It's a "reduced-pressure tube." A leak is still a big deal, isn't it?
Regardless, the core structural engineering is the focus of the criticism, not whether it might leak. Also, since Space X's whole point is to compete on cost savings, it was a little strange to hear cost projections that were so optimistic.
The entire purpose of the design is explicitly to keep the tolerance for leaks at a level where, to quote the whitepaper "standard commercial pumps could easily overcome an air leak and the transport pods could handle variable air density"
Section 4.5.4 otherwise covers this, and does point out that for large leaks, braking would be required, but smaller leaks are intended to be dealt with as part of regular maintenance, with no indication that it'd need to affect operations.
> Regardless, the core structural engineering is the focus of the criticism, not whether it might leak.
That may be so, but most of the criticism I've seen of it appears to just ignore large sections of the whitepaper.
EDIT: For example, with respect to handling expansion/contraction, consider that the world has gas and oil pipelines that has to deal with far worse conditions without leaks.
Because the hyperloop cars are discrete (as opposed to the continuous flow in a pipeline), I'd expect them to cause a lot of stress on the pipeline walls if they had to run around the bends in an expansion loop.
> But it would need to be very strong lining in order to prevent any leaks between the segments.
The entire point of not requiring vacuum is to avoid having nearly as strict tolerances for leaks.