The term Transonic refers to a range of velocities just below and above the local speed of sound ( generally taken as Mach 0. 8 – 1. 2 ).

It is defined as the range of speeds between the critical Mach number, when some parts of the airflow over an aircraft become supersonic, and a higher speed, typically near Mach 1. 2, when all of the airflow is supersonic.

A smokeless, solid-propellant, booster-sustainer rocket motor propels the missile at speeds over Mach 2.

The Mach 2 Tu-160 ' Blackjack ' was built only in tiny numbers, leaving the 1950s Tupolev Tu-16 and Tu-95 ' Bear ' heavy bombers to continue being used into the 21st century.

* Speed: Mach 2. 3

The sound barrier was broken, and after a few false starts due to required changes in controls, speeds quickly reached Mach 2 — past which aircraft can't maneuver to avoid attack.

The BrahMos cruise missile which is a joint venture between India and Russia, is the fastest cruise missile in the world with a top speed of Mach 2. 8-3.

* 1970 – The Soviet Tupolev Tu-144 becomes the first commercial transport to exceed Mach 2.

Because the Mach number is often viewed as a dimensionless quantity rather than a unit of measure, with Mach, the number comes after the unit ; the second Mach number is " Mach 2 " instead of " 2 Mach " ( or Machs ).

Mach received a major boost in visibility when the Open Software Foundation ( OSF ) announced they would be hosting future versions of OSF / 1 on Mach 2. 5, and were investigating Mach 3 as well.

When Mach was first being seriously used in the 2. x versions, performance was slower than traditional monolithic operating systems, perhaps as much as 25 %.

For instance, the L4 kernel ( version 2 ) includes only seven system calls and uses 12k of memory, whereas Mach 3 includes about 140 functions and uses about 330k of memory.

Aerodynamicists disagree over the precise definition of hypersonic flow ; minimum Mach numbers for hypersonic flow range from 3 to 12.

The ratio of the flow speed to the speed of sound was named the Mach number after Ernst Mach, who was one of the first to investigate the properties of supersonic flow which included Schlieren photography techniques to visualize the changes in density.

Theodore von Kármán and Hugh Latimer Dryden introduced the term transonic to describe flow speeds around Mach 1 where drag increases rapidly.

Because of the increase in drag approaching Mach 1, aerodynamicists and aviators disagreed on whether supersonic flight was achievable.

Image showing shock waves from NASA's X-43A hypersonic research vehicle in flight at Mach 7, generated using a computational fluid dynamics algorithm. On September 30, 1935 an exclusive conference was held in Rome with the topic of high velocity flight and the possibility of breaking the sound barrier.

The Mach number is used to evaluate whether the incompressibility can be assumed or the flow must be solved as compressible.

In air, compressibility effects are usually ignored when the Mach number in the flow does not exceed 0. 3 ( about 335 feet ( 102m ) per second or 228 miles ( 366 km ) per hour at 60 ° F ).

In general, this is the case where the Mach number in part or all of the flow exceeds 0. 3.

The Mach. 3 value is rather arbitrary, but it is used because gas flows with a Mach number below that value demonstrate changes in density with respect to the change in pressure of less than 5 %.

Thus, when the fluid finally does strike the object, it is forced to change its properties -- temperature, density, pressure, and Mach number -- in an extremely violent and irreversible fashion called a shock wave.

In the 1970s, the term generally came to refer to speeds of Mach 5 ( 5 times the speed of sound ) and above.

The Phoenix has several guidance modes and achieves its longest range by using mid-course updates from the F-14A / B AWG-9 radar ( APG-71 radar in the F-14D ) as it climbs to cruise between and at close to Mach 5.

Similarly, the Soviet Union used the intermediate-range Tu-22M ' Backfire ' in the 1970s, but their Mach 3 bomber project came to naught.

Avro proposed that Blue Steel would evolve over time, subsequent versions increasing speed ( to Mach 4. 5 ) and range.

On launch the rocket engine's first chamber developing thrust would power the missile along a predetermined course to the target at around Mach 1. 5.

