ES2943659T3 - A method for using air and helium in low pressure tube transport systems - Google Patents

Abstract

A method of keeping a gaseous composition within a tube (part of a tubular transportation system for transporting passengers or cargo via a capsule) is disclosed, wherein the tube is arranged along a predetermined route. The method comprises: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially emptied; (b) identifying a predetermined power value; (c) identifying a first percentage, x, of helium based on the predetermined power value identified in (b) and a leak rate associated with the tube; (d) maintaining, within each tube in the plurality of substantially vacuum tubes, a gaseous composition, a gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, (100-x), of air. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

A method for using air and helium in low pressure tube transport systems

Technical sector

The present invention relates generally to the field of tube transport. More specifically, the present invention relates to a method for using air and helium in low pressure tube transport systems.

state of the art

The recent effort to develop a new, high-speed and efficient mode of transportation, which Elon Musk dubbed the Hyperloop, began in 2013 with the release of his technical white paper. A team of scientists from Space-X and Tesla wrote this paper to define the technical advantages and engineering requirements for building such a device.

Essentially, the Hyperloop is a system where a capsule is levitated in a tube at low pressure (and, in turn, low air density). Levitation substantially reduces ground friction. The low air density substantially reduces air resistance.

The white paper proposed a capsule supported by hover skis traveling inside a vacuum tube, 100 Pascal (Pa) absolute, and powered by linear induction motors. An air compressor was attached to the nose of the pod to provide air to the ski pads and improve the pod's speed capability. The inclusion of a large compressor improved the speed of the capsule, but required a large set of batteries to power it during the hyperloop journey. Additionally, it took up valuable space from the passenger compartment and added significant complexity. Several groups took immediate notice of the white paper and began to develop the system proposed in the white paper.

Some design teams involved in such development moved away from the aeroski concept, as it required a ski-to-tube clearance of only 0.05-0.1 cm (0.020"-0.040"), which would make it difficult to maintain a smooth ride while fitting tube and installation tolerances. A replacement for the skis was a system based on Maglev (magnetic levitation). Such a Maglev system would eliminate the need for a compressor, thereby reducing the size/weight of the capsule, and would provide developers with the added benefit of more headroom and less vibration.

However, the elimination of the compressor in the design opened up another major problem in such tube-based conveying systems. In the original design as described in Musk's white paper, the compressor serves as an important component to improve the velocity of the capsule, where said improvement is not due to the thrust provided to push the capsule down the tube but to the reduction in the effective front area of the capsule. In Musk's design, the compressor provided a second path to direct air from the front of the capsule to the rear of the capsule, adding to the annular region between the capsule and tube. The ratio of this annular space to the total area of the tube, known as the bypass ratio, is a key predictor of throttling. Once the pod reaches a speed where throttling occurs in the bypass area, the pod would act like a huge plunger, creating a kind of syringe effect. At that key point, known as the Kantrowitz limit (or K-limit), the immense resistance due to the long column of air in front of the capsule being pushed requires much more energy and power to overcome. Overcoming the throttling or K limit, and achieving a significant reduction in the effects of the K limit is a key technology concern.

A discussion is now presented regarding the problems associated with resistance and the phenomenon of choked flow. Figure 1 shows a schematic of a vehicle (also called a pod or pod) inside a tube (Source: see Chin et al. article titled "Open-Source Conceptual Sizing Models for the Hyperloop Passenger Pod", 5-9 January 2015).

Resistance is mainly the contribution of two components: pressure resistance and friction resistance. Pressure resistance is the pressure exerted when the vehicle moves forward and pushes the air. Frictional resistance is the viscous force exerted by air flowing around the surface of the vehicle. The resistance is given by the following equation:

where:

ptubo= Pressure in the tube, absolute; pod = pod velocity squared;

Spod= surface area of the pod; and

where C ^d is the coefficient of resistance that includes the pressure resistance and the resistance due to the effects of friction.

In ECN 1, resistance is proportional to density. Consequently, reducing density has a substantial effect on drag and, in turn, propulsion power. This can be achieved with a low pressure tube. In ECN 1, resistance is proportional to the square of speed. Thus, resistance increases rapidly with increasing speed.

Reducing the density around the vehicle is a historical idea that was first applied in the field of aeronautics. Aircraft fly at high altitudes where they experience low density and therefore low drag. In a low pressure tube, the environment is controlled to reduce the density. However, reducing the pressure is only one of several options to reduce the density (other options are increasing the temperature and using light gases). Therefore, in a low pressure tube, the resistance is expected to be substantially reduced due to the much lower density, even at high speeds (this is true up to a certain limiting speed).

An unwanted flow phenomenon occurs when the vehicle reaches a high subsonic speed. The air flowing around the vehicle in the bypass space of Figure 1 is throttled. This results in a large increase in pressure at the front of the vehicle. In turn, the resistance increases and the necessary propulsive power becomes greater. A description of the physical phenomenon of choked flow is now provided where the key physics relates to the speed of sound.

As the vehicle moves forward, it pushes the air in front of it, which increases the pressure upstream. Since the rear of the vehicle is still under low pressure, a pressure difference is created. The pressure waves traveling from the rear of the vehicle to the front of the vehicle communicate the pressure status downstream to the front and report the pressure difference, like a spring. In reaction, the air mass at the front of the vehicle escapes through the bypass space. As long as enough air escapes back, an equilibrium is created and the pressures remain relatively low. Therefore, the amount of airflow must compensate for the difference in pressure between the front and the rear. So there is a balance. This balancing mechanism is illustrated in figure 2.

However, when the vehicle reaches a high speed, the airflow is accelerated in the bypass space and can reach the speed of sound. Therefore, the airflow in the bypass becomes as fast as the pressure waves in the opposite direction. As a result, the pressure waves cannot go back against the airflow and never reach the upstream location. Consequently, the downstream pressure state information can no longer come through the sonic flow point and communicate the pressure difference to the front of the capsule. The upstream air is not well informed of the pressure difference and the correct amount of air is no longer flowing into the low pressure region behind the capsule. This throttling scenario is depicted in Figure 3. A column of air builds up in front of the vehicle and upstream pressure builds. This choking flow is called the Kantrowitz limit. The result is that the upstream pressure increases substantially due to the movement of the vehicle which acts as a large piston and consequently increases the resistance. Consequently, the energy requirement to maintain the speed of the vehicle becomes very high.

Figure 4 depicts a drag vs. vehicle speed graph identifying the critical vehicle speed that delimits the pressure equilibrium scenario depicted in Figure 2 and the choked flow scenario depicted in Figure 3.

So a key physics is to let the pressure waves reach the front of the vehicle, where the pressure waves must be faster than the airflow in the bypass space. It should be noted that this phenomenon occurs if the bypass space is small, because the airflow is accelerated even more in small sections. Unfortunately, for engineering applications, the size of the vehicle must be maximized to accommodate passengers or cargo. In other words, the size of the derivation space must be minimized. The question therefore becomes: how fast can a vehicle go with a small bypass size?

Formally, a maximum vehicle speed can be defined at which a throttling flow occurs. This maximum speed has been studied in the previously mentioned article by Chin et al. (2015). Figure 5, taken from the article by Chin et al. (2015), shows a graph of the ratio of the bypass area (bypass/tube) versus the Mach number of the bypass airflow. Figure 5 demonstrates that for a reasonable vehicle size (bypass area less than 50% of the tube area), the maximum vehicle speed is approximately Mach 0.25. This corresponds to 300 km/h. This is clearly unacceptable for such a new transportation system.

There are several ways to fix this problem. One solution noted in Elon Musk's white paper is to use an axial compressor at the front of the capsule. Such a design is depicted in the article by Chin et al., mentioned above, which is reproduced in Figure 6(A). In the scenario depicted in Figure 6(A), the compressor forces a portion of air into an interior path within the vehicle instead of only going through the bypass space. The effect is to dramatically increase the net bypass area for airflow and thus prevent acceleration. and the phenomenon of choking at low speed of the vehicle. Fig. 6(B) represents a resistance curve (as indicated in the article by Chin et al., mentioned above) showing that the maximum speed of the vehicle is Ma = 0.6 before the throttling phenomenon. This corresponds to 600 km/h. While the speed increase is interesting, it is still far from higher speeds (like a target speed of 1,000 km/h, for example).

The drawback of the approach depicted in Figures 6(A)-(B) is that installing a compressor presents significant cost, vehicle design complexity, and safety concerns. Regarding safety, an uncontained engine failure (UERF) where the compressor blade can break and damage the vehicle itself, the tube and other vehicles, and induce great restrictions in the development of said transport system.

Another solution is to reduce the tube environment to extremely low pressure, as mentioned in Elon Musk's white paper mentioned above. It might be expected that at low enough tube pressures, the space between the gas molecules would become so far apart that they would flow around the capsule without being throttled. In the event that there was still a throttling effect, the increase in drag and power to push the air column at this very low air density would be negligible. At extremely low pressure, below 0.1 Pa-1 Pa, air can no longer be considered as a physical continuum, as in classical fluid dynamics, but must be treated with molecular flow theory. It is expected that in this flow regime, the strangulation phenomenon will not occur or have less repercussions. And even if it does exist, the pressure would be so low that the resistance might be negligible.

The drawback of this second solution is that the power, cost, and engineering design requirements to maintain extremely low pressure in such a large volume can be tremendous. The pump's power requirement to maintain a vacuum increases exponentially as the target tube pressure drops below 100 Pa. It becomes tremendous when it goes below 1 Pa. However, the limit between the dynamics of Classical fluids and molecular flow, has not been clearly demonstrated in such transport systems. Thus, effort was focused on modeling flow dynamics vs. pressure to find the key pressure below which high speeds and low drag could be achieved.

