Meteoroid

From Wikipedia, the free encyclopedia

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

A meteoroid shown entering the atmosphere, becoming visible as a meteor and hitting the Earth's surface as a meteorite.

A meteoroid (/ˈmiːtiərɔɪd/) is a small rocky or metallic body in outer space.

Meteoroids are significantly smaller than asteroids, and range in size from small grains to one-meter-wide objects. Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.

When a meteoroid, comet, or asteroid enters Earth's atmosphere at a speed typically in excess of 20 km/s (72,000 km/h; 45,000 mph), aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it leaves in its wake. This phenomenon is called a meteor or "shooting star". Meteors typically become visible when they are about 100 km above sea level. A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower. A meteorite is the remains of a meteoroid that has survived the ablation of its surface material during its passage through the atmosphere as a meteor and has impacted the ground.

An estimated 25 million meteoroids, micrometeoroids and other space debris enter Earth's atmosphere each day, which results in an estimated 15,000 tonnes of that material entering the atmosphere each year.

Meteoroids

Meteoroid embedded in aerogel; the meteoroid is 10 µm in diameter and its track is 1.5 mm long

 

2008 TC3 meteorite fragments found on February 28, 2009, in the Nubian Desert, Sudan

In 1961, the International Astronomical Union (IAU) defined a meteoroid as "a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom". In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society, proposed a new definition where a meteoroid would be between 100 µm and 10 m (33 ft) across. In 2010, following the discovery of asteroids below 10 m in size, Rubin and Grossman proposed a revision of the previous definition of meteoroid to objects between 10 µm and one meter (3 ft 3 in) in diameter in order to maintain the distinction. According to Rubin and Grossman, the minimum size of an asteroid is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered (based on absolute magnitude H) are 2008 TS₂₆ with H = 33.2 and 2011 CQ1 with H = 32.1both with an estimated size of one m (3 ft 3 in). In April 2017, the IAU adopted an official revision of its definition, limiting size to between 30 µm and one meter in diameter, but allowing for a deviation for any object causing a meteor.

Objects smaller than meteoroids are classified as micrometeoroids and interplanetary dust. The Minor Planet Center does not use the term "meteoroid".

Composition

Almost all meteoroids contain extraterrestrial nickel and iron. They have three main classifications: iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites. Stony meteoroids without these features are called "achondrites", which are typically formed from extraterrestrial igneous activity; they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earth's atmosphere from their trajectories and the light spectra of the resulting meteor. Their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams often associated with a parent comet, others apparently sporadic. Debris from meteoroid streams may eventually be scattered into other orbits. The light spectra, combined with trajectory and light curve measurements, have yielded various compositions and densities, ranging from fragile snowball-like objects with density about a quarter that of ice, to nickel-iron rich dense rocks. The study of meteorites also gives insights into the composition of non-ephemeral meteoroids.

In the Solar System

Most meteoroids come from the asteroid belt, having been perturbed by the gravitational influences of planets, but others are particles from comets, giving rise to meteor showers. Some meteoroids are fragments from bodies such as Mars or our moon, that have been thrown into space by an impact.

Meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest move at about 42 km/s (94,000 mph) through space in the vicinity of Earth's orbit. This is escape velocity from the Sun, equal to the square root of two times Earth's speed, and is the upper speed limit of objects in the vicinity of Earth, unless they come from interstellar space. Earth travels at about 29.6 km/s (66,000 mph), so when meteoroids meet the atmosphere head-on (which only occurs when meteors are in a retrograde orbit such as the Eta Aquariids, which are associated with the retrograde Halley's Comet) the combined speed may reach about 71 km/s (160,000 mph). Meteoroids moving through Earth's orbital space average about 20 km/s (45,000 mph).

On January 17, 2013 at 05:21 PST, a one meter-sized comet from the Oort cloud entered Earth atmosphere over California and Nevada. The object had a retrograde orbit with perihelion at 0.98 ± 0.03 AU. It approached from the direction of the constellation Virgo (which was in the south about 50° above the horizon at the time), and collided head-on with Earth's atmosphere at 72 ± 6 km/s (161,000 ± 13,000 mph) vaporising more than 100 km (330,000 ft) above ground over a period of several seconds.

Collision with Earth's atmosphere

When meteoroids intersect with Earth's atmosphere at night, they are likely to become visible as meteors. If meteoroids survive the entry through the atmosphere and reach Earth's surface, they are called meteorites. Meteorites are transformed in structure and chemistry by the heat of entry and force of impact. A noted 4-metre (13 ft) asteroid, 2008 TC3, was observed in space on a collision course with Earth on 6 October 2008 and entered Earth's atmosphere the next day, striking a remote area of northern Sudan. It was the first time that a meteoroid had been observed in space and tracked prior to impacting Earth. NASA has produced a map showing the most notable asteroid collisions with Earth and its atmosphere from 1994 to 2013 from data gathered by U.S. government sensors (see below).

Meteors

Meteor seen from the site of the Atacama Large Millimeter Array (ALMA)

 

World map of large meteoric events

A meteor, known colloquially as a shooting star or falling star, is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from 76 to 100 km (250,000 to 330,000 ft). The root word meteor comes from the Greek meteōros, meaning "high in the air".

Millions of meteors occur in Earth's atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand, i.e. they are usually millimeter-sized or smaller. Meteoroid sizes can be calculated from their mass and density which, in turn, can be estimated from the observed meteor trajectory in the upper atmosphere.  Meteors may occur in showers, which arise when Earth passes through a stream of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific stream of space debris. A number of specific meteors have been observed, largely by members of the public and largely by accident, but with enough detail that orbits of the meteoroids producing the meteors have been calculated. The atmospheric velocities of meteors result from the movement of Earth around the Sun at about 30 km/s (67,000 mph), the orbital speeds of meteoroids, and the gravity well of Earth.

Meteors become visible between about 75 to 120 km (250,000 to 390,000 ft) above Earth. They usually disintegrate at altitudes of 50 to 95 km (160,000 to 310,000 ft). Meteors have roughly a fifty percent chance of a daylight (or near daylight) collision with Earth. Most meteors are, however, observed at night, when darkness allows fainter objects to be recognized. For bodies with a size scale larger than 10 cm (3.9 in) to several meters meteor visibility is due to the atmospheric ram pressure (not friction) that heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles. The gases include vaporised meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere. Most meteors glow for about a second.

History

Although meteors have been known since ancient times, they were not known to be an astronomical phenomenon until early in the nineteenth century. Prior to that, they were seen in the West as an atmospheric phenomenon, like lightning, and were not connected with strange stories of rocks falling from the sky. In 1807, Yale University chemistry professor Benjamin Silliman investigated a meteorite that fell in Weston, Connecticut. Silliman believed the meteor had a cosmic origin, but meteors did not attract much attention from astronomers until the spectacular meteor storm of November 1833. People all across the eastern United States saw thousands of meteors, radiating from a single point in the sky. Astute observers noticed that the radiant, as the point is now called, moved with the stars, staying in the constellation Leo.

The astronomer Denison Olmsted made an extensive study of this storm, and concluded that it had a cosmic origin. After reviewing historical records, Heinrich Wilhelm Matthias Olbers predicted the storm's return in 1867, which drew the attention of other astronomers to the phenomenon. Hubert A. Newton's more thorough historical work led to a refined prediction of 1866, which proved to be correct. With Giovanni Schiaparelli's success in connecting the Leonids (as they are now called) with comet Tempel-Tuttle, the cosmic origin of meteors was now firmly established. Still, they remain an atmospheric phenomenon, and retain their name "meteor" from the Greek word for "atmospheric".

