[jyl]

PDF is interesting reading.

"Passenger Hyperloop Tube
The inner diameter of the tube is optimized to be 7 ft 4 in.

Passenger Plus Vehicle Hyperloop Tube
The inner diameter of the tube is optimized to be 10 ft 10 in. (3.30 m), larger
than the passenger version to accommodate the larger capsule."

This is intended to be a very narrow vehicle indeed. Hope you don't have to pee during the journey, 'cuz you can't even get out of your seat, nor can you walk around during the 0.5 g turns. Admittedly the trip from L.A. to S.F. is only supposed to take 35 minutes, so I guess you just hold it.

"4.5.3. Capsule Stranded in Tube
A capsule becoming stranded in the Hyperloop tube is highly unlikely as the
capsule coasts the majority of the distance at high speed and so there is no
propulsion required for more than 90% of the journey.
If a capsule were somehow to become stranded, capsules ahead would
continue their journeys to the destination unaffected. Capsules behind the
stranded one would be automatically instructed to deploy their emergency
mechanical braking systems. Once all capsules behind the stranded capsule had
been safely brought to rest, capsules would drive themselves to safety using
small onboard electric motors to power deployed wheels.
All capsules would be equipped with a reserve air supply great enough to
ensure the safety of all passengers for a worst case scenario event."

Emergency mechanical braking systems sufficient to bring a capsule (pod) from 800 mph to 0 mph how quickly? Then capsules drive themselves on auxiliary wheels and reserve power to somewhere, presumably not all the way to S.F.? In the meantime air pressure in the tube is <1 psi so the capsule must be pressurized so the passengers don't die horribly, by the nose compressor, whose batteries now have to last longer than the normal 35 minute trip? Or maybe the tube is flooded w/ ambient air?

"4. An onboard water tank is used for cooling of the air.
a. Water is pumped at 0.30 lb/s (0.14 kg/s) through two intercoolers
(639 lb or 290 kg total mass of coolant).
b. The steam is stored onboard until reaching the station.
c. Water and steam tanks are changed automatically at each stop."

For each trip, 640 lb of water is converted to steam, to cool the air that gets compressed and thus heated to 1,100 F (fig 10 p 18 of the PDF). The steam is stored onboard. I think that would be about 500 m^3 of uncompressed steam. Does the capsule have a 20 meter long section devoted to the steam tank, or is the steam cooled or compressed before storage? This also makes me wonder about the energy balance in the tube. Energy is entering the tube, some gets converted to the capsule's motion, some to heat, the tube has to radiate off the heat, how hot is it in there? The calculations assume air enters the compressor at 65 F. Of course, inside the tubes is very low pressure, maybe that chills the remaining air like commercial vacuum cooling.

I think this would be cool as heck. Seems like there is a lot of comfort, safety, redundancy, etc stuff that would have to be added - a lot.