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Comment by axus | Hacker News Reader

It's also scary that the passengers would suffocate if the life support system failed.

Isn't that the case with planes also? As far as I know, at 35,000 feet altitude you'd die, too, if cabin pressure drops and the plane's life support system fails. And I don't recall ever hearing of an air plane accident that involved suffocation.

There have been a few, but they're quite rare. Two of the more prominent:

https://en.wikipedia.org/wiki/Helios_Airways_Flight_522

https://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_cras...

Amazing that there are so many safeguards in place to prevent what happened to HCY 522, and yet the crew managed to miss/ignore them all. I'm sure there have been many thousands of instances where a safeguard prevented such an incident, but in this case I suppose the fates aligned.

That Helios article is just terrifying

Look at the Armstrong limit (at 62,000´), a mayor problem to overcome if the tube is going to be at the equivalent pressure of 150,000´

http://en.wikipedia.org/wiki/Armstrong_Limit

http://en.wikipedia.org/wiki/Time_of_useful_consciousness

Also look at the TUC (time of useful consciousness) that it´s below 5 secs when flying that high. That means that you have less than 5 secs to put your oxigen mask on before you lose conciousness, or behave with out knowing what is happening. Also due to the extreme low pressure, you´ll have a horrible a horrible stomach ache due to the expansion of the gases inside you. Your blood (or at least the corporal fluids exposed directly to the low pressure) will start boiling.

Not funny. Maybe one solution could be wearing some kind of pressure suit for this trips. But that is not going to be very convinient..

From the linked article:

    At or above the Armstrong limit, exposed bodily liquids 
    such as saliva, tears, and the liquids wetting the alveoli 
    within the lungs — but not vascular blood (blood within the     
    circulatory system) — will boil away without a pressure suit

As mentioned above, we have been boarding planes without pressure suits for decades, and the hyperloop has two security advantages: it has a large supply of compressed air to work with, and the tunnel can be quickly re-pressurized in the event of a severe rupture. A multitude of concurrent failures (much less likely than those in an airplane) would be necessary for a catastrophe.

> As mentioned above, we have been boarding planes without pressure suits for decades

The Armstrong Limit is at 62,000 feet. Jetliners fly at below 45,000 feet.

A dedicated hypoxia document by the FAA:

http://www.google.be/url?sa=t&rct=j&q=&esrc=s&source=web&cd=...

You got to think that a decompression will happen. Something traveling that fast inside a tube is probable to develope vibrations and material fatigue if something is not working properly (like the compressor or a air cushion), also there can be small parts released from the front pod impacting on the next one.

It doesn´t need to be a huge crash, just a crack on the hull, it will decompress that small pod in seconds.

Also what will happen when of tens of pods traveling that fast, find that there is a sudden recompression of the tube? How fast are they going to stop due to the front overpressure (the compressor is relatively low powered)?. Is not going to be a gentle stop either.

I still think that it´s a great idea, and that there will be ways of solving those problems, but it´s going to be difficult and require lots of R&D.

Obvious engineering issues for further investigation. I would just point out that fatal failure mechanisms can be pointed out in any transportation system. The acceptance criterion is a sufficiently low fatality rate.

Are you by any chance at the hyperloop team? I see that you only commented on this topic.

The great thing about the hyperloop, and other vactrain systems, is that you're at sea level... you're just not in atmosphere. The atmosphere can be restored in seconds. Sure, it'll stop the entire system and be a TOTAL pain in the arse because you'll have to restore the vacuum, but that's acceptable as long as it doesn't happen often.

Also, the Helios Airways Flight 522.

The paper discusses supplemental oxygen and emergency tube re-pressurization in the case of sudden evacuation of the atmosphere of a capsule.

It seems that detecting failures of this nature quickly would be the important thing. The fix looks to be relatively easy, though you would cause a major disruption to the whole Loop.

Not that different from a commercial aircraft in that regard. Loss of pressurization is a serious emergency in both cases.

You're pretty much done if the life support systems on a plane fail and you're pretty much done if your car has a massive failure while you're doing 70MPH. I can't imagine it being statistically more dangerous than driving.

Driving seems to get a special exemption in the public consciousness. Trains and planes are already much, much safer than driving, but they're still required to add additional redundant safety features, and there's still outcry when one crashes.

No different than planes.

Except that planes have (supposedly) trained staff that can go around and make sure everyone is getting oxygen. These pods are automated and would most likely have no staff on board.

Putting on an oxygen mask is not a difficult operation.

Unless you are otherwise incapacitated due to whatever is causing the emergency in the first place.

You can always push "emergency break, quickly depresurize tube and open doors" button. No such luck in plane, and planes are still safer than cars.

BYOO (Bring Your Own Oxygen)

Shouldn't that be BYOO2?

BYO3?

http://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_crash

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