Written by Casey Tilton
When Elon Musk released his white paper in 2013 on his theoretical ideas for a “Fifth mode of transportation,” he was careful to note that he had no short term plans to lead the construction of the Hyperloop himself; instead, he introduced the project as an open source form of transportation and welcome feedback from any interested parties. Since that time, several teams of engineers have published articles with the results of feasibility studies for the Hyperloop.
One such team at the NASA Glenn Research Center performed a feasibility study on the technical subsystems of the Hyperloop. Through the paper, the authors offer recommendations that take into account the aerodynamic and thermodynamic interactions between the tube and the pod. According to the authors’ recommendations, the tube should be nearly twice the size of the originally proposed 2.2 meters, which would also limit the maximum capsule travel speed to 620 mph, instead of 700 or more mph.
The authors report that there is a limit to how fast air can enter an air compressor if it is to be properly compressed. Therefore, they recommend adding a diffuser to the front of each pod to slow the air down before it enters the air compressor. The authors also recommend removing the proposed on-board heat exchanger, which is not an ideal solution to equalizing air temperature within the tube; this change would be accompanied by reduction in weight, energy requirements, and complexity of the pod. The authors conclude that despite the compelling nature of the core Hyperloop concept, further engineering and financial analysis is required before a feasible design is fully developed.
A transportation software developer company called Ansys performed a feasibility study that revealed similar findings related to the air flow around the capsule. According to the author, the pod shape that Musk proposes in his white paper could potentially cause the air flowing around the capsule to become supersonic, which would lead to several significant additional engineering challenges. He suggests increasing the taper of the front and rear of the pod to ensure the airflow around the capsule remains subsonic.
Our research has revealed that many experts agree that the Hyperloop is feasible despite the monumental engineering hurtles that still need to be addressed. However, it may be that the socio-political factors accompanying a transportation project of this magnitude will ultimately be what decides it fate.
 Jeffery C. Chin et al. “Open-Source Conceptual Sizing Models for the Hyperloop Passenger Pod.” Kissimmee, FL: AIAA SciTech, 2015.