Fireball

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Footage of a superbolide, a very bright fireball that exploded over Chelyabinsk Oblast, Russia in 2013

A fireball is a brighter-than-usual meteor that also becomes visible when about 100 km from sea level. The International Astronomical Union (IAU) defines a fireball as "a meteor brighter than any of the planets" (apparent magnitude −4 or greater). The International Meteor Organization (an amateur organization that studies meteors) has a more rigid definition. It defines a fireball as a meteor that would have a magnitude of −3 or brighter if seen at zenith. This definition corrects for the greater distance between an observer and a meteor near the horizon. For example, a meteor of magnitude −1 at 5 degrees above the horizon would be classified as a fireball because, if the observer had been directly below the meteor, it would have appeared as magnitude −6.

Fireballs reaching apparent magnitude −14 or brighter are called bolides. The IAU has no official definition of "bolide", and generally considers the term synonymous with "fireball". Astronomers often use "bolide" to identify an exceptionally bright fireball, particularly one that explodes. They are sometimes called detonating fireballs. It may also be used to mean a fireball which creates audible sounds. In the late twentieth century, bolide has also come to mean any object that hits Earth and explodes, with no regard to its composition (asteroid or comet). The word bolide comes from the Greek βολίς (bolis)  which can mean a missile or to flash. If the magnitude of a bolide reaches −17 or brighter it is known as a superbolide. A relatively small percentage of fireballs hit Earth's atmosphere and then pass out again: these are termed Earth-grazing fireballs. Such an event happened in broad daylight over North America in 1972. Another rare phenomenon is a meteor procession, where the meteor breaks up into several fireballs traveling nearly parallel to the surface of Earth.

A steadily growing number of fireballs are recorded at the American Meteor Society every year. There are probably more than 500,000 fireballs a year, but most go unnoticed because most occur over the ocean and half occur during daytime. A European Fireball Network and a NASA All-sky Fireball Network detect and track many fireballs.

Fireball Sightings reported to the American Meteor Society 

Year	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018
Number	724	668	941	1,653	2,172	3,556	3,778	4,233	5,371	5,470	4,301

Effect on atmosphere

A meteoroid of the Perseids with a size of about ten millimetres entering the earth's atmosphere in real time. The meteoroid is at the bright head of the trail, and the ionisation of the mesosphere is still visible in the tail.

The entry of meteoroids into Earth's atmosphere produces three main effects: ionization of atmospheric molecules, dust that the meteoroid sheds, and the sound of passage. During the entry of a meteoroid or asteroid into the upper atmosphere, an ionization trail is created, where the air molecules are ionized by the passage of the meteor. Such ionization trails can last up to 45 minutes at a time.

Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in any given region of the atmosphere, and thus ionization trails can be found in the upper atmosphere more or less continuously. When radio waves are bounced off these trails, it is called meteor burst communications. Meteor radars can measure atmospheric density and winds by measuring the decay rate and Doppler shift of a meteor trail. Most meteoroids burn up when they enter the atmosphere. The left-over debris is called meteoric dust or just meteor dust. Meteor dust particles can persist in the atmosphere for up to several months. These particles might affect climate, both by scattering electromagnetic radiation and by catalyzing chemical reactions in the upper atmosphere. Meteoroids or their fragments achieve dark flight after deceleration to terminal velocity. Dark flight starts when they decelerate to about 2–4 km/s (4,500–8,900 mph). Larger fragments fall further down the strewn field.

Colours

A meteor of the Leonid meteor shower; the photograph shows the meteor, afterglow, and wake as distinct components

The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and the speed of its movement through the atmosphere. As layers of the meteoroid abrade and ionize, the colour of the light emitted may change according to the layering of minerals. Colours of meteors depend on the relative influence of the metallic content of the meteoroid versus the superheated air plasma, which its passage engenders:

• Orange-yellow (sodium)
• Yellow (iron)
• Blue-green (magnesium)
• Violet (calcium)
• Red (atmospheric nitrogen and oxygen)

Acoustic manifestations

Sound generated by a meteor in the upper atmosphere, such as a sonic boom, typically arrives many seconds after the visual light from a meteor disappears. Occasionally, as with the Leonid meteor shower of 2001, "crackling", "swishing", or "hissing" sounds have been reported, occurring at the same instant as a meteor flare. Similar sounds have also been reported during intense displays of Earth's auroras.

Theories on the generation of these sounds may partially explain them. For example, scientists at NASA suggested that the turbulent ionized wake of a meteor interacts with Earth's magnetic field, generating pulses of radio waves. As the trail dissipates, megawatts of electromagnetic power could be released, with a peak in the power spectrum at audio frequencies. Physical vibrations induced by the electromagnetic impulses would then be heard if they are powerful enough to make grasses, plants, eyeglass frames, the hearer's own body, and other conductive materials vibrate. This proposed mechanism, although proven to be plausible by laboratory work, remains unsupported by corresponding measurements in the field. Sound recordings made under controlled conditions in Mongolia in 1998 support the contention that the sounds are real.

Meteor shower

Multiple meteors photographed over an extended exposure time during a meteor shower

 

Meteor shower on chart

A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet or other source. The passage of Earth through cosmic debris from comets and other sources is a recurring event in many cases. Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951, and by breakup. Each time a comet swings by the Sun in its orbit, some of its ice vaporizes and a certain amount of meteoroids are shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a "dust trail" (as opposed to a comet's "dust tail" caused by the very small particles that are quickly blown away by solar radiation pressure).

The frequency of fireball sightings increases by about 10–30% during the weeks of vernal equinox. Even meteorite falls are more common during the northern hemisphere's spring season. Although this phenomenon has been known for quite some time, the reason behind the anomaly is not fully understood by scientists. Some researchers attribute this to an intrinsic variation in the meteoroid population along Earth's orbit, with a peak in big fireball-producing debris around spring and early summer. Others have pointed out that during this period the ecliptic is (in the northern hemisphere) high in the sky in the late afternoon and early evening. This means that fireball radiants with an asteroidal source are high in the sky (facilitating relatively high rates) at the moment the meteoroids "catch up" with Earth, coming from behind going in the same direction as Earth. This causes relatively low relative speeds and from this low entry speeds, which facilitates survival of meteorites. It also generates high fireball rates in the early evening, increasing chances of eyewitness reports. This explains a part, but perhaps not all of the seasonal variation. Research is in progress for mapping the orbits of the meteors to gain a better understanding of the phenomenon.

Notable meteors

1992—Peekskill, New York

The Peekskill Meteorite was recorded on October 9, 1992 by at least 16 independent videographers. Eyewitness accounts indicate the fireball entry of the Peekskill meteorite started over West Virginia at 23:48 UT (±1 min). The fireball, which traveled in a northeasterly direction, had a pronounced greenish colour, and attained an estimated peak visual magnitude of −13. During a luminous flight time that exceeded 40 seconds the fireball covered a ground path of some 430 to 500 mi (700 to 800 km). One meteorite recovered at Peekskill, New York, for which the event and object gained their name, had a mass of 27 lb (12.4 kg) and was subsequently identified as an H6 monomict breccia meteorite. The video record suggests that the Peekskill meteorite had several companions over a wide area. The companions are unlikely to be recovered in the hilly, wooded terrain in the vicinity of Peekskill.

Comparison of approximate sizes of notable impactors with the Hoba meteorite, a Boeing 747 and a New Routemaster bus

2009—Bone, Indonesia

A large fireball was observed in the skies near Bone, Sulawesi, Indonesia on October 8, 2009. This was thought to be caused by an asteroid approximately 10 m (33 ft) in diameter. The fireball contained an estimated energy of 50 kilotons of TNT, or about twice the Nagasaki atomic bomb. No injuries were reported.

