# Case Study of an Integrated Design and Technical Concept for a Scalable Hyperloop System
## 5 Physical Definition
### Infrastructure  
While several components are necessary for seamless operation, including pumping stations, gates, lane switches, and operation control with the required servers, certified software, and sensory equipment along the route, the dominant part of the infrastructure is the tubes. The tubes can be elevated, placed in a trench using dig-and-cover methods, or integrated into a tunnel. In all cases, crossing this infrastructure is easily feasible, and there is no noise pollution to the surroundings. Tunnels and bridges constitute a significant portion of the construction costs for ground-based infrastructure. Due to the optimized cross-section and distributed force introduction of the maglev system, both tunnels and bridges for the hyperloop system are expected to have considerable cost advantages when compared to their HSR alternatives. Figure 9 provides the dimensions of the tubes required for different speed regimes based on aerodynamic considerations. The underlying BRs were selected to remain within the Kantrowitz limit at the corresponding speed. Even the full-speed tube requires less than half the space of a two-lane highway and enables more than double the throughput. Common single-lane train tunnels with a 9 m diameter occupy about 3.1 times as much volume as the nominal speed tunnel with a 5.1 m diameter. Nevertheless, two tubes with an outer diameter of potentially up to 6 m are substantial in terms of visual impact, financial costs, planning, and land acquisition. Consequently, three options to reduce the tube cross-section are considered, each requiring further research:  
* First, smaller tubes could be constructed, allowing pods to enter choked flow regions. Drag mitigation measures like lane switches or dedicated vacuum volumes as well as pressures as low as 1 mbar could help to keep the drag in bound. On the other hand, a long stator linear motor in these sections could handle the higher drag. Although this approach would result in a less energy-efficient system, it might be the overall better solution. However, the impact of expected aerodynamic phenomena, such as shock waves, on passenger comfort remains uncertain, requiring more research in this area. * Secondly, a promising option is to accommodate both directions within a single tube or connecting both tubes to enable air flow between them. This would effectively reduce construction costs by nearly 50% and involve a relatively small BR, which is  
Figure 8: Cross-sectional sketch showcasing the interaction of the subsystems. only significantly reduced when pods pass each other. The primary concerns here would be noise and vibrations due to the passing pods. * Thirdly, the concept of smaller pods without aisles, more akin to cars, is considered. An initial analysis indicates that for a capsule with an outer diameter of \(1.6\,\mathrm{m}\), a tube with an inner diameter of \(3.5\,\mathrm{m}\) would suffice for nom speed, and \(3.9\,\mathrm{m}\) would suffice for max speed. In this configuration, even the TUM Hyperloop Demonstrator tube would suffice for max speed. Although the throughput would decrease to \(10.000\,\frac{\mathrm{par}}{\mathrm{h}\,\mathrm{d}\mathrm{t}\mathrm{e}\mathrm{t} \mathrm{e}\mathrm{t}}\) due to the increased number of pods, it would still be comparable to HSR. However, the main concern is passenger acceptance of the reduced space, necessitating further research. Overall, during the next phases of development and detailed engineering of the system, keeping the tube diameter to a minimum will need to remain a key priority. For the above-ground tubes, the choice of construction material is crucial. While welded steel tubes have demonstrated excellent gas tightness in the pipeline industry and simplify recycling, concrete tubes promise better scalability in series production, cost advantages, and better damping. Experiences with the TUM Hyperloop Demonstrator compared to other test facilities showed that the leakage rate of steel tubes is indeed better than for concrete.