3
$\begingroup$

Always when reentering the atmosphere, the shuttle was pitched up, right? When gliding through the mesosphere, how was it that it didn't fly up again then? Was it due to a certain distribution of weight within the orbiter?

$\endgroup$
10
  • $\begingroup$ Pitch and direction of flight are not related. Note that every airliner lands while being pitched upwards. In general, the nose of a plane never points down (exceptions apply)! $\endgroup$ – asdfex Jan 13 at 11:12
  • $\begingroup$ @asdfex well, they are related, but not simply. Angle of attack, airspeed, air density all matter. $\endgroup$ – SF. Jan 13 at 11:47
  • 2
    $\begingroup$ The space shuttle did not so much as fly as do a Buzz Liteyear "Fall with style". $\endgroup$ – geoffc Jan 13 at 12:08
  • $\begingroup$ @asdfex This is because they're slow when landing. By flying a too heavy airliner too slow it's almost like a controlled stall that is applied for landing an airliner. But the shuttle glides at quite the highest speeds possible in the mesosphere. $\endgroup$ – Greenhorn Jan 13 at 12:21
  • $\begingroup$ What do you think would have made it "fly up"? $\endgroup$ – Organic Marble Jan 13 at 14:15
1
$\begingroup$

Mesosphere stretches roughly from Kármán line (air pressure 0.0000003atm) down to about 50km altitude (air pressure: 0.001 atm) - in technology these amounts of air are typically thought of as "vacuum".

That means even despite the hypersonic speed, the lift generated by such minuscule amounts of air is very low. Additionally, it flew at an excessive angle of attack - about 40 degrees. The effect of that is drag force being roughly the same as the lift force, so the shuttle would rapidly lose speed, and in effect any chance to generate more lift through moving through denser air was lost, as loss of speed was kept at pace with growth of air density.

In short, it never reached air sufficiently dense at speed sufficiently high to produce enough lift to make it rise.

$\endgroup$
17
  • $\begingroup$ So it's the excessive angle of attack. I see. But the mesosphere's lower boundary isn't the Armstrong line (at 19 km / 12 mi) but the stratopause at 50 km / 31 mi. You probably meant 'mesospace'. $\endgroup$ – Greenhorn Jan 13 at 13:07
  • $\begingroup$ @Greenhorn corrected. Eh, confusing feet with meters, reading things off wrong paragraph on the wikipedia... I'm too tired today. $\endgroup$ – SF. Jan 13 at 13:51
  • $\begingroup$ Why do you call the AOA "excessive"? $\endgroup$ – Organic Marble Jan 13 at 14:25
  • $\begingroup$ @OrganicMarble Know of any airplanes or such using this sort of AOA in normal use? I don't recall more than 30 degrees is ever in use outside of dogfight and aerobation (and occasionally, moments before a disaster). $\endgroup$ – SF. Jan 13 at 14:51
  • 1
    $\begingroup$ @OrganicMarble yikes, even worse! That's a factor of 27, goodness. $\endgroup$ – uhoh Jan 13 at 23:37

Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.