A testing facility that relies on rapid release of stored energy

Energy

In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 to generate a short period of high enthalpy

Enthalpy

Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...

 test conditions for testing of aerodynamic flow, aerodynamic heating and atmospheric reentry

Atmospheric reentry

Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...

, combustion

Combustion

Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

, chemical kinetics

Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...

, ballistics

Ballistics

Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

, and other effects. The rapid release of energy can result in very high instantaneous energy release rates even though the total energy released is modest. This effect also produces short test times, however, with some types of tests in these facilities lasting less than 100 microsecond

Microsecond

A microsecond is an SI unit of time equal to one millionth of a second. Its symbol is µs.A microsecond is equal to 1000 nanoseconds or 1/1000 millisecond...

s. Impulse facilities are a special case of blow down facilities

Blow down facility

A blow down facility is a testing facility that relies on charging an energy reservoir and releasing the energy over a relatively short time to produce test conditions at higher energy release rates than can be maintained continuously...

 where an energy storage mechanism is charged over a period of time and then released to initiate a test and must be charged again before the next test. This contrasts with continuous facilities

Continuous facility

A continuous facility is a type of testing facility that produces test conditions that can be maintained indefinitely, such as certain types of wind tunnels. In contrast to continuous facilities are blow down facilities that operate only in short bursts at conditions that cannot be maintained...

 such as wind tunnel

Wind tunnel

A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...

s that may run continuously. Examples of impulse facilities are the shock tube

Shock tube

For the pyrotechnic initiator, see Shock tube detonatorThe shock tube is an instrument used to replicate and direct blast waves at a sensor or a model in order to simulate actual explosions and their effects, usually on a smaller scale...

, the shock tunnel

Shock tunnel

Expansion and shock tunnels are aerodynamic testing facilities with a specific interest in high speeds and high temperature testing. Shock tunnels use steady flow nozzle expansion whereas expansion tunnels use unsteady expansion with higher enthalpy, or thermal energy. In both cases the gases are...

, the expansion tube

Expansion tube

An expansion tube is a type of impulse facility that is conceptually similar to a shock tube with a secondary diaphragm, an expansion section, a test section, and a dump tank where the endwall would be located in a shock tube. It is typically used to produce high enthalpy flows for high speed...

, the expansion tunnel

Expansion tunnel

Expansion and shock tunnels are aerodynamic testing facilities with a specific interest in high speeds and high temperature testing. Shock tunnels use steady flow nozzle expansion whereas expansion tunnels use unsteady expansion with higher enthalpy, or thermal energy. In both cases the gases are...

, and the Ludwieg tube

Ludwieg tube

A Ludwieg tube is a cheap and efficient way of producing supersonic flow. Mach numbers up to 4 are easily obtained without any additional heating of the flow. With heating, Mach numbers of up to 11 can be reached.-Principle:...

.