It has been clarified that the maximum speed of the RBCC engine of Feitian-2 is Mach 6.Even at an average speed of Mach 10 which is low for a skip glide vehicle spending lots of time near the Karman line, that is roughly 12,350km/hr average speed. Given a general straight line circumference of the Earth is approx 41,275 adjusted for a duration of flight at >99km altitude, a six hour flight is already more than one shortest distance circumnavigation of earth.
In reality, such a vehicle, like the hypersonic vehicle test flown in 21/22, the average speed would be well above mach 10. This would suggest at least a 2x circumnavigation "range".
Lets keep in mind this is a public university project. Affiliated with defence or not, PLA's own HGVs are leagues above this and only mentioned by US intelligence until their replacements are ready. At this point, China is clowning the US at hypersonics including powered hypersonic flight. India is still boasting about achieving scramjet combustion.
Actually, it's a good thing. Pneumatic heating becomes more severe at higher speeds.
Nowadays, in materials science, it is difficult to persist for longer under high temperature conditions.
1800s is the limit, this aircraft needs to fly for more than 21800 seconds.
Mach 6 can actually be controlled between 500-800 degrees at near space altitude (due to thin atmospheric density). If it is 8 Mach, this temperature range is the actual control temperature of 900-1200 degrees. The higher the speed, the higher the average temperature.