3
$\begingroup$

What are the effects on the speed of the plane, does it effects the body of the plane, and do shockwaves cause major damage to the plane.

I know that flying at Mach 1 is really risky, but what's the actual effect of the shockwave?

$\endgroup$
1
$\begingroup$

Not much, really, the shock wave just streams off of the nose of the plane, and an anti-shock from the tail. They stream away from the plane and don't hit it.

enter image description hereImage source

The shock itself is the compression that the flying aeroplane imparts upon the unsuspecting air in front of it: disturbances travel with the speed of sound, if the aeroplane travels faster there is no warning and air gets compressed suddenly when the aeroplane arrives. This is the nature of the shock.

The amount of compression is spread out It's not a shock like a bomb explodes, only a loud noise. Flying over Mach 1 is not inherently more risky than flying subsonic. When first attempted 70 years ago there was some unexpected behaviour to iron out, but that's aviation in a nutshell for you. Once understood, a problem is only an invitation to find a solution, and that is what the aero guys did.

$\endgroup$
1
$\begingroup$
  • Wave drag and Maximum Velocity Limitations

A shockwave can limit the maximum speed of an aircraft as for each airfoil there is a critical Mach value $M_{crit}$ which is associated with the onset of a sharp rise of the drag coefficient $c_d$. This is due to the wave drag which increases as the shock grows stronger.

For this reason, in order to obtain a higher $M_{crit}$ value (i.e. increase maximum speed for same power or have the same speed for less fuel consumption) supercritical airfoils are used for transport aircrafts which employ a rather flat upper surface to delay and attenuate shock.

An other indirect effect on speed for supersonic transport aircrafts is noise regulations. For example, in the years of Concord there were incidents of broken windows near the airport, leave aside the sonic booms (have you ever heard a combat aircraft during a low-pass?). For this reason, much research is being conducted for "Low Boom" optimized supersonic aircrafts.

  • Transonic Buffet

When shockwave-induced flow separation happens, a flow instability may appear which is called shock buffet. This involves an oscillatory move of the shock (back and forward) accompanied with an oscillation of pressure forces on the wing which will cause vibrations to the whole body of the aircraft. This is common in fighter aircrafts in maneuvering and in early stages it can warn the pilot that he/she is approaching stall. Usually pilots are aware of the flight envelope and within it, these vibrations are not likely to cause any harm to the structure (outside of the envelope many things can happen but loss of stability and control is more likely than a major structural failure). In either case, oscillatory loads are linked to structural fatigue, and this is another issue.

Transonic Buffet Cycle See publication

$\endgroup$
  • 1
    $\begingroup$ “in the years of Concord there were incidents of broken windows near the airport”—there are broken windows all the time and I am sure there were some near airports where Concorde was operated, but none of them were related to the Concorde operation. While it is possible for sonic boom to break windows, it takes the jet flying 200 ft away while Concorde only went supersonic around 25,000 ft and already over the ocean. $\endgroup$ – Jan Hudec Oct 14 '17 at 10:38
  • $\begingroup$ @Jan Hudec Let the broken windows aside, the point is not the broken windows, the point is that supersonic transport aircrafts produce a sonic boom that according to noise regulations must be attenuated. Even at 25.000 ft this sonic boom produces a loud noise on the land. $\endgroup$ – ares Oct 14 '17 at 20:56
  • 1
    $\begingroup$ Yes, it is definitely audible, and pretty annoying, from that altitude. And not only from that altitude. It is actually audible on the ground from any altitude. That is why supersonic flight is not permitted over settled land at all. Still, the talk about windows is (without further evidence) likely false and should not be mentioned. $\endgroup$ – Jan Hudec Oct 16 '17 at 13:12

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.