Discovery and exploration of the Solar System

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Discovery_and_exploration_of_the_Solar_System 

 

The Sun and planets of the Solar System. Pluto and the other dwarf planets are not shown. The relative sizes of objects are drawn to scale; the distances between them are not.

 

A photo of Earth (circled) taken by Voyager 1, 6.4 billion kilometers (4 billion miles) away. The streaks of light are diffraction spikes radiating from the Sun (off frame to the left). This photograph is known as Pale Blue Dot.

Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth's "cosmic neighborhood". This includes the Sun, Earth and the Moon, the major planets Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, their satellites, as well as smaller bodies including comets, asteroids, and dust.

In ancient and medieval times, only the Sun, Moon, five classical planets and comets were visible to the naked eye, along with phenomena now known to take place in Earth's atmosphere, like meteors and aurora. Ancient astronomers were able to make geometric observations with various instruments. The collection of precise observations in the early modern period and the invention of the telescope helped determine the overall structure of the solar system and discover new planets and asteroids. Telescopic observations resulted in the discovery of more planets and asteroids and moons, and determination of the distances to some other stars. The composition of stars and planets was investigated with spectroscopy. Observations of Solar System bodies with other types of electromagnetic radiation became possible with radio astronomy, infrared astronomy, ultraviolet astronomy, X-ray astronomy, and gamma-ray astronomy.

Robotic space probes, the Apollo program landings of humans on the Moon, and space telescopes have vastly increased human knowledge about atmospheric, geologic, and electromagnetic phenomena on other planets, giving rise to the new field of planetary science.

The Solar System is one of many planetary systems in the galaxy. The planetary system that contains Earth is named the "Solar" System because the local star, the Sun, is named Sol, after the Latin word for Sun, "solis". Anything related to the Sun is called "solar"; for example, stellar wind from the Sun is called solar wind.

Pre-telescope

See also: Planet § History, History of astronomy, and Timeline of Solar System astronomy

 

Illustration of Anaximander's models of the universe. On the left, summer; on the right, winter.

The first humans had limited understanding of the celestial bodies that could be seen in the sky. The Sun, however, was of immediate interest, as it generates the day-night cycle. Even more, the dawn and sunset always take part at roughly the same points of the horizon, which helped to develop the cardinal directions. The Moon was another body of immediate interest, because of its higher visual size. The Lunar phases allowed to measure time in longer periods than those of days, and predict the duration of seasons.

Prehistoric beliefs about the structure of the universe were highly diverse, often rooted in religious cosmology, and many are unrecorded. Many associated the classical planets (those visible with the naked eye) with deities. Systematic astronomical observations were performed in many areas around the world, and started to inform cosmological knowledge. Early historic civilizations in Egypt, the Levant, pre-Socratic Greece, Mesopotamia, and Ancient China, recorded beliefs in a Flat Earth. Vedic texts proposed a number of shapes, including a wheel (flat) and a bag (concave). Ancient models were typically geocentric, putting the Earth at the center of the universe, though the Vedic texts likely promote a spherical earth, which they refer to as bhugol (or भूगोल in Hindi and Sanskrit), which literally translates to spherical land or earth. Some traditions in Chinese cosmology proposed a surface to which planets and the Sun and Moon were attached; another proposed they were free-floating.

One important discovery made at different times in different places is that the bright planet sometimes seen near the sunrise (called Phosphorus by the Greeks) and the bright planet sometimes seen near the sunset (called Hesperus by the Greeks) were actually the same planet, Venus.

Animation depicting Eudoxus' model of retrograde planetary motion. The two innermost homocentric spheres of his model are represented as rings here, each turning with the same period but in opposite directions, moving the planet along a figure-eight, or hippopede

 

The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and an equant (•).

Though unclear if motivated by empirical observations, the concept of a Spherical Earth apparently first gained intellectual dominance in the Pythagorean school in Ancient Greece in the 5th century BC. Meanwhile, the Pythagorean astronomical system proposed the Earth and Sun and a Counter-Earth rotate around an unseen "Central Fire". Influenced by Pythagoran thinking and Plato, philosophers Eudoxus, Callippus, and Aristotle all developed models of the solar system based on concentric spheres. These required more than one sphere per planet in order to account for the complicated curves they traced across the sky. Aristotelian physics used the Earth's place at the center of the universe along with the theory of classical elements to explain phenomena such as falling rocks and rising flames; objects in the sky were theorized to be composed of a unique element called Aether (classical element). A later model developed by Ptolemy attached smaller spheres to a smaller number of large spheres to explain the complex motions of the planets, a system known as deferent and epicycle. Published in the Almagest, this model of celestial spheres surrounding a spherical Earth was reasonably accurate and predictive, and became dominant among educated people in various cultures, spreading from Ancient Greece to Ancient Rome, Christian Europe, the Islamic world, South Asia, and China via inheritance and copying of texts, conquest, trade, and missionaries. It remained in widespread use until the 16th century.

Various astronomers, especially those who had access to more precise observations, were skeptical of the geocentric Ptolemaic model and proposed alternatives, including the heliocentric theory (now known to be correct) where the planets and the Earth orbit the Sun. Many proposals did not diffuse outside the local culture, or did not become locally dominant. Aristarchus of Samos had speculated about heliocentrism in Ancient Greece; in Al-Andalus, Arzachel proposed that Mercury orbits the Sun, and heliocentric astronomers worked in the Maragha school in Persia. Kerala-based astronomer Nilakantha Somayaji proposed a geoheliocentric systems, in which the planets circled the Sun while the Sun and Moon and stars orbiting the Earth. Polish astronomer Nicolaus Copernicus developed a system called Copernican heliocentrism, in which the planets and the Earth orbit the Sun, and the Moon orbits the Earth. Though the by-then-late Copernicus' theory was known to Danish astronomer Tycho Brahe, he did not accept it, and proposed his own geoheliocentric Tychonic system. Brahe undertook a substantial series of more accurate observations. German natural philosopher Johannes Kepler at first worked to combine Copernican system with Platonic solids in line with his interpretation of Christianity and an ancient musical resonance theory known as Musica universalis. After becoming an assistant for Brahe, Kepler inherited the observations and was directed to mathematically analyze the orbit of Mars. After many failed attempts, he eventually made the groundbreaking discovery that the planets moved around the Sun in ellipses. He formulated and published what are now known as Kepler's laws of planetary motion from 1609 to 1615. This became the dominant model among astronomers, though as with celestial sphere models, the physical mechanism by which this motion occurred was somewhat mysterious and theories abounded.

