The Hyperloop system offers revolutionary transportation, aiming for near-sonic speeds in a low-pressure environment. The aerodynamic design challenges of multiple vehicles in a confined tube remain largely unexplored, particularly regarding vehicle spacing and suspension gaps. This study investigates a jet-propelled, multi-vehicle Hyperloop system using Reynolds-Averaged Navier–Stokes (RANS) equations and the $k-\omega$ turbulence model. Analysis of suspension gaps and vehicle spacing on drag and thrust revealed that suspension gaps cause significant jet deflection, reducing effective thrust and increasing drag. It was found that vehicle suspension, with a 75 mm suspension gap, increased drag by 58% at Mach 0.7 compared to the unsuspended configuration. Meanwhile, smaller vehicle spacing ($X_v=0.25L_v$) reduced the drag by up to 50%, enhancing system efficiency. The results emphasize the need to address the effect of jet deflection and optimize vehicle spacing for maximum energy savings. These findings offer valuable insights for enhancing aerodynamic performance in multi-vehicle Hyperloop systems.

This work investigates how the vehicle-to-tube suspension gap governs compressible flow physics and operating margins in Hyperloop-class transport at 10 kPa. To our knowledge, this is the first study to apply adjoint aerodynamic optimization to mitigate gap-induced choking and shock formation in a full pod–tube configuration. Using a steady, pressure-based Reynolds-averaged Navier-Stokes (RANS) framework with the GEnerlaized K-Omega (GEKO) turbulence model, a simulation for the cruise conditions was performed at M = 0.5–0.7 with a mesh-verified analysis (medium grid within 0.59% of fine) to quantify gap effects on forces and wave propagation. For small gaps, the baseline pod triggers oblique shocks and a near-Kantrowitz condition with elevated drag and lift. An adjoint shape update—primarily refining the aft geometry under a thrust-equilibrium constraint—achieves 27.5% drag reduction, delays the onset of choking by ~70%, and reduces the critical gap from d/D ≈ 0.025 to ≈0.008 at M = 0.7. The optimized configuration restores a largely subcritical passage, suppressing normal-shock formation and improving gap tolerance. Because propulsive power at fixed cruise scales with drag, these aerodynamic gains directly translate into operating-power reductions while enabling smaller gaps that can relax tube-diameter and suspension mass requirements. The results provide a gap-aware optimization pathway for Hyperloop pods and a compact design rule-of-thumb to avoid choking while minimizing power.

The concept of high-speed vehicles traveling in a low-pressure closed system has attracted global attention as an innovative, efficient, and safe mode of transport. So far, most the studies on Hyperloop aerodynamics has considered a single vehicle moving in a confined space, but limited work has been devoted to the succession of vehicles system. This paper deals with the analysis of vehicle suspension gap for multiple vehicles system running in a low-pressure environment. The vehicle’s system is traveling at Mach number = 0.7 in a low operating pressure of 10,000 Pa and blockage ratio of 0.36. Each vehicle is equipped with a compressor and jet exit to provide the thrust force. Three running vehicles at various vehicle-to-vehicle distances, Xv (0.25, 0.5, 1, 2Lv), were numerically investigated using RANS. The analysis was carried out at a gap distance of 75 mm. The obtained results showed that the suspension gap significantly impacts the aerodynamic performance of the entire system. The flow structure behind each vehicle was investigated, and its influence on thrust was presented. It was observed that the drag on the trailing vehicle is approximately six times the drag on the leading vehicle. The high drag on the trailing vehicle is attributed to the development of shock waves at its rear part.