Elon Musk’s dream of ultra-high speed travel through a tube came a small step closer to reality on Tuesday, when one of the companies set up to pursue the idea announced it had raised another $80m and said it was ready to show off a key part of the technology.

Mr Musk, chief executive officer of Tesla Motors and SpaceX, stirred a wave of interest in 2013 in a technology known as hyperloop — a tube from which air is pumped out to maintain a near-vacuum, theoretically making it possible for pods carrying people or freight to move at close to the speed of sound.

The idea was floated as a potential alternative to California’s plans for a high-speed rail line between San Francisco and Los Angeles. Coming from an entrepreneur who has come to be seen in some tech circles as a visionary, it attracted enough attention to trigger a race among start-ups trying to prove the technology is in fact practical.