Computational fluid dynamics (CFD) was used to explore this problem. One difficulty in CFD modeling is that the low pressure intervals that needed to be modeled were beyond normal continuous flow mechanics and thus standard computer models were stretched to give reliable results. Worse yet, the level of vacuum (tube pressure) that was required would require very large vacuum pump systems and would consume a lot of energy. Thus, a tradeoff was made to explore pressure ranges of 1-10 Pascals absolute, which were thought to be low enough to provide a Kantrowitz limit, but also high enough to make vacuum pump systems economical. .

Several difficulties with CFD models quickly became apparent: (1) this pressure range is in a region of transitional flow between continuous and molecular flow; since different modeling tools must be used in each region, it became problematic to obtain reliable data across that pressure region, (2) it was necessary to make many assumptions that had not yet been verified; thus, it would be necessary to develop a test apparatus to validate the computer models, and (3) there are currently no commercially available computers with the ultra-high processing power necessary to handle the complexity of a moving capsule inside a tube. This leads to another untested assumption: whether the validity of modeling a stationary capsule with moving air around it, rather than a capsule moving through stationary air inside the tube, is accurate. Testing the validity of this assumption would again require a test apparatus.

The effort to find the theoretical and economic pressure that would allow high speeds and low drag became the focus of various development groups. It was clear that with some pressure the throttling phenomena would be negligible. This is demonstrated by spacecraft flying in near-Earth orbit pressures, near and beyond the transition region to molecular flow, experiencing almost zero drag. Below this key pressure point and with a particular tube/capsule geometry, there would be the ability to have high velocity and low drag.

Prior art approaches have suggested the use of hydrogen to achieve this speed improvement. In such prior art systems, a tube that operates at atmospheric pressure (or slightly higher) and has at least the following disadvantages:

1) the standardized volume of hydrogen (or other small diameter gas) needed to fill a 4 meter diameter tube, perhaps 100 to 500 km long, at atmospheric pressure is significantly beyond any current construction. However, this preferred technique operates at 1/1,000 to 1/10,000 of an atmosphere, and thus the mass of gas required is also 1/1,000 to 1/10,000 less per kilometer,

2) no method is described to suggest how to replace the air inside the tube with hydrogen, and

3) Although hydrogen is not flammable above 75% concentration, a separate safety concern occurs in the event of a tube rupture which will introduce air into the tube and has the potential to create flammable or explosive relationships. A tube rupture event must be planned for and can be expected at some point. moment due to an earthquake, damage due to operations or even sabotage.

Another prior art, a German patent publication, DE 2054063 A1, discloses a high-speed passenger and container mass transit system using helium. However, the German patent publication, like current tube-based transport systems, does not use a mixture of air and helium, where the composition of each gas in the mixture is determined dynamically to optimize resistance. Also, the German patent publication, like current tube-based transport systems, does not use a mixture of air and helium, where the composition of each gas is determined dynamically based on the desired speed of the capsule.

Another prior art, DE 22 13210 A1, discloses a method for maintaining a gaseous composition inside a tube, comprising the steps of pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially emptied and identifying a predetermined power value.

Whatever the precise merits, features, and advantages of the above-cited references and the aforementioned prior art systems, none of them achieve or fulfill the purposes of the present invention.

Object of the invention

In one embodiment, the present invention provides a method of maintaining a gaseous composition within a tube, the tube being part of a tubular transportation system for transporting one or more passengers or one or more cargo via a capsule, the tube being arranged to along at least one predetermined route, the method comprising: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) identifying a predetermined power value; (c) identifying a first percentage, x, of helium based on the predetermined power value identified in (b) and a leak rate associated with the tube; and (e) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air. .

In another embodiment, the present invention provides a method for maintaining a gaseous composition within a tube, the tube being part of a tubular transportation system for transporting one or more passengers or one or more cargo by means of a capsule, the tube being arranged to along at least one predetermined route, the method comprising: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) identifying a predetermined power value; (c) identifying a desired capsule velocity; (d) identifying a first percentage, x, of helium based on the predetermined power value identified in (b) and the desired capsule velocity identified in (c) and a leak rate associated with each tube; (e) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 1o0-x), of air.

In yet another embodiment, the present invention provides a method for maintaining a gaseous composition within a tube, the tube being part of a tubular transportation system for transporting one or more passengers or one or more cargo via a capsule, the tube being arranged along at least one predetermined route, the method comprising: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) for each of a plurality of bypass ratios and a plurality of leak ratios, storing, in memory, data representative of a first range of total powers, a second range of helium percentages, and a third range of helium pressures. the tubes, each total power in the total power range representing a power value that is a function of a first power to pump each tube to the substantially empty state and a second power to overcome aerodynamic drag in each tube; (c) identifying a predetermined power value; (d) identifying a desired capsule velocity; (e) identifying a first percentage, x, of helium based on the data stored in (b) corresponding to the predetermined power value identified in (c), the desired capsule velocity identified in (d) and an associated leak rate with each tube; and (f) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air. .

Description of the figures

Figure 1 represents a schematic of a vehicle (also known as a pod or capsule) within a tube-based delivery system.

Figure 2 represents the balancing mechanism where when the pressure waves reach the front of the vehicle, the correct amount of airflow escapes to the rear of the vehicle.

Figure 3 represents the throttling phenomenon that occurs when the pressure waves from the rear of the vehicle do not reach the front of the vehicle.

Figure 4 represents a graph of resistance against the speed of the vehicle that identifies the critical speed. of the vehicle that delimits the pressure equilibrium scenario represented in figure 2 and the choked flow scenario represented in figure 3.

Figure 5 depicts a graph of the ratio of bypass area (bypass/tube) versus Mach number of bypass airflow.

Figure 6(A) depicts a scenario where an axial compressor is used at the front of the capsule in a tube-based transport system.

Figure 6(B) represents the aerodynamic resistance as a function of vehicle speed in the scenario of Figure 6(A).

Figure 7 depicts Table 2 showing the distinctive characteristics of the lightest weight gases, of which helium and hydrogen have the lowest densities.

Figure 8 represents Table 3 showing a list of speed of sound entries for various gases.

Figure 9 depicts Table 4 showing the medium-free path for different molecules.

Figure 10 represents a view of the 2D mesh used in the present simulations.

Figure 11 represents Table 5 that compares the density of air with that of helium at 100 Pa.

Figure 12 represents a graph showing the drag coefficient of the 2D simulation for air and helium.

Figure 13 investigates the effect of density by plotting the actual drag of a 3D capsule against the velocity of the capsule.

Figure 14 represents a graph illustrating power reduction based on the use of light gas.

Figure 15 represents the results of CFD studies comparing the maximum speeds achievable at the K limit due to variations in helium and air mixtures.

Figure 16 represents the identification of a capsule velocity given a power requirement for a specific combination of air and helium.

Figure 17 illustrates a comparison of resistance vs. velocity, in the Kantrowitz limit, graphs for four basic tube pressures from 1-1000 Pa together with percentages of helium in air.

Figure 18 illustrates a power vs. speed graph where power requirements for various pressures and various air-helium mixes are reviewed to identify optimum operating ranges.

Figure 19 illustrates a resistance vs. velocity plot, the same as Figure 17, but for a lower tap ratio of 0.208.

Figure 20 illustrates a graph of power vs. velocity, the same as Figure 18, but for the lower tap ratio of 0.208.

Figure 21 illustrates a comparison of two non-limiting tap ratio examples used in the present disclosure, along with a calculation example of how the tap ratio is calculated in each instance. Figure 22 illustrates that helium in the low bypass system (0.208) allows velocities compared to the high bypass region (0.489) for certain helium-air gas mixtures.

Figure 23 illustrates a table representing the volume charge at 50 slm/km by percentage of helium.

Figure 24 illustrates a table representing the volume charge at 5 slm/km by percentage of helium.

Figure 25 represents a graph of the power of the pump (in kW) against the percentage of helium for various pressures.

Figures 26A-C show a summary of the power (kW) requirements to balance drag at pressures of 1000 Pa, 100 Pa, and 10 Pa, respectively, for various capsule velocities versus percentages of helium and air.

Figure 27 represents a graph of the total power (in kW) (combining pumping power and aerodynamic power) against the percentage of helium for various speeds at 100 Pa.

Figures 28A-C represent a non-limiting example of this type, where the same analysis is carried out as in figures 25-27 for a leakage of 5 slm/km.

Figure 29 illustrates how these plots depicted in Figures 25-27 can be combined to provide optimum operating points for power (cost) and helium-air ratios.

Figure 30 represents a graph of diffusion coefficients for various gases in air.

Figure 31 depicts a first implementation including a set of helium tanks fixed uniformly along the length of the tube, where helium is injected with controlled valves that open or close to maintain the desired helium level.

Figure 32 represents a second implementation that includes helium tanks integrated into the vehicles. Figure 33 represents an approach that combines the approaches of Figures 31 and 32.

Figure 34 represents an embodiment of the method of the present invention for maintaining a gaseous composition inside a tube that is part of a tubular transport system where the percentage of helium is identified based on a predetermined power value and a leak rate. associated with each tube.

Figure 35 represents another embodiment of the method of the present invention for maintaining a gaseous composition within a tube that is part of a tubular transport system where the percentage of helium is identified based on a predetermined power value, a capsule speed desired and a leak rate associated with each tube.