2009—Southwestern US

A large bolide was reported on 18 November 2009 over southeastern California, northern Arizona, Utah, Wyoming, Idaho and Colorado. At 00:07 local time a security camera at the high altitude W. L. Eccles Observatory (9,610 ft (2,930 m) above sea level) recorded a movie of the passage of the object to the north. Of particular note in this video is the spherical "ghost" image slightly trailing the main object (this is likely a lens reflection of the intense fireball), and the bright fireball explosion associated with the breakup of a substantial fraction of the object. An object trail can be seen to continue northward after the bright fireball event. The shock from the final breakup triggered seven seismological stations in northern Utah; a timing fit to the seismic data yielded a terminal location of the object at 40.286 N, −113.191 W, altitude 90,000 ft (27 km). This is above the Dugway Proving Grounds, a closed Army testing base.

2013—Chelyabinsk Oblast, Russia

The Chelyabinsk meteor was an extremely bright, exploding fireball, known as superbolide, measuring about 17 to 20 m (56 to 66 ft) across, with an estimated initial mass of 11,000 tonnes, as the relatively small asteroid entered Earth's atmosphere. It was the largest known natural object to have entered Earth's atmosphere since the Tunguska event in 1908. Over 1,500 people were injured mostly by glass from shattered windows caused by the air burst approximately 25 to 30 km (80,000 to 100,000 ft) above the environs of Chelyabinsk, Russia on 15 February 2013. An increasingly bright streak was observed during morning daylight with a large contrail lingering behind. At no less than 1 minute and up to at least 3 minutes after the object peaked in intensity (depending on distance from trail), a large concussive blast was heard that shattered windows and set-off car alarms, which was followed by a number of smaller explosions.

2019—Midwestern United States

On November 11, 2019, a meteor was spotted streaking across the skies of the Midwestern United States. In the St. Louis Area, security cameras, dashcams, webcams, and video doorbells captured the object as it burned up in the earth's atmosphere. The superbolide meteor was part of the South Taurids meteor shower. It traveled east to west ending its visible flight path somewhere over the US state of South Carolina becoming visible once again as it entered the earth's atmosphere creating a large fireball. The fireball was brighter than the planet Venus in the night sky.

Gallery of meteors

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  Orionid meteor

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  Sporadic bolide over the desert of Central Australia and a Lyrid (top edge)

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  Meteor (center) seen from the International Space Station

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  Possible meteor (center) photographed from Mars, March 7, 2004, by MER Spirit

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  Comet Shoemaker–Levy 9 colliding with Jupiter: The sequence shows fragment W turning into a fireball on the planet's dark side

Meteorites

Murnpeowie meteorite, an iron meteorite with regmaglypts resembling thumbprints (Australia, 1910)

A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and hits the ground without being destroyed. Meteorites are sometimes, but not always, found in association with hypervelocity impact craters; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites. Geologists use the term, "bolide", in a different sense from astronomers to indicate a very large impactor. For example, the USGS uses the term to mean a generic large crater-forming projectile in a manner "to imply that we do not know the precise nature of the impacting body ... whether it is a rocky or metallic asteroid, or an icy comet for example".

Meteoroids also hit other bodies in the Solar System. On such stony bodies as the Moon or Mars that have little or no atmosphere, they leave enduring craters.

Frequency of impacts

The diameter of the largest impactor to hit Earth on any given day is likely to be about 40 centimeters (16 inches), in a given year about four metres (13 ft), and in a given century about 20 m (66 ft). These statistics are obtained by the following:

Over at least the range from five centimeters (2.0 inches) to roughly 300 meters (980 feet), the rate at which Earth receives meteors obeys a power-law distribution as follows:

${\displaystyle N(>D)=37D^{-2.7}\ }$

where N (>D) is the expected number of objects larger than a diameter of D meters to hit Earth in a year. This is based on observations of bright meteors seen from the ground and space, combined with surveys of near-Earth asteroids. Above 300 m (980 ft) in diameter, the predicted rate is somewhat higher, with a two kilometres (one point two miles) asteroid (one teraton TNT equivalent) every couple of million years — about 10 times as often as the power-law extrapolation would predict.

Impact craters

Meteoroid collisions with solid Solar System objects, including the Moon, Mercury, Callisto, Ganymede, and most small moons and asteroids, create impact craters, which are the dominant geographic features of many of those objects. On other planets and moons with active surface geological processes, such as Earth, Venus, Mars, Europa, Io, and Titan, visible impact craters may become eroded, buried, or transformed by tectonics over time. In early literature, before the significance of impact cratering was widely recognised, the terms cryptoexplosion or cryptovolcanic structure were often used to describe what are now recognised as impact-related features on Earth. Molten terrestrial material ejected from a meteorite impact crater can cool and solidify into an object known as a tektite. These are often mistaken for meteorites.

Gallery of meteorites

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  Two tektites, molten terrestrial ejecta from a meteorite impact

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  A partial slice of the Esquel pallasite

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  Willamette Meteorite, from Oregon, USA

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  Meteorite, which fell in Wisconsin in 1868

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  Marília Meteorite, a chondrite H4, which fell in Marília, Brazil (1971)

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  Children posing behind the Tucson Meteorite at the Arizona Museum of Natural History

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  Meteorite with brecciation and carbon inclusions from Tindouf, Algeria

 

Martian meteorite

From Wikipedia, the free encyclopedia

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

Martian meteorite (SNC meteorites)
Martian meteorite EETA79001, shergottite
Type	Achondrite
Subgroups	Shergottite Nakhlite Chassignite Orthopyroxenite Basaltic Breccia
Parent body	Mars
Total known specimens	277 as of 15 September 2020
Martian meteorite NWA 7034, nicknamed "Black Beauty," weighs approximately 320 g (11 oz).

A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. As of September 2020, 277 meteorites had been classified as Martian, less than half a percent of the 72,000 meteorites that have been classified.

There are three groups of Martian meteorite: shergottites, nakhlites and chassignites, collectively known as SNC meteorites. Several other Martian meteorites are ungrouped.

These meteorites are interpreted as Martian because they have elemental and isotopic compositions that are similar to rocks and atmospheric gases on Mars, which have been measured by orbiting spacecraft, surface landers and rovers. The term does not include meteorites found on Mars, such as Heat Shield Rock.

History

By the early 1980s, it was obvious that the SNC group of meteorites (Shergottites, Nakhlites, Chassignites) were significantly different from most other meteorite types. Among these differences were younger formation ages, a different oxygen isotopic composition, the presence of aqueous weathering products, and some similarity in chemical composition to analyses of the Martian surface rocks in 1976 by the Viking landers. Several scientists suggested these characteristics implied the origin of SNC meteorites from a relatively large parent body, possibly Mars. Then in 1983, various trapped gases were reported in impact-formed glass of the EET79001 shergottite, gases which closely resembled those in the Martian atmosphere as analyzed by Viking. These trapped gases provided direct evidence for a Martian origin. In 2000, an article by Treiman, Gleason and Bogard gave a survey of all the arguments used to conclude the SNC meteorites (of which 14 had been found at the time) were from Mars. They wrote, "There seems little likelihood that the SNCs are not from Mars. If they were from another planetary body, it would have to be substantially identical to Mars as it now is understood."

Subdivision

The Martian meteorites are divided into three groups (orange) and two grouplets (yellow). SHE = Shergottite, NAK = Nakhlite, CHA = Chassignite, OPX = Orthopyroxenite (ALH 84001), BBR = Basaltic Breccia (NWA 7034).

