0
$\begingroup$

as you know the transonic phase is often associate with the bang. The principal cons of the transonic phase is the noise,it's why there is not supersonic passenger aircraft( cause the end of the concorde).Nasa (x59) and Boom(xb-1) do research to reduce this noise at door slam.

How is it possible? I know that we need a aerodynamic plane respecting the aera rule and have a thin fuselage. Have you" wind tunnel" images?or theorical explications?

x-59

Edit: for those who want i found more information about the bang on this vidéo. (2:35 to 4:45)

$\endgroup$
  • 2
    $\begingroup$ Beautiful picture! $\endgroup$ – Super Apr 2 at 17:20
  • $\begingroup$ Transonic flight produces only localised shockwaves, the boom only occurs once true supersonic flight is achieved. $\endgroup$ – Guy Inchbald Apr 2 at 17:49
  • 1
    $\begingroup$ Related: Is there a boomless sonic technology in any state at this time? $\endgroup$ – fooot Apr 2 at 19:31
  • $\begingroup$ The noise is hardly the principal reason for the lack of supersonic passenger aircraft. The primary reason is cost: there aren't all that many people willing (or able!) to pay ~30 times as much as a subsonic plane to save a few hours. For instance, Google suggests that the Concorde's trans-Atlantic flights averaged only half full... $\endgroup$ – jamesqf Apr 2 at 19:32
4
$\begingroup$

Most supersonic aircraft have points where the cross-section suddenly changes, such as the fuselage nose, the wing root leading edge or the wing trailing edge. The points of sudden change produce sharp changes in air pressure, i.e. loud sonic booms. Concorde was one example.

By designing the plane's cross-section to vary smoothly from end to end, the handful of points of major change are replaced by many more points of minor change. The booms are thus reduced in loudness and spread out in time, making them less intrusive.

Other factors which help include overall aerodynamic efficiency, light weight and high cruise altitude. A small, carefully-profiled and aerodynamically modern high-flying aircraft can thus be a lot quieter.

| improve this answer | |
$\endgroup$
  • 1
    $\begingroup$ These changes help in mitigating the local shocks for drag purposes, but all supersonic vehicles experience oblique shock that produce bang when hitting the ground; how is that reduced/removed? $\endgroup$ – JZYL Apr 3 at 12:10
  • $\begingroup$ @JZYL At supersonic speeds the local shocks tend to extend and coalesce into a smaller number of travelling oblique shocks. By mitigating the local shocks one can also mitigate the travelling shocks. The bang cannot be wholly prevented as long as aerodynamic lift is required, but it can be made less intrusive. $\endgroup$ – Guy Inchbald Apr 3 at 16:25
0
$\begingroup$

If you are not afraid of UFOs, you can check MHD principles and plasmas. The idea is to interact with the ambient fluid to improve the flow, thus reducing the shockwave

Real results are very limited and it requires too much power to be airworthy.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Can you explain mhd please $\endgroup$ – L'aviateur Apr 6 at 8:45
  • $\begingroup$ If the fluid can be turned into a plasma - ionized gas, then the mhd (magneto-hydro-dyanmic) drive can generate a magnetic field to interact with it. It is reported as "impractical" as a boat engine in 1965 on wikipedia. However there are more recent studies done by China's University regarding modern jets physics but I don't know the outcome. $\endgroup$ – Alsushi Apr 6 at 11:51
  • $\begingroup$ So you say that to reduce noise we can(maybe) turn fluid in ionized gaz ?how this have a impact on the sound? What is the caracteristics of ionized gaz better than normal air? $\endgroup$ – L'aviateur Apr 6 at 13:04
  • $\begingroup$ Speaking as a sometime electromagnetics engineer working on plasma generation and control, I do not see how MHD can help greatly. Technically one might be able to use it to smooth out the airflow - if you can stop the plasma corroding the airframe, which is in fact your biggest theoretical challenge. Reprofiling the airframe is a lot easier. $\endgroup$ – Guy Inchbald Apr 6 at 15:49

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.