It took some time for the new theories to diffuse across the world. For example, with the Age of Discovery already well underway, astronomical thought in America was based on the older Greek theories, but newer western European ideas began to appear in writings by 1659.

Telescopic observations

See also: Timeline of discovery of Solar System planets and their moons

 

A replica of Isaac Newton's telescope.

Early telescopic discoveries

The invention of the telescope revolutionized astronomy, making it possible to see details about the Sun, Moon, and planets not available to the naked eye. It appeared around 1608 in the Netherlands, and was taken up by Kepler and many other astronomers.

Italian astronomer Galileo Galilei was an early user and made prolific discoveries, including the Phases of Venus, which definitively disproved the arrangement of spheres in the Ptolemaic system. Galileo discovered that the Moon was cratered, that the Sun was marked with sunspots, and that Jupiter had four satellites in orbit around it. Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn. Giovanni Domenico Cassini later discovered four more moons of Saturn and the Cassini division in Saturn's rings.

The Sun photographed through a telescope with special solar filter. Sunspots and limb darkening can be clearly seen. Mercury is transiting in the lower middle of the Sun's face.

Around 1677, Edmond Halley observed a transit of Mercury across the Sun, leading him to realise that observations of the solar parallax of a planet (more ideally using the transit of Venus) could be used to trigonometrically determine the distances between Earth, Venus, and the Sun. In 1705, Halley realised that repeated sightings of a comet were recording the same object, returning regularly once every 75–76 years. This was the first evidence that anything other than the planets orbited the Sun, though this had been theorized about comets in the 1st century by Seneca. Around 1704, the term "Solar System" first appeared in English.

Newtonian physics

English astronomer and mathematician Isaac Newton, incidentally building on recent scientific inquiries into the speed at which objects fall, was inspired by claims by rival Robert Hooke of a proof of Kepler's laws. Newton was able to explain the motions of the planets by hypothesizing a force of gravity acting between all solar system objects in proportion to their mass and an inverse-square law for distance - Newton's law of universal gravitation. Newton's 1687 Philosophiæ Naturalis Principia Mathematica explained this along with Newton's laws of motion, for the first time providing a unified explanation for astronomical and terrestrial phenomena. These concepts became the basis of classical mechanics, which enabled future advancements in many fields of physics.

Discovery of additional planets

The telescope made it possible for the first time to detect objects not visible to the naked eye. This took some time to accomplish, due to various logistical considerations such as the low magnification power of early equipment, the small area of the sky covered in any given observation, and the work involved in comparing multiple observations over different nights.

In 1781, William Herschel was looking for binary stars in the constellation of Taurus when he observed what he thought was a new comet. Its orbit revealed that it was a new planet, Uranus, the first ever discovered telescopically.

Giuseppe Piazzi discovered Ceres in 1801, a small world between Mars and Jupiter. It was considered another planet, but after subsequent discoveries of other small worlds in the same region, it and the others were eventually reclassified as asteroids.

By 1846, discrepancies in the orbit of Uranus led many to suspect a large planet must be tugging at it from farther out. Urbain Le Verrier's calculations eventually led to the discovery of Neptune. The excess perihelion precession of Mercury's orbit led Le Verrier to postulate the intra-Mercurian planet Vulcan in 1859, but that would turn out not to exist: the excess perihelion precession was finally explained by Einstein's general relativity, which displaced Newton's theory as the most accurate description of gravity on large scales.

Radar-imaging of 2006 DP₁₄, a small near-Earth asteroid that passed by Earth in early February 2014

Further apparent discrepancies in the orbits of the outer planets led Percival Lowell to conclude that yet another planet, "Planet X", must lie beyond Neptune. After his death, his Lowell Observatory conducted a search that ultimately led to Clyde Tombaugh's discovery of Pluto in 1930. Pluto was, however, found to be too small to have disrupted the orbits of the outer planets, and its discovery was therefore coincidental. Like Ceres, it was initially considered to be a planet, but after the discovery of many other similarly sized objects in its vicinity it was reclassified in 2006 as a dwarf planet by the IAU.

Discovery of the solar system as one among many

Although it is debatable when the Solar System was truly "discovered", three 19th century observations determined its nature and place in the Universe beyond reasonable doubt. First, in 1838, Friedrich Bessel successfully measured a stellar parallax, an apparent shift in the position of a star created by Earth's motion around the Sun. This was not only the first direct, experimental proof of heliocentrism, but also revealed, for the first time, the vast distance between the Solar System and the stars. Then, in 1859, Robert Bunsen and Gustav Kirchhoff, using the newly invented spectroscope, examined the spectral signature of the Sun and discovered that it was composed of the same elements as existed on Earth, establishing for the first time a physical similarity between Earth and the other bodies visible from Earth. Then, Father Angelo Secchi compared the spectral signature of the Sun with those of other stars, and found them virtually identical. The realisation that the Sun was a star led to the hypothesis that other stars could have systems of their own, though this was not to be proven for nearly 140 years.

Observational cosmology began with attempts by William Herschel to describe the shape of the galaxy. In 1785, he proposed the Milky Way was a disk, but assumed the Sun was at the center. This heliocentric theory was overturned by galactocentrism in the 1910s, after more observations by Harlow Shapley placed the Galactic Center relatively far away.

