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.

Right now, the hyper loop concept seems to me like a bad kickstarter project that is all full of dreams, but is missing a practical design. But safety can't be tacked on at the end, it has to be considered up front and will impact the design. Yet nothing in the designs shows any thoughts to safety or survivability. I was puzzle by this (as I know that Musk is a smart guy), but just now Bruce Perens made a comment below that made my head spin bit. Basically his comment is that Musk is somehow conspiring to kill high speed rail, with the implication that the hyper loop is just a tool for this purpose.

I have no knowledge of the politics of high speed rail, but the inadequacies of the hyper loop as passenger transport is puzzling. It is much better suited to transporting freight.

And how quick do you want to do that? And what do you think about being hit by a hypersonic shock wave?

Possibly the only comment that makes some sense. However if you just fully open up the pipe to the outside world then you will subject the capsule to one hell of a shockwave which would make pulp of the people inside (one way to solve the rescue problem), and would probably damage the pipe.

On the other hand if you bleed air in to restrict the shockwave you will still be in the same boat of needed to have air in the capsule - a 4 foot tube several hundred miles long has a huge volume and will take a very long time to fill

Alternatively breaking the pipe into sections that can be isolated and independently filled with air might work - but from the designs presented by musk I am betting that this would be cost prohibitive. (maintenance, regular testing, availability).

To quote from the link you so kindly supplied:

Do you want to speculate how long it will take to extract people from a hyper loop capsule?

Here, let me help you.
1. Time to locate the capsule
2. Time for the Hyperloop Emergency Extraction Team to respond.
3. Time transport man lifts to the location of the capsule at some arbitrary point between the start and finish location
4. Time to safely raise those man lifts to to the height of the pipe
5. Time to safely cut through the pipe and capsule.

I'd wager that it is a bit more than a standard aircraft emergency oxygen supply can hold out for - by at least an order of magnitude or two.

So you counter with "well make it bigger". And then I'll counter with "Here you are wanting to change the design so that the capsule carries more air than even needed for the transit of the trip itself. But the hyper loop capsule design was predicated on not having an internal air supply. If Musk couldn't make it work carrying its own air supply for the trip duration - how could he make it work when it needs to contain multiple times more air?" And so on.

Another false analogy. The chunnel is not hermetically sealed, and reduced pressure. It has an additional service tunnel. And trains are not the size of a metal coffin.

Worst case scenario: So the problem capsule stops halfway between LA and SFO. No problem, the tubes are running along the freeway, so are easily accessible by heavy equipment. But this occurred on a foggy day and there was a huge pile up on both sides of the freeway and all lanes in each direction are blocked - so no emergency services can get through.

Now how large are you going to size that emergency air supply?

Claustrophobia has nothing to do with seat size. Imagine a failure mode where the power goes off, the screens die and all movement stops. And the only way to get out is someone on the outside with a power saw.

And where do you think airplanes get their oxygen from? Its called the outside atmosphere. If a plane stops flying it descends to a lower height with a breathable atmosphere - something that the hyper loop can't do. And emergency oxygen in planes is predicated being able to descend to a safer level. So once the capsule stops the clock starts ticking until you run out of air. In this case the capsule is more comparable to a submarine than a plane.

Still sucks to be stuck in the tube with the issues, and at 5 minute launch intervals, there will be a lot a of people in the same boat.

And the capsules are designed with a power budget that only covers the duration of the trip. They can't even accelerate to speed by themselves. Once they are stopped, the only way out is that worker with the power saw that I mentioned above.

I did read the document several months ago when it was on here. I read it all in order to understand what it was about. And nowhere were any of these failure mechanisms addressed.

1. All the diagrams give the impression that it will be like people flying through tubes as in Futurama. Instead you will be sealed inside a metallic "bullet", that runs in a metallic tube - no windows for you (sort of like James Bond in The Living Daylights). It's a pity if you have any sort of claustrophobia.

2. While the device doesn't run in a complete vacuum, it runs in an atmosphere that is low to the point of being unbreathable. But the device doesn't contain any onboard air supply - instead it relies on the driving compressor/fan assembly to compress the air to a human sustainable amount. So if the device loses power for any reason (electrical, mechanical, computational) then you better be able to hold your breath for a long long time.

3. There was no indication that the loop itself was anything more than a single tube. Thus there is no capability to bypass any section. So if a device fails, all devices that are already in transit and behind it are screwed (see 2 above).

Can't you just switch off locations services for that application? I thought that both iOS and Android allowed you to do that (albeit in different factions).

On the other hand if they can grab location services data without the OS knowing - then that bank/app needs to be shamed.

On the third hand. Doesn't just collecting the IP address you are logging in from count as collecting location data?

And in the demo video on the site the "actor" walks into the room where the robot is working and is not wearing and eye protection, and is only wearing street clothes. So much for safety.

Given what MS just did with the Ask toolbar, it looks like the Ad Wars are starting.

Funny, I thought that was Google's business model.

I didn't know that knowledge was different at non-western universities. Please educate me on what I have been missing out on!

OTOH I read the award as "Knight Grand Master" and I had to check if this was the Nebula awards or something else.