Comment Re:Helium Leaks (Score 1) 297
That's not entirely accurate. While that's true for systems where the pressure is equal and they can exchange particles of one for particles of the other, it isn't for the situation he's describing. If it was built so only helium would leak, it would leak out until the pressure of the drive was equalized to the atmosphere, not the concentration. If it equalized concentration in this sort of system, it would end up with a near vacuum inside the drive. In practice, that's not how it happens.