Extrasolar planets and the Kuiper belt

In 1992, the first evidence of a planetary system other than our own was discovered, orbiting the pulsar PSR B1257+12. Three years later, 51 Pegasi b, the first extrasolar planet around a Sunlike star, was discovered. NASA announced in March 2022 that the number of discovered exoplanets reached 5,000, of several types and sizes.

Also in 1992, astronomers David C. Jewitt of the University of Hawaii and Jane Luu of the Massachusetts Institute of Technology discovered 15760 Albion. This object proved to be the first of a new population, which became known as the Kuiper belt; an icy analogue to the asteroid belt of which such objects as Pluto and Charon were deemed a part.

Mike Brown, Chad Trujillo and David Rabinowitz announced the discovery of Eris in 2005, a scattered disc object initially thought to be larger than Pluto, which would make it the largest object discovered in orbit around the Sun since Neptune. New Horizons' fly-by of Pluto in July 2015 resulted in more-accurate measurements of Pluto, which is slightly larger, though less massive, than Eris.

Observations by spacecraft

For a chronological guide, see Timeline of Solar System exploration.

 

Lineae on Europa by Galileo spacecraft

 

Timeline of Solar System exploration.

 

Artist's conception of Pioneer 10, which passed the orbit of Pluto in 1983. The last transmission was received in January 2003, sent from approximately 82 AU away. The 49–50-year-old space probe is receding from the Sun at over 43,400 km/h (27,000 mph), so long as it has not hit anything

Since the start of the Space Age, a great deal of exploration has been performed by robotic spacecraft missions that have been organized and executed by various space agencies.

All planets in the Solar System have now been visited to varying degrees by spacecraft launched from Earth. Through these uncrewed missions, humans have been able to get close-up photographs of all the planets and, in the case of landers, perform tests of the soils and atmospheres of some.

The first artificial object sent into space was the Soviet satellite Sputnik 1, launched in 1957, which successfully orbited Earth until 4 January the following year. The American probe Explorer 6, launched in 1959, was the first satellite to image Earth from space.

Flybys

The first successful probe to fly by another Solar System body was Luna 1, which sped past the Moon in 1959. Originally meant to impact with the Moon, it instead missed its target and became the first artificial object to orbit the Sun. Mariner 2 was the first planetary flyby, passing Venus in 1962. The first successful flyby of Mars was made by Mariner 4 in 1965. Mariner 10 first passed Mercury in 1974.

The first probe to explore the outer planets was Pioneer 10, which flew by Jupiter in 1973. Pioneer 11 was the first to visit Saturn, in 1979. The Voyager probes performed a grand tour of the outer planets following their launch in 1977, with both probes passing Jupiter in 1979 and Saturn in 1980–1981. Voyager 2 then went on to make close approaches to Uranus in 1986 and Neptune in 1989. The two Voyager probes are now far beyond Neptune's orbit, and are on course to find and study the termination shock, heliosheath, and heliopause. According to NASA, both Voyager probes have encountered the termination shock at a distance of approximately 93 AU from the Sun.

The first flyby of a comet occurred in 1985, when the International Cometary Explorer (ICE) passed by the comet Giacobini–Zinner, whereas the first flybys of asteroids were conducted by the Galileo space probe, which imaged both 951 Gaspra (in 1991) and 243 Ida (in 1993) on its way to Jupiter.

Launched on January 19, 2006, the New Horizons probe is the first human-made spacecraft to explore the Kuiper belt. This uncrewed mission flew by Pluto in July 2015. The mission was extended to observe a number of other Kuiper belt objects, including a close flyby of 486958 Arrokoth on New Year's Day, 2019.

As of 2011, American scientists are concerned that exploration beyond the Asteroid Belt will hampered by a shortage of Plutonium-238.

Orbiters, rovers and landers and flying probes

Curiosity rover self-portrait at "Rocknest" (October 31, 2012), with the rim of Gale Crater and the slopes of Aeolis Mons in the distance.

In 1966, the Moon became the first Solar System body beyond Earth to be orbited by an artificial satellite (Luna 10), followed by Mars in 1971 (Mariner 9), Venus in 1975 (Venera 9), Jupiter in 1995 (Galileo), the asteroid 433 Eros in 2000 (NEAR Shoemaker), Saturn in 2004 (Cassini–Huygens), and Mercury and Vesta in 2011 (MESSENGER and Dawn respectively). Dawn is orbiting the asteroid–dwarf planet Ceres as of 2015.

The first probe to land on another Solar System body was the Soviet Luna 2 probe, which impacted the Moon in 1959. Since then, increasingly distant planets have been reached, with probes landing on or impacting the surfaces of Venus in 1966 (Venera 3), Mars in 1971 (Mars 3, although a fully successful landing didn't occur until Viking 1 in 1976), the asteroid 433 Eros in 2001 (NEAR Shoemaker), and Saturn's moon Titan (Huygens) and the comet Tempel 1 (Deep Impact) in 2005. The Galileo orbiter also dropped a probe into Jupiter's atmosphere in 1995; because Jupiter has no physical surface, it was destroyed by increasing temperature and pressure as it descended.

To date, only two worlds in the Solar System, the Moon and Mars, have been visited by mobile rovers. The first robotic rover to visit another celestial body was the Soviet Lunokhod 1, which landed on the Moon in 1970. The first to visit another planet was Sojourner, which travelled 500 metres across the surface of Mars in 1997. The first flying probe on in solar system is Vega balloons, while first powered flight was undertook by Ingenuity. The only crewed rover to visit another world was NASA's Lunar Roving Vehicle, which traveled with Apollos 15, 16 and 17 between 1971 and 1972.

Spacecraft exploration

Overview of some missions to the Solar System.

