D40LF wrote:djlong wrote:1) It's not a vacuum.

It's basically a 99% vacuum, so if it fails, it'll be very similar to an actual vacuum failure.

The faster trains go, the higher the resistance from air.

Check out planes, and how altitudes effect the corresponding atmospheric pressure.

https://www.mide.com/pages/air-pressure ... calculator" onclick="window.open(this.href);return false;

-5000 feet 1.19 atm 17.55 psi

-4000 feet 1.15 atm 16.95 psi

-3000 feet 1.11 atm 16.36 psi

-2000 feet 1.07 atm 15.79 psi

-1000 feet 1.04 atm 15.24 psi

-500 feet 1.02 atm 14.96 psi

0 feet 1.00 atm 14.70 psi

500 feet 0.98 atm 14.43 psi

1000 feet 0.96 atm 14.17 psi

2000 feet 0.93 atm 13.66 psi

3000 feet 0.90 atm 13.17 psi

4000 feet 0.86 atm 12.69 psi

5000 feet 0.83 atm 12.23 psi

10000 feet 0.69 atm 10.11 psi

20000 feet 0.46 atm 6.75 psi

30000 feet 0.30 atm 4.36 psi

40000 feet 0.19 atm 2.72 psi

50000 feet 0.11 atm 1.68 psi

60000 feet 0.07 atm 1.04 psi

Between 30,000 and 40,000 feet above sea level is where most commercial jetliners fly, betwwn 1/4 and 1/5 atmosphere pressure, or if you want to look at it the other way around, between 75% and 80% vacuum. They could not reach the cruising speeds they fly at if there wasn't a partial vacuum. Trains can't either, hyperloop, meglev, or high speed rail.