Hypervelocity is very high

velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

, approximately over 3,000 meters per second (11,000 km/h, 6,700 mph, 10,000 ft/s, or

Mach The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a Boundary (thermodynamic), boundary to the local speed of sound. It is named after the Austrian physi ...

8.8). In particular, hypervelocity is velocity so high that the strength of materials upon impact is very small compared to

inertia Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...

l stresses. Thus,

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

s and

fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

s behave alike under hypervelocity impact. An impact under extreme hypervelocity results in

vaporization Vaporization (or vapo(u)risation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenome ...

of the impactor and target. For structural metals, hypervelocity is generally considered to be over 2,500 m/s (5,600 mph, 9,000 km/h, 8,200 ft/s, or Mach 7.3).

Meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

craters are also examples of hypervelocity impacts.

Overview

The term "hypervelocity" refers to velocities in the range from a few kilometers per

second The second (symbol: s) is a unit of time derived from the division of the day first into 24 hours, then to 60 minutes, and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of U ...

to some tens of kilometers per second. This is especially relevant in the field of

space exploration Space exploration is the process of utilizing astronomy and space technology to investigate outer space. While the exploration of space is currently carried out mainly by astronomers with telescopes, its physical exploration is conducted bo ...

and military use of space, where hypervelocity impacts (e.g. by

space debris Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...

or an attacking

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

) can result in anything from minor component degradation to the complete destruction of a

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

or missile. The impactor, as well as the surface it hits, can undergo temporary liquefaction. The impact process can generate plasma discharges, which can interfere with spacecraft electronics. Hypervelocity usually occurs during

meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at ext ...

s and deep space reentries, as carried out during the Zond,

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

and Luna programs. Given the intrinsic unpredictability of the timing and trajectories of meteors, space capsules are prime data gathering opportunities for the study of thermal protection materials at hypervelocity (in this context, hypervelocity is defined as greater than

escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for an object to escape from contact with or orbit of a primary body, assuming: * Ballistic trajectory – no other forces are acting on the object, such as ...

). Given the rarity of such observation opportunities since the 1970s, the '' Genesis'' and '' Stardust'' Sample Return Capsule (SRC) reentries as well as the recent '' Hayabusa'' SRC reentry have spawned observation campaigns, most notably at NASA's Ames Research Center. Hypervelocity collisions can be studied by examining the results of naturally occurring collisions (between micrometeorites and

, or between meteorites and planetary bodies), or they may be performed in laboratories. Currently, the primary tool for laboratory experiments is a light-gas gun, but some experiments have used linear motors to accelerate projectiles to hypervelocity. The properties of metals under hypervelocity have been integrated with weapons, such as explosively formed penetrator. The vaporization upon impact and liquification of surfaces allow metal projectiles formed under hypervelocity forces to penetrate vehicle armor better than conventional bullets.

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

studies the effects of simulated orbital debris at the White Sands Test Facility Remote Hypervelocity Test Laboratory (RHTL). Objects smaller than a

softball Softball is a Variations of baseball, variation of baseball, the difference being that it is played with a larger ball, on a smaller field, and with only underhand pitches (where the ball is released while the hand is primarily below the ball) ...

cannot be detected on radar. This has prompted spacecraft designers to develop shields to protect spacecraft from unavoidable collisions. At RHTL,

micrometeoroid A micrometeoroid is a tiny meteoroid: a small particle of rock in space, usually weighing less than a gram. A micrometeorite is such a particle that survives passage through Earth's atmosphere and reaches Earth's surface. The term "micrometeoro ...

and orbital debris (MMOD) impacts are simulated on spacecraft components and shields allowing designers to test threats posed by the growing orbital debris environment and evolve shield technology to stay one step ahead. At RHTL, four two-stage light-gas guns propel diameter projectiles to velocities as fast as .

Hypervelocity reentry events

Other definitions of hypervelocity

According to the

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

, ''hypervelocity'' can also refer to the muzzle velocity of a weapon system, with the exact definition dependent upon the weapon in question. When discussing

small arms A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions). The first firearms originate ...

a muzzle velocity of 5,000 ft/s (1524 m/s) or greater is considered hypervelocity, while for

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...

cannons A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during t ...

the muzzle velocity must meet or exceed 3,350 ft/s (1021.08 m/s) to be considered hypervelocity, and the threshold for

artillery Artillery consists of ranged weapons that launch Ammunition, munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during sieges, and l ...

cannons is 3,500 ft/s (1066.8 m/s).

References

{{Authority control Collision Materials science Physical quantities Space hazards Spaceflight concepts Velocity

Overview

Hypervelocity reentry events

Other definitions of hypervelocity

See also

References