Refer the answer for this question How strong and "hot" is the wind on the payload after the fairing is deployed at ~110km?

It is clear that the fairings are separated when the free molecular aero-thermal flux is less than 1135 W/m2, which usually happens at an altitude of around 110 km.

If the separation is event based, how are they measuring the flux? Else, the separation is timed for the altitudes?

  • $\begingroup$ It's not necessarily either-or. Possibilities for knowing the altitude can also include rocket-based GPS receivers and on-board inertial guidance system. $\endgroup$
    – uhoh
    Jan 28, 2019 at 14:00
  • $\begingroup$ @uhoh, So the separations are happening with respect to altitude? $\endgroup$
    – Vasanth C
    Jan 28, 2019 at 14:16
  • $\begingroup$ You listed two possibilities, A or B, I listed two more and these happen to be related to altitude. I would guess that they check the solar activity, make a prediction on the temperature of the upper atmosphere, and calculate the altitude necessary to get to 1135 on launch day, then use that altitude. But it could be a fixed altitude as well. There might be some jitter depending on other parameters as well; let's see what answers people post. $\endgroup$
    – uhoh
    Jan 28, 2019 at 14:31
  • $\begingroup$ I would be surprised if it's not a simple timer. $\endgroup$ Jan 29, 2019 at 1:47


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