The engine was intended to switch from jet propulsion to pure rocket propulsion at 26 – 32 km high, by which time the craft would be travelling at Mach 5 to 7.

The CD also contained videos for " Lump ," " Peaches ," " Mach 5 ," and " Dune Buggy.

For example, from the equation, with an of 0. 7, a rocket flying at Mach 0. 85 ( which most aircraft cruise at ) with an exhaust velocity of Mach 10, would have a predicted overall energy efficiency of 5. 9 %, whereas a conventional, modern, air-breathing jet engine achieves closer to 35 % efficiency.

* While at lower speeds, air-breathing engines are very efficient, the efficiency ( Isp ) and thrust levels of air-breathing jet engines drop considerably at high speed ( above Mach 5 – 10 depending on the engine ) and begin to approach that of rocket engines or worse.

On the other hand LACE-like precooled airbreathing designs such as the Skylon spaceplane ( and ATREX ) which transition to rocket thrust at rather lower speeds ( Mach 5. 5 ) do seem to give, on paper at least, an improved orbital mass fraction over pure rockets ( even multistage rockets ) sufficiently to hold out the possibility of full reusability with better payload fraction.

A rocket sled holds the land-based speed record for a vehicle, at Mach 8. 5.

The vehicle that achieved Mach 8. 5

A world speed record of Mach 8. 5 ( 6, 416 mph / 10, 325 km / h ) was achieved by a four-stage rocket sled at Holloman Air Force Base on, 2003.

" Former NASA sonic boom expert Dom Maglieri studied the 15-year old sonic boom data from the California Institute of Technology and has deemed that the data showed " something at 90, 000 ft ( c. 27. 4 km ), Mach 4 to Mach 5. 2 ".

Simulation of hypersonic speed ( Mach 5 )

Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above.

A contrasting position was taken by Ernst Mach, who contended that all motion was relative.

It was designed to fly below the enemy's radar at speeds above Mach 3 and carry a number of hydrogen bombs that it would drop on its path over enemy territory.

Work on this was delayed for three years due to uncertainty over whether CMU would release the Mach code under a suitable license.

From early on, the Hurd was developed to use GNU Mach as the microkernel.

However, some scientists ( called " relativists " by Mach ), even at the time of Newton, felt that absolute space was a defect of the formulation, and should be replaced.

Mach argued, beginning in the 1880s with The Science of Mechanics ( 1883 ), that the mind had a fundamental structure, and that subjective experience was based on the interplay of parts of the mind.

As a philosopher of science Ernst Mach was a major influence on logical positivism, and through his criticism of Isaac Newton, a forerunner of Einstein's theory of relativity.

Although the existence of molecules has been accepted by many chemists since the early 19th century as a result of Dalton's laws of Definite and Multiple Proportions ( 1803 – 1808 ) and Avogadro's law ( 1811 ), there was some resistance among positivists and physicists such as Mach, Boltzmann, Maxwell, and Gibbs, who saw molecules merely as convenient mathematical constructs.

The first microkernels, notably Mach, proved to have disappointing performance, but the inherent advantages appeared so great that it was a major line of research into the late 1990s.

It was a sardonic response to Mach, which claimed to be a microkernel while being monolithic, essentially unstructured, and slower than the systems it sought to replace.

This is somewhat reminiscent of the early modern ocean sounding unit " mark " ( a synonym for fathom ), which was also unit-first, and may have influenced the use of the term Mach.

The project at Carnegie Mellon ran from 1985 to 1994, ending in apparent failure with Mach 3. 0, which was finally a true microkernel.

Mach was developed as a replacement for the kernel in the BSD version of UNIX, so no new operating system would have to be designed around it.

The Mach virtual memory management system was also adopted by the BSD developers at CSRG, and appears in modern BSD-derived UNIX systems, such as FreeBSD.

Another of the original Mach developers, Avie Tevanian, was formerly head of software at NeXT, then Chief Software Technology Officer at Apple Computer until March 2006.