Open Top Track

If the rotor is exposed to high altitude air at 300K and ambient pressure, the air molecules will collide with the rotor surface and leave rotor velocity (WAG). They will collide with other molecules and heat them, creating a moving current of hot thin air that follows the rotor. Because they are very hot, maintaining ambient pressure with the surrounding air is accomplished at much lower density.

Assuming 100 km altitude: 200K, 32 mPa, 5.6e-7 kg/m³, N2 atmosphere. Molecular weight is 28, or 28×1.66e-27 = 4.65e-26 kg. 1.5kT = 1.5×200×1.38e-23 = 4.14e-21 J, so V_th_ = sqrt(2 * 4.14e-21 / 4.65e-26) = 300 m/s . Heated, ionized nitrogen with an atomic mass of 2.32e-26 kg and a thermal velocity of 14,000 m/s (!!!) has an energy of 2.3e-18 J and a "temperature" of 165,000 Kelvins and so is 550 times less dense as ambient air at the same pressure, about 60 μPa .