Figure 36 represents yet another embodiment of the method of the present invention for maintaining a gaseous composition within a tube that is part of a tubular transport system where the percentage of helium is identified based on stored data corresponding to a power value. preset, a desired capsule velocity and leak rate associated with each tube.

Detailed description of the invention

Although the present invention is illustrated and described in a preferred embodiment, the device can be produced in many different configurations, shapes, and materials. A preferred embodiment of the invention is depicted in the drawings, and will be described in detail herein, with the understanding that the present disclosure is to be regarded as exemplary of the principles of the invention and associated functional specifications for its use. construction and is not intended to limit the invention to the illustrated embodiment. Those skilled in the art will envision many other possible variations within the scope of the present invention.

As noted in the background, recent efforts to increase capsule velocity have focused on reducing tube pressure or improving bypass ratio with the use of a compressor. As mentioned above, reduced tube pressure has merit at some key vacuum level, but comes at the price of substantial increases in vacuum pump capacity and cost. Adding a compressor to the front of the capsule has some merit, but it only marginally increases speed and is also expensive and complex.

The present invention overcomes the pitfalls associated with the prior art by using a mixture of air and helium (in various ratios to be described later) to modify fluid properties, such as speed of sound, allowing high vehicle speeds to be achieved with acceptable propulsion power. The advantages of using a mixture of air and helium include obtaining different fluid properties, such as reduced density, higher speed of sound, and longer free molecular path. These different fluid properties can substantially reduce the vehicle's rolling resistance and required propulsion power.

It should be noted that having a lower density (by a factor of seven) has a substantial and direct effect on drag and propulsion power. Drag is directly proportional to density (and any means to reduce density is useful in a tube-based transportation scenario), which is why airplanes fly at high altitude (low density) and why tubes are considered low-pressure. (low density). The present invention looks at another way of achieving low density, ie using light gases instead of standard air. In addition, the present invention goes beyond simply reducing density by also taking advantage of the increased speed of sound and free molecular path as possible ways to counteract the Kantrowitz limit.

The present invention describes the mixture of different gases that are lighter than air, where these gases have a smaller molecular diameter. There are numerous gases that meet the requirement for a gas molecule smaller than air. The subject of this patent application is the use of helium, which has attractive properties that can be exploited in tube-based transport systems. Although, the air in the tube could be completely replaced by helium, this could be difficult to achieve. Instead, the present invention discloses the use of a mixture of air and helium in various ratios (discussed in detail later in this patent application), which still has interesting properties, while also providing cost effective implementation. lower (compared to prior art systems described above and compared to equivalent systems using helium only).

It should be noted that the cost associated with substituting all or part of air for other gases may be reasonable. Since the pressure is low, around 100 Pa in standard applications, the amount of gas injected into the tube must remain low. Table 1 below shows the mass of gas in the tube for a mixture of air and helium in different percentages.

TABLE 1

Table 1 shows that the amount of helium to be injected into a 10 km tube is low, whether considering pure helium or a mixture of helium and air. At 100 Pa, the entire 10 km tube could be filled with pure helium at a current cost of less than $300 (~$14.00/kg He). However, it is not possible to maintain 100% helium content in a large welded tube due to air leakage from outside the tube. The intention of this technique is to define the optimal percentages of helium and air that reduce drag in the tube.

Some of the advantages of the present invention are listed below. Gases that are lighter than air have lower density, higher speed of sound, and higher free medium path. This offers at least three advantages, simultaneously. The first advantage is the possibility of significantly reducing the density of the gas. Since resistance is proportional to density, a reduction in gas density directly impacts resistance. Table 2 below shows the density at atmospheric pressure for typical gases, taken from the website (Source: Engineering Toolbox website).

Table 2, as shown in Figure 7, represents the distinguishing characteristics of the lightest weight gases, of which helium and hydrogen have the lowest densities. Helium has a density seven times less than air at atmospheric pressure. This relationship is the same in a 100 Pa pressure tube, which means that the resistance can be expected to be reduced by a factor of approximately seven. This is a great advantage that goes to the root of high-speed transportation: reducing drag by reducing density.

The replacement of a portion of the air by a lighter gas offers two possibilities:

• benefit from lower density at the same ambient pressure (thus reducing propulsion power); or

• operate at higher ambient pressure and achieve the same density (thus reducing pump power).

Therefore, gases with a smaller diameter have a lower density, which reduces the resistance of the capsule. The use of a combination of air and helium (specifically, predetermined ratios, as will be detailed later) allows for higher capsule velocities, reduces the size and cost of the vacuum pump. Such a combination of gases provides a significant improvement in tube-based high-speed transportation technology and will reduce costs and improve economics and commercial viability.

Another advantage is the possibility of increasing the speed of sound. As shown in the previous section, a high speed of sound allows for higher vehicle speed without choked flow. The speed of sound of a gas is given by the following formula:

where ^y is the specific ratio, Rgas is the gas constant (8.3145 J/kg/K), Wgas is the molecular mass of the gas (kg/mol) and T is the temperature of the fluid. As of ECN 2, the speed of sound can be increased by changing the molecular mass. In particular, a light gas has a high speed of sound.

Table 3, as shown in Figure 8, is a list of the speed of sound entries for various gases (Source: Engineering Toolbox website):

From Table 3, it can be seen that the gases with less weight stand out for their speed of sound entry. Helium and hydrogen have the highest speed of sound. Helium has a speed of sound three times the speed of air, while hydrogen has a speed of sound four times the speed of air. for the purposes of the present patent application, it is preferred to use helium in the tube (as flammability issues would have to be overcome with hydrogen, which would require some design changes).

Referring again to the example of the article by Chin et al. (2015) described above, it was shown that in a tube filled with air, the maximum speed of the vehicle occurred around Mach 0.25, that is, 300 km/h for air. Since helium has a speed of sound three times that of air, Mach 0.25 in helium corresponds to 900 km/h. The present invention, therefore, provides a substantial gain, changing only the nature of the gas, and without modifying anything else in the design of the tube or capsule.

Referring to the same example, now consider a mixture of air and helium in the tube, which can be obtained more easily. The speed of sound of the mixture is

where Rmezcia is the specific gas constant of the mixture, Ymezcia is the specific heat ratio of the mixture, and T is the temperature. For a mixture of (17% air, 83% helium) by volume, which corresponds to (60% air, 40% helium) by mass, the speed of sound is 664 m/s, which is twice the speed of sound. speed of sound in pure air. Referring to the example of Chin et al. (2015), the maximum speed of Mach 0.25, which was 300 km/h in air, now, based on the teachings of the present invention, becomes 600 km/h in the aforementioned air-helium mixture. previously. This gain is achieved without any other changes to the tube or cartridge design.

A simpler way of looking at this makes the solution easier to understand. The Kantrowitz limit occurs when the gas flowing around the capsule is throttled, i.e. at a speed of Mach 1. Mach 1 for the air is 331 m/s at standard temperatures. Smaller molecular gases have a higher speed of sound, allowing them to flow much faster before being throttled. The capsule will not be subject to throttling flows until the preferred and much higher Mach speed is reached.

Thus, a gas of smaller molecular diameter allows higher velocities before entering the sonic region. The geometry of the capsule and tube will still determine when throttling occurs, but in the case of air it occurs at the relatively low speed of 331 m/s. By switching to a gas or mixture of gases with much higher Mach speeds, such as 972 m/s for helium and 1,290 m/s for hydrogen, much higher capsule speeds can be achieved before throttling occurs. It is observed that the capsule does not avoid the K limit, but increases the rate at which the K limit becomes a problem.

Finally, another advantage is the possibility of increasing the free path of the gases. If the free path of the medium is large enough, the fluid continuum assumption is no longer true, and the fluid must be treated by molecular flow theory. As explained above, this opens up the possibility that there are no throttling phenomena because the physics become different.

The Knudsen number is used to estimate whether the gas can be treated as a continuous or molecular flow. The continuum is true if Kn<0.001, and the molecular flow is true for Kn>0.01. In between, a transition region occurs, which can also be interesting.

The Knudsen number is compared to the free path of the medium, A, of the molecules and the characteristic size of the vehicle L (length or diameter). Therefore, the region of molecular flow can be achieved by increasing the free path of medium.

The medium-free path is given by the following formula:

where k is the Botzmann constant, P is the pressure, and d is the molecular diameter.

From ECN. 5, it is seen that an increase in the free path of medium is obtained by reducing the pressure, P or by reducing the molecular diameter, dm.

But a key insight comes from rearranging the basic Knudsen equation (ie ECN. 4). A pressure term appears in the ECN denominator. 5 and one can see directly what pressures are needed to create a number Kn in the molecular range. A suitably low number for pressure creates a large number Kn and leads to the conclusion that pressure is again the best way to find the operating region in which the limit K becomes negligible.

The most effective number Kn can be obtained not only by lowering the pressure, but rather by changing the diameter of the gas molecule, dm, in the denominator of the expanded free medium path (ECN. 5).

Previously, it has been explained that in order to achieve molecular flow, the pressure had to be reduced below 1 Pa for an air-filled tube. This requires a very large pump power to achieve such a low pressure. Instead, by using a gas with a smaller diameter (light gas), it is possible to increase the free path of the medium. Table 4 depicted in Figure 9 shows the medium-free path for different molecules (Source: Pfeiffer-Vacuum website).

From Table 4 it is seen that helium has one of the highest free paths of medium, some three times higher than air. This means that it is possible to reach the region of molecular flow with a higher pressure, about three times higher than if it were air. Therefore, in the present invention, the pump requirement to achieve molecular flux is significantly reduced.

