3
$\begingroup$

Using the Rayleigh drag equation, and approximations for the air density, drag and frontal area of the pilot, and mass, at around 300 m/s (subsonic) a pilot might experience deceleration forces of about 40G. BTW, I assumed a drag coefficient of 1 since a Human being strapped to a chair is not especially aerodynamically slippery.

Now, if that was raised by another 100 m/s making it supersonic, how much would the force increase disproportionately?

Note that one person has ejected at low altitude supersonic and lived - just. So, how much of a difference does being on the wrong side of that dividing line make?

$\endgroup$
  • 1
    $\begingroup$ That would be one heck of a head rush! That guy is remarkably luck to be alive. $\endgroup$ – user77400 Apr 17 '15 at 8:55
  • 1
    $\begingroup$ I would have expected his head to be twisted to one side so fast as to break his neck $\endgroup$ – user56903 Apr 17 '15 at 8:56
  • 1
    $\begingroup$ Absolutely! I wonder if a suit to withstand these forces, and the forces described in your question could be possible $\endgroup$ – user77400 Apr 17 '15 at 8:58
  • $\begingroup$ Precisely! at supersonic speed its a wonder he haven't burn up during re-entry. $\endgroup$ – user6760 Apr 17 '15 at 9:11
1
$\begingroup$

There are lots of papers reporting measurements of the drag coefficient of a sphere below and above supersonic speeds. Glancing through them, it appears the drag coefficient does increase as the speed goes supersonic, but by relatively modest amounts.

Obviously a pilot isn't a sphere, and the airflow will be affected by the presence of the plane, so I think we can at best guesstimate the drag. My guesstimate would be no dramatic increase in force with speed as the airflow goes supersonic.

$\endgroup$
1
$\begingroup$

The acceleration needs to be provided here to conclude the net force on the pilot. Zero g: it shows free fall. Let me elaborate simply : Weight= Mass × g force Now in your case if the pilot goes to 400m/s in 10 seconds from a standstill, he will experience( i deem he'll feel it more than he experiences it :)) his weight FOUR the times as against whilst he ain't driving. Moreover, g force, the name seemed misleading to me, it shows the acceleration, instead of the force. g-force=force AGAINST gravity. A book resting on table, g-force=1g, UPWARDS. The example i presented, g-force=5g(assuming the pilot goes straight upwards).

$\endgroup$
  • $\begingroup$ The calculation I did provided a ballpark figure for the instantaneous maximum force he would feel upon ejection. That would obviously reduce quite rapidly $\endgroup$ – user56903 Apr 17 '15 at 14:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy