

Pneumatic linkage between the capsules provides energy regeneration whenever the capsule stream traverses mountainous terrain. And as stated previously, there are no headwinds to overcome because the capsules move along with the air columns trapped between them. Aerodynamic losses are confined to the friction between the moving air columns and the pipe wall, along with some eddy current losses around the capsule seals. The total energy required for tube freight is substantially less than the energy used by trucks to move the same tonnage the same distance. However, the energy used by tube freight is in the form of electric energy, whereas trucks use diesel fuel.

SAFETY CONSIDERATIONS FOR TUBEXPRESS

The TubeXpress system is inherently safe because it operates automatically and almost entirely underground or underwater, protecting the system from the public and the public from the system. To the extent that tube freight displaces trucks, highway safety is improved and traffic congestion alleviated. In 1996, medium and heavy duty trucks were involved in more than 200,000 police-reported accidents, resulting in nearly 5,400 fatalities. Nearly all of these fatalities were occupants of vehicles other than the trucks. This does not include the untold number of injuries and property damage caused by truck accidents. Traffic delays, many of them caused by trucks, add billions of dollars to the cost of doing business. Reduced exhaust pollution is an added benefit of tube freight.

With tube freight, the only areas of concern from a safety standpoint will be at the terminals, where personnel are involved in transferring the cargo to door- to-door delivery trucks, to intermodal containers, or other distribution. Because the system is protected from the public, there will be no public exposure that could lead to safety problems. Tube freight cargo damage is minimized because the system operates at ambient pressures and temperatures in a benign environment, not subject to shock, vibration, or adverse climatic conditions.

Tube freight is well suited for the transport of hazardous cargoes. A loaded gasoline delivery truck moving through a crowded city is a disaster waiting to happen. A gasoline-filled capsule traveling through an underground tube is virtually explosion- and fireproof because the small supply of oxygen between adjacent capsules will quickly snuff out fires. Even this hazard may be academic because it is difficult to visualize an event that could lead to an underground accident. An earthquake or similar large movement of earth is virtually the only possible cause for trouble or accidents, and proper system design can mitigate the effects where such problems are expected.

MAINTENANCE CONSIDERATIONS FOR TUBEXPRESS

One main concern is minimizing maintenance problems within the pipelines. Buried reinforced concrete pipes have a service life of 50 to 100 years. The flat rails supporting the capsules are subject to minimum wear and expected to last a comparable life. Railroad rails suffer flange wear, particularly on curves, and the tracks wear because of accelerating and braking forces when trains start, stop, climb grades, slow down, or brake downgrade. None of these problems apply to tube freight because the capsules are freewheeling. Accordingly, it is estimated that the rail replacement period for tube freight (with respect to wear) will be much longer than that for railroad rails.

The linear or synchronous induction propulsion system uses magnetic coils embedded in the concrete base; these have a service life comparable to that of concrete pipes. If a single coil failure occurs, the system will continue to function without interruption. Nevertheless, manholes will be spaced at intervals, accessible from the surface, for use by maintenance personnel. The capsules, the only moving parts of the system, will require periodic maintenance, usually for replacement of the anti-friction wheel bearings. Incipient-failure analysis will provide timely warning, so a defective capsule can be side-tracked off line to the maintenance station(s) for replacement with a repaired capsule.

CONCLUSION

Most modem industries have adopted a substantial amount of automation. As a result, the productivity of these industries has risen dramatically, in many cases by several orders of magnitude. Trucks, on the other hand, have undergone little change for nearly a century, when the first Exide electric truck could manage to move 10 tons at 10 mph. Though there has been improvement in the logistical management of trucks, little progress has been made in automating trucks. Due to traffic, weather, and loading delays, one man, on average, still only moves 10 tons at about 10 mph, and productivity levels remain constrained by some highly labor-intensive practices.

Movement of freight by TubeXpress would result in a number of benefits to society when compared to movement of freight by trucks on highways. Tube freight systems are environmentally friendly, only causing a low and temporary disruption of the land surface. Tube freight systems cause less air and noise pollution. Tube freight systems could be installed under buildings, or parks or greenways, since full use of the land surface is available after the pipeline installation, or even during pipeline installation if tunneling methods are used. Tube freight systems would reduce interaction of interstate freight hauling with people traffic, making the total system safer for both people and freight. Use of tube freight systems could drastically reduce the wear on highways caused by trucks, and could significantly reduce demand for imported oil.

Businesses will also reap substantial benefits through use of TubeXpress. Tube freight will assure both security during the freight transit, and no interruptions in delivery due to accidents, weather or surface traffic. TubeXpress will provide a truly reliable just-in-time delivery system, allowing businesses to cut inventories and the related costs for security, warehousing, and financing. And tube freight can do all this at a lower cost than currently charged by trucks.

TubeXpress is expected to be developed privately, for the same reasons that all railroads, airlines, trucking companies and pipelines are privately owned and operated. However, government will need to be involved in legislating eminent domain rights for freight pipelines as such rights currently extend to rail roads, highways and fluid pipelines.

TubeXpress, arguably, is destined to become the greatest advance in our transportation infrastructure since the railroad displaced the stagecoach.

REFERENCES

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2. Vance, L. L., and P. Matson. Tube Transportation. Report RSPA/VNTCSSS- HW495- 01. Volpe National Transportation Systems Center, U.S. Department of Transportation, Cambridge, Mass., Feb. 1994.

3. Alexandrov, A. M. Theoretical Analysis of Motion Processes in Pneumatic Capsule Pipeline Systems. TRANSPROGRESS Research Station, Moscow, Russia,USSR,'79

4. Zhao, Y., and T. S. Lundgren. Dynamics and Stability of Capsules in Pipeline Transportation. Report 97-17. Aerospace Engineering and Mechanics Department, University of Minnesota, Minneapolis.

5. Hammitt, A. G. Aerodynamic Analysis of Tube Vehicle Systems. AIAA Journal, Vol. 10, No. 3, March 1972, pp. 282-290.

6. Laithwaite, E. R. A History of Linear Electric Motors. Macmillan, 1987.

7. 1995 Annual Report. American Concrete Pipe Association, 1995, Vienna, Va.

8. Transportation Statistics Annual Report 1996. Bureau of Transportation Statistics, U.S. Department of Transportation, 1996, p. 88

9. FHWA Transporter, Federal Highway Administration, US Dept. Transportation, July, '94