Computational fluid dynamics (CFD) simulations were performed with a two-dimensional configuration of the tube transport system. The setup is flat in 2D. It is an approximation to reality that is in 3D. Still, it gives a useful idea about the dependence of drag on vehicle speed and gas. The 2D flat CFD provides a coefficient of drag at different vehicle speeds. These drag coefficients can be used to estimate the actual drag in the actual capsule in 3D. Both the drag coefficient and the estimated drag in the real capsule are presented in 3D.

The scheme of Chin et al. (2015) shown in figure 1 and a view of the 2D mesh used in the present simulations was represented in figure 10. The tube has a diameter of 4 m and the branch-tube-area ratio is approximately 0.489. These numbers are similar to the previous study by Chin et al. (2015). However, in stark contrast to Chin et al. (2015), the present invention operates at a pressure of 100 Pa, with a mixture of air and helium. Note that the operating density of helium is about seven times less than that of air. Therefore, a reduction in resistance by a factor of 7 is expected.

Figure 11 represents Table 5 which lists the density figures by mass for both air and helium at 100 Pa. As mentioned above, the reduction in density of more than seven times (0.00116/0, 00016) reduces resistance by a similar ratio (ie, seven times). This advantage is maintained at different pressures in the continuous range. (Note: due to rounding errors, the tap ratio is sometimes shown as 0.488 or 0.489)

In the results below, both the drag coefficient and the estimated drag are presented in the actual 3D configuration.

Resistance, as previously noted in ECN. 1, is related to the resistance coefficient by

2D simulations provide the drag coefficient at different case speeds. The estimated 3D drag is then obtained by multiplying the drag coefficient 1/2 ptUboviasheaths where ptube is the operating density of the tube, Vvana is the velocity of the sheath, and Svana is the front surface area of the sheath.

Figure 12 represents a graph showing the drag coefficient of the 2D simulation for air and helium. The drag coefficient increases substantially when the speed exceeds the Kantrowitz limit. It is observed that the Kantrowitz limit for helium is reached at a velocity of approximately three times that of air, which is in line with expectations. It is also observed that below the Kantrowitz limit, the drag coefficients of helium and air are similar (about 3.5 to 375 km/h). This is because the resistance coefficient formula is resistance divided by density.

Figure 13 investigates the effect of density by plotting the actual drag of a 3D capsule against the velocity of the capsule. The following graph illustrates the behavior of the estimated resistance of the real 3D capsule for helium and air. The 3D resistance is estimated using the 2D resistance coefficients and multiplying them by 1/2ptuboVv2ainaS sheath .

The graph in Figure 13 confirms two important claims of the present invention:

1. Benefits of low density

Consider the region of vehicle velocity below the Kantrowitz limit for both helium and air. The resistance of helium is less than that of air. For the same pod speed of 300 km/h, the drag with helium is about 5.5 times less than with air. This is close to the density ratio of 7 between air and helium.

2. Higher speed before reaching the Kantrowitz limit

The Kantrowitz velocity limit for helium is about three times that of air. Above the Kantrowitz limit, drag begins to increase substantially with speed due to throttling. The results shown in Figure 13 confirm that helium can reach three times the speed of air before reaching the Kantrowitz limit. Thus, helium can reach three times the speed for a reasonable power demand. Helium can therefore allow a capsule speed of almost 1,000 km/h before the need to exceed the Kantrowitz limit.

The benefits of low drag directly correspond to lower power requirements for propulsion. Lower power equals lower cost of operation, which is key to putting this technology into practice. Less cost provides cheaper tickets and more passengers, leading this technology to widespread adoption.

Figure 14 depicts a graph illustrating power reduction based on the use of a light gas, where the graph compares the requirements to overcome drag with air versus helium (at 100 Pa). The same power to compensate for aerodynamic drag can reach speeds of over 900 km/h in a helium-based system, but can only reach 425 km/h in an air-based tube. Twice the speed is achieved for the same cost in aerodynamic power.

Therefore, the replacement of the air or part of the air in the tube by light gases provides at least the following advantages: lower density (and, therefore, lower resistance, which implies lower propulsion power), higher speed of sound (and thus higher vehicle speed before throttling occurs), and higher media free path (and therefore lower pump power to achieve molecular flow, since molecular flow can prevent the throttling phenomenon and thus decrease the propulsion power).

As previously explained, implementing a mixture of air and light gases, such as helium, into the tube can substantially reduce vehicle drag and, in turn, the propulsion power required to overcome drag. Some additional charts are valuable in determining optimum mix percentages and pressure ranges for air and light gas.

Figure 15 represents the results of CFD studies comparing the maximum speeds achievable at the K limit due to variations in helium and air mixtures. Drag is a useful indicator to plot against speed, as there is no economic advantage to achieving higher speeds if drag increases correspondingly.

At a tube pressure of 100 Pa, the increasing velocities achievable with increasing percentages of helium are seen. The dashed vertical lines show the speed in the K limits, first, on the left, for pure air and lastly for pure helium. The second vertical line, on the right, is for a tube filled with 100% helium by volume and shows a top speed of over 1,200 km/h with a nominal increase in drag. When you compare that to the top airspeed line, you see that the achievable speed has increased almost three times, from 425 km/h to over 1,225 km/h.

As previously mentioned, the operating cost is a function of power. Choosing an optimal speed with reference to cost can be seen qualitatively in the power vs. gas mix plot shown in Figure 16. For example, given a power potential of approximately 27 kW, a target speed of 800 km can be achieved. /h using a gas mixture of 5% air 95% helium.

Speed is nearly doubled (compared to pure air) at the same power using a conservative mix of 95% helium and 5% air. Additionally, this mix allows for much higher pod speeds, but at the cost of more thrust power. This is an important consideration as it is anticipated that long and remote sections of the route will need to provide propulsion power from the capsule. This can only be provided by on-board power until improved methods of non-contact power transfer are proven. Thus, keeping the wattage low allows for the use of smaller and lighter pod power packs. Top speeds do not guarantee optimal operating costs as economy depends on length, curvature and elevation changes within the route and the source of propulsion power.

Light gas performance has been demonstrated primarily at pressures of 100 Pa to keep exposures similar and also due to the ease of holding this vacuum. But, there is a much wider range of achievable pressures that have trade-offs. Results for different pressure ranges are presented below as gas percentages are further optimized with operating pressures.

Figure 17 illustrates a comparison of Resistance vs. Velocity, in the Kantrowitz limit, graphs for four basic tube pressures from 1-1000 Pa together with percentages of helium in air. First, it is observed that the speed at the Kantrowitz limit increases as the percentage of helium in the mixture increases, for all pressures. The velocity increase in the Kantrowitz limit has a relatively low dependence on pressure. Now, different graphs are examined for various pressures. These pressure comparisons are made first of all on the basis of resistance and are most interesting for the lowest pressure regime, 1 Pa, where the low pressure and high percentage of helium transform the flow to laminar, thus increasing resistance by 80% in the range of 1-100% helium. It is also seen that the 1000 Pa tube creates a very high resistance despite all the air and helium combinations. This will no doubt result in high propulsion power requirements leading to impractical onboard pod energy storage systems.

It is seen from the 1 Pa pressure plot that the resistance, despite the laminar flow, is quite low and the power requirements will also be low. But, the pumping power to achieve that level of vacuum, combined with the expected air leak rates (45 SLM (standard liter per minute)/km), will result in that pressure not being viable without higher, and more than offset, costs in capital expenditures.

At higher pressures, such as 10 Pa, resistance is seen to increase slightly as vehicle speed more than doubles. This is a critical point to consider. Drag is one of the key energy consumers that must be overcome by the propulsion system, the others being acceleration and gravity. Once the vehicle is up to operating speed and is running on level ground, drag is the largest loss of energy consumption for propulsion purposes. Thus, economical operation depends on minimizing resistance at the highest operating speeds and vacuum levels obtainable. Notice above that drag is shown to increase at a low rate (<25%) with significant speed increases. Operation at higher speeds can be achieved with only incremental resistance increases. Today's high-speed train does not have this advantage and is thus limited to lower speeds or much higher power requirements or both.

Figure 18 illustrates a power vs. speed graph where power requirements for various pressures and various air-helium mixes are reviewed to identify optimum operating ranges. Graphs of aerodynamic energy consumption with different percentages of helium at pressures of 1, 10, 100 and 1000 Pascals.

Based on extensive CFD runs, proven gas properties and behavior at various pressures, our operating intervals can be shortened according to power requirements. This is the main factor in determining operating costs, how much power is required and practical to operate at high speeds. The power ranges represented in figure 18 for 100 Pa and 10 Pa can be achieved with current battery technology for on-board storage systems. Existing lithium ion batteries used in cars have a capacity of 30-100 kWh and so with several of these packs they would be adequate to support pod propulsion (to overcome shown aerodynamic drag) for smooth routes and straight lines and have adequate safety reserves. As previously mentioned, variations in elevation and curve radii will affect power requirements, as will drag due to other propulsion elements, life support, etc. Due to the limited volume and weight available for onboard pod battery storage capacity, the opportunity to reduce battery power is closely scrutinized and must be weighed against increasing vacuum pump power to obtain those lower pressures. At this large scale, low power regimes can be achieved with modest helium percentages and reasonable vacuum levels.

The present invention identifies that percentages of helium in air ranging from 75%-99% are practical and effective in increasing capsule speeds from a base 400 km/h in pure air up to 1,150 km/h in a mixture. of 99% He and 1% air. Lower helium percentages also provide improvements as shown, but due to the relatively low cost of helium, they do not provide optimal or most cost effective operating points. Helium percentages in the range of 75%-99% are practical to control with the latest generation mass flow controllers, sensors and control systems.