Examples of missions

#	Spacecraft	Launch year	Mercury	Venus	Mars	Ceres	Jupiter	Saturn	Uranus	Neptune	Pluto	End year
1	Venera 3	1965		Crash landing								1966
2	Pioneer 10	1972					Flyby					2003
3	Pioneer 11	1973					Flyby	Flyby				1995
4	Mariner 10	1973	Flyby	Flyby								1975
5	Voyager 1	1977					Flyby	Flyby				—
6	Voyager 2	1977					Flyby	Flyby	Flyby	Flyby		—
7	Galileo	1989		Flyby			Orbiter					2003
8	Ulysses	1990					Flyby					2009
9	Cassini	1997		Flyby			Flyby	Orbiter				2017
10	Mars Odyssey	2001			Orbiter							—
11	MER-A / B	2003			Rovers							2010 / 2018
12	Mars Express	2003			Orbiter							—
13	MESSENGER	2004	Orbiter	Flyby								2015
14	MRO	2005			Orbiter							—
15	Venus Express	2005		Orbiter								2014
16	New Horizons	2006					Flyby				Flyby	—
17	Dawn	2007				Orbiter						2018
18	Juno	2011					Orbiter					—
19	Curiosity (MSL)	2011			Rover							—
20	Perseverance (Mars 2020)	2020			Rover							—
20	Ingenuity (Mars 2020)	2020			Flying probe							—

See also the categories for missions to comets, asteroids, the Moon, and the Sun.

Crewed exploration

Owen Garriott on an Earth orbit EVA, 1973

The first human being to reach space (defined as an altitude of over 100 km) and to orbit Earth was Yuri Gagarin, a Soviet cosmonaut who was launched in Vostok 1 on April 12, 1961. The first human to walk on the surface of another Solar System body was Neil Armstrong, who stepped onto the Moon on July 21, 1969 during the Apollo 11 mission; five more Moon landings occurred through 1972. The United States' reusable Space Shuttle flew 135 missions between 1981 and 2011. Two of the five shuttles were destroyed in accidents.

The first orbital space station to host more than one crew was NASA's Skylab, which successfully held three crews from 1973 to 1974. True human settlement in space began with the Soviet space station Mir, which was continuously occupied for close to ten years, from 1989 to 1999. Its successor, the International Space Station, has maintained a continuous human presence in space since 2001. In 2004, U.S. President George W. Bush announced the Vision for Space Exploration, which called for a replacement for the aging Shuttle, a return to the Moon and, ultimately, a crewed mission to Mars.

Further information: Human spaceflight and Space exploration

Exploration by country

See also: Timeline of first orbital launches by country

Legend:
☄ - orbit or flyby
Ѫ - successful landing on an object
⚗ - sample return
⚘ - crewed mission
ↂ - permanent inhabited space station

Country	LEO	Moon	Mars	Mars moons	SSSBs	Venus	Mercury	Outer Solar System
United States	☄⚘ↂ	☄Ѫ⚗⚘	☄Ѫ	☄	☄Ѫ⚗	☄Ѫ	☄	☄
Soviet Union	☄⚘ↂ	☄Ѫ⚗	☄Ѫ	☄	☄	☄Ѫ
Russia (since 1992)	☄⚘ↂ
Ukraine (since 1992)	☄
People's Republic of China	☄⚘ↂ	☄Ѫ⚗	☄Ѫ		☄
European Union	☄ↂ	☄	☄	☄	☄Ѫ	☄		☄Ѫ
Japan	☄ↂ	☄			☄Ѫ⚗	☄
India	☄	☄	☄
Iran	☄
Israel	☄	☄
North Korea	☄
New Zealand	☄
United Arab Emirates			☄
Commercial	☄⚘	☄

Notes:

• Only successful or partially successful missions are counted; instruments on a spacecraft made by another country are not counted as a separate mission
• Clicking on the symbol opens an article describing the first successful mission in that category

Sample return

A Moon rock returned by Apollo 17

• Moon (Misc. missions including Apollo, Luna and Chang'e)
• Comet dust (Stardust)
• Solar wind (Genesis)
• Asteroid (Hayabusa and Hayabusa2)

See also: Meteorites and Cosmic dust

Non-lethal weapon

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Non-lethal_weapon 

 

An instruction on oleoresin capsicum (pepper spray) at Marine Corps Base Camp Lejeune

Non-lethal weapons, also called nonlethal weapons, less-lethal weapons, less-than-lethal weapons, non-deadly weapons, compliance weapons, or pain-inducing weapons are weapons intended to be less likely to kill a living target than conventional weapons such as knives and firearms with live ammunition. It is often understood that unintended or incidental casualties are risked wherever force is applied, but non-lethal weapons try to minimise the risk of casualties (e.g. serious/permanent injuries or death) as much as possible. Non-lethal weapons are used in policing and combat situations to limit the escalation of conflict where employment of lethal force is prohibited or undesirable, where rules of engagement require minimum casualties, or where policy restricts the use of conventional force. These weapons occasionally cause serious injuries or death; the term "less-lethal" has been preferred by some organizations as it describes the risks of death more accurately than the term "non-lethal", which some have argued is a misnomer.

Non-lethal weapons may be used by conventional military in a range of missions across the force continuum. They may also be used by military police, by United Nations forces, and by occupation forces for peacekeeping and stability operations. Non-lethal weapons may also be used to channelize a battlefield, control the movement of civilian populations, or to limit civilian access to restricted areas (as they were utilized by the USMC's 1st Marine Expeditionary Force in Somalia in 1995). Similar weapons, tactics, techniques and procedures are employed by police forces domestically in riot control, prisoner control, crowd control, refugee control, and self-defense, where the terminology of "less-than-lethal" is often used.

History

Military

Demonstration of the use of Taser gun on US military personnel. The device was originally developed for use by civilian police.