As of April 25, 2018, 192 of the 207 Martian meteorites are divided into three rare groups of achondritic (stony) meteorites: shergottites (169), nakhlites (20), chassignites (3), and ones otherwise (15) (containing the orthopyroxenite (OPX) Allan Hills 84001, as well as 10 basaltic breccia meteorites). Consequently, Martian meteorites as a whole are sometimes referred to as the SNC group. They have isotope ratios that are said to be consistent with each other and inconsistent with the Earth. The names derive from the location of where the first meteorite of their type was discovered.

Shergottites

Roughly three-quarters of all Martian meteorites can be classified as shergottites. They are named after the Shergotty meteorite, which fell at Sherghati, India in 1865. Shergottites are igneous rocks of mafic to ultramafic lithology. They fall into three main groups, the basaltic, olivine-phyric (such as the Tissint group found in Morocco in 2011) and Lherzolitic shergottites, based on their crystal size and mineral content. They can be categorised alternatively into three or four groups based on their rare-earth element content. These two classification systems do not line up with each other, hinting at complex relationships between the various source rocks and magmas from which the shergottites formed.

NWA 6963, a shergottite found in Morocco, September 2011.

The shergottites appear to have crystallised as recently as 180 million years ago, which is a surprisingly young age considering how ancient the majority of the surface of Mars appears to be, and the small size of Mars itself. Because of this, some have advocated the idea that the shergottites are much older than this. This "Shergottite Age Paradox" remains unsolved and is still an area of active research and debate.

The 3-million-year-old crater Mojave, 58.5 km in diameter and the youngest crater of its size on the planet, has been identified as a potential source of these meteorites.

Nakhlites

Nakhla meteorite's two sides and its inner surfaces after breaking it

Nakhlites are named after the first of them, the Nakhla meteorite, which fell in El-Nakhla, Alexandria, Egypt in 1911 and had an estimated weight of 10 kg.

Nakhlites are igneous rocks that are rich in augite and were formed from basaltic magma from at least four eruptions, spanning around 90 million years, from 1416 ± 7 to 1322 ± 10 million years ago. They contain augite and olivine crystals. Their crystallization ages, compared to a crater count chronology of different regions on Mars, suggest the nakhlites formed on the large volcanic construct of either Tharsis, Elysium, or Syrtis Major Planum.

It has been shown that the nakhlites were suffused with liquid water around 620 million years ago and that they were ejected from Mars around 10.75 million years ago by an asteroid impact. They fell to Earth within the last 10,000 years.

Chassignites

The first chassignite, the Chassigny meteorite, fell at Chassigny, Haute-Marne, France in 1815. There has been only one other chassignite recovered, named Northwest Africa (NWA) 2737. NWA 2737 was found in Morocco or Western Sahara in August 2000 by meteorite hunters Bruno Fectay and Carine Bidaut, who gave it the temporary name "Diderot." It was shown by Beck et al. that its "mineralogy, major and trace element chemistry as well as oxygen isotopes revealed an unambiguous Martian origin and strong affinities with Chassigny."

Ungrouped meteorites

Allan Hills 84001 (ALH 84001)

Among these, the famous specimen Allan Hills 84001 has a different rock type from other Martian meteorites: it is an orthopyroxenite (an igneous rock dominantly composed of orthopyroxene). For this reason it is classified within its own group, the "OPX Martian meteorites". This meteorite received much attention after an electron microscope revealed structures that were considered to be the fossilized remains of bacteria-like lifeforms. As of 2005, scientific consensus was that the microfossils were not indicative of Martian life, but of contamination by earthly biofilms. ALH 84001 is as old as the basaltic and intermediate shergottite groups – i.e., 4.1 billion years old.

In March 2004 it was suggested that the unique Kaidun meteorite, which landed in Yemen on December 3, 1980, may have originated on the Martian moon of Phobos. Because Phobos has similarities to C-type asteroids and because the Kaidun meteorite is a carbonaceous chondrite, Kaidun is not a Martian meteorite in the strict sense. However, it may contain small fragments of material from the Martian surface.

The Martian meteorite NWA 7034 (nicknamed "Black Beauty"), found in the Sahara desert during 2011, has ten times the water content of other Mars meteorites found on Earth. The meteorite contains components as old as 4.42 ± 0.07 Ga (billion years), and was heated during the Amazonian geologic period on Mars.

Origin

The majority of SNC meteorites are quite young compared to most other meteorites and seem to imply that volcanic activity was present on Mars only a few hundred million years ago. The young formation ages of Martian meteorites was one of the early recognized characteristics that suggested their origin from a planetary body such as Mars. Among Martian meteorites, only ALH 84001 and NWA 7034 have radiometric ages older than about 1400 Ma (Ma = million years). All nakhlites, as well as Chassigny and NWA 2737, give similar if not identical formation ages around 1300 Ma, as determined by various radiometric dating techniques. Formation ages determined for many shergottites are variable and much younger, mostly ~150-575 Ma. The chronological history of shergottites is not totally understood, and a few scientists have suggested that some may actually have formed prior to the times given by their radiometric ages, a suggestion not accepted by most scientists. Formation ages of SNC meteorites are often linked to their cosmic-ray exposure (CRE) ages, as measured from the nuclear products of interactions of the meteorite in space with energetic cosmic ray particles. Thus, all measured nakhlites give essentially identical CRE ages of approximately 11 Ma, which when combined with their possible identical formation ages indicates ejection of nakhlites into space from a single location on Mars by a single impact event. Some of the shergottites also seem to form distinct groups according to their CRE ages and formation ages, again indicating ejection of several different shergottites from Mars by a single impact. However, CRE ages of shergottites vary considerably (~0.5–19 Ma), and several impact events are required to eject all the known shergottites. It had been asserted that there are no large young craters on Mars that are candidates as sources for the Martian meteorites, but subsequent studies claimed to have a likely source for ALH 84001 and a possible source for other shergottites.

In a 2014 paper, several researchers claimed that all shergottites meteorites come from the Mojave Crater on Mars.

Age estimates based on cosmic ray exposure

A Martian meteorite crafted into a small pendant and suspended from a silver necklace.

The amount of time spent in transit from Mars to Earth can be estimated by measurements of the effect of cosmic radiation on the meteorites, particularly on isotope ratios of noble gases. The meteorites cluster in families that seem to correspond to distinct impact events on Mars.

It is thought, therefore, that the meteorites all originate in relatively few impacts every few million years on Mars. The impactors would be kilometers in diameter and the craters they form on Mars tens of kilometers in diameter. Models of impacts on Mars are consistent with these findings.

Ages since impact determined so far include

Type	Age (mya)
Dhofar 019, olivine-phyric shergottite	19.8 ± 2.3
ALH 84001, orthopyroxenite	15.0 ± 0.8
Dunite (Chassigny)	11.1 ± 1.6
Six nakhlites	10.8 ± 0.8
Lherzolites	3.8–4.7
Six basaltic shergottites	2.4–3.0
Five olivine-phyric shergottites	1.2 ± 0.1
EET 79001	0.73 ± 0.15

Possible evidence of life

Several Martian meteorites have been found to contain what some think is evidence for fossilized Martian life forms. The most significant of these is a meteorite found in the Allan Hills of Antarctica (ALH 84001). Ejection from Mars seems to have taken place about 16 million years ago. Arrival on Earth was about 13 000 years ago. Cracks in the rock appear to have filled with carbonate materials (implying groundwater was present) between 4 and 3.6 billion-years-ago. Evidence of polycyclic aromatic hydrocarbons (PAHs) have been identified with the levels increasing away from the surface. Other Antarctic meteorites do not contain PAHs. Earthly contamination should presumably be highest at the surface. Several minerals in the crack fill are deposited in phases, specifically, iron deposited as magnetite, that are claimed to be typical of biodepositation on Earth. There are also small ovoid and tubular structures that might be nanobacteria fossils in carbonate material in crack fills (investigators McKay, Gibson, Thomas-Keprta, Zare). Micropaleontologist Schopf, who described several important terrestrial bacterial assemblages, examined ALH 84001 and opined that the structures are too small to be Earthly bacteria and don't look especially like lifeforms to him. The size of the objects is consistent with Earthly "nanobacteria", but the existence of nanobacteria itself is controversial.