The present invention also shows optimum tube pressures that are economical to achieve, ranging from 10 to 100 Pa. Pressures below 10 Pa, such as 1-10 Pa, hold promise in reducing resistance, but move into the range of laminar flow and the transition to a lower maximum velocity at the K limit. It is evident, however, that even in these very low pressure ranges below 1-10 Pa, helium shows an increase in achievable velocities and, thus, this operating environment will improve with the addition of helium from a speed perspective. But, it is equally interesting that the change in power requirements is very small compared to a fresh air system. Thus the power range at 1 Pa with and without helium is only 0.5 to 2.5 kW. A light gas system does not gain much incremental advantage in these pressure ranges (1-10 Pa) in endurance/power regimes. However, top speeds enjoy a large incremental increase from 400kph to 1,150kph and so operations below 10 Pa are expected to also include large percentages of helium similar to the 10 to 100 Pa ranges.

All of the above analysis was performed with a bypass ratio of 0.489 (4m tube diameter and 6.4m2 sheath area) and showing examples of helium pressures and percentages for optimal performance. Now, a different derivation relationship is discussed.

Figure 19 illustrates a resistance vs. velocity plot, the same as Figure 17, but for a lower tap ratio of 0.208. Figure 19 depicts a 0.208 low shunt system (4 m tube diameter and 10 m2 cladding area) and its drag improvements due to the use of light gas mixtures. The advantages of a larger bypass ratio can be clearly seen in any of the pressure charts above, as the achievable speeds are more than double with the .489 bypass versus the .208 bypass. Top speed will be a great advantage on long routes and thus larger yaw ratios are preferred, but on short routes the speed advantage diminishes and smaller ratios may be acceptable. Similarly, smaller bypass ratios may be relevant for low speed charging operations during off hours and allow the use of larger charging capsules in the same tube. Although top speeds are reduced with the smaller bypass ratio, the advantages over fresh air systems are still obtained.

It is worth noting that for these two quite different tap ratios of 0.489 and 0.208, the power requirements remain within similar ranges. Different bypass ratios affect top speed more than power. Since the power of the capsule may be limited (for example, due to the energy density of the battery and the available space), the low-bypass system will be able to operate with such limited power, but at the disadvantage of speeds. very reduced.

Figure 20 illustrates a graph of power vs. velocity, the same as Figure 18, but for the lower tap ratio of 0.208. Similar to figure 18, power requirements can be reviewed for various pressures and various air/helium mixes to identify optimal operating ranges. Due to the higher drag of low ratio systems at the same speeds, more power is required to achieve the same speed. However, with the 0.208 bypass system, top speeds are still significantly increased over 100% air systems.

Figure 21 illustrates a comparison of two non-limiting branch relationship examples used herein. disclosure, along with an example calculation of how the branch ratio is calculated in each instance. It should be noted that while the present disclosure uses two tap ratios, i.e., the tap ratio of 0.489 for a human-carrying capsule and the tap ratio of 0.208 for a cargo capsule, these ratios should not be used in any way. manner to limit the scope of the present invention, since the teaching of the present invention may be applied to other derivation relationships.

As seen in Figure 22, the use of helium in the low bypass system (0.208) allows for velocities compared to the high bypass region (0.489) for certain mixes, as indicated by the velocities limited by the dashed lines in the figures. graphs of 10 Pa and 100 Pa.

Much can be deduced about optimum operating conditions by comparing the power for the two different bypass ratios, as seen in Figure 22. First of all, the maximum achievable speed (before the K limit) with low bypass is drastically reduced. Even at the lowest tube pressures (1 and 10 Pa) it is seen that even with 100% helium, the speed achievable is only half the speed with much lower He percentages incorporating the higher bypass ratio. Second, for the smallest bypass ratio, those lower gears have nearly three times the power of similar speeds using a higher bypass ratio. It is therefore seen that capsule-to-tube geometry optimizations, creating the largest possible bypass, results in much higher speed with much less power.

Greater system operating flexibility for speed and power is achieved by adding specific mixes of air and helium for any of the bypass ratios described. For lower bypass ratios (ie 0.208) equivalent speeds can be obtained at high bypass ratios (ie 0.489) as seen in the figures above between the vertical dashed arrows.

At tube pressures of 10 Pa and 100 Pa, intervals of equal velocity are shown for both bypass ratios. At 100 Pa, the resistance in the small bypass ratio scenario increases almost three times at the same rate, but only by adding 75-100% helium. For larger shunts, the same speeds can be achieved, but with one third the resistance. Adding helium helps significantly for the small bypass system scenario (compared to a pure air system), where such addition can be leveraged for larger capsules, such as payload types. Such helium addition allows for almost three times the speed (compared to a pure air system), with only marginal increases in drag. The smaller bypass system pays a significant speed penalty, as top speed is limited to about half that of the larger bypass system. The use of much lower pressures (eg down to as low as 1 Pa) does not outweigh the overwhelming advantages of large bypass systems.

A key to putting He-Air mixes for high speed tube travel to practical use is to reduce the proper mix percentages based on an economic model. That process is described below and clearly identifies why many higher He percentages are not optimal and which ranges are not even achievable.

Although higher percentages (for example, 99% or 100%) of helium are preferred, it should be noted that such high percentages are not possible with commercial piping construction, due to residual air leakage through welds, joints , cable glands and material imperfections. The amount of air leakage does not change with tube pressure since each leak can be modeled as a hole. In this model, each orifice follows standard gas laws and plugs at pressure drops greater than about 0.53 AP and will be limited to flow at sonic velocities. Throttling each orifice maintains constant flow up to a tube pressure of approximately 53,700 Pa. Tube pressures in the region of 1-1000 Pa essentially create equal air leakage. Thus each of these holes will supply a small amount of air to the vacuum vessel that must be continuously pumped if base pressure is to be maintained. This continuous leakage makes it impossible to achieve 100% He content unless a perfectly airtight tube can be designed. However, practical implementations of such tube-based transport systems will suffer from these leaks, making achieving 100% helium not a practical solution.

A range of leaks that can be expected per km of tube is noted based on the experience of experts in the field and under conditions observed with other large tube vacuum systems. For the disclosures of this patent, the upper range of 50 slm/km (standard liter per minute/km) is chosen as the worst case and 5 slm/km as the best case. Figure 23 illustrates a table representing the volume charge at 50 slm/km by percentage of helium. Figure 24 illustrates a table representing the volume charge at 5 slm/km by percentage of helium. Such leak rates are provided merely as examples and should not be used to limit the scope of the invention. A discussion is now presented on how this leak rate should be taken into account when calculating the preferred helium ratios, as well as the ideal operating pressure.

This leak rate is directly related to the tube construction methods and materials, where with knowledge of such methods and materials, one can fill in the Table of figures 23 or 24 with more accurate numbers. Leak rate can be calculated using standard vacuum system practices and should be measured to each part of the route. Such estimated data associated with different portions of the route are critical to estimating the base tube pressures and helium percentages that can reasonably be achieved within each portion of the route.

As seen in Figures 23 and 24 above, with increasing percentages of helium, the Volume Added column increases geometrically at constant leak rates. Very high percentages of helium necessitate increasing amounts of injected helium where those injected amounts approach infinity as the helium requirement reaches 100%. This additional volume of air/helium mix must be pumped to maintain the required vacuum levels and can therefore load the pumps beyond their capacity. Although from the above discussions it appears that higher percentages of helium are always preferred, there is a counter trend of increasing bomb charges that must also be taken into account.

Figure 25 represents a graph of the power of the pump (in kW) against the percentage of helium for various pressures. As can be seen in figure 25, vacuum pumps are very sensitive to volumetric flow rates with power (kW), increasing geometrically in percentages of He-Air above approximately 90%. These pump power curves show the diminishing returns of trying to maintain high percentages of helium with respect to pump power (kW). This deleterious effect is more pronounced at low tube pressures, which goes against the desire to operate at low pressure to reduce drag. Figure 25 shows the negative effects of high percentages of helium versus the pumping power required to maintain those percentages. More is not better. The present invention takes advantage of this effect to achieve optimal performance within a tube-based conveying system. In one embodiment, the most economical operating percentages can be derived by coupling this result with the power required to overcome aerodynamic drag.

There is a complex interplay of tube pressure, velocity, bypass ratio, air leakage, He-Air %, resistance, and pumping power that has not hitherto been presented in an organized manner in the prior art. All these physical parameters limit the ideal operating speed. These key tradeoffs have been analyzed in various typical regimes and can now present a system and method for finding optimum operating conditions. The number of combinations is enormous, but by simulation and using physical properties, while operating at typical or expected intervals of those regimes, the most practical and economical use of a tube-based conveying system can be formulated.

The present invention discloses a system and method for identifying optimal He-Air ranges based on economics of energy use, both for pumping the vacuum tube and for overcoming resistance at operating speeds. Ideally, 100% He results in the lowest drag and highest speeds due to its reduced molecular size (improved speed) and lower density (reduced drag). The following calculations show that not only 100% helium is not possible.

First, it is required to obtain particular pump curves for a 1 km long, 4 meter diameter steel pipe at various base pressures. These curves include a tolerance for air leakage of 50 slm of air per km. As mentioned above, said leak rate is provided merely as an example and should not be used to limit the scope of the present invention. Since the basis for optimization is power consumption, the curves show the amount of pumping power required to keep the tube at constant pressure (as shown in figure 25), based on a given leak rate. Different leak rates will change the graph, but the conclusion will always show that at higher He-ratios, the pumps must operate at increasing power to evacuate the increasing volume of He-Air injected. As the percentage of helium required within the tube increases, increasing amounts of He must be injected to maintain the ratio. The higher the percentage of helium, the more power the bombs need.

