HYPERLOOP HEAD-SCRATCHER

In your September issue, there is an article on the proposed Hyperloop transport system, which consists of an evacuated tube fitted with electromagnets inside which a capsule will ride on a cushion of air at 1 100 km/h, being pulled along with a fan and obtaining extra propulsion from the magnets. I can understand the power of the magnets, but how can the fan work and the capsule float on air if the tube has been evacuated? Have I missed something? JM KIRBY HOWICK

( Musk’s original concept used a partial vacuum and borrowed the “air castor” idea, envisaging transportation pods riding on an extremely thin layer of air, with fans balancing pressure build-up. Subsequent implementations have explored maglev principles. – Editor) PM