The pressurised volume of Tiangong-1 and 2 is said to be 15 cubic metres. Contrast to the space shuttle at 74 cubic metres, and Skylab at 350 cubic metres. They

The pressurised volume of Tiangong-1 and 2 is said to be 15 cubic metres. Contrast to the space shuttle at 74 cubic metres, and Skylab at 350 cubic metres. They're a sixth the size of any space station to have flown previously. Both were also only occupied for about 20 days, not far off the longest space shuttle missions. I think it makes sense to look at them more as orbital testbeds than space stations as such.