Next, the power required to overcome the resistance at various speeds and percentages is examined. Figures 26A-C show a summary of the power (kW) requirements to balance drag at pressures of 1000 Pa, 100 Pa, and 10 Pa, respectively, for various capsule velocities versus percentages of helium and air. As stated above, the highest velocities can only be achieved with the highest percentages of helium. It is seen in this case that the propulsion power/capsule (drag x speed) is significantly reduced at the higher percentages of helium. But as shown in Figure 25, such helium-rich environments come at the cost of a lot of extra pumping power. These two interactions must be combined to formulate the lowest power and best operating points. Figure 27 represents such a combination by plotting total power (in kW) (combining pumping power at a given leak rate and aerodynamic power) versus percent helium for various speeds at 100 Pa.

Before proceeding, it may be useful to discuss the impact of varying air leak rates on the optimization method and system of the present invention. Leaks affect pump capacity in two key areas. An order of magnitude smaller leak can allow an order of magnitude lower pressure to be achieved in the system. Thus, reducing the leak rate is a very efficient method of achieving lower tube pressures. The same relationship between pump power and leak rate is observed, since power can (theoretically) be reduced by an order of magnitude at the same pressure if the leak rate is reduced by a factor of 10. disclosure of the present invention uses a non-limiting example of air leakage of 50 slm/km, but the specific number of air leaks should not be used to limit the scope of the present invention. However, it should be noted that the teachings of the present invention can be applied to another leak rate, eg 5 slm/km, without departing from the scope of the invention.

Figures 28A-C represent a non-limiting example of this type, where the same analysis is carried out as in figures 25-27 for a leakage of 5 slm/km. Figure 28A depicts a graph of pump power (in kW) vs. helium percentage for various pressures for an air leak of 5 slm/km. Figure 28B represents a graph of the capsule power (in kW) at 100 Pa. Since the capsule power does not depend on the leak rate, this is the same as the graph 26B shown above. Figure 28C depicts a plot of total power (in kW) (combining pumping power and aerodynamic power) versus percent helium for various speeds at 100 Pa for 5 slm/km air leakage. These calculations for the leak rate of 5 slm/km validate the effect in the optimization model.

It should be noted that the plots depicted in Figures 25-27 relate to a tap ratio of 0.489 but similar, but smaller effects can be obtained for tap ratios less than 0.489. The basis of the method is to separate the various inputs, observe the effect of He-Air blends on those inputs, then combine the inputs into a simple graph showing ideal operating conditions. The graphs shown in figure 27 summarize the results presented in figures 25-26 combining them to allow finding the optimal helium-air percentages. These are made for expected speeds with a pressure of 100 Pa and a bypass ratio of 0.489, even assuming a leakage of 50 slm/km.

The graphs in Figure 27 represent fairly consistent power requirements at 600, 700 and 800 km/h with blends up to 90% He. Looking closely at the plot in Figure 27 (and using the data behind the plot to further identify), you see that 75-85% helium in the tube seems acceptable. An operator would not want to operate at 75% He and 800 km/h, however, as there would be very little margin of safety before reaching the K limit and causing a bypass area discharge.

Figure 29 illustrates how these plots depicted in Figures 25-27 can be combined to provide optimum operating points for power (cost) and helium-air ratios. Figure 29 shows an optimum point of helium operation at 600 kph based solely on power requirements, lowest cost per km for 100 Pa tube pressures for this set of speeds. This could be considered the most economical mode (or eco mode) at that pressure and set of speeds. The same optimization can be done at 700 km/h requiring 80% helium and 20% air, with almost 50% more energy consumed, but resulting in 17% shorter transit times (based on speed increase from 600 km/h to 700 km/h). Near top operating speed of 1,000 km/h is observed requiring more than triple the power compared to 600 km/h (145 kW vs. 40 kW) and requiring a mixture of 90% helium and 10% air , but which will result in a reduction of transit times by 67% (based on increasing the speed from 600 km/h to 1,000 km/h).

Operating restrictions at 1,000-1,100 km/h can be identified by witnessing the need for much higher power while being very sensitive to small changes in the helium-air mixture. While these very high speeds can be achieved for this condition, bypass ratio, and pressure, speeds this high may not be ideal. A professional would prefer to reduce the tube pressure or increase the bypass ratio if he wanted to operate safely and reliably in that region. It should be noted that while Figure 29 is provided merely as an example for specific pressures, speeds and bypass ratios, similar plots can be created for other specific pressures, speeds, geometries, to obtain optimum conditions for other operating points in a manner similar.

Helium concentrations are seen to be desirable in the high range but have a higher cost relative to power. Also, in one embodiment, the present invention envisions maintaining, or creating, ideal helium-air ratios from both safety and benefit standpoints. In the examples described, power consumption has been used as an analog for profit purposes, however, there are various operating power points that can be chosen depending on the motives of the operator. For example, minimum power is not produced at maximum speeds and therefore lengthens travel time. Some operators (military, medical transport, etc.) may choose "optimal" power to achieve top speeds. The methods according to the present invention identify what percentages of helium are needed to achieve said maximum speeds. At the other extreme is minimum power operation, which provides the longest pod battery life and allows for longer routes where ground power is not available. Often there will be a mid-power range, "affordable" power that allows for some higher speed operations but still allows for increased path length. Route calculations are based on length, curvature and elevation changes within the route and the source of propulsion power. Different operating reasons will dictate what percentage of helium is ideal based on the route and whether operating in "optimal", "minimum" or "affordable" conditions.

In order to optimize this realization, it is necessary to focus not only on the percentages of helium, but also on the distribution of helium in the tube and methods for controlling said distribution. Similar optimizations can be made for 1 -1000 Pa and large to small tap ratios using examples as shown above. Power requirements for all combinations of pressure, bypass ratio, leakage, air-helium percentages, and velocities can be calculated based on the teachings of the present invention. In one embodiment, this process is fully automated with software, whereby optimum speeds and helium-air ratios are quickly determined. Compared to the effort to: change the size of the capsule or tube (which affects the bypass ratio), increase the number and size of vacuum pumps (to reduce pressure), add a compressor in the front of the capsule (to improve bypass ratio) or change tube construction methods (to reduce air leakage), the process of adding helium to the tube is certainly a simple and very cost-effective method of improving performance. tube-based conveying system. Using helium to optimize improves both capital and operating economics. With these new techniques, identifying and operating at these sweet spots, and even varying the helium percentage based on changing operations (passenger vs. cargo), can be automated and implemented during daily operations.

Helium percentage is seen to be an important determinant of maximum speed and minimum power along with bypass ratio, air leakage, and tube pressure. Thus, the distribution and percentages of the light gas within the length of the tube is an important consideration in maintaining these advantages. The ability to maintain that percentage of helium and homogeneously within the tube is important to achieving these advantages. However, it is also seen that much higher percentages of the light gas are sometimes desired or needed. Different portions of a route may have speed restrictions due to curves, seasons, elevation changes, etc., while other portions of the route will allow maximum speeds. A homogeneous mix must be achieved, but there are several conditions under which the most economically helium-rich mix is preferred, such as on high-speed sections of route. Methods for achieving both homogeneous and enriched He atmospheres are described below.

A description of the technologies that allow to maintain a homogeneous or lightly enriched gas mixture in the tube is provided.

First, some standard components of the conveying system are considered:

1. The vehicle that transports passengers or cargo

2. The tube that guides and encloses the vehicles

3. The pump that maintains low pressure in the tube and compensates for air leaks (from atmosphere to tube)

The present invention proposes additional components to create and maintain a homogeneous mixture of gases and additionally how to improve some areas of the tubes resulting in higher local percentages of light gases.

The following is a list of the components required to achieve the system:

1. A source of gas (other than air)

to. One or more gas tanks built into the side of the tube, distributed along the length of the tube whose position can be determined by the velocity of the capsule at that location in the tube,

b. A series of pipes connected from the gas sources to the sides of the tubes, with injection points distributed along the length of the tube whose position can be determined by the velocity of the capsule at that location in the tube,

c. One or more gas tanks in each vehicle or in some vehicles, located at known critical geometry locations in the capsule that are most prone to shock or disturbance from the high-velocity flow around the capsule. These are specifically near the tip, such that the concentration of light gas can increase as the flow begins its movement over the capsule body, along the capsule body at points where the flows are near the bottom. critical K limit, near the tail to reduce shock waves and instability created in the tail, and finally in the tail to increase the gas concentration in preparation for any subsequent capsule.

2. A system for injecting light gases consisting of a valve, regulator, mass flow controller, electronic controls, and injector nozzles located at any of several locations within the Hyperloop system. This system is under the control of the operations control center, which continuously monitors the gas concentrations within the tube and provides commands to the injection system on the proper amounts to inject in order to maintain optimal gas ratios.

3. A system to recycle gas. A system integrated into the pumping system, which separates the light gases from the air/gas mixture, in such a way that they do not escape into the atmosphere but are recycled back into the tube. This consists of either an air separation unit or a membrane-type gas separation unit that takes the exhaust from the tube vacuum pump and separates the light gases for recycling to the gas injection system or to an exhaust system. storage for future use when the preferred gas ratio is out of balance.

