Hypervelocity is very high

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...

, approximately over 3,000

meters per second The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...

(6,700 mph, 11,000 km/h, 10,000 ft/s, or Mach 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 idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...

l stresses. Thus,

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

s and

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...

s behave alike under hypervelocity impact. Extreme hypervelocity results in

vaporization Vaporization (or vaporisation) 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 phenomen ...

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 solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

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 the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...

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

space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by robotic spacec ...

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, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...

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 in ...

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

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

or missile. The impactor, as well as the surface it hits, can undergo temporary

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the ...

. The impact process can generate

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

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 extre ...

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

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

and

Luna Luna commonly refers to: * Earth's Moon, named "Luna" in Latin * Luna (goddess), the ancient Roman personification of the Moon Luna may also refer to: Places Philippines * Luna, Apayao * Luna, Isabela * Luna, La Union * Luna, San Jose Roma ...

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 a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically ...

). Given the rarity of such observation opportunities since the 1970s, the

Genesis Genesis may refer to: Bible * Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind * Genesis creation narrative, the first several chapters of the Book of ...

and Stardust Sample Return Capsule (SRC) reentries as well as the recent

Hayabusa was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. ''Hayabusa'', formerly known as MUSES-C ...

SRC reentry have spawned observation campaigns, most notably at NASA's

Ames Research Center The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) laborat ...

. Hypervelocity

collision In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...

s can be studied by examining the results of naturally occurring collisions (between

micrometeorites A micrometeorite is a micrometeoroid that has survived atmospheric entry, entry through the atmosphere of Earth, Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more a ...

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 The light-gas gun is an apparatus for physics experiments. It is a highly specialized gun designed to generate extremely high velocities. It is usually used to study high-speed impact phenomena (hypervelocity research), such as the formation of ...

, but some experiments have used

linear motor A linear motor is an electric motor that has had its stator and rotor "unrolled", thus, instead of producing a torque (rotation), it produces a linear force along its length. However, linear motors are not necessarily straight. Characteristicall ...

s to accelerate projectiles to hypervelocity. The properties of metals under hypervelocity have been integrated with weapons, such as

explosively formed penetrator An explosively formed penetrator (EFP), also known as an explosively formed projectile (EFP), a self-forging warhead, or a self-forging fragment, is the product of a shaped charge designed to penetrate armor effectively. As the name suggests, the ...

. The vaporization upon impact and liquefaction 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 agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

studies the effects of simulated orbital debris at the

White Sands Test Facility White Sands Test Facility (WSTF) is a U.S. government rocket engine test facility and a resource for testing and evaluating potentially hazardous materials, space flight components, and rocket propulsion systems. NASA established WSTF on the Whi ...

Remote Hypervelocity Test Laboratory (RHTL). Objects smaller than a softball 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 "micrometeoroid ...

and

orbital debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecr ...

(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 0.05 mm to 22.2 mm diameter projectiles to velocities as fast as 8.5 km/s.

Hypervelocity reentry events

Other definitions of hypervelocity

According to the

United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...

, ''hypervelocity'' can also refer to the

muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...

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 designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes c ...

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 good battlefield mobility provided by tracks and a powerful engin ...

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 dur ...

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 is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during siege ...

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

References

{{Doomsday Physical quantities Velocity Spaceflight concepts Space hazards Materials science Collision

Overview

Hypervelocity reentry events

Other definitions of hypervelocity

See also

References