Many studies disputed the validity of the fossils. For example, it was found that most of the organic matter in the meteorite was of terrestrial origin. But, a recent study suggests that magnetite in the meteorite could have been produced by Martian microbes. The study, published in the journal of the Geochemical and Meteoritic Society, used more advanced high resolution electron microscopy than was possible in 1996. A serious difficulty with the claims for a biogenic origin of the magnetites is that the majority of them exhibit topotactic crystallographic relationships with the host carbonates (i.e., there are 3D orientation relationships between the magnetite and carbonate lattices), which is strongly indicative that the magnetites have grown in-situ by a physico-chemical mechanism.

While water is no indication of life, many of the meteorites found on Earth have shown water, including NWA 7034 which formed during the Amazonian period of Martian geological history. Other signs of surface liquid water on Mars (such as recurring slope lineae) are a topic of debate among planetary scientists, but generally consistent with the earlier evidence provided by martian meteorites. Any liquid water present is likely too minimal to support life.

 

Space Launch System

From Wikipedia, the free encyclopedia

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

Space Launch System

An artist's rendering of SLS Block 1 with Orion spacecraft on the pad before launch.
Function	Super heavy-lift launch vehicle
Country of origin	United States
Project cost	US$18.6 billion (as of 2020)
Cost per launch	Over US$2 billion excluding development (estimate)
Cost per year	US$2.5 billion for 2020
Size
Height	111.25 m (365.0 ft), Block 2 Cargo
Diameter	8.4 m (28 ft), core stage
Stages	2
Capacity
Payload to LEO
Mass	Block 1: 95 t (209,000 lb)  Block 2: 130 t (290,000 lb)
Payload to trans-lunar injection
Mass	Block 1: > 27 t (60,000 lb) Block 1B Crew: 38 t (83,700 lb) Block 1B Cargo: 42 t (92,500 lb) Block 2 Crew: > 43 t (94,700 lb) Block 2 Cargo: > 46 t (101,400 lb)
Associated rockets
Comparable	Energia N1 Saturn V SpaceX Starship Space Shuttle
Launch history
Status	Active
Launch sites	Kennedy Space Center, LC-39B
First flight	NET 22 November 2021
Notable payloads	Artemis 1, Orion
Boosters (Block 1, 1B)
No. boosters	2 five-segment Solid Rocket Boosters
Length	54 m (177 ft)
Gross mass	730 t (1,610,000 lb)
Thrust	14.6 MN (1,490 tf; 3,300,000 lbf) sea level 16 MN (1,600 tf; 3,600,000 lbf) vacuum
Total thrust	29.2 MN (2,980 tf; 6,600,000 lbf) sea level 32 MN (3,300 tf; 7,200,000 lbf) vacuum
Specific impulse	269 s (2.64 km/s)
Burn time	126 seconds
Propellant	PBAN, APCP
First stage (Block 1, 1B, 2) – Core stage
Length	65 m (212 ft)
Diameter	8.4 m (27.6 ft)
Empty mass	85 t (187,990 lb)
Gross mass	979 t (2,159,322 lb)
Engines	4 RS-25D/E
Thrust	9.1 MN (930 tf) vacuum
Specific impulse	366 s (3.59 km/s) (sea level) 452 s (4.43 km/s)
Burn time	480 seconds
Propellant	LH2 / LOX
Second stage (Block 1) – ICPS
Length	13.7 m (45 ft)
Diameter	5 m (16 ft)
Empty mass	3.5 t (7,690 lb)
Gross mass	30.7 t (67,700 lb)
Engines	1 RL10B-2
Thrust	110.1 kN (11.23 tf; 24,800 lbf)
Specific impulse	465.5 s (4.565 km/s)
Burn time	1125 seconds
Propellant	LH2 / LOX
Second stage (Block 1B, Block 2) – Exploration Upper Stage
Length	17.6 m (58 ft)
Diameter	8.4 m (28 ft)
Engines	4 RL10C-3, later 4 RL10C-X
Thrust	440 kN (45 tf; 99,000 lbf)
Propellant	LH2 / LOX

The Space Launch System (SLS) is an American super heavy-lift expendable launch vehicle, which has been under development by NASA since its announcement in 2011. It replaced the Ares I, Ares V, and Jupiter planned launch vehicles, which all never left the development phase. Like those proposals, it is a design derived from the components and technology of the earlier Space Shuttle.

It had been planned to become the primary launch vehicle of NASA's deep space exploration plans throughout the 2010s (now 2020s), including the planned crewed lunar flights of the Artemis program and a possible follow-on human mission to Mars. SLS is intended to replace the retired Space Shuttle as NASA's flagship vehicle. Following the cancellation of the Constellation program, the NASA Authorization Act of 2010 envisioned a single launch vehicle usable for both crew and cargo. In 2013, SLS was projected to be the most capable super-heavy lift launch vehicle ever built.

The initial variant of SLS, Block 1, was required by the U.S. Congress to lift a payload of 70 t (69 long tons; 77 short tons) to low Earth orbit (LEO), but it was later planned to exceed that requirement with a rated payload capacity of 95 t (93 long tons; 105 short tons). As of 22 December 2019, this variant is planned to launch Artemis 1, Artemis 2, and Artemis 3. The later Block 1B is intended to debut the Exploration Upper Stage and launch the notional Artemis 4 through Artemis 7. Block 2 is planned to replace the initial Shuttle-derived boosters with advanced boosters and would have a LEO capability of more than 130 t (130 long tons; 140 short tons), again as required by Congress. Block 2 is intended to enable crewed launches to Mars.

As of 2018, SLS was planned to have the world's highest-ever total LEO payload capability, but not the world's highest ever injection mass. The SLS is planned to launch the Orion spacecraft and use the ground operations and launch facilities at NASA's Kennedy Space Center in Florida. The rocket will use the Launch Complex 39B at the Kennedy Space Center. The first launch is currently scheduled for 4 November 2021.

Vehicle description

The SLS is a Space Shuttle-derived launch vehicle, with the first stage of the rocket being powered by one central core stage and two outboard boosters. The upper stage is being developed from the Block 1 variant to a Block 1B and 2 variant, the Exploration Upper Stage.

Core stage

The Space Launch System's core stage contains the Main Propulsion System (MPS) of the launch vehicle. It is 65 m (212 ft) long by 8.4 m (27.6 ft) in diameter and fuels the four RS-25 rocket engines at its base. The core stage is structurally and visually similar to the Space Shuttle external tank, containing the liquid hydrogen fuel and liquid oxygen oxidizer. Flights 1 through 4 are planned to use modified RS-25D engines left over from the Space Shuttle program. However, the RS-25 engines were designed with reuse in mind for the Space Shuttle, so later flights are planned to switch to a expendable optimized RS-25 variant, lowering per engine costs over 30%.