4. A system for monitoring gas pressure and gas concentrations, including gas sensors, a data logging and feedback function, plus a data control system.

to. A network of pressure transducers and gas concentration transducers integrated along the pipe and/or in the vehicles.

b. The output from these transducers is sent to the OCC unit which uses software algorithms to compare measured vs ideal concentrations and responds with control outputs to the gas injection system. c. The gas control system further has optimization routines to provide closed loop control of required gas concentrations and homogeneity based on sensor output. d. Commercially available gas type sensors may be used, where they could be located in the capsule, at points along the tube, or in the vacuum piping at pump stations. Its output would be directed to an operations control center (OCC) to track deviations from ideal, changes to be made by the gas injection equipment, and results of those changes.

It should be noted that the actual implementation can be as modular as possible, combining a plurality of the aforementioned components.

The methods used to place the preferred gases in the tube is an area to optimize. Multiple methods are envisioned for filling the tube with these gases. Individual and/or combined methods such as injection through the tube wall, injection from the capsule, from valves placed on the tube or tube fittings, from the capsule or potentially from the vacuum pump system, all are viable methods.

Injecting the small diameter gas through various critical points in the capsule has some significant potential advantages for enriching the helium content in localized areas around the capsule to reduce shock waves, turbulence, and possible capsule instability due to these factors. It can also be assumed that capsules in the tube behind a driven injection capsule can benefit significantly from these same factors. Such an optimized capsule shell injection method is another advantage of the present invention.

A major challenge is to compensate for air leaks, coming from the atmosphere. Air leaks tend to both increase tube pressure and change the concentration of gases (increasing the air concentration). At these vacuum levels, there are conventional air leakage rates that have been identified for welded steel pipe. As mentioned above, the estimate of an expert in this science, Leybold Vacuum, is a rate of 45 standard liters per minute based on a tube 4 m in diameter and 1 km in length. Thus, achieving a 100% helium filled tube is not practical using accepted materials and manufacture. Comparison of that 45 slm/km (.05512 kg/km) leak rate with the volume of helium in the tube provides a qualitative answer to the achievable helium purity level.

Fortunately, there are no leaks of gases escaping from the tube into the atmosphere because the pressure in the tube is very low compared to atmospheric air. The only way gases can get out of the tube is because of the pumping system that pumps the fluid out of the tube to lower its pressure. At the same time, it removes gas from the tube.

The entire system must be carefully designed so that gases can be recycled and reinjected into the tube as needed. For example, a gas separator can be attached to the pumping system. It would separate the air and reinject the recovered gas. Regarding the helium example above, there are air/helium separators on the market, although their practical applications are limited today.

Novel methods of capturing the exhaust from the vacuum pump and separating the smaller diameter gases through typical air separation units or other types of separation to recycle the gas back to the tube could be used and are also contemplated as part of the present invention.

Additionally, there are certain methods of introducing the gas into the tube that are preferred, such as evacuating the tube and partially refilling it with the preferred gas. Several repetitions of this pump and fill can be done until the preferred gas percentage or gas mixture is at the proper level. Said methods are also contemplated as part of the present invention.

The homogeneity of the mixture is another challenge. Homogeneity can be ensured by evenly spaced gas tanks or gas tanks. Homogeneity can also be ensured by the movement of the vehicle, possibly creating vortices and/or turbulence in its wake that mix the gases.

Finally, the diffusion coefficient is a good indicator of the ability of a gas to mix with air. The diffusion coefficient of a gas in air is the ability of a gas to become homogeneous in calm air, without agitation or turbulence. Figure 30 shows a graph of diffusion coefficients for various gases in air (source: Engineering Toolbox website). Figure 30 shows that light gases, such as helium and hydrogen, have much higher diffusion coefficients in air than other gases. At room temperature, helium has a diffusion coefficient almost four times greater than methane or water vapor, with hydrogen being slightly higher. This makes helium and hydrogen the best candidates for obtaining and maintaining a homogeneous mixture within the tubes.

Two possible implementations of a tube with a helium/air mixture are described below. Figure 31 depicts a first implementation including a set of helium tanks fixed uniformly along the length of the tube, where helium is injected with controlled valves that open or close to maintain the desired helium level. The pumping system is linked to a separator system that removes air and reinjects helium into the tank. For a no-loss system, the helium that escaped from the tube due to the pump is constantly replenished in the tank.

Figure 32 represents a second implementation that includes helium tanks integrated into the vehicles. Tanks open helium release through command control. The helium can be released in the wake of the vehicle, taking advantage of the vortices for good mixing. The helium tank can be filled when the vehicles are docked. The helium is collected by the separation system integrated into the pumping system.

Since the approach of the present invention is modular, it is possible to combine the first and second implementations to obtain a third with helium tanks, both along the tube and in the vehicles. Figure 33 represents an approach that combines the approaches of Figures 31 and 32.

The embodiment depicted in Figure 31 involves injecting the gases or mixtures directly into the tube through ports connected to mass flow controllers and valves, supplied by gas lines or compressed gas cylinders, to precisely control the quantities of each gas introduced. The amount will depend on the analysis of the gases inside the tube and will be controlled by the operations control center (OCC). The spacing of these injection points should be designed. It may be that injecting He into the tube just in front of the moving capsule helps the capsule's aerodynamics. Injecting He, in such a way that its percentage is very high as the capsule approaches the injection point, could help reduce shock waves and resistance.

The embodiment depicted in Figure 32, i.e. capsule body injection, uses, in one embodiment, cylinders of compressed gas inside the capsule to inject the gas or gas mixture at the front, along the body. , at the rear or at a combination of points along the capsule. This design would more precisely inject the gases into the areas most susceptible to drag and shock around the capsule.

The embodiment shown in Fig. 33 combines the teachings of the embodiments shown in Fig. 30 and Fig. 31.

Figure 34 represents an embodiment of the method of the present invention for maintaining a gaseous composition inside a tube that is part of a tubular transport system for transporting one or more passengers or one or more loads by means of a capsule, where the tube is arranged along a predetermined path. According to this embodiment, the method comprises the steps of: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty - step 3402; (b) identify a predetermined power value - step 3404; (c) identifying a first percentage, x, of helium based on the predetermined power value identified in (b) and a leak rate associated with the tube - stage 3406; (d) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air - stage 3408.

Figure 35 represents another embodiment of the method of the present invention for maintaining a gaseous composition inside a tube that is part of a tubular transport system for transporting one or more passengers or one or more loads by means of a capsule, where the tube is arranged along a predetermined path. According to this embodiment, the method comprises the steps of: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty - step 3502; (b) identify a predetermined power value - step 3504; (c) identifying a desired capsule speed - step 3506; (d) identifying a first percentage, x, of helium based on the predetermined power value identified in (b), the desired capsule velocity identified in (c), and a leak rate associated with each tube - stage 3508; (e) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air - stage 3510.

Figure 36 represents another embodiment of the method of the present invention for maintaining a gaseous composition inside a tube, the tube being part of a tubular transport system for transporting one or more passengers or one or more loads by means of a capsule, the tube being arranged along at least one predetermined route, the method comprising: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty - step 3602; (b) for each of a plurality of bypass ratios and a plurality of leak ratios, storing, in memory, data representative of a first range of total powers, a second range of helium percentages, and a third range of helium pressures. the tubes, each total power in the total power range representing a power value that is a function of a first power to pump each tube to the substantially empty state and a second power to overcome aerodynamic drag in each tube - stage 3604; (c) identifying a predetermined power value - step 3606; (d) identifying a desired capsule speed - step 3608; (e) identifying a first percentage, x, of helium based on the data stored in (b) corresponding to the predetermined power value identified in (c), the desired capsule velocity identified in (d) and an associated leak rate with each tube - stage 3610; (f) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air - stage 3612.

The system and processes of the figures are not exclusive. Other systems, processes and menus can be obtained in accordance with the principles of the invention to achieve the same objectives. Although the present invention has been described with reference to particular embodiments, it is to be understood that the embodiments and variations shown and described herein are for illustrative purposes only. Those skilled in the art can implement modifications to the current design, without departing from the scope of the invention. As described herein, the various systems and processes may be implemented using hardware components, software components, and/or combinations thereof.

For example, the feature of maintaining within each tube (in a plurality of substantially empty tubes) particular percentages of helium and air can be implemented in a software process where a processor (or controller) executes instructions to control mechanisms, such as valves, to release specific percentages of helium or release specific percentages of helium and air. Also, as another example, the feature of choosing a percentage of helium based on a predetermined power value and leak rate associated with each tube can be implemented in a software process where a processor (or controller) executes instructions stored in the storage to identify said percentage of helium. As another example, the feature of choosing a helium percentage based on a predetermined power value that is a function of both pump power and power to overcome resistance and a leak rate associated with each tube can be implemented in a software process where a processor (or controller) executes instructions stored in storage to identify said percentage of helium. As yet another example, the feature of choosing a helium percentage based on a predetermined power value, a desired capsule speed, and a leak rate associated with each tube can be implemented in a software process where a processor (or controller) executes instructions stored in storage to identify said percentage of helium. One skilled in the art will see that many of the other features described above can be implemented using hardware, software, or a combination of both.

The features and applications described above may be implemented as software processes that are specified as a set of instructions recorded on a computer-readable storage medium (also called a computer-readable medium). When these instructions are executed by one or more processing units (for example, one or more processors, processor cores, or other processing units), they cause the processing unit(s) to perform the actions indicated in the instructions. Embodiments within the scope of the present disclosure may also include tangible and/or non-transient computer-readable storage media for carrying or having computer-executable instructions or data structures stored therein. Said non-transient computer-readable storage media may be any available media that can be accessed by a general-purpose or special-purpose computer, including the functional design of any special-purpose processor. By way of example, and not limitation, such non-transient computer-readable media may include flash memory, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code media in the form of computer executable instructions, data structures, or processor chip design. Computer-readable media does not include carrier waves or electronic signals that pass wirelessly or over wired connections.