In the past, military and police faced with undesirable escalation of conflict had few acceptable options. Military personnel guarding embassies often found themselves restricted to carrying unloaded weapons. National guards or policing forces charged with quelling riots were able to use only batons or similar club-like weapons, or bayonet or sword charges, or fire live ammunition at crowds. In the late 1980s and early 1990s, the Non-lethality Policy Review Group at U.S. Global Strategy Council in Washington and other independent think tanks around the world called for a concerted effort to develop weapons that were more life-conserving, environmentally friendly, and fiscally responsible than weapons available at that time. The U.S. Congress and other governments agreed and began an organized development of non-lethal weapons to provide a range of options between talking and shooting.

Recognizing the need to limit the escalation of force, research and development of a range of non-lethal weapons has since been undertaken internationally by governments and weapons manufacturers to fill the need for such weapons. Some non-lethal weapons may provide more effective riot control than firearms, truncheons or bayonets with less risk of loss of life or serious injury. Before the general availability of early military non-lethal weapons in the mid 1990s, war-fighters had few or no casualty-limiting options for the employment of scalable force and were continually at risk whenever lethal force was prohibited during sensitive missions.

In 2001, the United States Marine Corps revealed its development of a less-than-lethal energy weapon called the Active Denial System, a focused high frequency microwave device said to be capable of heating all living matter in the target area rapidly and continuously for the duration of the beam, causing transient intolerable pain but no lasting damage. The skin temperature of a person subjected to this weapon can jump to approximately 130 °F (54 °C) in as little as 2 seconds depending on the skin's starting temperature. The system is nonlethal (the penetration of the beam into human skin is only a few millimeters).

In 2004, author Jon Ronson cited an unclassified military report titled "Non-Lethal Weapons: Terms and References" 21 acoustic weapons were listed, in various stages of development, including the Infrasound ("Very low-frequency sound which can travel long distances and easily penetrate most buildings and vehicles ... biophysical effects are projected to be: nausea, loss of bowels, disorientation, vomiting, potential internal organ damage or death may occur. Superior to ultrasound...)", however no such effects had been achieved as of 2002.

In 2010, the Joint Non-Lethal Weapons Directorate Non-Lethal Weapons Reference Book was created. The weapons in this book are currently in development.

Police

• 

  Long range acoustic device mounted on police vehicle, 2004 Republican National Convention, New York City

• 

  Swedish police in riot gear, carrying an extended telescopic baton

• 

  A Taser X26 making an electrical arc between its two electrodes

• 

  Pepper spray training

• 

  Exploded tear gas canister in the air

Until the development of non-lethal weapons, police officers around the world had few if any non-lethal options for riot control. Common tactics used by police that were intended to be non-lethal or less lethal included a slowly advancing wall of men with batons, officers on horses trained to deal with policing situations, or a charge into a riot using the flats of sabers. Other reasonably successful approaches included shotguns with lower-powered cartridges, "salt shells", using bean-bag rounds and ricocheting shots off of the ground. In the mid-20th century, with the integration of fire-control systems into major cities, police found that high-pressure fire hoses could be effective in dispersing a crowd (the use of water cannons and fire trucks has remained an effective non-lethal tactic to disperse riots). Trained police dogs were also commonly used to scare and disperse rioters and apprehend individuals. In the 1980s the development of high-tensile plastics like Kevlar and Lexan revolutionized personal armor and shields, and led to new tactics for riot squads and other special-purpose teams. Officers could now stand up against violent rioters throwing dangerous projectiles without having to resort to lethal methods to quickly disperse the danger. Coupled with the introduction of effective non-lethal chemical agents such as tear gas and offensive-odor canisters, and non-lethal impact rounds such as rubber bullets and "bean bag" flexible baton rounds, riot tactics were modified to rely less on violent response to attacking rioters than on a return to the slowly advancing wall, with supporting officers firing non-lethal ordnance into the crowd to discourage advance.

Police officers on patrol were traditionally armed with batons or pistols or both, and non-lethal methods of subduing an attacker centered on hand-fighting techniques such as jujutsu and baton use. In the 1980s and 1990s officers began deploying non-lethal personal sidearms such as pepper sprays, and eventually electroshock weapons such as tasers, which were developed for use by police and also found a market in self-defense by private citizens. However, these weapons were developed for non-lethal resolution of one-on-one conflicts.

During the 1990s and early 2000s (decade), interest in various other forms of less-than-lethal weapons for military and police use rose. Amongst other factors, the use of less-than-lethal weapons may be legal under international law and treaty in situations where weapons such as aerosol sprays or gases defined as chemical are not.

Between the years of 1987–1990, after a three-year field study by the FBI's Firearm's Training Unit; In 1990, the use of oleoresin capsicum was approved and used by the FBI, the first official law enforcement agency to do so.

In the late 1990s and early 2000s (decade), police began to adopt a new pepper spray delivery system based on the equipment used in paintball. A specialized paintball, called a "pepperball", is filled with liquid or powdered capsaicin, the active ingredient in pepper spray, and is propelled by compressed gas using a paintball marker similar to those used for the sport but operating at a higher pressure. The impact of the capsule is immediately painful (a pepperball's shell is thicker than a standard paintball and is fired at a higher velocity), and it breaks open on impact, dispersing the capsaicin with similar effect to aerosol-delivered pepper spray. However, to be most effective, pepper spray must contact the eyes, nose, or mouth of the target; pepper spray on clothing or tougher skin has a much reduced effect.

Effects

Non-lethal weapons have a design intent to provide an effect to reliably elicit a degree of incapacitation but without the typically lethal or permanent lasting effects of conventional weapons. This design intent has often made them a weapon of choice for use by law enforcement during civil protests, etc. Effect modalities vary by the technology being employed: kinetic projectiles function by blunt impact which actuate pain receptors to elicit a behavioral change, lights affect visual perception, acoustics affect hearing, etc.

Notwithstanding their design intent, non-lethal weapons can still cause harm. This is particularly true with certain technologies that interact with appropriately vulnerable regions; an example is kinetic munitions on the head, neck, eyes, abdominal and urogenital regions of the body. As a result, some analysts describe "non-lethal" as a misnomer and recommend defining them as "less-lethal", whereas other sources identify "non-lethal" as representing a goal of minimization of producing fatalities or permanent injuries while not literally requiring minimization to a zero probability thereof.