The core stage is fabricated at NASA's Michoud Assembly Facility and is common across all currently planned evolutions of the SLS to avoid the need for redesigns to meet varying requirements.

Boosters

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SLS Booster test at Orbital ATK/Northrop Grumman's desert facility northwest of Ogden, Utah, March 2015

Block 1 and 1B boosters

Blocks 1 and 1B of the SLS are planned to use two five-segment Solid Rocket Boosters (SRBs). These new SRBs are derived from the four-segment Space Shuttle Solid Rocket Boosters, with the addition of a center booster segment, new avionics, and lighter insulation. The five-segment SRBs provide approximately 25% more total impulse than the Shuttle SRB, but will no longer be recovered after use.

Booster Obsolescence and Life Extension program

The stock of SLS boosters is limited by the number of casings left over from the Shuttle program, since they modify flown boosters to add an additional segment. There are enough to last through eight flights of the SLS, but a replacement will be required for further flights. On 2 March 2019, the Booster Obsolescence and Life Extension (BOLE) program was announced. This program will use new solid rocket boosters built by Northrop Grumman Innovation Systems for further SLS flights. These boosters would be derived from the composite-casing SRBs in development for the OmegA launch vehicle before it was canceled, and are projected to increase Block 1B's payload to TLI by 3–4 metric tons, which is still 1 ton below the payload capacity of Block 2.

Block 2 – advanced boosters

Block 2 will have special advanced boosters which will enable Block 2 to carry 130 metric tons (130 long tons; 140 short tons) to LEO and at least 46 metric tons (45 long tons; 51 short tons) to TLI.

Upper stage

ICPS – Block 1

The Interim Cryogenic Propulsion Stage (ICPS) is planned to fly on Artemis 1. It is a stretched and human-rated Delta IV 5-meter (16 ft) Delta Cryogenic Second Stage (DCSS) powered by a single RL10B-2 engine. Block 1 is intended to be capable of lifting 95 tonnes to low Earth orbit (LEO) in this configuration if the ICPS is considered part of the payload. Artemis 1 is to be launched into an initial 1,800 by −93 km (1,118 by −58 mi) suborbital trajectory to ensure safe disposal of the core stage. ICPS will then perform an orbital insertion burn at apogee and a subsequent translunar injection burn to send Orion towards the Moon. The ICPS for Artemis 1 was delivered by ULA to NASA about July 2017, and was housed at Kennedy Space Centre as of November 2018. As of February 2020, ICPS (not EUS) is planned for Artemis 1, 2, and 3. ICPS will be human-rated for the crewed Artemis 2 flight.

EUS – Block 1B and 2

The Exploration Upper Stage (EUS) is planned to fly on Artemis 4. Similar to the S-IVB, the EUS will complete the SLS ascent phase and then re-ignite to send its payload to destinations beyond LEO. It is expected to be used by Block 1B and Block 2, share the core stage diameter of 8.4 meters, and be powered by four RL10C-3 engines. It will eventually be upgraded to use four RL10C-X engines instead.

Payload carrying capacity

Resilience

The SLS is planned to have the ability to tolerate 23 tanking cycles, 13 are reserved for launch attempts on Artemis 1. The assembled rocket is to be able to remain at the launch pad for at least 180 days and can remain in a stacked configuration for at least 200 days.

Development history

Planned evolution of the Space Launch System, 2018

Program history

During the joint Senate-NASA presentation in September 2011, it was stated that the SLS program had a projected development cost of US$18 billion through 2017, with US$10 billion for the SLS rocket, US$6 billion for the Orion spacecraft and US$2 billion for upgrades to the launch pad and other facilities at Kennedy Space Center. These costs and schedule were considered optimistic in an independent 2011 cost assessment report by Booz Allen Hamilton for NASA.

An internal 2011 NASA document estimated the cost of the program through 2025 to total at least $41 billion for four 95-tonne launches (1 uncrewed, 3 crewed), with the 130-tonne version ready no earlier than 2030.

The Human Exploration Framework Team (HEFT) estimated unit costs for Block 0 at US$1.6 billion and Block 1 at US$1.86 billion in 2010. However, since these estimates were made the Block 0 SLS vehicle was dropped in late 2011, and the design was not completed.

In September 2012, an SLS deputy project manager stated that US$500 million per launch is a reasonable target cost for SLS.

In 2013, the Space Review estimated the cost per launch at US$5 billion, depending on the rate of launches. NASA announced in 2013 that the European Space Agency (ESA) will build the Orion service module.

In 2011, NASA announced an "Advanced Booster Competition", to be decided in 2015, which would select whose boosters would be used for Block 2 of the SLS.

Several companies proposed boosters for this competition:

• Aerojet, in partnership with Teledyne Brown, offered a booster powered by three new AJ1E6 LOX/RP-1 oxidizer-rich staged combustion engines, each producing 4,900 kN (1,100,000 lbf) thrust using a single turbopump to supply dual combustion chambers. On 14 February 2013, Aerojet was awarded a US$23.3 million, 30-month contract to build a 2,400 kN (550,000 lbf) main injector and thrust chamber.
• Alliant Techsystems (ATK) proposed an advanced SRB nicknamed "Dark Knight", which would switch to a lighter composite case, use a more energetic propellant, and reduce the number of segments from five to four.
  

• Some comparable launch vehicles
• Pratt & Whitney Rocketdyne and Dynetics proposed a liquid-fueled booster named Pyrios.

In 2013, the manager of NASA's SLS advanced development office indicated that all three approaches were viable.

However, this competition was planned for a development plan in which Block 1A would be followed by Block 2A, with upgraded boosters. NASA canceled Block 1A and the planned competition in April 2014. Due to this cancellation, it was reported in February 2015 that SLS is expected to fly with the original five-segment SRB until at least the late 2020s. This decision was vindicated as a later study found that the advanced booster would have resulted in unsuitably high acceleration. The overly powerful booster would need modifications to Launch Pad 39B (LC-39B), its flame trench, and Mobile Launcher, which are being evaluated.

In August 2014, as the SLS program passed its Key Decision Point C review and entered full development, costs from February 2014 until its planned launch in September 2018 were estimated at US$7.021 billion. Ground systems modifications and construction would require an additional US$1.8 billion over the same time period.

In October 2018, NASA's inspector general reported that the Boeing core stage contract had made up 40% of the US$11.9 billion spent on SLS as of August 2018. By 2021, core stages were expected to have cost a total of US$8.9 billion, which is twice the initially planned amount.

In December 2018, NASA estimated that yearly budgets for SLS will range from US$2.1 to US$2.3 billion between 2019 and 2023.

In March 2019, the Trump Administration released its Fiscal Year 2020 Budget Request for NASA. This budget did not include any money for the Block 1B and Block 2 variants of SLS. It was therefore uncertain whether these future variants of SLS will be developed, but congressional action restored this funding in the passed budget. Several launches previously planned for the SLS Block 1B are now expected to fly on commercial launcher vehicles such as Falcon Heavy, New Glenn and Vulcan. However, the request for a budget increase of US$1.6 billion towards SLS, Orion, and crewed landers along with the launch manifest seem to indicate support of the development of Block 1B, debuting Artemis 3. The Block 1B will be used mainly for co-manifested crew transfers and logistical needs rather than constructing the Gateway. An uncrewed Block 1B is planned to launch the Lunar Surface Asset in 2028, the first lunar outpost of the Artemis program. Block 2 development will most likely start in the late 2020s after NASA is regularly visiting the lunar surface and shifts focus towards Mars.

