Comment Re:Reasons why I don't like Musk's hyper loop (Score 1, Interesting) 124
That's a tough one.
Maybe over a span of fifteen minutes or so?
So do you want to fill the whole pipe up at once? Or are you going to break it into airtight sections with pressure proof doors at each end? Because each set of doors you insert into the system will cost money in maintenance and testing and will have to be available 100% of the time.
Now lets do some basic math. Suppose that you let the air in at 1/3 the speed of sound in order to protect equipment and people. Assume no friction and that the air travels down the pipe as a plug. So the maximum distance between doors is constrained by the time it takes the air to traverse that distance. 15 minutes is 900 seconds. At 100m/s the air will travel a maximum of 90000 metres.
So in a perfect world you have to have emergency self sealing doors located every 90km along the pipe. So lets round that down to 50 miles. GIven 400 miles between LA and SFO, that means you need 8 sets of emergency doors. But there is the chance that a capsule could stop on a door, or a door could fail. So you need at least to double the number of doors in order to stay within your safety limit. So that's 16 sets. Plus we ignored friction, so lets add another 4 to round it up to 20 sets of doors.
So that's 20 sets of mechanical devices that need regular maintenance and weekly (if not more) testing - and that testing has to be done when the hyper loop is not in use - because if a door does not fully retract after testing then the capsule is screwed. They also need high availability power supplies to operate the doors, and pumps to pump each individual section back down to its working pressure, and a staff of people to service them (probably another 5 to 10 people on payroll based up and down the hyper loop just to do that on a sustainable basis).
So we have just added a shitload more money to the operating costs of the hyper loop.