Because the design intent is to avoid/minimize permanence, the effects invariably have been transient in nature. Some effects may be momentary while others may persist for some finite period of time.

Mechanics

Non-lethal weapons are intended to minimize injury or death. While people are occasionally seriously injured or killed by these weapons, fatalities are relatively infrequent. Causes of death from non-lethal weapons are varied and occasionally uncertain. Misplaced or ricocheting shots, pre-existing medical conditions, inadequate user training, repetitive applications and intentional misuse have been implicated in different cases where death has occurred.

As different parts of the body differ in vulnerability, and because people vary in weight and fitness, any weapon powerful enough to incapacitate may be capable of killing under certain circumstances. Thus, "non-lethal force" does have some risk of causing death: in this context, "non-lethal" means only "not intended to kill".

Several groups maintain there is great room for improvement in non-lethal weapons and procedures for their use. Claims for the relative safety of such weapons are usually contingent on their being used "properly". For example, the rubber bullets developed during the 1960s were supposed to be fired at the ground and hit the target only after ricochet, and other non-lethal bullets are designed to be fired at the lower body; they can be lethal if fired directly at the head.

Ammunition

Non-lethal rounds are firearm rounds which are designed to incapacitate, but not kill, a target. The rounds rely on the transfer of kinetic energy and blunt force trauma to accomplish this incapacitation. Rubber bullets, rubber buckshot, soft polymer rounds, wax bullets, plastic bullets, beanbag rounds, sponge grenades, ring airfoil projectiles (both kinetic and tear gas projectiles) and rubber bullets with electroshock effect (e.g. Taser XREP rounds) are less lethal than conventional metal bullets, and are also propelled at lower speed by using less propellant. "Bean bag" type bullets are sometimes referred to as flexible baton rounds. More recently, high-velocity paintball guns are also used to launch less-lethal rounds, including the FN 303 launcher and PepperBall commercial products. There is also the Variable Velocity Weapon Concept, for which a propulsion energy source may not yet have been clearly established and/or finalized. In any case, all of these technologies apply the same basic mechanism, which is to launch a mass at the target that interacts kinetically.

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  Fiocchi 12-gauge rubber buckshot: containing 15, 8.3 mm, .58 gram rubber pellets, with a muzzle velocity of 790 fps.

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  12-gauge beanbag rounds and exposed bean bag round projectile

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  U.S. M234 launcher ring airfoil projectile rounds

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  Launcher, projectile, 64 mm, riot control, M234

Explosives

Hand grenades come in several less-lethal varieties, such as "flashbang" (stun) grenades, "sting" grenades with rubber shrapnel, and grenades designed to release chemical irritants (described below).

In 1972, stun grenades were used to capture the hijacked Sabena Flight 571, allowing the Israeli forces headed by Ehud Barak and including Benjamin Netanyahu to storm the plane and take it over within 10 minutes while capturing two terrorists and killing Ali Taha, the leader of the terrorist group and his aide, while rescuing all passengers (three were wounded, and one died of her injuries several days later).

A stun grenade was apparently used by members of the IHH against the IDF soldiers during the Gaza flotilla raid at the beginning of the IDF storming of the Mavi Marmara.

In June 2010, in Kenya, a stun grenade was used to draw attention, and then a real grenade along with an explosive package were used, killing many people. In April, during the 2010 Kyrgyzstani uprising, police attempted to use stun grenades to stop a demonstration but the crowd overwhelmed the police. In March stun grenades were used by Belarusian police in Minsk against demonstrators, and in September they were used by Greek police in Athens. In these latter two cases, the demonstrations were dispersed with no injuries.

In February 2011, stun grenades were seen used by Egyptian police against rioters.

Gases and sprays

Further information: Incapacitating agent

Water

Water cannon during a German demonstration, 2001

Water cannons are commonly used in crowd and riot control, for dispersal or to prevent movement on a particular position. These water cannons are intended to disperse crowds with little risk of harm, but the pressure can still cause eye injuries or even death. Water-filled rounds for small arms are in experimental stages. Electrified water cannons were in development but was abandoned.

Scent-based weapons

Malodorants produce strong odours that cause people to leave the affected area. In 2008, the Israeli Defence Forces began using Skunk for crowd control. It is a form of mist sprayed from a water cannon, which leaves a terrible odor of rot or sewage on whatever it touches, and does not wash off easily.

Pepper spray

The active ingredient in pepper spray is oleoresin capsicum (OC), an acrid irritant chemical derived from cayenne pepper plants.

A 1998 estimate by the Internet Association of Chiefs of Police suggested at least 113 pepper spray-related fatalities had occurred in the United States, all with aggravating factors such as intoxication, pre-existing health problems, or from the police use of airway-restrictive immobilizing holds that can cause positional asphyxia. The Southern California chapter of the American Civil Liberties Union recommends against maximal prone restraint techniques following pepper spray application, and they caution that anyone sprayed should be monitored to ensure effective breathing.

Tear gas

Vancouver Police Department officers in anti-riot gear and armed with tear gas grenade launchers confront Stanley Cup rioters.

The use of chemical weapons such as tear gas (CS) and pepper spray (OC) has come under increasing scrutiny and criticism due to studies showing serious long term side effects. Many police forces are no longer exposing their members to the chemicals during training.

Journalist Rubén Salazar was killed in Los Angeles in 1970 by an errant CS gas canister during the Chicano riots. Other serious injuries and fatalities have occurred from either tear gas itself or the projectiles it is delivered in, including the critical injury of veteran Scott Olsen from a tear gas canister during the 2011 Occupy Oakland protests.

Psychochemical

Main article: Psychochemical weapons

Psychochemical weapons are psychoactive drugs, such as BZ, LSD, Kolokol-1, EA-3167, and 3-Methylamphetamine designed to have a disorienting effect when used during combat or interrogation.