Blue Origin submitted a proposal to replace the Exploration Upper Stage with an alternative to be designed and fabricated by the company, but it was rejected by NASA in November 2019 on multiple grounds. These included lower performance compared to the existing EUS design, unsuitability of the proposal to current ground infrastructure, and unacceptable acceleration in regards to Orion components.

On March 18th 2021, CS-1 successfully completed its 8 minute Green Run test.

Funding history

For fiscal years 2011 through 2020, the SLS program had expended funding totaling US$18.648 billion in nominal dollars. This is equivalent to US$20.314 billion in 2020 dollars using the NASA New Start Inflation Indices.

For fiscal year 2021, US$2.257 billion.

Fiscal year	Funding (millions)		Status
	Nominal	In US$2020
2011	US$1,536.1	US$1,819.9	Actual (Formal SLS Program reporting excludes the Fiscal 2011 budget.)
2012	US$1,497.5	US$1,755.5	Actual
2013	US$1,414.9	US$1,634.1	Actual
2014	US$1,600.0	US$1,812.3	Actual
2015	US$1,678.6	US$1,863.8	Actual
2016	US$1,971.9	US$2,159.6	Actual
2017	US$2,127.1	US$2,286.8	Actual
2018	US$2,150.0	US$2,256.6	Actual
2019	US$2,144.0	US$2,199.9	Actual
2020	US$2,525.8	US$2,525.8	Enacted
2021	US$2,585.9	US$2,585.9	Enacted
2011–2020	Total: US$18,648	Total: US$20,314

On top of this, the costs to assemble, integrate, prepare and launch the SLS and its payloads are funded separately under Exploration Ground Systems, currently about US$600 million per year.

Excluded from the above SLS costs are:

• Costs of payloads for the SLS (such as Orion crew capsule)
• Costs of the predecessor Ares V / Cargo Launch Vehicle (funded from 2008 to 2010)
• Costs for the Ares I / Crew Launch Vehicle (funded from 2006 to 2010, a total of US$4.8 billion in development that included the 5-segment Solid Rocket Boosters that will be used on the SLS)

Included in the above SLS costs are:

• Costs of the interim Upper Stage for the SLS, the Interim Cryogenic Propulsion Stage (ICPS) for SLS, which includes a US$412 million contract 
• Costs of the future Upper Stage for the SLS, the Exploration Upper Stage (EUS) (funded at US$85 million in 2016, US$300 million in 2017, US$300 million in 2018, and US$150 million in 2019)

Per launch costs

The per launch costs for SLS have varied widely, partly due to uncertainty over how much the program will expend during development and testing before the operational launches begin, and partly due to various agencies using differing cost measures (for example, a marginal cost per one additional launch, which ignores development and annual recurring fixed costs vs. total cost per launch, including recurring costs but excluding development); but also based on differing purposes for which the cost estimates were developed.

There are no official NASA estimates for how much SLS will cost per launch, nor for the SLS program annual recurring costs once operational. Cost per launch is not a straightforward figure to estimate as it depends heavily on how many launches occur per year. For example, similarly, the Space Shuttle was estimated (in 2012 dollars) to cost US$576 million per launch had it been able to achieve 7 launches per year, while the marginal cost of adding a single additional launch in a given year was estimated to be less than half of that, at just US$252 million of marginal cost. However, at the rate that it actually flew, the cost in the end was US$1.64 billion per Space Shuttle launch, including development.

NASA associate administrator William H. Gerstenmaier said in 2017 that there would be no official per flight cost estimates of any variety provided by NASA for SLS. Other bodies, such as the Government Accountability Office (GAO), the NASA Office of Inspector General, the Senate Appropriations Committee, and the White House Office of Management and Budget have put out cost per launch figures, however.

Several internal NASA programs and project concept study reports have released proposed budgets that include future SLS launches. For example, a concept study report for a space telescope was advised by NASA HQ in 2019 to budget US$500 million for an SLS launch in 2035. Another study in 2019 also proposing a space telescope assumed a budget for their launch of US$650 million in current day dollars, or US$925 million for when the launch would occur, which is also in the "mid-2030s".

Europa Clipper is a NASA scientific mission that was required by Congress to launch on the SLS. Oversight bodies both internal and external to NASA disagreed with this requirement. First, NASA's Inspector General office published a report in May 2019 that stated Europa Clipper would need to give up US$876 million for the "marginal cost" of its SLS launch. Then, an addendum to the letter published in August 2019 increased the estimate and stated that switching to a commercial rocket would actually save over US$1 billion. (Although this savings may have included a portion of costs related to the delay in launch schedule; a commercial alternative could launch sooner than SLS) A JCL (Joint Cost and Schedule Confidence Level) analysis cited in that letter put the cost savings at US$700 million, with SLS at US$1.05 billion per launch and the commercial alternative at US$350 million.

Finally, a letter from the White House Office of Management and Budget (OMB) to the Senate Appropriations Committee in October 2019 revealed that SLS's total cost to the taxpayer was estimated at "over US$2 billion" per launch after development is complete (program development has cost US$20 billion to date in 2020 dollars). The letter urged Congress to remove this requirement, in agreement with the NASA Inspector General, adding that using a commercial launch vehicle for Europa Clipper instead of SLS would save US$1.5 billion overall. NASA did not deny this US$2 billion cost of launch and an agency spokesperson stated it "is working to bring down the cost of a single SLS launch in a given year as the agency continues negotiations with Boeing on the long-term production contract and efforts to finalize contracts and costs for other elements of the rocket". This OMB figure is dependent on the rate of construction, so building more SLS rockets faster could decrease the per-unit cost. For example, Exploration Ground Systems – whose only role is to support, assemble, integrate, and launch SLS – has separately budgeted fixed costs of US$600 million per year on facilities, spread across however many rockets launch that year. Then NASA Administrator Jim Bridenstine shared informally that he disagrees with the US$2 billion figure since the marginal cost of an SLS launch should decrease after the first few, and is expected to end up around US$800 million to US$900 million, although contract negotiations were only just beginning for those later cores.

On 1 May 2020, NASA awarded a contract extension to Aerojet Rocketdyne to manufacture 18 additional RS-25 engines with associated services for US$1.79 billion, bringing the total RS-25 contract value to almost US$3.5 billion.

Constellation

From 2009 to 2011, three full-duration static fire tests of five-segment SRBs were conducted under the Constellation Program, including tests at low and high core temperatures, to validate performance at extreme temperatures. The 5-segment SRB would be carried over to SLS.

Early SLS

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Engineers with Exploration Ground Systems and Jacobs prepare to lift and place the core stage of the Space Launch System rocket for the Artemis I mission on the mobile launcher and in-between the already assembled twin rocket boosters.

During the early development of the SLS a number of configurations were considered, including a Block 0 variant with three main engines, a Block 1A variant with upgraded boosters instead of the improved second stage, and a Block 2 with five main engines and the Earth Departure Stage, with up to three J-2X engines. In February 2015, it was determined that these concepts would exceed the congressionally mandated Block 1 and Block 1B baseline payloads.

On 14 September 2011, NASA announced the new launch system, which is intended to take the agency's astronauts farther into space than ever before and provide the cornerstone for future U.S. human space exploration efforts in combination with the Orion spacecraft.

On 31 July 2013, the SLS passed the Preliminary Design Review (PDR). The review included not only the rocket and boosters but also ground support and logistical arrangements. On 7 August 2014, the SLS Block 1 passed a milestone known as Key Decision Point C and entered full-scale development, with an estimated launch date of November 2018.

