Well, that's because they're Tesla. Benz has had very similar features on their higher-end cars, and it was well received (I think) in the automotive industry, but not the tech community, because Tesla is more well known in tech compared to Benz.
Also consider this is bus-tier people moving, not even train. You just have small individual units moving along one track. With even passenger rail, you have to have set departure times measured in at least 10 minute blocks, something like this could have a departing train every 5 minutes and you could go through a turnstable the same way you get on a subway.
I recall reading that the pylons had vertical and horizontal dampers to protect against earthquakes (among other minor natural changes), so wouldn't those dampers be able to cancel out the shear waves?
No. Well, I suppose you could design an active vibration system to (almost) completely cancel the vertical vibration motion, but know you're talking about a powered system in each pylon of incredible complexity.
Passive resilient systems could help with higher frequency vibration (above say 100 Hz or so, depending on the forces and weights involved), but for lower frequency vibration (especially below 20 Hz), the resilient elements would have to be so compliant that even a gentle breeze would create very high vibrations in the guideway itself, which would be incompatible with the speeds of the cars inside.
You could make the pylons so massive that the forces from the vehicles couldn't move it, but again you're talking about higher construction and material costs, as well as visual impacts.
Vibration from trains is proportional to the unsprung weight of the vehicle (basically the axle, wheels and traction motors) rather than the vibration of the whole vehicle (which is isolated by the primary and secondary train suspensions). For a heavy rail transit vehicle (NYC transit, MBTA Red Line, CTA vehicle, etc), you're talking about 2,700 kg. I don't have numbers handy for HSR trainsets.
The plan uses an air bearing partly because an air bearing is exceptionally stiff. It's not like a hovercraft, with all that ability to squoosh up and down. So the unsprung weight might be the weight of the entire vehicle.
edit: though, mind you, the whole capsule also has mechanical suspension
IIRC, the choice was between no trains and a train. I think a lot of people voted for it so they had a cheaper alternative than planes and a less time/effort intensive alternative than driving.
I wonder what the security checkpoints would be like on the HyperLoop if it ever got built? They are saying capsules could depart 30 seconds apart. Imagine is there was an attack in on of them, with several others travelling at high speed just behind.
If they turn off the compressor there's a giant air cushion in front of them and the capsule no longer has air bearings. It probably lands on wheels and can then engage the breaks. A small capsule has low inertia as well.
Unfortunately the passengers inside still have high inertia. It doesn't matter if the capsule stops without damage if all the people inside are crushed by G-forces.
This is covered in some detail in the proposal. The capsules will be able to stop in the event of an emergency without hitting capsules in front or crushing passengers.
This system would seem very weak to criminals / terrorists / whatever firing bullets at it. It would be exceptionally difficult to track where the shot/s came from, and it would cause serious pressure problems.
Even if the pressure problems could be countered, a bullet hole is likely to leave a pretty ragged profile on the inside of the steel tube. The specification calls for the air bearing skis to ride 0.5 to 1.3mm off the tunnel wall. They'd need to be pretty robust to take hitting the ragged edge of a bullet hole at 700mph.
I think that a bullet hole in the type of tube that supports this much weight is unlikely. Oil pipeline tubes would typically be thinner (less weight to support) and the concept of a bullet piercing those tubes is unlikely.
I wonder - could you line the high-speed part of the tube with half an inch of soft wax or something similar? Then any dents or imperfections caused by bullets would rapidly be smoothed out again, and the damage to the skis would be minimized by vaporizing the wax you hit.
Aircraft sitting on the tarmac doesn't have to take off if it has been shot at. In the process of taking off could be more of a problem, I suppose. On the other hand, at least airports are a relatively small area to keep secure.
Airplanes leak so much air that a couple more half-inch holes would not affect overall integrity. Most control systems are implemented with redundancy, so taking out a control point would just failover to a backup. Occupants aside, there little such damage could do to an airplane; noting the occupants, worst case is a couple casualties, not loss of everyone on board. And, of course, you could simply choose to not take off.
As mhandley noted, Hyperloop might be more susceptible, as the concern is more like your airplane flying an inch off the ground and hitting a stationary large brick.
...which reminds me of an old analogy: Back when large-capacity (ooh! 10MB!) hard drives were becoming common, I recall hearing the comparison that the read head was akin to a 747 traveling Mach 3 just 1 inch off the ground. Perhaps Elon wondered how this might work in real life, and so came up with Hyperloop.
Aircraft are actually supposed to leak air. In non-bleedless aircraft, the engine compressors pressurize air to be used in the A/C unit, which then sends all the pressurized air throughout the cabin. To prevent excess pressure buildup, valves are opened partially most of the flight with a veinlike network of tubes venting air to the exterior of the aircraft.
Of course, if any damage occurred on the ground, this would be a non-issue entirely as the aircraft wouldn't be pressurized at all.
The Shanghai maglev has no security at all... or at least not last time I went on it. Neither do any of the European HSR systems I've been on.
Remember a big part of TSA isn't to protect the people on the planes, but to protect other people from the planes themselves. It's pretty hard to weaponize a vehicle that's stuck inside a tube or on rails.