Computer-executable instructions include, for example, instructions and data that cause a general-purpose computer, special-purpose computer, or special-purpose processing device to perform a certain function or group of functions. Computer-executable instructions also include program modules that are executed by computers in stand-alone or network environments. In general, program modules include routines, programs, components, data structures, objects, and the functions inherent in the design of special purpose processors, etc., that perform particular tasks or implement particular abstract data types. The computer executable instructions, associated data structures, and program modules represent examples of the program code means for executing the steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represent examples of corresponding actions to implement the functions described in such steps.

Processors suitable for executing a computer program include, by way of example, general purpose and special purpose microprocessors, and one or more processors of any type of digital computer. In general, a processor will receive instructions and data from read-only memory or access memory. random or both. The essential elements of a computer are a processor to carry out or execute instructions and one or more memory devices to store instructions and data. In general, a computer will also include or be operatively coupled to receive data or transfer data to, or both, one or more mass storage devices for storing data, for example, magnetic disks, magneto-optical disks, or optical disks. However, a computer need not have such devices. On the other hand, a computer can be embedded in another device, for example, a controller, a programmable logic controller, just to name a few.

As used herein, the term "software" includes firmware residing in read-only memory or applications stored on magnetic storage or flash storage, for example, a solid-state drive, that can be read into memory for processing by a processor. Also, in some implementations, multiple software technologies may be implemented as subparts of a larger program while remaining distinct software technologies. In some implementations, multiple software technologies may also be implemented as separate programs. Finally, any combination of separate programs that together implement a software technology described herein is within the scope of that technology. In some implementations, the software programs, when installed to operate on one or more electronic systems, define one or more implementations of specific machines that run and perform the operations of the software programs.

A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but need not, correspond to a file on a file system. A program may be stored in a portion of a file containing other programs or data (for example, one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files. (for example, files that store one or more modules, applets, or pieces of code). A computer program may be implemented to run on one computer or on multiple computers that are located at one site or distributed at various sites and interconnected by a communication network.

These functions described above can be implemented in digital electronic circuitry, in computer programs, firmware or hardware. The techniques may be implemented using one or more software products. Programmable processors and computers can be included or packaged as mobile devices. Logic processes and flows may be performed by one or more programmable processors and by one or more programmable logic circuits. Computing devices and storage devices for general and special purposes can be interconnected through communication networks.

Some implementations include electronic components, for example, microprocessors, storage, and memory that store computer program instructions on a machine- or computer-readable medium (alternatively referred to as computer-readable storage media, machine-readable media, or computer-readable storage media). machine). Some examples of such computer-readable media include RAM, ROM, read-only compact discs (CD-ROM), recordable compact discs (CD-R), rewritable compact discs (CD-RW), read-only digital versatile discs (for example, DVD-ROM, Double Layer DVD-ROM), a variety of recordable/rewritable DVDs (for example, DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (for example, SD cards, mini SD cards, micro S ^d cards, etc.), magnetic or solid-state hard drives, read-only and recordable Blu-ray® discs, ultra-density optical discs, any other optical or magnetic media, and floppy disks. Computer readable media can store a computer program that can be executed by at least one processing unit and includes instruction sets to perform various operations. Examples of computer programs or computer code include machine code, for example, that is produced by a compiler, and files that include higher-level code that is executed by a computer, electronic component, or microprocessor using an interpreter.

While the discussion above is primarily concerned with microprocessors or multi-core processors running software, some implementations are realized by one or more integrated circuits, for example, application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs). ). In some implementations, such integrated circuits execute instructions that are stored in the circuit itself.

Likewise, it is understood that any specific order or hierarchy of steps in the disclosed processes is an illustration of exemplary approaches. Depending on design preferences, it is understood that the specific order or hierarchy of steps in the processes can be rearranged or that all illustrated steps can be performed. Some of the steps can be performed simultaneously.

The various embodiments described above are provided by way of illustration only and should not be construed as limiting the scope of the disclosure. Those skilled in the art will readily recognize various modifications and changes that can be made to the principles described herein without follow the exemplary embodiments and applications illustrated and described herein, and without departing from the spirit and scope of the disclosure.

Although this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or what can be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described herein in the context of separate embodiments may also be implemented in combination with a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple separate embodiments or in any suitable sub-combination. On the other hand, although features may have previously been described as operating in certain combinations and even initially claimed as such, in some cases one or more features of a claimed combination may be removed from the combination, and the claimed combination may refer to a subcombination or variation of a subcombination.

CONCLUSION

In the above embodiments, a system and a method for the efficient implementation of tube transport systems using a gaseous mixture of air and helium have been shown. While various preferred embodiments have been shown and described, it is to be understood that the invention is not intended to be limited by such disclosure, but rather is intended to cover all modifications and alternative constructions that fall within the scope of the invention. , as defined in the appended claims.

Claims (30)

1. A method of maintaining a gaseous composition within a tube, the tube being part of a tubular transportation system made of a plurality of tubes for transporting one or more passengers or one or more cargo by means of a capsule, the tube being arranged to along at least one predetermined route, comprising the method: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) identifying a predetermined power value; characterized by (c) identifying a first percentage, x, of helium based on the predetermined power value identified in (b) and a leak rate associated with the tube; and (d) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air. The method of claim 1, wherein the predetermined power value is any of the following: affordable power, minimum power, or acceptable power. The method of claim 1, the method further comprising the step of choosing the predetermined power value based on a first power to pump each tube to the substantially empty state and a second power to overcome drag in each tube. The method of claim 1, wherein the pressure is chosen from the following range: 1 Pa to 100 Pa. The method of claim 1, wherein 50% < x < 99 %. The method of claim 1, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube. The method of claim 1, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule. The method of claim 1, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube and injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule. The method of claim 1, the method further comprising capturing the gaseous composition in each tube using a recirculation mechanism and recirculating at least some of those gases back into the same tube. The method of claim 9, the method further comprising the step of concentrating the gases using at least one separation unit that is part of the recirculation mechanism, before recirculating them back into the tube. The method of claim 1, the method further comprising the step of maintaining required gas concentrations through a pump-and-refill mechanism. 12. A method for keeping a gaseous composition inside a tube, the tube being part of a tubular transport system for transporting one or more passengers or one or more loads by means of a capsule, the tube being arranged along at least one default route, understanding the method: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) identifying a predetermined power value; characterized by (c) identifying a desired capsule velocity; (d) identifying a first percentage, x, of helium based on the predetermined power value identified in (b), the desired capsule velocity identified in (c), and a leak rate associated with each tube; (e) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air. The method of claim 12, wherein the predetermined power value is any of the following: affordable power, minimum power, or acceptable power. The method of claim 12, the method further comprising the step of choosing the power value predetermined as a function of a first power to pump each tube to the substantially empty state and a second power to overcome aerodynamic resistance in each tube. The method of claim 12, wherein the pressure is chosen from the following range: 1 Pa to 100 Pa. The method of claim 12, wherein 50 % < x < 99 %. The method of claim 12, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube. The method of claim 12, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule. The method of claim 12, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube and injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule. The method of claim 12, the method further comprising capturing the gaseous composition in each tube using a recirculation mechanism and recirculating at least some of those gases back into the same tube. The method of claim 20, the method further comprising the step of concentrating the gases using at least one separation unit that is part of the recirculation mechanism, before recirculating them back into the tube. The method of claim 12, the method further comprising the step of maintaining required gas concentrations through a pump and fill mechanism. 23. A method for maintaining a gaseous composition within a tube, the tube being part of a tubular transportation system for transporting one or more passengers or one or more cargo by means of a capsule, the tube being arranged along at least one default route, understanding the method: (a) pumping the tube at a pressure that is below atmospheric pressure until the tube is substantially empty; (b) identifying a predetermined power value; characterized by (c) for each of a plurality of bypass ratios and a plurality of leak ratios, storing, in memory, data representative of a first range of total powers, a second range of helium percentages, and a third range of helium pressures. the tubes, each total power in the total power range representing a power value that is a function of a first power to pump each tube to the substantially empty state and a second power to overcome aerodynamic drag in each tube; (d) identifying a desired capsule velocity; (e) identifying a first percentage, x, of helium based on the data stored in (b) corresponding to the predetermined power value identified in (c), the desired capsule velocity identified in (d) and an associated leak rate with each tube; and (f) maintaining, within each tube in the plurality of substantially empty tubes, a gaseous composition, the gaseous composition comprising a mixture of a first percentage, x, of helium and a second percentage, ( 100-x), of air. The method of claim 23, wherein the predetermined power value is any of the following: affordable power, minimum power, or acceptable power. The method of claim 23, the method further comprising the step of choosing the predetermined power value based on a first power to pump each tube to the substantially empty state and a second power to overcome drag in each tube. The method of claim 23, wherein the pressure is chosen from the following range: 1 Pa to 100 Pa. The method of claim 23, wherein 50 % < x < 99 %. The method of claim 23, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube. The method of claim 23, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule. The method of claim 23, the method further comprising the step of injecting helium or a combination of helium and air into the gaseous composition through a wall associated with the at least one tube and injecting helium or a combination of helium and air into the gaseous composition in at least one tube per capsule.