In 2013, NASA and Boeing analyzed the performance of several EUS engine options. The analysis was based on a second-stage usable propellant load of 105 metric tons, and compared stages with four RL10 engines, two MARC-60 engines, or one J-2X engine.

In 2014, NASA also considered using the European Vinci instead of the RL10. The Vinci offers the same specific impulse but with 64% greater thrust, which would allow for the same performance at lower cost.

Northrop Grumman Innovation Systems has completed full-duration static fire tests of the five-segment SRBs. Qualification Motor 1 (QM-1) was tested on 10 March 2015. Qualification Motor 2 (QM-2) was successfully tested on 28 June 2016.

SLS History

Artemis I core stage going into the Vehicle Assembly Building

As of 2020, three SLS versions are planned: Block 1, Block 1B, and Block 2. Each will use the same core stage with four main engines, but Block 1B will feature the Exploration Upper Stage (EUS), and Block 2 will combine the EUS with upgraded boosters.

In mid-November 2014, construction of the first core stage hardware began using a new welding system in the South Vertical Assembly Building at NASA's Michoud Assembly Facility. Between 2015 and 2017, NASA test fired RS-25 engines in preparation for use on SLS.

As of late 2015, the SLS program was stated to have a 70% confidence level for the first crewed Orion flight by 2023, and as of 2020, NASA is continuing to project a 2023 launch.

A test article build for the core stage began on 5 January 2016 and was expected to be completed in late January 2016. Once completed the test article was to be sent to ensure structural integrity at Marshall Space Flight Center. A structural test article of the ICPS was delivered in 2015. the core stage for Artemis 1 completed assembly in November 2019.

The first core stage left Michoud for comprehensive testing at Stennis in January 2020. The static firing test program at Stennis Space Center, known as the Green Run, will operate all the core stage systems simultaneously for the first time. Test 7 (of 8), the wet dress rehearsal, was carried out in December 2020 and the hot fire (test 8) took place on 16 January 2021, but shut down earlier than expected, about 67 seconds in total rather than the desired eight minutes. The reason for the early shutdown was later reported to be because of conservative test commit criteria on the thrust vector control system, specific only for ground testing and not for flight. If this scenario occurred during a flight, the rocket would have continued to fly normally. There was no sign of damage to the core stage or the engines, contrary to initial concerns. The second hot fire test was successfully completed March 18, with all 4 engines igniting, throttling down as expected to simulate in-flight conditions, and gimballing profiles. The core stage was shipped down to Kennedy Space Center to be mated with the rest of the rocket for Artemis 1. It left Stennis on April 24, and arrived at Kennedy on April 27. It was refurbished there in preparation for stacking. On 12 June 2021, NASA announced the assembly of the first SLS rocket was completed at the Kennedy Space Center. The assembled SLS is planned to be used for the unmanned Artemis 1 mission later in 2021.

The intended uncrewed first flight of SLS has slipped multiple times: originally from late 2016  to October 2017, then to November 2018, then to 2019, then to June 2020, then to April 2021, and most recently to November 2021.

Criticism

NASA moved out US$889 million of costs relating to SLS boosters, but did not update the SLS budget to match, a March 2020 Inspector General report found. This kept the budget overrun to 15% by FY 2019. At 30%, NASA would have to notify Congress and stop funding unless Congress reapproves and provides additional funding. The Inspector General report found that were it not for this "masking" of cost, the overrun would be 33% by FY 2019. The GAO separately stated "NASA's current approach for reporting cost growth misrepresents the cost performance of the program".

The SLS has been criticized on the basis of program cost, lack of commercial involvement, and the non-competitive nature of a vehicle legislated to use Space Shuttle components.

In 2009, the Augustine commission proposed a commercial 75 t (74 long tons; 83 short tons) launcher with lower operating costs, and noted that a 40–60 t (39–59 long tons; 44–66 short tons) launcher was the minimum required to support lunar exploration.

In 2011–2012, the Space Access Society, Space Frontier Foundation and The Planetary Society called for the cancellation of the project, arguing that SLS will consume the funds for other projects from the NASA budget. U.S. Representative Dana Rohrabacher and others proposed that an orbital propellant depot should be developed and the Commercial Crew Development program accelerated instead. A NASA study that was not publicly released and another from the Georgia Institute of Technology showed this option to be possibly cheaper. In 2012, the United Launch Alliance also suggested using existing rockets with on-orbit assembly and propellant depots as needed. The lack of competition in the SLS design was highlighted. In the summer of 2019, a former ULA employee claimed that Boeing, NASA's prime contractor for SLS, viewed orbital refueling technology as a threat to SLS and blocked further investment in it.

In 2011, Mars Society/Mars Direct founder Robert Zubrin suggested that a heavy lift vehicle could be developed for US$5 billion on fixed-price requests for proposal.

In 2010, SpaceX's CEO Elon Musk claimed that his company could build a launch vehicle in the 140- to 150-tonne payload range for US$2.5 billion, or US$300 million (in 2010 dollars) per launch, not including a potential upper-stage upgrade. In the early 2010s, SpaceX went on to start development of SpaceX Starship, a planned fully reusable super-heavy launch system. Reusability is claimed to allow the lowest-cost super-heavy launcher ever made. If the price per launch and payload capabilities for the Starship are anywhere near Musk's claimed capabilities, the rocket will be substantially cheaper than the SLS.

In 2011, Rep. Tom McClintock and other groups called on the Government Accountability Office (GAO) to investigate possible violations of the Competition in Contracting Act (CICA), arguing that Congressional mandates forcing NASA to use Space Shuttle components for SLS are de facto non-competitive, single source requirements assuring contracts to existing Shuttle suppliers. The Competitive Space Task Force, in September 2011, said that the new government launcher directly violates NASA's charter, the Space Act, and the 1998 Commercial Space Act requirements for NASA to pursue the "fullest possible engagement of commercial providers" and to "seek and encourage, to the maximum extent possible, the fullest commercial use of space". Opponents of the heavy launch vehicle have critically used the name "Senate launch system", a name that was still being used by opponents to criticize the program in 2021, as "the NASA Inspector General said the total cost of the rocket would reach $27 billion through 2025."

In 2013, Chris Kraft, the NASA mission control leader from the Apollo era, expressed his criticism of the system as well. Lori Garver, former NASA Deputy Administrator, has called for canceling the launch vehicle alongside the Mars 2020 rover. Phil Plait has voiced his criticism of SLS in light of ongoing budget tradeoffs between the Commercial Crew Development and SLS budgets, also referring to earlier critiques by Garver.

In 2019, the Government Accountability Office found that NASA had awarded Boeing over US$200 million for service with ratings of good to excellent despite cost overruns and delays. As of 2019, the maiden launch of SLS was expected in 2021. NASA continued to expect that the first orbital launch would be in 2021 as late as May 2020.

On 1 May 2020, NASA awarded a US$1.79 billion contract extension for the manufacture of 18 additional RS-25 engines. Ars Technica, in an article published on the same day, highlighted that over the entire RS-25 contract the price of each engine works out to US$146 million and that the total price for the four expendable engines used in each SLS launch will be more than US$580 million. They critically commented that for the cost of just one engine, six more powerful RD-180 engines could be purchased, or nearly an entire Falcon Heavy launch with two thirds of the SLS lift capacity.

Former NASA Administrator Charlie Bolden, who oversaw the initial design and development of the SLS, also voiced his criticism of the program in an interview with Politico in September 2020. Bolden said that the "SLS will go away because at some point commercial entities are going to catch up". Bolden further stated "commercial entities are really going to build a heavy-lift launch vehicle sort of like SLS that they will be able to fly for a much cheaper price than NASA can do SLS".