Sleep gas

During the 2002 Moscow theater hostage crisis, Russian special forces used an unidentified gas (thought to be 3-methylfentanyl or another fentanyl variant dissolved in halothane gas) in an attempt to induce sleep in both hostages and terrorists. Many of the hostages and terrorists (including all of the suicide bombers) were anesthetized, but some terrorists donned gas masks and thus were able to avoid the effects of the gas. Because the agent used was a potent Fentanyl derivative (a synthetic opioid), it causes respiratory depression and ultimately respiratory failure if administered in high enough dosages. The central nervous system effects, such as anesthesia and respiratory depression could have been reversed by an opioid antagonist such as naloxone, which is stocked by hospitals and most ambulances. However, because the Russian authorities did not release any information regarding what type of agent was used, medical professionals were unaware that an opioid had been used during the rescue attempt and thus were unable to administer the antidote which could have saved most hostages. Approximately 700 hostages were rescued, while 130 died from exposure to the gas. All the terrorists were ultimately killed by Russian forces through some combination of gas exposure and gunfire.

Other chemical agents

Further information: Incapacitating agent

Blister agents, including CR gas, are less often used riot control agents. Other irritants include CS gas and nonivamide (PAVA).

Sticky foam

Main article: Sticky foam

Sticky foam was tried by the U.S. Marine Corps in the peacekeeping Operation United Shield in 1995 with some success, but as a result various complications in its field use were also discovered.

Area denial

Main article: Area denial weapons

Area denial weapons work by either incapacitating or deterring the enemy.

Anti-vehicle

Iron caltrops

Vehicle stoppers include a wide range of methods and devices meant to disable a vessel or vehicle to prevent attack by an oncoming vessel or vehicle or to stop that vessel or vehicle for evaluation. Vessel and vehicle stoppers may include kinetic, chemical, or electromagnetic means.

Anti-personnel

Caltrops

Simple rows or clusters of sharpened sticks (also known as punji sticks), and the use of small caltrops have been a feature of anti-infantry warfare for centuries. They are known to have been in use since Roman times and may have been used earlier: the concept was familiar to the 4th century BC Greeks, who used rocks, brush, nets and trees placed in the path of enemy conveyances on land or ensnarement devices hidden under water to achieve the same result: stop the enemy or suspected hostile in his tracks for examination or to prevent or limit incursions. Contemporary caltrops look something like large jacks from the childhood game. Placed in the path of oncoming wheeled or tracked vehicles, they are meant to foul wheels, destroy tires and tracks, and incapacitate vehicles.

However, due to the difficulty of mass-producing them in the pre-modern age, they were rarely used except in the defense of limited areas or chokepoints, especially during sieges, where they were used to help seal breaches. Increasing ease of production still did not prevent these methods from slowly falling out of favor from the late Middle Ages onward.

Caltrops are still sometimes used in modern conflicts, such as during the Korean War, where Chinese troops, often wearing only light shoes, were particularly vulnerable. In modern times, special caltrops are also sometimes used against wheeled vehicles with pneumatic tires. Some South American urban guerrillas as the Tupamaros and Montoneros called them "miguelitos" and used these as a tactic to avoid pursuit after ambushes.

Riot gun

In current usage a riot gun or less-lethal launcher is a type of firearm that is used to fire "non-lethal" or "less-lethal" ammunition for the purpose of suppressing riots. Less-lethal launchers may be special purpose firearms designed for riot control use, or standard firearms, usually shotguns and grenade launchers, adapted to riot control use with appropriate ammunition. The ammunition is most commonly found in 12 gauge (.729 inches) shotguns and 37mm and 40 mm (1.46 and 1.57 inches) grenade launchers.

In the United States, the term riot gun more commonly refers to a riot shotgun.

Electroshock weapons

Electroshock weapons are incapacitant weapons used for subduing a person by administering electric shock aimed at disrupting superficial muscle functions. One type is a conductive energy device (CED), an electroshock gun popularly known by the brand name "Taser", which fires projectiles that administer the shock through a thin, flexible wire. Other electroshock weapons such as stun guns, stun batons, and electroshock belts administer an electric shock by direct contact.

Directed energy weapons

An NYPD officer stands ready with a sonic weapon, the LRAD 500X, at an Occupy Wall Street protest on November 17, 2011 near the New York City Hall

 

Main article: Directed-energy weapon

Directed energy weapons are weapons that emit energy in an aimed direction without the means of a projectile. They are non-lethal and can immobilize people as well as machines (e.g. vehicles). Directed energy weapons include electromagnetic weapons, (including laser weapons) and microwave weapons, particle beam weapons, sonic weapons and plasma weapons.

Ultraviolet laser

HSV Technologies, Inc. (named for its founders, Herr, Schlesinger and Vernon; not to be confused with Holden Special Vehicles), formerly of San Diego, California, USA, then Port Orchard, WA, designed a non-lethal device which was profiled in the 2002 TIME magazine article "Beyond the Rubber Bullet". It is an electrolaser using ultraviolet laser beams of 193 nm, and promises to immobilize living targets at a distance without contact. There is plan for an engine-disabling variation for use against the electronic ignitions of cars using a 248 nm laser. The lead inventor, Eric Herr, died in 2008 and the company appears to have been dissolved, with their website defunct as of September 2017.

Pulsed energy projectile

Pulsed energy projectiles or (PEP) is a technology of non-lethal directed energy weaponry currently under development by the US military. It involves the emission of an invisible laser pulse which, upon contact with the target, ablates the surface and creates a small amount of exploding plasma. This produces a pressure wave designed to stun the target and knock them off their feet, and electromagnetic radiation that affects nerve cells causing a painful sensation.

The pulsed energy projectile is intended for riot control and is said to work over distances of up to 2 km. It weighs about 230 kg and will probably be mounted on vehicles. The weight could become lighter as laser production technology improves.

