Sonic booms kaouri-2015
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A popularised talk on sonic booms-suitable for the public but also as school lesson material. Note: This talk (and similar versions of it) have been delivered several times to diverse audiences since 2004
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Sonic booms kaouri-2015
- 1. 1 Sonic Booms Dr Katerina Kaouri
- 2. Outline • Supersonic aircraft • Sonic Booms • Where do sonic booms land? • How loud are sonic booms?
- 3. F-14 breaking the sound barrier What do you hear?
- 4. 4 •What is a Sonic boom? Sound created by an object traveling faster than sound • Thunder-like sound Concorde: Mach 2
- 5. Basics of Sound • Sound needs material (e.g. air) in order to travel • Sound travels at 340m/s (1200Km/h) in the air - One million times slower than light (We see lightnings and then hear their sound) • Sound travels along rays (similar to light rays) Almost everything around us produces sound
- 6. 7 Still sourceStill source Still source Wavefronts are circles -they all grow at the speed of sound
- 7. Moving source: Mach number Mach numberMach number =ratio of aircraft speed to sound speed •Subsonic aircraft: Mach < 1 •Supersonic aircraft: Mach > 1 (Concorde: Mach 2)Ernst Mach, 1838-1916
- 8. 9 Subsonic source Supersonic source Sound source movesSound source moves Wavefronts are nested Wavefronts overlap and form Mach wedge
- 10. Hyperbol a In this way we can calculate the area affected by sonic booms In 3D: The Mach cone cuts the ground Boom carpet
- 11. How loud are sonic booms? N-wave The N-wave is continuously emitted from a supersonic aircrqaft -Like we are throwing stones out of a car continuously -It is heard as a single boom by human ears overpressure recovery •Pressure signature Overpressure From aircraft nose Underpressure from aircraft tail
- 12. A supersonic car also produces sonic booms Mach Cone •Name: ThrustSSC •World's first Supersonic land speed Record (1km in 2.9s) •Where: Blackrock Desert, Nevada •When: 15th October 1997 •Who: Andy Green (driver), Ron Ayers (engineer)
- 13. Sonic booms in nature • Thunders • Volcanoes (Kracatoa, 1883) • Meteorites falling to Earth
- 14. 15 “It was the sonic boom that caused the destruction – not the actual landing of the meteorite.” M. Grady, Professor of Planetary Science Meteorite falling in Russia! Meteorite: Mach 50 Meteorite FallMeteorite Fall Russia 15 Feb, 2013
- 15. Do the following produce sonic booms? Space Shuttles Bullets Bullwhips
Editor's Notes
- Aircraft vs nature shock waves
- Lockheed SR-71 &quot;Blackbird&quot; a record holding reconnaissance aircraft. 32 were built in secret at Lockheed&apos;s &quot;Skunk Works&quot;. The first was delivered to SAC in 1964. A few are believed to have been re-activated and stand in ready storage. The Tupolev Tu-144 was definitely the Sovjet Unions least fortunate commercial aviation project. It was built as a competitor to the British and French Concorde supersonic jetliner. The Sovjet Aerospace industry therefore hoped that the Tu-144 would catapult it into a leading position. The whole program suffered a first almost fatal blow when one of the aircraft crashed in front of press and TV-cameras during a presentation at the Paris Air Show 1973. Although it seems today that the reason of the crash was a clear handling error of the flight crew, the fatal headlines, combined with other technical concerns such as a much higher fuel burn than anticipated that cut the range to unattractive figures, raised concern about the type&apos;s future. After several modifications, the type was nevertheless put into service on mail flights - which must have been the world&apos;s costliest air mail operation ever - between Alma Ata and Moscow in 1975 in order to collect data and establish safe operating procedures. A second crash that occured shortly after the type had been put into passenger service in 1977 brought the ambitious project to a fall. The last commericial service operated by a Tu-144 took place on June 1, 1978. While several Tu-144 were donated to museums in Moscow Monino, Samara and Ulyanovsk, at least four Tu-144 remained in open storage in Moscow Zhukovsky. In 1995, one of them was reactivated for a series of test flights operated jointly by Russia and the United States.
- Question: About sources of light
- How to put a realistic line around Mach number definition?
- The image is a schlieren picture showing an attached bow shock and a few waves coming from unseen obstacles. These waves are seen to be slowly catching up with the bow shock.
- Should have mentioned primary booms already-make sure!
- A sonic boom is a type of “shock wave” that you get when the sound waves generated by the plane add together to make a really abrupt sound wave. The V-shaped wake behind a boat is very similar to a sonic boom. The boat moves faster than the waves on the surface of the water do - this is just like the plane travelling faster than the speed of sound. If you look carefully at the wake of the boat on the water, you’ll see that there are usually two separate V-shaped wakes - one from the tip of the boat and one from the tail. In the same way, most planes travelling faster than sound will give off two sonic booms, one from the nose and the other from the tail. It looks a little bit like the letter N - a sudden rise in pressure, then a drop down to less than the local air pressure, and then a recovery back to the normal air pressure. So this is called the N-wave. And the twin sonic booms that you hear are the overpressure from the nose of the plane, and the underpressure from the tail of the plane.
- Questions: Are craters in Mars related to this? Note: This eruption of Guagua Pichincha volcano, at whose foot Quito is located took place on October 7th, 1999 (Ecuador). What is a volcano anyway? Volcanoes are fissures in the earth&apos;s crust through which the earth&apos;s magma reaches the surface. Volcanoes form a cone by way of depositions of solid and molten rocks (lava) ejected or flowing from the earth&apos;s inside through a chimney and then exiting from its crater opening. You could also imagine the volcanoes being safety valves of the earth&apos;s hot interior permitting extra pressure of gases and materials to escape.What makes a volcano work?Plate Tectonics (or the movement of the earth&apos;s major plates) are the driving force behind volcanoes and earthquakes, which go hand in hand. Two major interrelated belts, which divide earth&apos;s surface into 12 major crustal plates are found and responsible for most quakes and volcanic eruptions. One, the Mid-Ocean Ridge, runs through the Atlantic and Indian oceans and is an area, where plates move away from each other. The other one, called Ring of Fire (see map) circles the Pacific Ocean and there the plates converge or subduct (see map). The Andes Mountains were folded upwards by this subducting of the plates and therefore is a major region of volcanic activities. Ecuador, being part of this ring, boasts therefore of many volcanoes in different stages of activities in the Andes (see map).