The system was developed by Mission Research Corporation (now owned by Orbital ATK). It uses a chemical deuterium fluoride laser device producing infrared laser pulses. The plasma (produced by the early part of the pulse) explodes because its electrons absorb the energy of the later part of the pulse.

In 2003, a US military review reported that the electromagnetic radiation produced by PEPs had been shown to cause pain and temporary paralysis in animal experiments.

United States Special Operations Command FY 2010 plans included starting developmental work on a counter UAV pulsed energy projectile.

Active denial system

An active denial system (ADS) is a dish that projects electromagnetic radiation just powerful enough to penetrate human skin and make the victim feel as though they are on fire, although no physical damage is done. Future combat vehicles such as the American GCV Infantry Fighting Vehicle incorporate non-lethal weapons. The ADS is a non-lethal, directed-energy weapon developed by the US military, designed for area denial, perimeter security and crowd control. Informally, the weapon has also been referred to as a "heat ray", since it works by heating the surface of targets, such as the skin of targeted human subjects.

In 2011, the ADS was redesigned to make it smaller, more reliable, and able to be used on the move. The ADS II is being designed to operate from moving aircraft, as well as moving ground vehicles. The redesign does not address problems in different environmental conditions.

Air Force Special Operations Command is experimenting with mounting an ADS on the AC-130J Ghostrider gunship to target threatening crowds or individuals on the ground. This is to give the gunship a non-lethal option so the crew has more engagement options. Due to the increasing number of engagements in populated areas, the Air Force is aiming to field a system within 10 years to have enough aircraft available with non-lethal systems. The aircraft will apparently use the ADS II version.

Dazzler

A Dazzler is a directed-energy weapon intended to temporarily blind or disorient its target with intense directed radiation. Targets can include sensors or human vision. Dazzlers emit infrared or invisible light against various electronic sensors, and visible light against humans, when they are intended to cause no long-term damage to eyes. The emitters are usually lasers, making what is termed a laser dazzler. Most of the contemporary systems are man-portable, and operate in either the red (a laser diode) or green (a diode-pumped solid-state laser, DPSS) areas of the electromagnetic spectrum.

Initially developed for military use, non-military products are becoming available for use in law enforcement and security.

Weapons designed to cause permanent blindness are banned by the 1995 United Nations Protocol on Blinding Laser Weapons. The dazzler is a non-lethal weapon intended to cause temporary blindness or disorientation and therefore falls outside this protocol.

PHASR Rifle

The personnel halting and stimulation response rifle (PHASR) is a prototype non-lethal laser dazzler developed by the Air Force Research Laboratory's Directed Energy Directorate, U.S. Department of Defense. Its purpose is to temporarily disorient and blind a target. Blinding laser weapons have been tested in the past, but were banned under the 1995 UN Protocol on Blinding Laser Weapons, which the United States acceded to on 21 January 2009. The PHASR rifle, a low-intensity laser, is not prohibited under this regulation, as the blinding effect is intended to be temporary. It also uses a two-wavelength laser. The PHASR was tested at Kirtland Air Force Base, part of the Air Force Research Laboratory Directed Energy Directorate in New Mexico.

Blinding laser weapons

Several nations developed blinding laser weapons and they were allegedly used during War in Donbass by Russia.

Long Range Acoustic Device

The Long Range Acoustic Device (LRAD) is an acoustic hailing device developed by LRAD Corporation to send messages and warning tones over longer distances or at higher volume than normal loudspeakers. LRAD systems are used for long-range communications in a variety of applications including as a means of non-lethal, non-kinetic crowd control. Though they have been called "sonic weapons",  LRADs are not inherently for military use. The round black devices on top of New York City police Hummers are LRADs.

According to the manufacturer's specifications, the systems weigh from 15 to 320 pounds (6.8 to 145.1 kg) and can emit sound in a 30°- 60° beam at 2.5 kHz. The manufacturer also produces systems for public address and mass notification use that broadcast 360°.

Safety and legal status

In the United States, the University of Texas-Austin Institute for Advanced Technology (IAT) conducts basic research to advance electrodynamics and hypervelocity physics related to electromagnetic weapons.

Although generally considered "non-lethal weapons", electromagnetic weapons do pose health threats to humans. In fact, "non-lethal weapons can sometimes be deadly."

United States Department of Defense policy explicitly states that non-lethal weapons "shall not be required to have a zero probability of producing fatalities or permanent injuries." Although a Human Effects Advisory Panel was established in 1998 to provide independent assessment on human effects, data, and models for the use of 'non-lethal weapons' on the general population, the TECOM Technology Symposium in 1997 concluded on non-lethal weapons: "Determining the target effects on personnel is the greatest challenge to the testing community," primarily because "the potential of injury and death severely limits human tests." However, "directed energy weapons that target the central nervous system and cause neurophysiological disorders" may violate the Convention on Certain Conventional Weapons of 1980. And weapons that go beyond non-lethal intentions and cause "superfluous injury or unnecessary suffering" could violate the Protocol I to the Geneva Conventions of 1977." Safety and evaluation of the physical and psychological effects of the long-term or repetitive uses of the pain-inducing non-lethal weapons on humans have not been well understood or studied in any great details. Any such studies require explicit consent of all participants so as not to violate the UN Convention against torture and other cruelties.

Misuse

Pepper spray is one non-lethal weapon alleged to have been misused by American police. In two incidents in California in 1997, police swabbed pepper spray directly into the eyes of protesters. Amnesty International condemned these actions, and claimed that they were likely a violation of the 1984 United Nations Convention Against Torture.

Terrorism concerns

Loren Thompson, chief operating officer of the Lexington Institute in Virginia states that: "The relevant (electromagnetic weapon) technology is well within the grasp of some countries and transnational terrorist groups", and further states that U.S. hardware is susceptible to microwave and other directed-energy weapons.

Suitable materials and tools to create electromagnetic weapons are commonly available. "The threat of electromagnetic bomb proliferation is very real."